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BSR/IIAR 2-201x
Standard for Safe Design of Closed-Circuit Ammonia Refrigeration Systems
July 30th, 2014
Public Review #2 Draft
Notes on the Standard Text
Metric Policy
The IIAR metric policy for ANSI standards, bulletins and all IIAR publications is to use the common
engineering “inch-pound” (IP) unit system as the primary unit of measure, and the International System
of Units (SI), as defined in United States National Institute of Standards and Technology Special
Publication 330 “The International System of Units,” for secondary units.
Normative/Informative Elements
This standard includes both Normative (required) and Informative (advisory) language. The bodies of
the standard and labeled Appendices are Normative. The Foreword, Notes, and any Appendices labeled
Informative are non-mandatory. Informative material shall never be regarded as a requirement.
Notice
The information contained in this Standard has been obtained from sources believed to be reliable.
However, it shall not be assumed that all acceptable methods or procedures are contained in this document,
or that additional measures may not be required under certain circumstances or conditions. The Standards
Committee and Consensus Body that approved the Standard were balanced to assure that individuals from
competent and concerned interests have had an opportunity to participate. The proposed Standard was
made available for review and comment for additional input from industry, academia, regulatory agencies
and others.
The IIAR makes no warranty or representation and assumes no liability or responsibility in connection
with the use of any information contained in this document.
Use of and reference to this document by private industry, government agencies and others is intended to
be voluntary and not binding unless and until its use is mandated by authorities having jurisdiction.
The IIAR does not “approve” or “endorse” any products, services or methods. This document shall not
be used or referenced in any way which would imply such approval or endorsement.
Note that the various codes and regulations referenced in this document may be amended from time to
time and the versions referenced herein are the versions of such codes and regulations set forth in Chapter
3 of this Standard.
The IIAR uses its best efforts to promulgate Standards for the benefit of the public in light of available
information and accepted industry practices. However, the IIAR does not guarantee, certify, or assume
the safety or performance of any products, components or systems tested, installed, or operated in
accordance with IIAR’s Standards or that any tests conducted under its Standards will be nonhazardous
or free from risk.
This Standard is subject to periodic review. Up-to-date information about the status of the Standard may
be received by contacting IIAR.
Copyright
This document may not, in whole or in part, be reproduced, copied or disseminated, entered into or stored
in a computer database or retrieval system, or otherwise utilized without the prior written consent of the
IIAR.
Copyright © 201x by
INTERNATIONAL INSTITUTE OF AMMONIA REFRIGERATION
All Rights Reserved
Foreword (Informative)
This document is a standard for the safe design of closed-circuit ammonia refrigeration
systems. The safety focus is on persons and property located at or near the premises
where the refrigeration systems are located. Additional precautions may be necessary
because of particular circumstances, project specifications or other jurisdictional
considerations. This standard is not intended to serve as a comprehensive technical
design manual and shall not be used as such.
Experience shows that ammonia is very stable under normal conditions and rarely ignites when a release occurs because of the flammability range in air is narrow and the minimum flammable concentration in air is very high as compared to other gases. Ammonia has a published flammability range of 160,000 ppm to 250,000 ppm. This concentration far exceeds ammonia’s odor detection threshold and the 50 ppm permissible exposure level published by OSHA. Ammonia’s strong odor alerts those nearby to its presence at levels well below those that present either flammability or health hazards. This “self-alarming” odor is so strong that a person is unlikely to voluntarily remain in an area where ammonia concentrations are hazardous. The principal hazard to persons is ammonia vapor, since exposure occurs more readily by inhalation than by other routes. As with any hazardous vapor, adequate ventilation will dilute the vapor and greatly reduce exposure risk. Ammonia in vapor form is lighter than air. Typically, ammonia vapor rises and diffuses simultaneously when released into the atmosphere. It is biodegradable, and when released it combines readily with water and/or carbon dioxide to form relatively harmless compounds. Ammonia may also neutralize acidic pollutants in the atmosphere. Additional information regarding the properties of ammonia is published in the IIAR Ammonia Data Book.
This standard was first issued in March of 1974 by the International Institute of Ammonia
Refrigeration (IIAR) as IIAR 74-2. . The standard was first approved as an American
National Standard by the American National Standards Institute (ANSI) in March 1978
as ANSI/IIAR 74−2−1978. A revision of the standard, ANSI/IIAR 2−1984 was approved
by ANSI in July 1985, as were subsequent revisions in December 1992, August 1999,
October 2005, June 2008, August 2010, and December, 2012. The most recent revision,
ANSI/IIAR 2-201x, received approval from ANSI on MONTH, YEAR.
This standard was prepared using the ANSI Consensus Method whereby organizations
and individuals recognized as having interest in the subject of the standard were
contacted prior to the approval of this revision for participation on the Consensus Body
and public reviews.. It was prepared and approved for submittal to ANSI by the IIAR
Standards Committee and the IIAR Board of Directors.
ANSI/IIAR 2-201x: Changes for this new edition
IIAR 2 has undergone extensive revision since the 2008 (with Addendum B) edition, published December 3, 2012. Some of the more significant are highlighted here to assist users of this document. A major focus of changes made to the 2014 edition, has been incorporating topics traditionally addressed in other codes and standards so that IIAR 2 can serve as a single, comprehensive standard covering safe design of closed-circuit ammonia refrigeration systems. As part of the update process, a gap analysis was performed that compared information in IIAR 2, ASHRAE Standard 15 - Safety Standard for Refrigeration Systems, the Uniform Mechanical and Fire Codes, and the International Mechanical and Fire Codes. Where differences were identified, the IIAR 2 rewrite drafting committee either included or revised the information in this standard, or determined that the information was not necessary to meet minimum safe design standards for ammonia refrigeration systems. In addition to the changes brought about by the gap analysis, this standard has been revised to clarify provisions that previously existed in IIAR 2. In some cases, information previously included in IIAR 2 was deemed un-necessary and was deleted from the 2014 edition. Additionally, new provisions not previously addressed by any code or standard have been added based on public proposals or at the recommendation of the rewrite draft committee. Some of the major changes to the 2014 edition of IIAR 2 are summarized in the following paragraphs. However, users of this standard are cautioned that there are many other revisions that can only be identified and understood by reviewing the standard in its entirety. The title of the standard has been changed. The new title makes it clear that the scope of IIAR 2 have been expanded to include safety. The standard is now organized into Parts and Chapters. There are four parts: General, Design Considerations affecting Construction, Equipment and Components, and Appendices. The Chapter numbers remain sequential and the four parts are simply provided as an aid for users in navigating the standard. Part 1, General includes sections on Purpose, Scope, and Applicability. The scope now clarifies that the standard applies only to stationary closed–circuit refrigeration systems. Further, the standard now prescribes restrictions on the permissible use of ammonia refrigeration based on the occupancy classifications of the facility.
Definitions that appeared in previous editions (and were not changed) have been relocated to IIAR 1, Definitions and Terminology Used in IIAR Standards. New or revised definitions used within this standard are included in the definitions chapter to provide context to new terms. It is intended that, once this standard has been published, these new terms will also be relocated to IIAR-1. References were updated. Normative references now include only those references that are mandatory for compliance with this standard. Some references that were normative in prior editions of this standard have been relocated to become informative. Part 2, Design Considerations Affecting Construction. Chapter 4, Occupancy Classifications, is new. This chapter includes restrictions on the use of ammonia refrigeration systems, as applicable, based on the occupancy classification of the facility where the system will be located. Chapter 5, System Design, largely retains information that was included in previous editions. Notable changes include a revision when selecting system design pressures. Requirements that apply to selecting system design pressures were provided. The minimum low-side and high-side design pressure is 250 psig. Required components for the removal of oil from oil pots have been changed such that there is no longer a requirement to temporarily install a rigid-piped connection. Direction for the provision of maintenance and functional testing was added. Information on field leak tests has been removed and a reference to IIAR 5 was added in its place. Minimum valve tagging standards for system emergency shut-down procedures have been added, as well as a section on equipment enclosures. Chapter 6, Machinery Rooms, largely retains information that was included in previous editions. Notable changes have been made to alarm and detection requirements. Ventilation requirements have been modified and ventilation alternatives have been added. A section regulating site considerations has been added. Changes have been made to the requirements for eyewash/safety showers to harmonize the standard with OSHA and ANSI/ISEA regulatory requirements. A section regulating ventilation requirements for systems located outdoors or in partially-enclosed mechanical rooms has been added. Chapter 7, Areas Other than Machinery Rooms, represents a change from previous editions. Heretofore, guidance concerning certain types of refrigeration equipment located in areas other than machinery rooms has not been provided. In industrial occupancies, it is often necessary to have some refrigeration equipment located outside of a machinery room, such as, in production areas. Further, it is often more energy-efficient and practical to locate some equipment closer to refrigeration loads. This chapter provides minimum safety requirements for locating refrigeration equipment in areas other than machinery rooms.
Part 3, Equipment and Components, includes several chapters that cover major equipment categories. Most of the information has been retained from previous editions. Notable changes are the inclusion of an alarm and detection section in each chapter, plus, alarm and detection levels for equipment in areas other than machinery rooms. Chapter 8, Compressors, includes a notable change specifying the minimum size for relief connections of ¾”. Chapter 9, Refrigerant Pumps, separates refrigerant pumps from compressors. Chapter 10, Condensers, includes a significant change establishing that the minimum design pressure for condensers is now 300 psig, which is consistent with the minimum design pressure for all high-side components. Chapter 11, Evaporators, includes a significant change establishing that the minimum design pressure for evaporators is now 250 psig, or alternatively, the high-side design pressure if hot gas is used to defrost the evaporator. New sections on scraped- (swept-) surface heat exchangers and jacketed tanks have also been added. Chapter 12, Pressure Vessels, reflects the minimum design pressure requirements described above. In addition, the chapter establishes that the minimum size for a relief connection is ¾” for vessels that are over 6” in diameter and 1” for vessels that are 10 ft3 or larger. Chapter 14, Packaged Systems and Components, covers a new topic. This chapter was added in recognition of a need to regulate pre-assembled systems, subsystems and components, which are becoming increasingly common. Chapter 15, Overpressure Protection, provides expanded content, which includes methods for evaluating and designing for worst-case scenarios to avoid overpressurizing components. Direction regarding pressure relief piping termination has been added to address adjacent roofs in the vicinity of the relief termination. Further, requirements for termination of relief piping above evaporative condensers have been clarified. An option of using diffusion tanks has also been included and requirements for hydrostatic overpressure protection have been clarified. Chapter 16, Instrumentation and Controls, includes clarified requirements for automated controls and their functionality. Chapter 17, Ammonia Detection and Alarms, establishes the requirements for detection and system response functions. This chapter is intended to help standardize
requirements that have historically varied depending on jurisdiction, designer, contractor, supplier and end-user interpretations. Normative Appendix A was modified by deleting single-relief vent line sizing tables. The size of relief vents must be calculated in all cases using the formula provided. Informative Appendix B has been revised to cover methodologies for calculating relief valve capacity for various heat exchangers. The former Appendix B, Minimum Values of Design Pressure and Leak Test Pressure, has been removed. Design pressure information can be found within the main body of this standard. Leak pressure information can be found in IIAR 5, Start-up and Commissioning of Closed Circuit Ammonia Refrigeration Systems. Information pertaining to insulation found in prior editions of this standard has been relocated to IIAR 4. Information pertaining to purging found in prior editions of this standard has been relocated to IIAR 5. Appendix K provides guidance on calculating ventilation rates for newly recognized alternative ventilation methods. Appendix L includes guidance information on Pipe, Fittings, Flanges, and Bolting that have been historically most commonly used in ammonia industrial refrigeration systems. Appendix M provides guidance on Operational Containment as a rare alternative ventilation method. Appendix N provides guidance on site considerations. Appendix 0 includes non-mandatory references, which were relocated from the main body of the Standard.
At the time of publication of this edition of the standard, the IIAR Standards Committee
Included the following members:
Robert J. Czarnecki, Chair - Campbell Soup Company Don Faust, Vice Chair - Gartner Refrigeration & Mfg., Inc. Eric Brown - ALTA Refrigeration, Inc. Dennis R. Carroll - Johnson Controls Eric Johnston - ConAgra Foods, Inc. Gregory P. Klidonas - GEA Refrigeration North America, Inc. Thomas A. Leighty - Refrigeration Systems Company Brian Marriott - Marriott and Associates
Rich Merrill - Retired, EVAPCO, Inc. Ron Worley - Nestlé USA Trevor Hegg - EVAPCO, Inc. Joseph Pillis - Johnson Controls Dave Schaefer - Bassett Mechanical, Inc. Peter Jordan - MDB Risk Management Services, Inc. John Collins - American Industrial Refrigeration
The subcommittee responsible for rewriting this standard had the following members at the time of publication:
Thomas A. Leighty, Subcommittee Chair - Refrigeration Systems Company Dave Schaefer, Subcommittee Vice Chair - Bassett Mechanical, Inc. Trevor Hegg - EVAPCO, Inc. Don Faust - Gartner Refrigeration & Mfg., Inc. Peter Jordan - MDB Risk Management Services, Inc. Glen Heron - Tyson Foods, Inc. Eric Johnston - ConAgra Foods, Inc. John Collins - American Industrial Refrigeration Carl Burris - Tyson Foods, Inc. Robert A. Sterling - Sterling Andrews Engineering, P.L. Luke Facemyer - Stellar Eric Smith - IIAR Staff Tony Lundell - IIAR Staff
Table of Contents
Notes on the Standard Text ........................................................................................................................................2
Metric Policy ..............................................................................................................................................................2
Normative/Informative Elements ...............................................................................................................................2
Notice .........................................................................................................................................................................2
Copyright ....................................................................................................................................................................3
Foreward (Informative) ..............................................................................................................................................4
Table of Contents .................................................................................................................................................... 10
Part 1 General .......................................................................................................................................................... 12
Chapter 1 Purpose, Scope and Applicability .................................................................................................... 12
Chapter 2 Definitions ....................................................................................................................................... 12
Chapter 3 Reference Standards........................................................................................................................ 16
Part 2 Design Considerations Affecting Construction............................................................................................. 18
Chapter 4 Location and Use of Refrigeration Machinery ............................................................................... 18
Chapter 5 System Design ................................................................................................................................. 22
Chapter 6 Machinery Rooms ........................................................................................................................... 33
Chapter 7 Areas Other Than Machinery Rooms .............................................................................................. 44
Part 3 Equipment and Components ......................................................................................................................... 47
Chapter 8 Compressors .................................................................................................................................... 47
Chapter 9 Refrigerant Pumps ........................................................................................................................... 51
Chapter 11 Evaporators ...................................................................................................................................... 63
Chapter 13 Piping ....................................................................................................................................................
Chapter 14 Packaged Systems and Components ................................................................................................ 82
Chapter 15 Overpressure Protection Devices ..................................................................................................... 85
Chapter 17 Ammonia Detection and Alarms ..................................................................................................... 99
Appendix A (Normative) Allowable Equivalent Length of Discharge Piping ..................................................... 102
Appendix B (Informative) Methods for Calculating Relief Valve Capacity for Heat Exchanger Internal Loads 105
Appendix C (Informative) Ammonia Characteristics and Properties ................................................................ 113
Appendix D (Informative) Duplicate Nameplates on Pressure Vessels ............................................................. 115
Appendix E (Informative) Method for Calculating Discharge Capacity of a Positive Displacement Compressor
Pressure Relief Device ....................................................................................................................................... 116
Appendix F (Informative) Pipe Hanger Spacing, Hanger Rod Sizing, and Loading ............................................ 119
Appendix G (Informative) Hydrostatic Overpressure Relief .............................................................................. 122
Appendix H (Informative) Stress Corrosion Cracking ........................................................................................ 130
Appendix I (Informative) Emergency Pressure Control Systems ....................................................................... 132
Appendix J (Informative) Machine Room Signs ................................................................................................. 137
Appendix K (Informative) Alternative Ventilation Calculation Methods .......................................................... 141
Appendix L (Informative) Pipe, Fittings, Flanges, and Bolting ........................................................................... 145
Appendix M (Informative) Operational Containment ....................................................................................... 141
Appendix N (Informative) Site Considerations .................................................................................................. 147
Appendix O (Informative) Sources of References………………………………………………………………………………………….153
Part 1 General
Chapter 1 Purpose, Scope and Applicability
1.1 Purpose
1.1.1 This standard specifies minimum requirements for the safe design of closed-circuit ammonia
refrigeration systems.
1.2 Scope
1.2.1 Stationary closed-circuit refrigeration systems utilizing ammonia as the refrigerant shall
comply with this standard.
1.2.2 This standard shall not apply to:
(a) Ammonia absorption refrigeration systems;
(b) Replacements of parts with functionally equivalent parts;
(c) Equipment and systems installed prior to the effective date of this standard established by
the AHJ. Such equipment and systems shall be maintained in accordance with regulations
that applied at the time of installation.
1.3 Applicability
1.3.1 Conflicts: Where there is a conflict between this standard and an adopted building, fire,
mechanical or electrical code, the requirements of the locally-adopted code shall take
precedence unless otherwise stated in such code.
1.3.2 Alternative Materials and Methods: The AHJ is authorized to approve the use of devices,
materials or methods not prescribed by this standard as an alternative means of compliance,
provided that any such alternative has been shown to be equivalent in quality, strength,
effectiveness, durability and safety.
Chapter 2 Definitions
2.1 General.
Definitions shall be in accordance with this chapter and ANSI/IIAR-1 Definitions and Terminology used
in IIAR Standards.
2.2 Defined Terms.
The following words and terms, which are used in this standard, shall be defined as specified in this
chapter.
authority having jurisdiction (AHJ): The organization, office, or individual responsible for enforcing
the requirements of this standard, or for approving equipment, materials, an installation, or a procedure.
authorized personnel: Persons who have been specifically granted permission to enter a restricted area.
auxiliary door: Any non-principal door communicating with a machinery room.
building code: The building code adopted by the jurisdiction.
building opening: A permanent or operable area that allows outdoor air into the building envelope
including operable doors (e.g. swinging doors, slide doors, roll-up doors, fire doors, access hatches),
operable make-up air intakes (where the intakes are not equipped with the ability to close automatically
when ammonia is present), and other vents with a permanent opening.
combustible: A material with a flashpoint over 100°F that is more difficult to ignite than a flammable
material, but will burn once ignited.
commercial occupancy: A premises or a portion of a premises where people transact business, receive
personal service, or purchase food or other goods. This includes office, work, and/or storage areas that
do not qualify as industrial occupancies.
component: A uniquely identifiable piece of equipment, accessory, assembly, or subassembly of a
refrigeration system.
direct system: A system in which a refrigerant heat exchanger directly cools or heats air that will be
delivered to an occupied space, process area, or storage area or a substance, such as a product being
processed or manufactured.
double-indirect-open-spray system: A system in which the secondary substance for an indirect open
spray system is heated or cooled by the secondary-coolant from a second enclosure.
equipment enclosure: An enclosure designed to house refrigeration equipment and/or components of a
closed-circuit refrigeration system, or both, that is not intended for occupancy.
flammable: A material with a flashpoint of 100°F or below that is easy to ignite and burn.
indicating device: An instrument that measures and registers certain operating conditions used for
monitoring and control, such as temperatures and pressures, which can be read on a gauge and/or control
display screen.
indirect system: A system in which a secondary-coolant which is cooled or heated by the refrigeration
system is circulated to the air or other substance to be cooled or heated.
indirect-closed system: A system in which a secondary-coolant passes through a closed circuit in the air
or other substance to be cooled or heated.
indirect-open-spray system: A system in which a secondary-coolant is in direct contact with the air or
other substance to be cooled or heated.
industrial occupancy: A premises or that portion of a premises that is not open to the public, where
access is controlled such that only authorized persons are admitted and that is used to manufacture,
process, or store goods.
large mercantile occupancy: A premises or that portion of a premises where more than 100 persons
congregate to purchase merchandise.
machinery: The refrigeration equipment forming a part of the refrigeration system, including, but not
limited to, the following: compressors, condensers, pressure vessels, evaporators and pumps.
machinery room: An enclosed space that is designed specifically to safely contain machinery.
monitored: A means of continual oversight such as notification to on-site staff, a third party alarm
service or a responsible party.
noncombustible material: A material that, when tested in accordance with ASTM E136, has at least
three of four specimens tested meeting all of the following criteria:
1. The recorded temperature of the surface and interior thermocouples shall not at any time during
the test rise more than 54°F (30°C) above the furnace temperature at the beginning of the test.
2. There shall not be flaming from the specimen after the first 30 seconds.
3. If the weight loss of the specimen during testing exceeds 50 percent, the recorded temperature of
the surface and interior thermocouples shall not at any time during the test rise above the furnace
air temperature at the beginning of the test, and there shall not be flaming of the specimen.
occupied space: That portion of the premises accessible to or occupied by people on a routine part-
time or full-time basis.
operational containment: An optional control sequence wherein all ventilation for a room is de-
energized so that ammonia vapor is retained in the room.
packaged system: A fabricated and assembled self-contained closed-circuit refrigeration system, or a
large portion thereof, either enclosed within its case or framework or unenclosed (e.g. of large portions:
recirculator packages, condenser packages, compressor packages, chiller packages).
principal machinery room door: An exterior door that has been designated as a primary emergency
egress door for a machinery room.
public assembly occupancy: A premises or that portion of a premises where large numbers of people
congregate and from which occupants cannot quickly vacate the space. Public assembly occupancies
include, among others, auditoriums, stadiums, arenas, ballrooms, classrooms, passenger depots,
restaurants, and theaters.
restricted (access): Open to access only by approved and qualified personnel. Public access is excluded.
self-contained: Having all essential working parts of a complete closed circuit mechanical refrigeration
system, except energy and control connections, and contained in a case or framework.
surge drum: A lowside receiver close-coupled to one or more evaporators that provides liquid feed and
liquid-from-vapor disengagement space to assure that dry vapor is returned to the compressor.
tight construction: Constructed with no holes or openings to prevent liquid or moisture transfer and
prevent air or vapor infiltration (e.g. leakage spread).
tight-fitting door: A tight constructed door with seals to minimize gap clearances between the entire
door perimeter and its fixed door stop frame to prevent liquid or moisture transfer and prevent air or
vapor infiltration (e.g. leakage spread).
trained operator: An individual having training and experience which qualify that individual to operate
and perform basic system inspections on a closed-circuit refrigeration system with which he or she has
become familiar.
unoccupied space: A portion of premises accessible to only authorized personnel performing scheduled
walk-throughs for operational checks or maintenance services on equipment.
Chapter 3 Reference Standards
3.1 American Society of Heating, Refrigerating and Air Conditioning Engineers, Inc. (ASHRAE), 2013
ASHRAE Handbook, Fundamentals, Chapter 14, Climate Design Information.
3.2 American Society of Mechanical Engineers (ASME), editions as shown below:
3.2.1 ASME Boiler and Pressure Vessel Code, Pressure Vessels, Section VIII, Division 1, 2013;
3.2.2 ASME B31.5, Refrigeration Piping and Heat Transfer Components, 2013.
3.3 American Society of Testing and Materials (ASTM), editions as shown below:
3.3.1 ASTM A53/A53M-12, Standard Specification for Pipe, Steel, Black and Hot-Dipped, Zinc-
Coated, Welded and Seamless;
3.3.2 ASTM A120-84, Specification for Pipe, Steel, Black and Hot-Dipped Zinc-Coated
(Galvanized) Welded and Seamless for Ordinary Uses (Withdrawn 1987, replaced by ASTM
A53 [ref.3.1.5.1]);
3.3.3 A197/A197M-00 (2011), Standard Specification for Cupola Malleable Iron;
3.3.4 ASTM A575-96 (2013), Standard Specification of Steel Bars, Carbon, Merchant Quality, M
Grades;
3.3.5 ASTM E136 (2012), Standard Test Method for Behavior of Materials in a Vertical Tube
Furnace at (750°C).
3.4 Compressed Gas Association G-2, 1995, Eighth Edition.
3.5 International Institute of Ammonia Refrigeration (IIAR):
3.5.1 ANSI/IIAR 1-2012, Definitions and Terminology Used in IIAR Standards;
3.5.2 ANSI/IIAR 3-2012, Ammonia Refrigeration Valves;
3.5.3 Reserved;
3.5.4 ANSI/IIAR 5-2013, Start-up and Commissioning of Closed-Circuit Ammonia Mechanical
Refrigeration Systems;
3.5.5 Reserved;
3.5.6 ANSI/IIAR 7-2013, Developing Standard Operating Procedures for Closed-Circuit Ammonia
Mechanical Refrigeration Systems.
3.6 International Safety Equipment Association (ISEA), ANSI/ISEA Z358.1, World Safety Standard for
Emergency Eyewash and Shower Equipment, 2009 edition.
3.7 National Fire Protection Association (NFPA), NFPA Standard 70, National Electrical Code (NEC),
2011.
3.8 U.S. Department of Transportation (US DoT), 49 CFR Part 172, Hazardous Materials Regulations,
2013.
3.9 Occupational Safety and Health Administration (OSHA), U.S. Department of Labor, 2012:
3.9.1 29 CFR 1910.212, General Requirements for All Machines;
3.9.2 29 CFR 1910.219, Mechanical Power Transmission Apparatus.
Part 2 Design Considerations Affecting Construction
Chapter 4 Location and Use of Ammonia Refrigeration Machinery
4.1 General
4.1.1 Ammonia refrigeration machinery shall be installed outdoors or in a machinery room
complying with Chapter 6 except where an alternative location is permitted by this chapter.
Occupancy Classifications referenced by this chapter shall be in accordance with the
definitions in Chapter 2.
EXCEPTION: Listed equipment containing not more than 6.6 lbs (3 kg) of refrigerant
provided the equipment is installed in accordance with the listing and with
the manufacturer’s instructions.
4.2 Outdoor Installations
4.2.1 Ammonia refrigeration machinery, other than piping, installed outdoors shall be located not
less than 20 feet from building openings, except for openings to a machinery room
complying with Chapter 6 or openings to an industrial occupancy complying with Section
4.3.
4.3 Industrial Occupancies
4.3.1 All ammonia refrigeration equipment shall be located in a machinery room or outdoors with
the following exceptions:
EXCEPTION 1: Evaporators, including their associated surge drums, used for refrigeration
or dehumidification.
EXCEPTION 2: Condensers used for heating.
EXCEPTION 3: Any valves and connecting piping associated with Exception 1 or 2 above.
EXCEPTION 4: Any control and pressure-relief valves associated with Exception 1 or 2
above.
EXCEPTION 5: Hermetic or semi-hermetic ammonia refrigerant pumps.
EXCEPTION 6: A refrigeration system or components thereof with a total connected
compressor power not exceeding 100 HP (74.6 kW) installed in
accordance with Chapter 7.
4.3.1.1 Areas containing the equipment shall be separated from non-industrial occupancies by
tight construction with tight-fitting doors.
4.3.1.2 Access to the equipment shall be restricted to authorized personnel.
4.3.1.2.1 A means of egress directly to the outdoors, an enclosed exit stairway, or to a
horizontal exit or exit passageway complying with the local building code shall be
provided for areas containing the equipment, or a floor area per occupant of not
less than 100 ft² (9.3 m²) shall be provided.
EXCEPTION 1: Areas not more than 500 square feet equipped with a fire
sprinkler system need not have a door that opens directly to the
outdoors or a vestibule leading directly to the outdoors.
EXCEPTION 2: The minimum floor area per occupant shall not apply where the
space is provided with egress directly to the outdoors or into
approved building exits.
4.3.1.3 Areas containing ammonia refrigeration equipment shall have ammonia refrigerant
detection and alarms in accordance with the applicable chapters of Part 3 Equipment and
Components.
4.4 Public Assembly, Commercial and Large Mercantile Occupancies
4.4.1 Ammonia refrigeration machinery shall be permitted in designated areas of public assembly,
commercial and large mercantile occupancies that are outside of a machinery room where in
accordance with all of the following:
4.4.1.1 The quantity of ammonia shall be limited such that a complete discharge from any
independent refrigerant circuit will not result in an ammonia concentration exceeding
320 parts per million (ppm) in any space where components containing ammonia are
located. For volume calculation in determining the concentration level, see Section 4.6.
4.4.1.2 Areas containing the equipment shall be enclosed by tight construction with tight-fitting
doors or access panels.
4.4.1.3 Access to the equipment shall be restricted to authorized personnel.
4.4.1.4 A means of egress directly to the outdoors, an enclosed exit stairway, or to a horizontal
exit or exit passageway complying with the local building code shall be provided for
areas containing the equipment, or a floor area per occupant of not less than 100
ft² (9.3 m²) shall be provided.
4.4.1.5 Areas containing the equipment shall be equipped with Level 3 refrigerant detection
and alarms in accordance with Chapter 17.
4.5 Use of Ammonia Refrigeration Secondary-Coolants
4.5.1 Where ammonia refrigeration is used in conjunction with a secondary-coolant that serves
occupied spaces in occupancies other than industrial, the system shall be one of the
following types:
4.5.1.1 Indirect Closed System
4.5.1.2 Indirect open-sprayed system with the pressure of the secondary-coolant always
exceeding the pressure of the primary coolant, regardless of whether the system is in
operation or standby and considering all temperature conditions to which system
components could be exposed.
4.5.1.3 Double-indirect open-sprayed system
4.6 Volume Calculation
4.6.1 The volume used to calculate the potential refrigerant level concentration shall be based on
the gross volume of the area into which the refrigerant will disperse.
4.6.2 The designer shall analyze the area and the refrigeration system to determine the worst case
(smallest) volume in which refrigerant could concentrate based on the following criteria:
4.6.2.1 Where a refrigeration system, or part thereof, is located in one or more rooms or spaces
that are not connected by permanent openings or a mechanical ventilation system, the
volume of the smallest room or space shall be used to determine the gross volume for the
refrigerant concentration level.
4.6.2.2 Where different stories or floor levels connect through an open atrium or when there is a
mezzanine open to the area, the combined volume of the floors and mezzanines are
permitted to be used in determining the gross volume for the refrigerant concentration
level.
4.6.2.3 Where a refrigeration system, or part thereof, is located within an air handler, in an air
distribution duct system, or in an area served by a mechanical ventilation system, the
gross volume of the rooms or spaces connected by the ventilation or duct system is
permitted to be used to determine the refrigerant concentration level. The volume of the
connected supply and return air ducts and any connecting plenum is permitted to be
included in determining the gross volume.
EXCEPTION: If portions of the ventilation or duct system can be isolated (e.g. with air
dampers), the designer shall determine the worst-case distribution of
leaked refrigerant. The worst case (smallest) gross volume in which
leaked refrigerant can concentrate shall be used to determine the
concentration level.
4.6.2.4 The space above a suspended ceiling shall not be used in determining the gross volume
of the area in which the ceiling is located, except where the space above the ceiling is
used as part of the air distribution system.
4.6.2.5 Permanent wall openings (e.g. doors, passages, or conveyors) between rooms or spaces
containing a refrigeration system, or parts thereof, shall not be considered when
determining the gross volume.
EXCEPTION: Permanent wall openings are permitted to be used when determining the
gross volume if they are clearly defined as part of the design analysis.
Chapter 5 System Design
This chapter applies to general design requirements for close-circuit ammonia refrigeration systems.
5.1 General Design Requirements
5.1.1 Refrigerant-Grade Anhydrous Ammonia Specifications
5.1.1.1 Refrigerant-grade anhydrous ammonia that meets or exceeds the minimum requirements
of Compressed Gas Association CGA G-2, 1995, Eighth Edition, (ref.3.4) shall be
used for the initial charge and subsequent top-off (fill the system to the operating
intended inventory) of all ammonia refrigeration systems.
5.1.1.2 A grade specifying less than 99.95 percent ammonia shall not be used.
5.1.1.3 Purity requirements are shown in the table below:
Purity Requirements
Ammonia Content 99.95% Min.
Non-Basic Gas in Vapor Phase 25 ppm Max.
Non-Basic Gas in Liquid Phase 10 ppm Max.
Water 33 ppm Max.
Oil (as soluble in petroleum ether) 2 ppm Max.
Salt (calculated as NaCl) None
Pyridine, Hydrogen Sulfide, Naphthalene None
5.1.1.4 See Appendix H (Informative) for information regarding stress corrosion cracking with
anhydrous ammonia.
5.1.1.5 See Appendix C (Informative) for additional information regarding the characteristics
and properties of ammonia.
5.1.2 Minimum Design Pressure
The following shall apply to selecting system design pressures:
5.1.2.1 Design pressures shall not be less than pressure arising under maximum operating,
standby, or shipping conditions.
5.1.2.2 When selecting the design pressure, allowance shall be provided for setting pressure-
limiting devices and pressure relief devices to avoid nuisance shutdowns and loss of
refrigerant. The ASME Boiler and Pressure Vessel Code, Section VIII, Division I,
Appendix M, contains information on the appropriate allowances for design pressure.
5.1.2.3 Refrigeration equipment shall be designed for a vacuum of 29.0 in. Hg (3.12 kPa).
Design pressure for ammonia refrigeration systems shall not be less than the saturation
pressure (gage) corresponding to the following temperatures:
5.1.2.3.1 Lowsides of all systems: 10°F (5.6°C) greater than the 1% ambient dry bulb
temperature for the installation location or 114.6°F (45.9°C), whichever is greater
(250 psig minimum design pressure).
5.1.2.3.2 Highsides of all water-cooled or evaporatively cooled systems:
30°F (16.7°C) higher than the summer 1% wet-bulb temperature for the location as
applicable or 15°F (8.3°C) higher than the highest design leaving condensing water
temperature for which the equipment is designed or 114.6°F (45.9°C), whichever is
greater (250 psig minimum design pressure).
5.1.2.3.3 Highsides of all air-cooled systems: 30°F (16.7°C) higher than the highest summer
1% design dry-bulb temperature for the location but not lower than 122°F (50°C).
5.1.2.3.4 The design pressure selected shall exceed maximum pressures attained under any
anticipated normal operating conditions, including conditions created by expected
fouling of heat exchange surfaces.
5.1.2.3.5 Standby conditions are intended to include normal conditions that are capable of
being attained when the system is not in operation (e.g., maintenance, shutdown,
power failure). Selection of the design pressure for lowside components shall also
consider pressure developed in the lowside of the system from equalization, or
heating due to changes in ambient temperature, after the system has stopped.
5.1.2.3.6 The design pressure for both lowside and highside components that are shipped as
part of a gas or refrigerant charged system shall be selected with consideration of
internal pressures arising from exposure to maximum temperatures anticipated
during the course of shipment.
5.1.2.3.7 The design pressure for either the highside or lowside need not exceed the critical
pressure of the refrigerant unless such pressures are anticipated during operating,
standby, or shipping conditions.
5.1.2.3.8 When part of a limited charge system is protected by a pressure-relief device, the
design pressure of the part need not exceed the setting of the pressure-relief device.
A limited charge system is defined as a system containing no more than 22 pounds
of ammonia.
5.1.2.3.9 When a compressor is used as a booster and discharges into the suction side of
another compressor, the booster compressor shall be considered a part of the
lowside.
5.1.2.3.10 Components connected to pressure vessels and subject to the same pressure as the
pressure vessel shall have a design pressure no less than the pressure vessel.
5.1.2.3.11 Where an existing system, in operation prior to the adoption of this Standard, is
connected to new lowside portions of the same system operating at the same
conditions as the existing system, the design pressure of the new portions of the
lowside need not be higher than that of the existing portions of the lowside.
5.1.3 System Design Temperature
5.1.3.1 All equipment and components of the closed-circuit ammonia refrigeration system shall
be designed to meet the full temperature range requirements for its intended system
design and for the ambient environment it is exposed to at its installation location.
5.2 Materials
5.2.1 General
5.2.1.1 All materials used in the construction of the equipment designated in Chapters 6–17 shall
be suitable for ammonia refrigerant at the coincident temperature and pressure to which
the component shall be subjected.
5.2.1.2 No materials shall be used that will deteriorate because of the presence of ammonia,
refrigerant lubricating oil, or a combination of both or any normal contaminant
such as air or water.
5.2.2 Metallic Materials
Cast iron, malleable iron, nodular iron, steel, cast steel, and alloy steel are permitted to be
used as governed by ASME B31.5-2013 [ref.3.2.2] or Section VIII, Division 1, 2013, ASME
Boiler and Pressure Vessel Code [ref.3.2.1], as applicable.
5.2.2.1 Zinc, copper, and copper alloys shall not be used in contact with or for the containment
of ammonia. Copper-containing anti-seize and/or lubricating compounds shall not be
used. Copper, as a component of brass alloys, is permitted to be used in rotating shaft
bearings or for other non-refrigerant containment uses.
5.2.2.2 Other metallic materials, such as aluminum, aluminum alloys, lead, tin, and lead-tin
alloys are permitted to be used if they conform to Section 5.2.1. Where tin and tin-lead
alloys are used, the alloy composition shall be suitable for the temperatures of
application.
5.2.3 Non-Metallic Materials
Non-metallic materials are permitted to be used as governed by ASME B31.5-2013 [ref.3.2.2]
or Section VIII, Division 1, 2013, ASME Boiler and Pressure Vessel Code [ref.3.2.1], as
applicable.
5.2.3.1 Non-metallic materials are permitted to be used if they conform to Section 5.2.1.
5.3 Purging
Means shall be provided to separate, collect, and remove air and other noncondensible gases from
the refrigeration system. Non-condensable gases may be purged to atmosphere through a water
column or in accordance with the vent requirements given in Section 15.4.1.
5.4 Oil Management
Provisions shall be made in the design for removing oil from piping and equipment where oil is
likely to collect.
Compressor packages shall have oil sampling provisions for periodic oil analysis in accordance
with the manufacturer’s recommendations.
5.4.1 Detailed operating procedures suitable for each drain point shall be considered when
designing safe oil draining operations. See Standard IIAR 7-2013 for developing operating
procedures (ref.3.5.6).
5.4.2 Oil draining shall be conducted only by a trained technician(s). Designs shall reflect that the
oil draining process shall not be left unattended by the trained technician(s) while in progress.
EXCEPTION:
Permanently-piped automatic return systems.
5.4.3 Oil removal shall be accomplished by one or more of the following:
5.4.3.1 A rigid-piped oil return system.
5.4.3.2 A vessel equipped with an oil drain valve in series with a self-closing emergency stop
valve.
5.4.3.3 Piping which provides capability for isolation and refrigerant removal to another portion
of the system.
5.4.3.4 A valve and piping assembly at the oil draining point where oil is removed from the
system. At a minimum, an oil drain valve in series with a self-closing emergency stop
valve is required.
Note: Use of temporarily-attached rigid piping and self-closing emergency stop valves is
permitted.
5.5 Insulation
5.5.1 Equipment surfaces, not intended for heat exchange, shall be insulated for energy
conservation and to prevent or control condensation. See Section 5.8 Condensation Control
regarding piping and fittings.
EXCEPTION 1:
Valve groups or equipment are permitted to be left uninsulated to accommodate access for
service, provided the vapor retarder is sealed to the piping or equipment where insulation of
adjoining piping terminates.
EXCEPTION 2:
Piping and fittings constructed of corrosion resistant materials or are protected with
a corrosion resistant treatment are permitted to be un-insulated if they are intended to be
routinely defrosted to prevent excessive buildup of ice and are provided with safe and
adequate condensate drainage. Alternatively, a safe ice-removal procedure is
permitted in lieu of routine defrosting.
5.5.2 Hot discharge lines less than 7.25 feet (2.2 m) high and those near passageways, aisles, or
walkover stairs and landings (i.e. on roofs) having an external surface temperature of 140
degrees F (60 degrees C) or higher shall be either labeled with warning signs, insulated, or
suitably guarded in such a manner as to prevent contact.
5.6 Foundations, Piping, Tubing, and Equipment Supports
5.6.1 Supports and foundations shall be adequate to prevent excessive vibration and movement of
the piping, tubing, and equipment.
5.6.2 Supports and foundations shall meet or exceed the manufacturers’ recommendations and
withstand expected loads.
5.6.3 Supports and anchorage for refrigeration equipment shall be designed in accordance with
the locally-adopted Building Code.
5.6.4 Structural supports shall be non-combustible. Base supports for piping and equipment
supported from stands resting on the finished roof (e.g. roof “sleepers”, shims) are permitted
to be pressure-treated lumber.
5.6.5 Seismic joints and restraints shall be provided as required by the locally-adopted Building
Code.
5.7 Service Provisions
5.7.1 All serviceable components of a closed-circuit ammonia refrigeration system shall be
provided with safe access, which can be permanent or portable, for maintenance and
inspection. An unobstructed readily-accessible opening and passageway not less than thirty-
six (36) inches [3.00 feet or 0.914 m] in width and eighty-seven (87) inches [7.25 feet or 2.2
m] in height shall be provided for equipment and components of the system requiring
routine maintenance.
EXCEPTION:
Air filters, brine control or stop valves, fan motors or drives, and remotely de-energized
electrical connections shall be permitted to be provided access by an unobstructed space not
less than 30 inches (0.762 m) in depth, width, and height. Where an access opening is
immediately adjacent to these items and the equipment is capable of being serviced,
repaired, and replaced from this opening, the dimensions shall be permitted to be reduced to
22 inches (0.559 m) by 30 inches (0.762 m) provided the largest removable component of
the equipment or the entire piece of equipment can be removed through the opening.
5.7.2 Refrigeration system charging connections located outdoors shall be locked or otherwise
access-restricted to authorized personnel only.
5.7.3 Design provisions for maintenance and functional testing of safety controls (e.g. liquid level
indicators, float switches, high-pressure cut out switches) shall be provided. Design
provisions are permitted to include shut-off valves, capped or plugged connection points
(installed in accordance with this standard) for the connection of temporary piping, or other
provisions that allow functional testing without compromising other safety provisions or
requiring the disassembly of refrigerant-containing portions of the system.
5.7.4 When a pressure gauge is permanently installed on the high-side of the refrigeration system,
its dial shall be graduated to be at least 1.2 times (120%) the system design pressure.
5.7.5 All serviceable components of the refrigeration system shall be designed so that they can be
safely serviced without risk of injury (e.g. accessible, tool clearances).
Note: OSHA 29 CFR 1910.24 should be consulted to determine where fixed stairs are
required.
5.7.6 All serviceable components of the refrigeration system shall have hand isolation valves
where needed in the piping system. In lieu of providing hand isolation valves at each
serviceable component, packaged systems or portions of built-up systems are permitted to
have pump-down arrangements that provide for the safe removal or isolation of refrigerant
for servicing one or more components.
5.8 Condensation Control
5.8.1 Piping and fittings that convey brine, refrigerant, or coolants that during normal operation
could reach a surface temperature below the dew point of the surrounding air and that are
located in spaces or areas where condensation would develop and cause a hazard to the
building occupants or damage to the structure or electrical or other equipment shall be
insulated (See Section 5.5 Insulation) or treated (protected) to mitigate such an occurrence.
5.9 Testing
5.9.1 Design Pressure
Every refrigerant-containing component shall be strength tested to a minimum as specific in
each equipment chapter (e.g. ____ times the design pressure), subsequently leak tested, and
proven tight at a pressure not less than design.
5.9.2 Ultimate Strength Requirements
5.9.2.1 Every pressure-containing component of a closed-circuit ammonia refrigeration system,
other than pressure vessels, piping (which includes evaporators, condensers, and heating
coils with refrigerant as the working fluid, where they are not part of a pressure vessel),
valves, pressure gages, refrigerant pumps, and control mechanisms, shall be either listed
individually or as part of the complete refrigeration system or a subassembly by an
approved, nationally-recognized testing laboratory. Alternatively, they shall be designed,
constructed, and assembled to have an ultimate strength sufficient to withstand three
times the design pressure for which it is rated. Such components, where applicable, are
permitted to be designed according to the rules of Section VIII, Division 1, 2013, of the
ASME Boiler and Pressure Vessel Code [ref.3.2.1] and shall be presumed to comply with
the requirements of this Standard.
5.9.2.2 Components exempt from the requirement of Section 5.9.2.1 shall comply with additional
requirements listed in this Standard and ASME B31.5-2013 [ref.3.2.2] where applicable.
5.9.2.3 Secondary-coolant sides of components exempted from the rules of Section VIII,
Division 1, 2013, ASME Boiler and Pressure Vessel Code [ref.3.2.1], shall be designed,
constructed and assembled to have ultimate strength sufficient to withstand 150 psig
[1724 kPa gage] or two times the design pressure for which they are rated, whichever is
greater.
5.10 Signage and Nameplates
5.10.1 Machinery Room Signage
5.10.1.1 See Section 5.10.5 Pipe Markings and Section 5.10.6 Equipment Labels.
5.10.1.2 Refrigeration systems shall be provided with approved informative signs, emergency
signs, charts and labels in accordance with NFPA 704. Hazard signs shall be in
accordance with the International Mechanical Code (IMC) Table 1103.1.
5.10.1.3 See Section 6.13.4 and Section 17.4 for alarm signage.
5.10.1.4 See Section 6.3.4 for authorized personnel signage.
5.10.2 Emergency Shutdown Signage
It shall be the duty of the person in charge of the premises on which the closed-circuit
ammonia refrigeration system is installed to provide a schematic drawing or placard giving
directions for the emergency shutdown of the system at a readily-accessible location by the
trained refrigeration system staff and trained emergency responder personnel familiar
with the system.
When a refrigeration machinery room is used, the emergency procedures shall be posted
outside and immediately adjacent to or on each principal door.
Schematic drawing(s) or signage shall include all of the requirements in Sections 5.10.2.1
through 5.10.2.6.
5.10.2.1 Instructions (details/steps) for shutting down the system in case of emergency.
5.10.2.2 The name and contact telephone numbers of the refrigeration operating, maintenance
and management staff, emergency responders, and safety personnel.
5.10.2.3 The names and telephone numbers of all corporate, local, state, and federal agencies to
be contacted as required in the event of a reportable incident.
5.10.2.4 Type and quantity of refrigerant(s) in the system(s).
5.10.2.5 Type and quantity of lubricant(s) in the system(s).
5.10.2.6 Field test pressures applied.
5.10.3 Wind Indicator
5.10.3.1 When a wind indicator (sock or pennant) is installed, it shall be suitable for the
environment and mounted where it is readily visible for use as incorporated into the
facility emergency action and response plan (EPA Alert 550-F-01-1999, August 2001).
5.10.4 Valve Tagging
Valves required for system emergency shutdown procedure(s) shall be clearly
identified on a readily-available diagram. The procedures and diagram shall be reviewed
and updated, if necessary, when changes (not a replacement-in-kind) are made to the
system that affects emergency shutdown procedures. These valves shall also be uniquely
identified (e.g. tags, signs, etc.) on the actual system.
5.10.5 Pipe Marking
5.10.5.1 All ammonia piping mains, headers and branches shall be identified with “AMMONIA”
as the refrigerant, the physical state of the refrigerant (liquid, vapor, or both), the
relative pressure level of the refrigerant (low, high, where applicable), name of the pipe
(abbreviations are permitted), and the direction of flow. The identification system used
shall either be one established as a standard by a recognized code or standards body or
one described and documented by the facility owner.
NOTE: IIAR Bulletin No. 114 (Appendix 0, ref 1.7.4) provides guidance on
identification of ammonia piping and system components.
5.10.6 Equipment Labels
5.10.6.1 The refrigeration system equipment shall be provided with permanent labels.
5.10.6.2 Refrigeration equipment having an internal volume of more than three (3) cubic feet
(0.085 cubic meters) containing the refrigerant shall each be equipped with a permanent
label that sets forth the state of the refrigerant (liquid, vapor, or both) within it, the type
of equipment, and its title that matches with the refrigeration management plan
drawings.
5.10.7 Nameplates
5.10.7.1 Equipment and applicable components shall have a nameplate with minimum data that
describes or defines the manufacturer’s information and its design limits/purpose. See
specific equipment chapters in Part 3, Equipment and Components.
5.10.7.2 Nameplate Mounting
5.10.7.2.1 The original nameplate shall be affixed to the equipment as specified in Section
VIII, Division 1, 2013, ASME Boiler and Pressure Vessel Code [ref.3.2.1]
paragraph UG-119(e).
5.10.7.2.2 Where duplicate nameplates are supplied, they shall comply with Section 5.10.8.
5.10.8 Duplicate Nameplates
5.10.8.1 Where duplicate nameplates are required for pressure vessels and heat exchangers
constructed in accordance with Section VIII, Division 1, 2013, ASME Boiler and
Pressure Vessel Code [ref.3.2.1], they shall comply with the governing edition of
paragraph UG-119(e) of that Code or equivalent (See Section 12.1.2).
5.10.8.2 A duplicate nameplate, if used, shall be installed on the skirt, support, vessel insulation
jacket, or other permanent attachment to a vessel.
5.10.8.3 Duplicate nameplates shall be permanently marked “DUPLICATE.”
5.10.8.4 Duplicate nameplates shall be obtained only from the original equipment manufacturer
or its assignee.
5.10.8.5 The installer shall certify to the manufacturer that the duplicate nameplate has been
applied to the proper vessel, in accordance with the governing edition of Section VIII,
Division 1, 2013, ASME Boiler and Pressure Vessel Code [ref.3.2.1] paragraph UG-
119(d) or equivalent (See Section 12.1.2). The installer shall provide a copy of the
certification to the owner, who shall retain the copy with the U1A form (or equivalent)
for the vessel.
NOTE:
Appendix D (Informative) provides further information on duplicate nameplates.
5.11 Equipment Enclosures
5.11.1 Enclosures shall be designed to allow the equipment or components to operate effectively and
safely in the location in which they are to be installed.
5.11.2 Enclosures shall allow for safe operational and maintenance service egress of the equipment
and/or components at its installed location by access panels and/or doors or the design shall
allow for the removal of the enclosure and/or its contents from its installed location for
remote service.
5.11.3 Enclosures shall provide protection from inadvertent physical and/or environmental damage
and meet the cleanliness requirements of the area.
5.12 General Safety Requirements
5.12.1 All refrigeration system components shall be installed in locations to mitigate external
damage and include guarding or barricading as necessary.
5.12.2 All exposed rotating components (e.g. shafts, belts, pulleys, flywheels, couplings) shall be
protected with screens or guards in accordance with OSHA 29 CFR 1910.212 [ref.3.9.1] and
29 CFR 1910.219 [ref.3.9.2].
5.12.3 Refrigerant shall be stored only in cylinders or vessels designed for refrigerant containment.
5.12.4 Used equipment to be installed in a new design/project shall meet the requirements of this
Standard.
5.12.5 Equipment and components shall be designed and approved to structurally withstand the
expected static and dynamic loads in accordance with locally-adopted code. See Section 5.6
for Foundations, Piping, Tubing, and Equipment Supports.
5.12.6 Condensers, receivers, and other outdoor refrigeration equipment and/or components shall
have lighting requirements that comply with OSHA 29 CFR 1926.56 to permit adequate
nighttime inspection.
Chapter 6 Machinery Rooms
This Chapter provides requirements for the design of machinery rooms housing stationary closed-circuit
ammonia refrigeration systems or system components.
6.1 Room Layout
6.1.1 Equipment installed in machinery rooms shall be located in such a manner as to allow egress
from any part of the room in the event of an emergency and to provide adequate clearances
for maintenance operations and inspections according to manufacturers’ instructions.
6.2 Construction
6.2.1.1 Machinery rooms shall be constructed in accordance with the locally-adopted Building
Code and the requirements of this section.
6.2.1.2 The machinery room shall be separated from the remainder of the building by tight-
fitting construction. See Section 6.10 for Entrances and Exits.
6.2.1.3 Where piping is supported by the floor, roof or ceiling structure, the structure or
foundation supporting the piping shall be designed to support the expected static and
dynamic loads, including seismic loads.
6.2.1.4 Fire prevention shall be part of the machinery room design considerations.
6.2.1.4.1 The machinery room shall be separated from the remainder of the building by a
one-hour (1-hour) fire-resistance rated separation.
EXCEPTION:
The one-hour (1-hour) fire-resistance rated separation shall not be required where
the machinery room is equipped with an automatic fire sprinkler system.
6.2.1.5 Foundations, floor slabs, and supports for compressor units and other equipment located
within the machinery room shall be of noncombustible construction and capable of
supporting the expected static and dynamic loads imposed by such units, including
seismic loads.
6.2.1.6 A compressor or condenser supported from the ground shall rest on a concrete pad/base
or shall be furnished with a support base for setting directly on and anchoring to the
foundation.
6.2.1.7 All machinery shall be mounted in such a manner as to prevent excessive vibration from
being transmitted to the building structure or connected equipment. Isolation materials
are permitted between the foundation and equipment.
6.2.1.8 There shall be no airflow to or from an occupied space through a machinery room unless
the air is ducted and sealed in such a manner as to prevent any refrigerant leakage from
entering the airstream. Access doors and panels in ductwork and air-handling units shall
be gasketed and tight fitting.
6.3 Accessibility
6.3.1 See Section 5.7 Service Provisions for safe access opening and passageway clearance
requirements for serviceable equipment and components.
6.3.2 All manually-operated valves inaccessible from floor level shall be operable from portable
platforms, fixed platforms, ladders, or shall be chain-operated. (Regarding ladders – see
ref.1.9.3).
6.3.3 Isolation valve(s) identified as being part of a system emergency shutdown procedure(s) shall
be readily-accessible to be directly-operable or chain-operated from a permanent work
surface. These valves shall be clearly-identified - See Section 5.10.4 Valve Tagging.
6.3.4 Access to the refrigeration machinery room shall be restricted to authorized personnel. Doors
shall be clearly marked and permanent signs shall be posted at each entrance to indicate this
restriction.
6.4 Combustible Materials
6.4.1 Flammable and Combustible materials shall not be stored in machinery rooms.
EXCEPTION:
This provision shall not apply to spare parts, tools (ex. lighter and sulfur sticks), and materials (ex. oil,
paint, packages) as required for use to be present only during scheduled operational checks,
inspections, and maintenance activities for the refrigeration system.
6.5 Open Flames
6.5.1 Fuel-burning appliances and equipment shall not be installed in a machinery room.
EXCEPTION 1:
Fuel-burning appliances and equipment are permitted in the same machinery room where
combustion air is ducted from outside the machinery room and sealed in such a manner as to
prevent any refrigerant leakage from entering the combustion chamber, or where a refrigerant
detector automatically shuts off the combustion process in the event of refrigerant leakage.
EXCEPTION 2:
The use of matches, lighters, sulfur sticks, welding equipment and similar portable devices are
permitted, other than during charging or removal of oil or ammonia, where the machinery
room meets the requirements of Chapter 6.
EXCEPTION 3:
Machinery rooms where internal combustion engines are used as the prime mover for the
compressors.
6.6 Piping
6.6.1 Piping and fittings shall be insulated, where applicable, to conserve energy and be adequately-
placed to mitigate condensation that could cause a hazard to personnel (e.g. slips on a wet
walking surface) or damage to the structure (e.g. mold or mildew) or other equipment (See
Section 5.5 Insulation and Section 5.8 Condensation Control).
6.6.2 All pipes penetrating the walls, ceiling, or floor of the machinery room shall be tightly sealed
to the walls, ceiling, or floor through which they pass to maintain the fire rating (See Section
6.2.1.4).
6.6.3 All piping shall have appropriate pipe markers attached to indicate its use and the direction of
flow. See Pipe Marking Section 5.10.5.
6.6.4 There shall be no refrigerant cylinders with temporary or permanent connections to the system
unless actual transfer of refrigerant is being conducted by a qualified individual(s).
6.7 Eyewash/Safety Shower
6.7.1 A minimum of one eyewash/safety shower unit shall be installed in each machinery room.
6.7.2 A minimum of one eyewash/safety shower unit shall be installed outside of each machinery
room.
6.7.3 Additional eyewash/safety showers shall be installed such that there is a unit no greater than
55 feet from a potential hazard.
6.7.4 The path of travel from a potential hazard to an eyewash/safety shower must be unobstructed.
Doors are considered an obstruction.
6.7.5 Refer to ANSI/ISEA Z358.1-2009 for additional emergency eyewash/safety shower
installation requirements.
EXCEPTION:
It is permitted to install only one permanent eyewash/safety shower unit, located either inside or
outside each machinery room. When only one unit is permanently installed, a procedure shall be in
place to provide a portable or temporary eyewash/safety shower unit either outside the machinery
room, when the permanent installation is located inside, or inside the machinery room and located at
a distance not greater than 55 feet of a potential hazard, when the permanent installation is located
outside. The procedure shall be affective when maintenance procedures are performed that could
result in exposure to ammonia or other hazards.
6.8 Electrical Safety
6.8.1 Electrical equipment and wiring shall be installed in accordance with NFPA Standard 70:
National Electrical Code (NEC) (ref.3.7) and the requirements of the authority having
jurisdiction (AHJ).
6.8.2 A machinery room shall be classified per the NFPA Standard 70 National Electric Code
(NEC) as a “Non-Hazardous (Unclassified) Location,” when the machinery room is provided
with an independent mechanical ventilation system that meets the requirements of Section
6.14 Ventilation.
6.8.3 Per the National Electric Code (NEC), where a mechanical ventilation system is not provided
in accordance with Section 6.14, the room shall be classified as Class I, Division 2, Group D.
6.8.4 Electrical Classification shall be clearly documented in the refrigeration management plan
process safety information.
6.9 Drains
6.9.1 Floor drains shall be provided to properly dispose of all wastewater. The accumulation of
wastewater or the running of wastewater across the floor shall be avoided or be kept to a
minimum.
6.9.2 When required, a means shall be provided to prevent contamination (keep out unintended
substances - oil, secondary coolants, etc.) of the drainage system.
6.9.3 A means of controlling a liquid ammonia spill through the machinery room drainage system
from reaching occupied work areas outside the machinery room shall be provided.
6.10 Entrances and Exits
6.10.1 Machinery rooms larger than 1,000 square feet (93 m2) shall have not less than two exits or
exit access doorways. Where two exit access doorways are required, one such doorway is
permitted to be served by a fixed ladder or an alternating tread device. Exit access doorways
shall be separated by a horizontal distance equal to one-half the maximum horizontal
dimension of room. All portions of machinery rooms shall be within 150 feet (45,720 mm) of
an exit or exit access doorway. An increase in travel distance is permitted in accordance with
the applicable Building Code.
6.10.2 Machinery room personnel doors communicating with the building shall be self-closing,
tight-fitting, side-swinging, 1-hour fire-rated, outwardly opening doors equipped with
latching panic-type hardware.
6.10.3 The machinery room shall have a personnel door(s) that opens directly to the outside, or to a
vestibule that leads directly to the outside. The personnel door(s) shall be self-closing, tight-
fitting, side swinging, 1-hour fire-rated, outward opening and equipped with latching panic-
type hardware.
EXCEPTION: Machinery rooms equipped with a fire sprinkler system and having a floor
area of not more than 500 square feet (46.5 m²) need not have a door that opens directly to
the outside or to a vestibule leading directly to the outside.
6.10.4 Exterior exits shall not be under any fire escape or any open stairway.
6.10.5 Each site shall have an appropriate evacuation plan readily available. Contact information for
persons responsible for emergency procedures shall be clearly shown on the plan. See
Section 5.10.2 for Emergency Shutdown Signage requirements.
6.11 Lighting
6.11.1 Machinery rooms shall be equipped with light fixtures to provide a minimum of 30 foot-
candles [320 lumens/m2] at the working level, 36 in (3.0 feet or 0.91 m) above the floor or
platform. See Section 7.1 for lighting requirements for equipment and components located
outside.
6.11.2 Control of the illumination source shall be provided at the access entrance(s). In lieu of
manual controls, the use of occupancy sensors to control lighting or continuous illumination
is permitted.
6.11.3 For emergency and exit sign lighting, see informative Appendix O (ref.1.9.5).
6.12 Refrigeration Machinery Remote Controls
6.12.1 Refrigeration system emergency shutoff: A clearly-identified switch with a tamper-resistant
cover shall be located outside and adjacent to the designated principal machinery room
door(s) which shall provide off-only control of refrigerant compressors, refrigerant pumps,
and normally-closed automatic refrigerant valves located in the machinery room.
6.12.2 Refer to Section 6.13 for Refrigerant Detection for additional control requirements.
6.12.3 Refer to Section 6.14.11 for Ventilation Remote Controls.
6.13 Refrigerant Detection
Each machinery room shall contain refrigerant detection that will activate an alarm and
mechanical ventilation as described in this section. Refer to Chapter 17 Detection and Alarms
for general requirements.
6.13.1 Alarm
6.13.1.1 The leak detection sensor(s) shall actuate an alarm(s) that notifies a monitored location
so that corrective action can be taken.
6.13.1.2 The leak detection sensor(s) shall actuate visual and audible alarms inside the
machinery room and outside each entrance to the machinery room.
6.13.2 Detector Placement
6.13.2.1 The leak detection sensor(s), or the inlet of sampling tube(s) that draw air to the leak
detection sensor(s), shall be mounted in a position where refrigerant from a leak is
most likely to concentrate [e.g. exhaust fan intake(s)].
6.13.3 Detection Levels
6.13.3.1 Detection of ammonia vapor concentrations below 25 ppm requires no alarm or
detection device action.
6.13.3.2 Detection of ammonia vapor concentrations at or above 25 ppm shall activate a visual
indicator(s) (e.g. strobe or other distinct type) and an audible alarm.
6.13.3.2.1 The visual indicator and audible alarm can be automatically reset when the
ammonia vapor concentration falls below 25 ppm.
6.13.3.3 Detection of ammonia vapor concentrations at or above 150 ppm shall activate a visual
indicator(s) and an audible alarm and shall turn on the emergency exhaust ventilation
system at the emergency exhaust ventilation rate. Ventilation fans activated at the 150
ppm detection level shall be latched in and shall require a manual reset within the
machinery room.
6.13.3.4 Detection of ammonia vapor concentrations that exceeds the detector’s upper detection
limit or 40,000 ppm (25% LFL), whichever is lower, shall activate all visual and
audible indicators and automatically shut down normally-closed automatic refrigerant
valves, rotating equipment (ex. ammonia pumps, water pumps), and compressors in un-
classified locations.
6.13.3.5 Emergency lighting and power to the emergency ventilation system, as well as other
critical systems, shall remain powered (e.g. independent circuit) to stay on during an
emergency machinery room equipment shutdown.
6.13.4 Signage
6.13.4.1 The meaning of each alarm shall be clearly marked by signage near the visual and
audible alarms.
6.13.5 Testing
6.13.5.1 The facility shall establish a time schedule for testing of the ammonia detectors and the
alarm system. The manufacturer’s recommendations shall be followed or modified
based on documented experience.
6.13.5.2 Where no manufacturer’s recommendations are provided, these devices shall be
functionally tested on an annual basis.
6.14 Ventilation
6.14.1 Each machinery room shall be vented to the outdoors by means of a mechanical exhaust
ventilation system(s) actuated automatically by refrigerant leak detection sensor(s),
temperature sensors, and also operable manually.
6.14.1.1 The mechanical exhaust ventilation system(s) shall be designed to produce at least the
normal ventilation rate as required by Section 6.14.6, and an emergency exhaust
ventilation rate as required by Section 6.14.7.
6.14.1.2 The emergency mechanical exhaust ventilation system shall be powered independently
of the equipment within the machinery room and independently of the emergency
shutdown controls such that if the machinery room equipment is shut down, the
exhaust ventilation remains in operation.
6.14.2 Multiple fans or multispeed fans are permitted in order to produce the emergency exhaust
ventilation rate (See Section 6.14.7) and to obtain a reduced airflow for normal exhaust
ventilation (See Section 6.14.6). Fans that are used for normal ventilation and which are also
used for emergency ventilation must be controlled such that the emergency rate is achieved
when required.
6.14.3 Inlet Air
6.14.3.1 Provisions shall be made for inlet air to replace that being exhausted. Inlet air make-up
shall be designed to provide a negative pressure in the machinery room not to exceed
0.25 in. water column.
6.14.3.2 Distribution of makeup air shall be arranged to prevent short-circuiting of the makeup
air directly to the exhaust.
6.14.3.3 Openings for inlet air shall be suitably guarded (e.g. covered with a corrosion-resistant
screen of not less than ¼” mesh).
6.14.3.4 Openings for inlet air shall be positioned to avoid recirculation of exhausted air and to
avoid inducing anything except for uncontaminated (e.g. no fumes or trash particles)
ambient air across the machinery.
6.14.3.5 Inlet air ducts to the machinery room shall serve no other area.
6.14.3.6 If motorized dampers are utilized, they shall be of the power to close and spring to
open type (normally open).
6.14.3.7 Supply fans shall be used to provide makeup air to the machinery room where it is
impractical or impossible to use openings with ducts.
6.14.4 Discharge
6.14.4.1 Exhaust from machinery room mechanical ventilation systems shall be discharged to
the outdoors in such a manner as not to cause a nuisance or hazard, taking into account
the natural airflow around the building, prevailing winds and surrounding structures.
6.14.4.2 Exhaust from machinery room mechanical ventilation systems shall be discharged not
less than 20 feet (6 m) from a property line or openings into buildings. The distance is
considered to be horizontal, vertical, or a combination of both.
6.14.4.3 Discharge air ducts from the machinery room shall serve no other area.
6.14.5 Exhaust Fans
6.14.5.1 Exhaust from all fans used for exhausting ammonia vapor shall discharge up vertically
with a minimum discharge velocity of 2500 FPM at the required emergency ventilation
volume (cfm) flow rate.
6.14.5.2 All machinery room exhaust fans, regardless of function, shall be equipped with non-
sparking blades.
6.14.5.3 Machinery room exhaust fans or air conditioning equipment that is not used for
exhausting ammonia vapor shall be de-energized and fan dampers shall close upon
detection of ammonia.
6.14.5.4 All emergency exhaust fan motors located in the air stream or inside the machinery
room shall be of the totally-enclosed type. Fan motors meeting this requirement are not
required to be NEC Class 1, Division 2.
6.14.6 Normal Mechanical Ventilation
6.14.6.1 Normal mechanical ventilation design capacity shall be the volume required to limit
the room dry bulb temperature to 104°F (40°C) taking into account the ambient heating
effect of all machinery in the room and with the ventilation air entering the room at a
1% ASHRAE design dry bulb (ref. 3.1). The emergency ventilation system is permitted
to be used to supplement the normal ventilation.
EXCEPTION:
A reduced normal ventilation rate can be used on applications where a means of
cooling is provided or room electrical equipment is designed to accommodate
temperatures exceeding a dry bulb temperature of 104°F (40°C), in accordance with
UL and NEC standards.
6.14.6.2 To obtain the reduced airflow to maintain space temperatures for normal ventilation,
partial operation of a multiple-fan system or multi-speed fans may be utilized.
6.14.6.3 Normal ventilation need not be continuous and shall be actuated by:
6.14.6.3.1 Space temperature, when fans are used for temperature control (thermostat).
6.14.6.3.2 A refrigerant detector (when normal ventilation fans meeting the requirements of
Section 6.14.5 Exhaust Fans are used to obtain the emergency ventilation rate),
see Section 6.13 Refrigerant Detection.
6.14.6.3.3 Manual controls. See Section 6.14.11.3.
6.14.7 Emergency Mechanical Ventilation
6.14.7.1 Emergency mechanical ventilation systems shall be capable of providing at least one air
change every two (2) minutes, which is 30 air changes per hour (30 ACH) based on the
gross machinery room volume. Appendix K (Informative) provides an example
calculation for determining emergency ventilation rates. The emergency ventilation
system is permitted to use normal ventilation fans that meet the requirements of Section
6.14.5. See Section 6.14.6.3.2.
6.14.7.2 Emergency mechanical ventilation shall be actuated by:
6.14.7.2.1 A refrigerant detector, see Section 6.13 Refrigerant Detection.
6.14.7.2.2 Manual controls. See Section 6.14.11.3.
6.14.8 Alternative Ventilation Methods
6.14.8.1 Section 6.14 describes the criteria to be followed for the design of a mechanical
ventilation system for a machinery room. Variance from these criteria is permitted per
the requirements of the following sections:
6.14.8.1.1 In machinery rooms with enough volume in the space where the refrigeration
equipment is a low-charge or limited-charge design and the release of the entire
charge of the largest independent refrigeration circuit will not exceed ammonia
concentrations of 40,000 ppm [25% of the lower flammability limit (LFL)],
emergency ventilation is not required. Normal ventilation is required only to
control room temperature, as necessary, and can be used for exhausting ammonia
vapor if it meets the requirements of Section 6.14.5 Exhaust Fans.
6.14.8.1.1.1 Machinery rooms shall be provided with ammonia detection and alarms that
meet the requirements set forth in Section 6.13, except for the requirements
for the activation of ventilation fans.
6.14.8.1.1.2 Calculations shall be provided and retained which demonstrate that the
ammonia concentrations will never exceed 40,000 ppm (25% LFL) if the
entire charge of the largest independent refrigeration circuit was released
from the system. Appendix K (Informative) contains sample calculations for
the design of a ventilation system using this option. For volume calculation,
see Section 4.6.
6.14.9 Ventilation for Systems Located Outdoors or in Partially Enclosed Mechanical Rooms
6.14.9.1 When a refrigeration system or a component of a refrigeration system is located
outdoors and is enclosed or partially enclosed by a penthouse, lean-to, or other
structure, it shall be at least 20 feet from building entrances and exits, and natural or
mechanical ventilation meeting the requirements of Section 7.1.8.3 shall be provided.
6.14.10 Alarm on Failure
6.14.10.1 A monitored location shall be notified when the emergency mechanical ventilation
system fails.
6.14.11 Ventilation Remote Controls
6.14.11.1 Emergency remote controls for the emergency mechanical ventilation systems shall be
provided and shall be located immediately outside the designated principal exterior
machinery room door(s).
6.14.11.2 The function of the emergency remote controls shall be clearly marked by signage
near the controls.
6.14.11.3 Provide an “ON / AUTO” override for emergency ventilation immediately outside the
designated principal exterior machinery room door.
6.14.12 Testing
6.14.12.1 The facility shall establish a time schedule for conducting a functional test of the alarm
system. The manufacturer’s recommendations shall be followed or modified based on
documented experience.
6.14.12.2 Where no recommendations are provided, the alarm system shall be functionally tested
on an annual basis.
6.14.12.3 The facility shall establish a time schedule for conducting a functional test of the
mechanical ventilation system. This can be in conjunction with the ammonia detection
calibration schedule. The manufacturer’s recommendations shall be followed or
modified based on documented experience. The functional test is for proving
operability that it goes on/off at the setpoint.
6.14.12.4 Where no recommendations are provided, the mechanical ventilation system shall be
functionally tested at a minimum twice per year. A reduced frequency for testing may
be established after enough test data is accumulated to support the reliability of the
ventilation equipment. An increased frequency for testing may be established for sites
with a single fan installation to support the reliability of the ventilation equipment.
Chapter 7 Areas Other Than Machinery Rooms
This chapter applies to areas other than machinery rooms which are industrial occupancies only (See
Chapter 4 Sections 4.1- 4.3).
7.1 COMMON CONSIDERATIONS
When installing refrigerant-containing components of a closed-circuit ammonia refrigeration
system outside a machinery room, the following considerations must be addressed:
7.1.1 Physical Protection: Components shall be protected from physical damage.
7.1.1.1 Where refrigeration equipment containing ammonia refrigerant is located in an area
where heavy vehicle traffic is present during normal operations and potential for impact
at ground/floor level is significant, physical protection of the equipment shall be provided
in accordance with the International Fire Code (IFC) Section 312.
7.1.2 Environment: Components shall be specifically designed to operate in the environmental
conditions of the area in which they are to be installed.
7.1.3 Personnel: Restrict access to refrigeration system components to authorized personnel only.
7.1.4 Provide safe access for the inspection and maintenance of the components including all
required clearances for servicing. See Section 5.7 Service Provisions.
7.1.5 Components that require servicing or replacement shall be provided with isolation valves and
pump-out provisions.
7.1.6 Ventilation
Where required, provide a mechanical exhaust ventilation system(s) per the requirements of
this section and Chapter 17.
7.1.6.1 Where the quantity of ammonia in a refrigeration system would exceed 40,000 ppm (25%
LFL) upon release to the space, based on the volume calculation determined by Section
4.6, provide emergency ventilation for thirty (30) air changes per hour (ACH).
7.1.6.1.1 Emergency ventilation shall be activated in accordance with Section 17.6.4 Level
4 ammonia detection.
7.1.6.2 Where all refrigeration equipment is self-contained [the entire refrigeration circuit resides
on an assembled package(s)] and the release to the space of the entire charge of the
largest independent refrigeration circuit will not raise the ammonia concentration above
40,000 ppm (25% LFL), emergency exhaust ventilation is not required.
7.1.6.2.1 Obtain and retain calculations which demonstrate that the ammonia concentration
will not exceed 40,000 ppm (25% LFL). See Section 4.6.
7.1.6.2.2 Ammonia detection and alarm(s) shall be provided for notification of an ammonia
release to personnel in accordance with Chapter 17.
7.1.6.2.3 Ventilation to maintain room temperature is required if necessary to prevent room
dry bulb temperature rom rising above 104°F (40°C).
7.1.6.3 Ventilation for Systems Located Outdoors
7.1.6.3.1 When a refrigeration system or a component of a refrigeration system is located
outdoors and is enclosed or partially enclosed by a penthouse, lean-to, or other
structure, it shall be at least 20 feet from building entrances and exits and natural
or mechanical ventilation shall be provided. The requirements for such natural
ventilation are as follows (Appendix O ref.1.3):
The free-aperture cross section for the ventilation shall be at least:
F = G0.5 (I-P)
F = 0.138G0.5 (SI)
where:
F = the free opening area, ft² (m²)
G = the mass of refrigerant in the largest independent circuit, any part
of which is located within the enclosure or structure, lb (kg)
7.1.6.4 Ventilation Systems for Equipment Pits Located Indoors
7.1.6.4.1 When refrigeration equipment containing ammonia is located within an indoor pit
that is 60 inches (5.0 feet or 1.52 m) or more below the floor or grade level,
emergency ventilation shall be 30 air changes per hour (ACH) in accordance with
Chapter 6.
7.1.6.4.2 Make-up air shall be provided near the floor of the indoor pit. Air shall be directed
toward the equipment or components and away from the pit exit.
7.1.6.4.3 The ventilation provisions of the room in which it is located shall be met. The
volume of the pit shall be included in the air quantity calculations.
7.2 LOCATIONS
This section provides additional location design criteria.
7.2.1 Penthouses
7.2.1.1 Penthouses open to the interior space are considered part of the refrigerated storage area
and shall be treated as such.
7.2.1.2 Penthouses isolated from the interior space shall be treated as an equipment enclosure.
See Chapter 2 Definitions - Equipment Enclosure and Section 5.11.
7.2.2 Electrical Room
7.2.2.1 Electrical rooms shall not contain direct-ammonia evaporators. Indirect-closed systems
in which a secondary-coolant passes through a closed-circuit in the evaporator unit, are
permitted.
7.2.3 Utility Areas
7.2.3.1 Utility areas include unoccupied spaces where refrigerant-containing components (e.g.
control valve assemblies) are located.
7.2.3.2 A utility area shall use a minimum level 1 detection per Chapter 17.
EXCEPTION: Areas with only continuous piping with no valves, valve assemblies,
equipment, or equipment connections.
Part 3 Equipment and Components
Chapter 8 Compressors
This chapter applies to compressors which are used in closed-circuit ammonia refrigeration systems.
8.1 Design
8.1.1 For minimum design pressure, see Section 5.1.2.
8.2 Positive-Displacement Compressor Protection
8.2.1 When equipped with a stop valve in the discharge connection, every positive-displacement
compressor shall be equipped with a pressure relief device selected to prevent the discharge
pressure from increasing to more than 10% above the lowest of the maximum allowable
working pressures of the compressor or any other components located in the path between the
compressor and the stop valve or in accordance with Section 15.2.7, whichever is larger. The
pressure relief device shall discharge into the low pressure side of the system or in accordance
with Section 15.4.1 Atmospheric Discharge.
The relief device shall be sized based on compressor flow at a minimum of 50°F (10°C)
saturated temperature at the compressor suction or at design saturated suction temperature,
whichever is greater.
The minimum size compressor pressure vessel relief connection shall be in accordance
with Section 12.1.3.
The opening through all pipe, fittings, and pressure relief devices (if installed), including 3-
way valves for dual reliefs, between a compressor pressure vessel (e.g. oil separators) and its
pressure relief valve, shall have at least the area of the pressure relief valve inlet. See Section
15.3.2.
EXCEPTION 1:
For compressors capable of operating only when discharging to the suction of a higher-stage
compressor, calculate flow at the saturated suction temperature equal to the design operating
intermediate temperature.
EXCEPTION 2:
When the compressor is equipped with automatic capacity regulation which actuates to
minimum flow at 90% or below of the pressure-relief device setting and a pressure-limiting
device is installed and set in accordance with Section 8.2.2, the discharge capacity of the
relief device is allowed to be the minimum regulated flow rate of the compressor.
NOTE:
Appendix E (Informative) describes an acceptable method of calculating the discharge
capacity of positive-displacement compressor pressure-relief devices.
8.2.2 All compressors shall be provided with high-discharge-temperature, low-suction-pressure,
and high-discharge-pressure limiting devices for operable safety controls at a minimum (i.e.
low pressure cutout, high pressure cutout). Compressors using forced feed oil lubrication shall
be provided with an indicating-type lubrication failure control for operable safety control at a
minimum (i.e. low oil pressure cutout). Except for booster compressors, high-pressure-
limiting devices shall be of the manual-reset type. The setting of high-pressure-limiting
devices shall not exceed the lower of the compressor manufacturer’s recommendation or 90%
of the setting of the pressure-relief device on the discharge side of the compressor. The limiter
may be set no lower than the minimum design metal temperature (MDMT) or the
manufacturer’s recommended minimum temperature of the compressor. The setting of low-
pressure-limiting devices shall be the higher of:
8.2.2.1 The system’s minimum design pressure to protect against freeze-up or other damage.
8.2.2.2 The compressor manufacturer’s recommendations.
8.2.3 Protection from exposed rotating components, see Section 5.12.2.
8.2.4 If rotation is to be in only one direction, a rotation arrow shall be cast in or permanently
attached to the compressor frame (e.g. attached label or plate).
8.2.5 For ultimate strength requirements, see Section 5.9.2.
8.3 Procedures/Testing
8.3.1 Compressors shall be strength tested to a minimum of 1.5 times the design pressure,
subsequently leak tested, and proven tight at a pressure not less than design.
8.4 Equipment Identification
8.4.1 The following data shall be provided on nameplates or labels affixed to compressors:
8.4.1.1 Manufacturer’s name
8.4.1.2 Manufacturer’s serial number
8.4.1.3 Manufacturer’s model number
8.4.1.4 Year manufactured (may be encoded with serial number)
8.4.1.5 Maximum allowable working pressure (MAWP)
8.4.1.6 Maximum rotation speed in rpm
8.4.1.7 Direction of rotation (where applicable; see Section 8.2.4).
8.4.2 A compressor without a nameplate per the requirements of Section 8.4.1 (i.e. a used
compressor) shall not be used unless the applicable compressor operating limitations have
been verified through the identification of the manufacturer and the manufacturer’s model
number of the compressor from casting numbers or similar positive identification.
8.5 Compressor Installation Considerations
The following must be addressed for the installation of compressors:
8.5.1 All compressors shall have a valved pump-out connection(s) for removal of ammonia.
Compressors that are packaged with other components may have the pump-out connection(s)
located elsewhere on the package.
8.5.2 Design provisions shall account for the impact on the compressor if operating in low ambient
temperatures, to avoid condensation of refrigerant in the compressor package or piping
during operation or standby.
8.5.3 At a minimum, designs shall include provisions for installing compressor foundations
according to manufacturers’ instructions, grouting, and/or for installing isolation from the
floor or structure of the building, when required.
8.5.4 When a variable frequency drive (VFD) is used to operate a compressor, the manufacturer’s
instructions shall be followed and the compressor with the mounted VFD shall be stable at
frequencies during its operation.
8.5.4.1 If resonant harmonics are encountered, identified, and cannot be isolated from the
system, frequencies are permitted to be skipped, if applicable.
8.5.5 The refrigeration compressor(s) shall be selected that operate(s) within the design limitations
specified by the compressor manufacturer while meeting the intended refrigeration system
design requirements.
8.5.6 Each compressor shall be fitted with a discharge check valve. Refer to Sections 13.2.5.6 and
13.2.5.6.1 for stop valves.
EXCEPTION: Self-contained systems are not required to have a discharge check valve.
8.5.7 Before being applied in a new design, any previously used compressor shall be inspected for
any signs of alteration, modification, or physical repair that might affect the integrity of the
compressor casing. Any compressor integrity issue shall be corrected and verified before
operation.
8.5.7.1 If the compressor casing has been altered, modified or repaired, the casing shall already
have been recertified for pressure compliance by the manufacturer or insurance
underwriter and recertification papers shall be maintained on site with the refrigeration
management program.
8.5.8 The compressor shall be fitted with pressure and temperature indicating device(s) such that an
observer can visually determine (e.g. gauges, readouts on a control display screen) the
compressor’s suction pressure, discharge pressure, oil pressure (if the compressor uses forced
feed lubrication), and discharge temperature.
8.6 Alarms and Detection
8.6.1 Compressors located indoors in areas outside the machinery room shall use level 3
detection (See Section 17.6.3).
Chapter 9 Refrigerant Pumps
This chapter applies to mechanical refrigerant pumps for use in closed-circuit ammonia refrigeration
systems. This section does not apply to liquid refrigerant transfer employing pressure differential to
move liquid refrigerant (e.g. pumper drum systems).
9.1 Design
9.1.1 For minimum design pressure, see Section 5.1.2.
EXCEPTION:
Application design pressures which exceed these minima shall prevail.
9.1.2 A hydrostatic or differential overpressure relief device (or vent pipe containing a normally-
open isolation valve) shall be used for pressure protection of a liquid pump and its associated
piping. The inlet connection for the relief device or vent pipe shall be located on the pump
casing or piping between the stop valves or stop check valves at the pump inlet and outlet,
except that when a check valve is located between the pump and its outlet stop valve, the
relief device or vent pipe inlet shall be connected to the pipe between the discharge check
valve and stop valve. The discharge of this relief or vent pipe shall connect either to the pump
suction line upstream of the pump suction stop valve or to the vessel to which the pump
suction is connected. This pressure relief device or vent pipe shall be external to the pump
housing.
9.1.3 For ultimate strength requirements, see Section 5.9.2.
9.1.4 Protection from exposed rotating components, see Section 5.12.2.
9.1.5 Refrigerant pumps shall be suitable for the service in which they are being applied. For
refrigerant pumps used in areas other than machinery rooms, see Section 7.1.6.
9.1.6 Refrigerant pumps shall be installed with isolation valves.
9.1.7 Refrigerant pumps shall be installed on a foundation designed for anticipated loads.
9.2 Procedures/Testing
9.2.1 Refrigerant pumps shall be strength tested to a minimum of 1.5 times the design pressure,
subsequently leak tested, and proven tight at a pressure not less than design.
9.3 Equipment Identification
Manufacturers producing refrigerant pumps shall permanently affix to the pump a nameplate
providing the following minimum data:
9.3.1 Manufacturer’s name
9.3.2 Manufacturer’s serial number
9.3.3 Manufacturer’s model number
9.3.4 The pump data sheet submittals shall include the following information from the manufacturer
(a manufacturer may also include some of the following items on their pump nameplate):
Refrigerant Type (e.g. Ammonia)
Operating Condition data
Performance data
Construction data – including maximum (allowable) pressure at operating temperature,
test pressure, bearing type, and impeller data
Head – differential pressure (ft, m, or psi)
Impeller identification (diameter size)
RPM (Speed) - for fixed-speed pumps and minimum, maximum, & operating RPM’s for
adjustable speed pumps)
Capacity (maximum rated gpm or liters/min) with identified impeller
Materials – metals and gaskets
Motor (Driver) information
Electric motor rating(s) (if applicable) - volts, full load amps (FLA), frequency (Hz), phase,
output (HP and/or KW)
Electric heater rating(s) (if applicable) - volts, amps, phase, output (KW)
Insulation Classification
Piping Connections (Schematic)
Pump Operating Procedure Description
Inspections & Tests verification – Performance and Pressure Test
Minimum Circuit Amps (MCA) and Maximum Over-Current Protection (MOCP) – (if
Applicable)
Weight
Direction of rotation shall be confirmed and documented (Mark or Label a directional arrow
on the unit)
Year manufactured
9.4 Refrigerant Pumps Installation Considerations
The following considerations, in addition to the Section 7.1 Common Considerations and Section 7.2
Locations, must be addressed for the installation of refrigerant pumps:
9.4.1 Refrigerant pumps are permitted to be semi-hermetic seal-less, hermetically sealed, or open
drive. For pumps used in occupied areas other than machinery rooms or outdoors, see Section
7.1.6.
9.4.2 Where pumps are equipped with safety devices, they shall stop the action of the pump.
9.4.3 All pumps shall be capable of being pumped out for removal of ammonia.
9.5 Alarms and Detection
9.5.1 For refrigerant pumps located in machinery rooms, see Section 6.13 Detection.
9.5.2 Semi-hermetic seal-less and hermetically sealed refrigerant pumps located indoors in areas
outside the machinery room shall use level 3 Detection (See Section 17.6.3).
Chapter 10 Condensers
10.1 Air-Cooled Condensers and Air-Cooled Desuperheaters
This chapter applies to tube-and-fin and micro-channel type air-cooled condensers and air-cooled
desuperheaters which are applied to closed-circuit ammonia refrigeration systems.
10.1.1 Design
10.1.1.1 For minimum design pressure, see Section 5.1.2.
10.1.1.2 For ultimate strength requirements, see Section 5.9.2.
10.1.1.3 Where the refrigerant inlet and outlet piping of air-cooled condensers and
desuperheaters can be automatically isolated, they shall be protected from hydrostatic
overpressure per Section 15.5.
10.1.1.4 Protection from exposed rotating components, see Section 5.12.2.
10.1.1.5 Fan speeds shall not exceed the safe design speed recommended by the manufacturer.
10.1.2 Procedures/Testing
10.1.2.1 Air-cooled condensers and desuperheaters shall be strength tested to a minimum of 1.1
times the design pressure, subsequently leak tested, and proven tight at a pressure not
less than design.
10.1.3 Equipment Identification
The following data shall be provided on nameplates or labels affixed to the equipment or
components of the equipment:
EXCEPTION:
Nameplate data is not required on air-cooled desuperheaters that are integral with condensers.
10.1.3.1 Manufacturer’s name
10.1.3.2 Manufacturer’s serial number
10.1.3.3 Manufacturer’s model number
10.1.3.4 Year manufactured
10.1.3.5 Design pressure
10.1.3.6 Direction of fan rotation
10.1.3.7 Electric motor power
10.1.3.8 Electric supply: volts, full load amps, frequency (Hz), phase.
10.1.3.9 At a minimum, if not on the nameplate, the condenser submittal sheets shall have the
MDMT (Minimum Design Metal Temperature).
10.1.4 Air-Cooled Condenser Installation Considerations
The following considerations, in addition to the Section 7.1 Common Considerations and Section 7.2
Locations, must be addressed when designing for the installation of air-cooled condensers:
10.1.4.1 Air-cooled condensers shall be installed with manufacturer-recommended minimum
clearances for position of the units and their respective air inlets and air outlets to avoid
short-circuiting and to ensure unobstructed air flow.
10.1.4.2 Consideration shall be given to the location of the air-cooled condenser relative to the
receiver to assure the design allows sufficient refrigerant head for the refrigerant to
properly drain.
10.1.5 Alarms and Detection
10.1.5.1 Air-cooled condensers located indoors (e.g. ducted intakes and exhausts) in areas
outside the machinery room shall use, at a minimum, level 2 detection. See Section
17.6.
10.2 Evaporative Condensers
This section applies to evaporative condensers which are applied to closed-circuit ammonia refrigeration
systems.
10.2.1 Design
10.2.1.1 For minimum design pressure, see Section 5.1.2.
10.2.1.2 For ultimate strength requirements, see Section 5.9.2.
10.2.1.3 Pressure vessels incorporated into evaporative condensers shall comply with Chapter 12
Pressure Vessels.
10.2.1.4 Where the refrigerant coil inlet and outlet piping of evaporative condensers can be
automatically isolated, the condenser shall be protected from refrigerant hydrostatic
overpressure per Section 15.5.
10.2.1.5 Protection from exposed rotating components, see Section 5.12.2.
10.2.1.6 Fan speeds shall not exceed the safe design speed recommended by the manufacturer.
10.2.1.7 All evaporative condensers shall be adequately anchored and supported.
10.2.2 Procedures/Testing
10.2.2.1 Evaporative condensers shall be strength tested to a minimum of 1.1 times the design
pressure, subsequently leak tested, and proven tight at a pressure not less than design.
10.2.3 Equipment Identification
The following data shall be provided on nameplates or labels affixed to the equipment or
components of the equipment:
10.2.3.1 Manufacturer’s name
10.2.3.2 Manufacturer’s serial number
10.2.3.3 Manufacturer’s model number
10.2.3.4 Year manufactured
10.2.3.5 Design pressure
10.2.3.6 Direction of fan rotation (and water circulating pump, if supplied)
10.2.3.7 Electric motor rating for fan(s) (and water circulating pump, if supplied)
10.2.3.8 Electric supply: volts, full load amps, frequency (Hz), phase.
10.2.4 Evaporative Condensers Installation Considerations
The following design considerations, in addition to the Section 7.1 Common Considerations and
Section 7.2 Locations, must be addressed when designing for the installation of evaporative
condensers:
10.2.4.1 Evaporative condensers shall be installed with manufacturer-recommended minimum
clearances for position of the units and their respective air inlets and air outlets to
avoid short-circuiting and to ensure unobstructed air flow.
10.2.4.2 Provide freeze protection, if applicable, for the sump and water piping.
10.2.4.3 Provide proper drainage of overflow and waste water.
10.2.4.4 Consideration shall be given to the location of the evaporative condenser relative to
the receiver to assure the design allows sufficient refrigerant head for the refrigerant to
properly drain.
10.2.5 Alarms and Detection
10.2.5. 1 Evaporative condensers located indoors (with the tops open to the outdoors) in areas
outside the machinery room shall use, at a minimum, level 2 detection. See Section
17.6.
10.3 Shell-and-Tube Condensers
This section applies to shell-and-tube condensers which are applied in closed-circuit ammonia
refrigeration systems.
Equipment covered by this section are horizontal and vertical shell-and-tube condensers with
closed water passes and vertical shell-and-tube condensers with open water passes.
10.3.1 Design
10.3.1.1 For minimum design pressure, see Section 5.1.2.
10.3.1.2 For secondary-coolant-side ultimate strength requirements, see Section 5.9.2.
10.3.1.3 Pressure vessels incorporated into shell-and-tube condensers shall comply with Chapter
12 Pressure Vessels.
10.3.1.4 Where the refrigerant inlet and outlet piping of shell-and-tube condensers can be
isolated,
The refrigerant side shall be pressure-relief protected per Section 15.2.
EXCEPTION:
Where the condenser is not a pressure vessel, it shall be protected from hydrostatic
overpressure per Section 15.5 in place of Section 15.2.
10.3.1.5 Where the secondary-coolant inlet and outlet piping of shell-and-tube condensers can be
automatically isolated, they shall be protected from hydrostatic overpressure.
10.3.2 Procedures/Testing
10.3.2.1 Shell-and-tube condensers shall be tested per the provisions of Section VIII, Division 1,
2013, ASME Boiler and Pressure Vessel Code [ref.3.2.1], if applicable, but at a
minimum, shall be strength tested to a minimum of 1.1 times the design pressure,
subsequently leak tested, and proven tight at a pressure not less than design.
Equipment Identification
10.3.3.1 Manufacturers producing shell-and-tube condensers shall provide the following
minimum data on a nameplate affixed to the equipment:
10.3.3.1.1 ASME stamp (where applicable)
10.3.3.1.2 National Board Number (where applicable)
10.3.3.1.3 Manufacturer’s name (preceded by the words “certified by” on nameplates of
integral ASME-stamped vessels)
10.3.3.1.4 Shell-side maximum allowable working pressure (MAWP) _____ at _____
temperature
10.3.3.1.5 Tube-side maximum allowable working pressure (MAWP) _____ at _____
temperature
10.3.3.1.6 Shell-side minimum design metal temperature (MDMT) _____ at _____ pressure
10.3.3.1.7 Tube-side minimum design metal temperature (MDMT) _____ at _____ pressure
10.3.3.1.8 Manufacturer’s serial number
10.3.3.1.9 Manufacturer’s model number (where applicable)
10.3.3.1.10 Year manufactured
10.3.3.1.11 Type of construction (in accordance with ref.3.2.1, where applicable)
10.3.3.2 Manufacturers producing shell-and-tube condensers with integral pressure vessels (e.g.
condensers with refrigerant in a shell qualifying as a pressure vessel) shall provide data
in accordance with the relevant “UG” sections of Section VIII, Division 1, 2013, ASME
Boiler and Pressure Vessel Code [ref.3.2.1] or equivalent.
10.3.4 Shell-and-Tube Condenser Installation Considerations
The following considerations, in addition to the Section 7.1 Common Considerations and Section 7.2
Locations, must be addressed when designing for the design of shell-and-tube condensers:
10.3.4.1 Consideration shall be given for proper clearance for the maintenance and/or
replacement of the condenser tubes.
10.3.4.2 Secondary-coolant supply and discharge connections shall be made in accordance with
the requirements of the authority having jurisdiction (AHJ).
10.3.4.3 Consideration shall be given to the location of the shell-and-tube condenser relative to
the receiver to assure the design allows sufficient refrigerant head for the refrigerant to
properly drain.
10.3.4.4 Shell-and-tube condensers shall be designed for the range of ambient temperatures at
the installed location.
10.3.5 Alarms and Detection
10.3.5.1 Shell-and-tube condensers located indoors in areas outside the machinery room shall
use, at a minimum, level 3 detection. See Section 17.6.
10.4 Plate Heat Exchanger Condensers
This section applies to plate heat exchanger condensers which are applied in closed-circuit
ammonia refrigeration systems.
Equipment covered by this section include plate heat exchanger condensers of the plate-and-shell
type and of the plate-and-frame type.
10.4.1 Design
10.4.1.1 For minimum design pressure, see Section 5.1.2.
10.4.1.2 For ultimate strength requirements, see Section 5.9.2.
10.4.1.3 Pressure vessels incorporated into plate heat exchanger condensers (e.g., the shell of a
plate-and-shell condenser with refrigerant in a shell qualifying as a pressure vessel)
shall comply with Chapter 12 Pressure Vessels.
10.4.1.4 Where the refrigerant inlet and outlet piping of refrigerant-containing plate packs can be
isolated, the refrigerant side of the plate pack shall be pressure-relief protected per
Section 15.5.
EXCEPTION:
Where the condenser is not a pressure vessel, it shall be protected from hydrostatic
overpressure per Section 15.5 in place of Section 15.2.
10.4.1.5 Where the process fluid (i.e., non-refrigerant) inlet and outlet lines of plate packs can be
automatically isolated, they shall be protected from hydrostatic overpressure per Section
15.5.
10.4.2 Procedures/Testing
10.4.2.1 Plate heat exchanger condensers shall be tested per the provisions of Section VIII,
Division 1, 2013, ASME Boiler and Pressure Vessel Code [ref. 3.2.1], if applicable, but
at a minimum, shall be strength tested to a minimum of 1.1 times the design pressure,
subsequently leak tested, and proven tight at a pressure not less than design.
Equipment Identification
10.4.3.1 Manufacturers producing plate heat exchanger condensers shall provide the following
minimum data on a nameplate affixed to the equipment.
10.4.3.1.1 ASME stamp (where applicable)
10.4.3.1.2 National Board Number (where applicable)
10.4.3.1.3 Manufacturer’s name (preceded by the words “certified by,” if the heat exchanger
is ASME-stamped)
10.4.3.1.4 Hot-side maximum allowable working pressure (MAWP) _____ at_____
temperature (where applicable)
10.4.3.1.5 Cold-side maximum allowable working pressure (MAWP) _____ at _____
temperature
10.4.3.1.6 Hot-side minimum design metal temperature (MDMT) _____ at_____ pressure
(where applicable)
10.4.3.1.7 Cold-side minimum design metal temperature (MDMT) _____ at _____
pressure
10.4.3.1.8 Manufacturer’s serial number
10.4.3.1.9 Manufacturer’s model number (where applicable)
10.4.3.1.10 Year manufactured
10.4.3.1.11 Test pressure (note test type; hydraulic or pneumatic)
10.4.3.1.12 Type of construction (in accordance with ref.3.2.1, where applicable)
10.4.3.2 Manufacturers producing plate heat exchanger condensers with integral pressure vessels
(e.g., plate-and-shell heat exchangers with refrigerant in a shell qualifying as a pressure
vessel) shall provide data in accordance with Section VIII, Division 1, 2013, ASME
Boiler and Pressure Vessel Code [ref.3.2.1] or equivalent.
10.4.4 Plate Heat Exchanger Condenser Installation Considerations
The following considerations, in addition to the Section 7.1 Common Considerations and Section 7.2
Locations, must be addressed when designing for the installation of Plate Heat Exchanger
condensers:
10.4.4.1 Secondary-coolant supply and discharge connections shall be made in accordance with
the requirements of the authority having jurisdiction (AHJ).
10.4.4.2 Consideration shall be given for proper clearance for the removal and replacement of
the condenser plates if this service is to be done in its installed location.
10.4.4.3 Consideration shall be given to the location of the plate heat exchanger condenser
relative to the receiver to assure the design allows sufficient refrigerant head for the
refrigerant to properly drain.
10.4.4.4 Plate heat exchanger type condensers shall be designed for the range of ambient
temperatures at the installed location.
10.4.5 Alarms and Detection
10.4.5.1 Plate heat exchanger condensers located indoors in areas outside the machinery room
shall use, at a minimum, level 3 detection. See Section 17.6.
10.5 Double-Pipe Condensers
This section applies to double-pipe condensers which are applied in closed-circuit ammonia
refrigeration systems.
Equipment covered by this section are double-pipe condensers with closed-water passes.
10.5.1 Design
10.5.1.1 For minimum design pressure, see Section 5.1.2.
10.5.1.2 For secondary-coolant-side ultimate strength requirements, see Section 5.9.2.
10.5.1.3 Pressure vessels incorporated into double-pipe condensers shall comply with
Chapter 12 Pressure Vessels.
10.5.1.4 Where the refrigerant inlet and outlet piping of double-pipe condensers can be
isolated, the refrigerant side shall be pressure-relief protected per Section 15.5.
EXCEPTION:
Where the condenser is not a pressure vessel it shall be protected from hydrostatic
overpressure per Section 15.5 in place of Section 15.2.
10.5.1.5 Where the secondary-coolant inlet and outlet piping of double-pipe condensers
can be automatically isolated, they shall be protected from hydrostatic
overpressure per Section 15.5.
10.5.2 Procedures/Testing
10.5.2.1 Double-pipe condensers shall be tested per the provisions of Section VIII,
Division 1, 2013, ASME Boiler and Pressure Vessel Code [ref.3.2.1], if
applicable, but at a minimum, shall be strength tested to a minimum of 1.1 times
the design pressure, subsequently leak tested, and proven tight at a pressure not
less than design.
10.5.3 Equipment Identification
10.5.3.1 Manufacturers producing double-pipe condensers shall provide the following minimum
data on a nameplate affixed to the equipment:
10.5.3.1.1 ASME stamp (where applicable)
10.5.3.1.2 National Board Number (where applicable)
10.5.3.1.3 Manufacturer’s name (preceded by the words “certified by” on nameplates of
integral ASME-stamped vessels)
10.5.3.1.4 Shell-side maximum allowable working pressure (MAWP) _____ at _____
temperature
10.5.3.1.5 Tube-side maximum allowable working pressure (MAWP) _____ at _____
temperature
10.5.3.1.6 Shell-side minimum design metal temperature (MDMT) _____ at _____ pressure
10.5.3.1.7 Tube-side minimum design metal temperature (MDMT) _____ at _____ pressure
10.5.3.1.8 Manufacturer’s serial number
10.5.3.1.9 Manufacturer’s model number (where applicable)
10.5.3.1.10 Year manufactured
10.5.3.2 Type of construction (in accordance with Section VIII, Division 1, 2013, ASME Boiler
and Pressure Vessel Code [ref.3.2.1], where applicable).
10.5.3.3 Manufacturers producing double-pipe condensers with integral pressure vessels (e.g.,
condensers with refrigerant in a shell qualifying as a pressure vessel) shall provide data
in accordance with the relevant “UG” sections of Section VIII, Division 1, 2013, ASME
Boiler and Pressure Vessel Code [ref.3.2.1] or equivalent.
10.5.4 Double-Pipe Condenser Installation Considerations
The following considerations, in addition to the Section 7.1 Common Considerations and Section 7.2
Locations, must be addressed when designing for the installation of Double-Pipe condensers:
10.5.4.1 Secondary-coolant supply and discharge connections shall be made in accordance with
the requirements of the authority having jurisdiction (AHJ).
10.5.4.2 Consideration shall be given for proper clearance for the removal and replacement of
the condenser pipes if this service is to be done in its installed location.
10.5.4.3 Consideration shall be given to the location of the Double-Pipe condenser relative to the
receiver to assure the design allows sufficient refrigerant head for the refrigerant to
properly drain.
10.5.4.4 Double-Pipe condensers shall be designed for the range of ambient temperatures at the
installed location.
10.5.5 Alarms and Detection
10.5.5.1 Double pipe condensers located indoors in areas outside the machinery room shall use,
at a minimum, level 3 detection. See Section 17.6.
Chapter 11 Evaporators
11.1 Forced-Air Evaporator Coils
This chapter applies to evaporator coils and micro-channel heat exchangers which are applied to
closed-circuit ammonia refrigeration systems.
11.1.1 Design
11.1.1.1 For minimum design pressure, see Section 5.1.2.
11.1.1.2 For ultimate strength requirements, see Section 5.9.2.
11.1.1.3 Where refrigerant coil inlet and outlet lines can be automatically isolated, they shall be
protected from hydrostatic overpressure per Section 15.5.
11.1.1.4 Protection from exposed rotating components, see Section 5.12.2.
11.1.1.5 Fan speeds shall not exceed the safe design speed recommended by the manufacturer.
11.1.1.6 Pressure vessels coupled to evaporators shall comply with Chapter 12 Pressure Vessels.
11.1.2 Procedures/Testing
11.1.2.1 Evaporator coils shall be strength tested to a minimum of 1.1 times the design pressure,
subsequently leak tested, and proven tight at a pressure not less than design.
11.1.3 Equipment Identification
The following data shall be provided on nameplates or labels affixed to the equipment or
components of the equipment:
11.1.3.1 Manufacturer’s name
11.1.3.2 Manufacturer’s serial number
11.1.3.3 Manufacturer’s model number
11.1.3.4 Year manufactured
11.1.3.5 Design pressure
11.1.3.6 Direction of fan rotation (if supplied)
11.1.3.7 Electric motor size for fans (if supplied)
11.1.3.8 Electric defrost heater and drain pan heater ratings (as applicable)
11.1.3.9 Electric supply: volts, full load amps, frequency (Hz), phase
11.1.3.10 Minimum Design Metal Temperature (MDMT), if applicable, or at a minimum,
submitted with the equipment manufacturer’s data sheets.
11.1.4 Forced-Air Evaporator Coil Installation Considerations
The following considerations, in addition to the Section 7.1 Common Considerations and Section 7.2
Locations, must be addressed when designing for the installation of forced-air evaporator coils in
areas other than the machinery room:
11.1.4.1 Manufacturer’s recommended clearances for unobstructed airflow at the inlet and
outlet of the forced-air evaporator shall be provided.
11.1.4.2 A means for preventing freezing inside condensate drain lines shall be provided where
lines are exposed to freezing temperatures. (e.g. sufficient line slope, heat trace,
insulation, clean-out provisions).
11.1.5 Alarms and Detection
11.1.5.1 Forced-air evaporators located in refrigerated areas outside the machinery room (e.g.
freezers, cold rooms, docks, corridors) shall require at a minimum, level 2 detection.
See Section 17.6 for detection levels.
11.2 Shell-and-Tube Evaporators (with refrigerant in shell)
This section applies to shell-and-tube evaporators which are applied to closed-circuit ammonia
refrigeration systems at any temperature level when evaporating refrigerant is used to cool another
fluid.
11.2.1 Design
11.2.1.1 For minimum design pressure, see Section 5.1.2.
11.2.1.2 Pressure vessels coupled to shell-and-tube evaporators shall comply with Chapter
12 Pressure Vessels.
11.2.1.3 Where the tube-side inlet and outlet lines of shell-and-tube evaporators with the
refrigerant in the shell are automatically isolated, the tube-side shall be protected from
hydrostatic overpressure per Section 15.5.
11.2.2 Procedures/Testing
11.2.2.1 Shell-and-tube evaporators shall be tested per the provisions of Section VIII, Division 1,
2013, ASME Boiler and Pressure Vessel Code [ref.3.2.1], where applicable, but at a
minimum, shall be strength tested to a minimum of 1.1 times the design pressure,
subsequently leak tested, and proven tight at a pressure not less than design.
11.2.3 Equipment Identification
11.2.3.1 Manufacturers producing shell-and-tube evaporators for refrigerant in the shell shall
provide data in accordance with the relevant “UG” sections of Section VIII, Division 1,
2013, ASME Boiler and Pressure Vessel Code [ref.3.2.1], but in any case shall provide
the following minimum data on a nameplate affixed to the equipment:
11.2.3.1.1 ASME stamp (where applicable)
11.2.3.1.2 National Board Number (where applicable)
11.2.3.1.3 Manufacturer’s name (preceded by the words “certified by,” if the vessel is
ASME-stamped)
11.2.3.1.4 Shell side maximum allowable working pressure (MAWP) _____ at _____
temperature
11.2.3.1.5 Tube side maximum allowable working pressure (MAWP) _____ at _____
temperature
11.2.3.1.6 Shell side minimum design metal temperature (MDMT) _____ at _____ pressure
11.2.3.1.7 Tube side minimum design metal temperature (MDMT) _____ at _____ pressure
11.2.3.1.8 Manufacturer’s serial number
11.2.3.1.9 Manufacturer’s model number (where applicable)
11.2.3.1.10 Year manufactured
11.2.3.1.11 Test pressure (note test type; hydraulic or pneumatic)
11.2.3.1.12 Type of construction (in accordance with Section VIII, Division 1, 2013, ASME
Boiler and Pressure Vessel Code [ref.3.2.1], where applicable)
11.2.4 Shell-and-Tube Evaporators (with refrigerant in shell) Installation Considerations
11.2.4.1 See Section 11.3.4.
11.2.5 Alarms and Detection
11.2.5.1 See Section 11.3.5.
11.3 Shell-and-Tube Evaporators (with refrigerant in tubes)
This section applies to shell-and-tube evaporators which are applied to closed-circuit ammonia
refrigeration systems at any temperature level when evaporating refrigerant is used to cool another
fluid.
11.3.1 Design
11.3.1.1 For minimum design pressure, see Section 5.1.2.
11.3.1.2 Where the tube-side inlet and outlet lines of shell-and-tube evaporators (with refrigerant
in tubes) can be isolated, the tube-side shall be hydrostatic over- pressure-relief
protected per Section 15.5.
EXCEPTION:
Where the tube-side of the evaporator is built and stamped in accordance with Section
VIII, Division 1, 2013, ASME Boiler and Pressure Vessel Code [ref.3.2.1] it shall
protected from overpressure per Section 15.2.
11.3.1.3 Pressure Vessels coupled to shell-and-tube evaporators with refrigerant in the tubes
shall comply with Chapter 12 Pressure Vessels.
11.3.1.4 Tube-side shall comply with the rules of Section 5 of ASME B31.5-2013 [ref.3.2.2]
and/or with Section VIII, Division 1, 2013, ASME Boiler and Pressure Vessel Code
[ref.3.2.1].
11.3.1.5 Heat loads from cleaning operations and process loads shall be considered when
designing the relief capacity and control of process heat exchangers.
11.3.2 Procedures/Testing
11.3.2.1 Shell-and-tube evaporators shall be tested per the provisions of Section VIII, Division 1,
2013, ASME Boiler and Pressure Vessel Code [ref.3.2.1], if applicable, but at a
minimum, shall be strength tested to a minimum of 1.1 times the design pressure,
subsequently leak tested, and proven tight at a pressure not less than design.
11.3.3 Equipment Identification
11.3.3.1 Manufacturers producing shell-and-tube evaporators for refrigerant in the tubes shall
provide the data in accordance with the relevant “UG” section of Section VIII, Division
1, 2013, ASME Boiler and Pressure and Vessel Code [ref.3.2.1], where applicable, and
in any case shall provide the following minimum data on a nameplate affixed to the
equipment:
11.3.3.1.1 ASME stamp (where applicable)
11.3.3.1.2 National Board Number (where applicable)
11.3.3.1.3 Manufacturer’s name (preceded by the words “certified by,” if the vessel is
ASME-stamped)
11.3.3.1.4 Shell side maximum allowable working pressure (MAWP) _____ at _____
temperature
11.3.3.1.5 Tube side maximum allowable working pressure (MAWP) _____ at _____
temperature
11.3.3.1.6 Shell side minimum design metal temperature (MDMT) _____ at _____ pressure
11.3.3.1.7 Tube side minimum design metal temperature (MDMT) _____ at _____ pressure
11.3.3.1.8 Manufacturer’s serial number
11.3.3.1.9 Manufacturer’s model number (where applicable)
11.3.3.1.10 Year manufactured
11.3.3.1.11 Test pressure (note test type; hydraulic or pneumatic)
11.3.3.1.12 Type of construction (in accordance with Section VIII, Division 1, 2013, ASME
Boiler and Pressure and Vessel Code [ref.3.2.1], where applicable)
11.3.4 Shell-and-Tube Evaporators (with refrigerant in shell or in tubes) Installation
Considerations
The following considerations, in addition to Section 7.1 Common Considerations and Section 7.2
Locations, must be addressed when designing for the installation of shell-and-tube evaporators:
11.3.4.1 Consideration shall be given for proper clearance for the maintenance and/or
replacement of the evaporator tubes.
11.3.4.2 Water supply and discharge connections shall be made in accordance with the
requirements of the authority having jurisdiction (AHJ).
11.3.4.3 The ambient temperatures in the area the shell-and-tube evaporator is installed shall be
considered in the design of the secondary-coolant side of the evaporator.
11.3.5 Alarms and Detection
11.3.5.1 Shell-and-Tube evaporators (with refrigerant in shell or in tubes) located indoors in
areas outside the machinery room shall use, at a minimum, level 2 detection. See
Section 17.6.
11.4 Plate Heat Exchanger Evaporators
This section applies to plate heat exchanger evaporators which are applied to closed-circuit
ammonia refrigeration systems.
Equipment covered by this section include plate heat exchanger evaporators of the plate-and-shell
type, and of the plate-and-frame type in which the heat transfer plate stack is axially contained
between two pressure plates and where the plate joints may be fully elastomeric, paired plate sets
welded with adjacent sets elastomeric, fully welded, or fully nickel brazed.
11.4.1 Design
11.4.1.1 For minimum design pressure, see Section 5.1.2.
11.4.1.2 For ultimate strength requirements, see Section 5.9.2.
11.4.1.3 Pressure vessels coupled to plate heat exchanger evaporators (e.g. plate-and-shell
designed with the refrigerant in a shell qualifying as a pressure vessel) shall comply
with Chapter 12 Pressure Vessels.
11.4.1.4 Where the refrigerant inlet and outlet lines of refrigerant-containing plate packs can be
isolated, the refrigerant side of the plate pack shall be hydrostatic overpressure-relief
protected per Section 15.5.
EXCEPTION:
Where the evaporator is not a pressure vessel, it shall be protected from hydrostatic
overpressure per Section 15.5 in place of Section 15.2.
11.4.1.5 Where the process fluid (i.e., non-refrigerant) inlet and outlet lines of plate packs can be
isolated, they shall be protected from hydrostatic overpressure per Section 15.5 on the
process side.
11.4.1.6 Heat loads from cleaning operations or process loads shall be considered when
designing the relief capacity and control of process heat exchangers.
11.4.2 Procedures/Testing
11.4.2.1 Plate heat exchanger evaporators shall be tested per the provisions of Section VIII,
Division 1, 2013, ASME Boiler and Pressure Vessel Code [ref.3.2.1], if applicable, but
a minimum, shall be strength tested to a minimum of 1.1 times the design pressure,
subsequently leak tested, and proven tight at a pressure not less than design.
11.4.3 Equipment Identification
11.4.3.1 Manufacturers producing plate heat exchanger evaporators shall provide the following
minimum data on a nameplate affixed to the equipment:
11.4.3.1.1 ASME stamp (where applicable)
11.4.3.1.2 National Board Number (where applicable)
11.4.3.1.3 Manufacturer’s name (preceded by the words “certified by,” if the vessel is
ASME-stamped)
11.4.3.1.4 Hot-side maximum allowable working pressure (MAWP) _____ at _____
temperature (where applicable)
11.4.3.1.5 Cold-side maximum allowable working pressure (MAWP) _____ at _____
temperature
11.4.3.1.6 Hot-side minimum design metal temperature (MDMT) _____ at _____ pressure
(where applicable)
11.4.3.1.7 Cold-side minimum design metal temperature (MDMT) _____ at _____ pressure
11.4.3.1.8 Manufacturer’s serial number
11.4.3.1.9 Manufacturer’s model number (where applicable)
11.4.3.1.10 Year manufactured
11.4.3.1.11 Test pressure (note test type; hydraulic or pneumatic)
11.4.3.1.12 Type of construction (in accordance with Section VIII, Division 1, 2013,
ASME Boiler and Pressure Vessel Code [ref.3.2.1], where applicable)
11.4.3.2 Manufacturers producing plate heat exchanger evaporators incorporating pressure
vessels (e.g., plate-and-shell evaporators with refrigerant in a shell qualifying as a
pressure vessel) shall provide data in accordance with the “UG” section of Section VIII,
Division 1, 2013, ASME Boiler and Pressure Vessel Code [ref.3.2.1], where applicable.
11.4.4 Plate Heat Exchanger Evaporators Installation Considerations
The following considerations, in addition to the Section 7.1 Common Considerations and Section 7.2
Locations, must be addressed when designing for the installation of plate heat exchanger
evaporators.
11.4.4.1 Consideration shall be given for proper clearance for the maintenance and/or
replacement of the evaporator plates.
11.4.4.2 Water supply and discharge connections shall be made in accordance with the
requirements of the authority having jurisdiction (AHJ).
11.4.4.3 The ambient temperatures in the area the plate heat exchanger evaporator is installed
shall be considered in the design of the secondary-coolant side of the evaporator.
11.4.5 Alarms and Detection
11.4.5.1 Plate Heat Exchanger evaporators located indoors in areas outside the machinery room
shall use, at a minimum, level 2 detection. See Section 17.6.
11.5 Scraped (Swept) Surface Heat Exchangers
This section applies to scraped (swept) surface heat exchangers which are applied to closed-circuit
ammonia refrigeration systems.
11.5.1 Design
11.5.1.1 For minimum design pressure, see Section 5.1.2.
11.5.1.2 Pressure vessels coupled to scraped (swept) surface heat exchangers shall comply with
Chapter 12 Pressure Vessels.
11.5.1.3 Heat loads from cleaning operations or process loads shall be considered when
designing the relief capacity and control of scraped surface heat exchangers.
11.5.2 Procedures/Testing
11.5.2.1 Scraped (swept) surface heat exchangers shall be tested per the provisions of Section
VIII, Division 1, 2013, ASME Boiler and Pressure Vessel Code [ref.3.2.1], if
applicable, but at a minimum, shall be strength tested to a minimum of 1.1 times the
design pressure, subsequently leak tested, and proven tight at a pressure not less than
design.
11.5.3 Equipment Identification
11.5.3.1 Manufacturers producing scraped (swept) surface heat exchangers for refrigerant in the
shell shall provide data in accordance with the relevant “UG” sections of Section VIII, Division 1,
2013, ASME Boiler and Pressure Vessel Code [ref.3.2.1] or equivalent, but in any case shall provide
the following minimum data on a nameplate affixed to the equipment:
11.5.3.1.1 ASME stamp (where applicable)
11.5.3.1.2 National Board Number (where applicable)Manufacturer’s name (preceded by the
words “certified by,” if the vessel is
ASME-stamped)
11.5.3.1.4 Shell maximum allowable working pressure (MAWP) _____ at _____
temperature
11.5.3.1.5 Shell minimum design metal temperature (MDMT) _____ at _____ pressure
11.5.3.1.6 Manufacturer’s serial number
11.5.3.1.7 Manufacturer’s model number (where applicable)
11.5.3.1.8 Year manufactured
11.5.3.1.9 Test pressure (note test type; hydraulic or pneumatic)
11.5.3.1.10 Type of construction (in accordance with Section VIII, Division 1, 2013, ASME
Boiler and Pressure Vessel Code [ref.3.2.1], where applicable)
11.5.4 Scraped (Swept) Surface Heat Exchanger Installation Considerations
The following considerations, in addition to the Section 7.1 Common Considerations and Section 7.2
Locations, must be addressed when designing for the installation of scraped (swept) surface heat
exchangers:
11.5.4.1 Consideration shall be given for proper clearance for the maintenance and/or
replacement of components.
11.5.4.2 The ambient temperatures in the area the scraped (swept) surface heat exchanger is
installed shall be considered in the design.
11.5.6 Alarms and Detection
11.5.6.1 Scraped (Swept) Surface Heat Exchangers located indoors in areas outside the
machinery room shall use, at a minimum, level 2 detection. See Section 17.6.
11.6 Jacketed Tanks
This section applies to jacketed tanks which are applied to closed-circuit ammonia refrigeration
systems.
11.6.1 Design
11.6.1.1 For minimum design pressure, see Section 5.1.2.
11.6.1.2 For ultimate strength requirements, see Section 5.9.2.
11.6.1.3 Pressure vessels coupled to jacketed tanks evaporators shall comply with Chapter 12
Pressure Vessels.
11.6.1.4 Where the refrigerant inlet and outlet lines of the jacketed tank refrigerant-containing
evaporator can be isolated, the refrigerant side of the evaporator shall be hydrostatic
overpressure-relief protected per Section 15.5.
EXCEPTION:
Where the jacketed tank evaporator is not a pressure vessel, it shall be protected from
hydrostatic overpressure per Section 15.5 in place of Section 15.2.
11.6.1.5 Heat loads from cleaning operations or process loads shall be considered when
designing the relief capacity and control of jacked tanks.
11.6.2 Procedures/Testing
11.6.2.1 Jacketed tanks shall be tested per the provisions of Section VIII, Division 1, 2013,
ASME Boiler and Pressure Vessel Code [ref.3.2.1], if applicable, but at a minimum,
shall be strength tested to a minimum of 1.1 times the design pressure, subsequently
leak tested, and proven tight at a pressure not less than design.
11.6.3 Equipment Identification
11.6.3.1 Manufacturers producing jacketed tanks shall provide the following minimum data on a
nameplate affixed to the equipment:
11.6.3.1.1 ASME stamp (where applicable)
11.6.3.1.2 National Board Number (where applicable)
11.6.3.1.3 Manufacturer’s name (preceded by the words “certified by,” if the vessel is
ASME-stamped)
11.6.3.1.4 Maximum allowable working pressure (MAWP) _____ at _____ temperature
(where applicable)
11.6.3.1.5 Minimum design metal temperature (MDMT) _____ at _____ pressure
(where applicable)
11.6.3.1.6 Manufacturer’s serial number
11.6.3.1.7 Manufacturer’s model number (where applicable)
11.4.3.1.8 Year manufactured
11.4.3.1.9 Test pressure (note test type; hydraulic or pneumatic)
11.4.3.1.10 Type of construction (in accordance with Section VIII, Division 1, 2013,
ASME Boiler and Pressure Vessel Code [ref.3.2.1], where applicable)
11.6.3.2 Manufacturers producing jacketed tanks incorporating pressure vessels (e.g., plate-and-
shell evaporators with refrigerant in a shell qualifying as a pressure vessel) shall provide
data in accordance with the “UG” section of Section VIII, Division 1, 2013, ASME
Boiler and Pressure Vessel Code [ref.3.2.1], where applicable.
11.6.4 Jacketed Tank Installation Considerations
The following considerations, in addition to the Section 7.1 Common Considerations and Section 7.2
Locations, must be addressed when designing for the installation of jacketed tanks.
11.6.4.1 The ambient temperatures in the area the jacketed tank is installed shall be considered
in the design.
11.6.5 Alarms and Detection
11.6.5.1 Jacketed tanks located indoors in areas outside the machinery room
shall use, at a minimum, level 2 detection. See Section 17.6.
Chapter 12 Pressure Vessels
This chapter applies to pressure vessels for use in closed-circuit stationary ammonia refrigeration
systems.
12.1 Design
12.1.1 For minimum design pressure, see Section 5.1.2.
EXCEPTION:
When ammonia liquid is to be transferred from pressure vessels by pressurized ammonia gas,
the pressure vessel design pressure shall accommodate the maximum possible transfer
pressure and take into account the lowest possible coincident metal temperature.
12.1.2 Pressure vessels exceeding 6 in [15 cm] inside diameter shall comply with Section VIII,
Division 1, 2013, ASME Boiler and Pressure Vessel Code [ref.3.2.1] and shall comply with
paragraph UG-119(e) of that Code or equivalent (e.g. Conformité Européenne (CE) –
European Union (EU) conforming to the European Pressure Equipment Directive (PED)]
covering the requirements for design, fabrication, inspection and testing during construction
of unfired pressured vessels.
NOTE:
For pressure vessels having inside diameters less than 6 in [15 cm], see Section 5.9.2 for
ultimate strength requirements.
12.1.3 For vessels larger than 6” [150 mm] in diameter but less than 10 cubic feet [0.283 m³] in
internal volume, the pressure relief valve connection shall not be smaller than ¾” [20 mm].
For vessels with an internal volume of 10 cubic feet [0.283 m³] or larger, the pressure relief
valve connection shall not be smaller than 1” [25 mm].
12.1.4 Pressure vessels shall be provided with adequate opening(s) for the attachment of pressure
relief device(s) as required in Section 15.3.2.
12.1.5 The heads of pressure vessels shall be hot-formed or stress relieved after cold-forming.
NOTE:
It is recommended that high-side vessels receive post-weld heat treatment per Appendix H
(Informative).
12.1.6 A vessel shall be designed and stamped with a MDMT (minimum design metal temperature)
no higher than its lowest expected operating temperature.
12.1.7 Carbon Steel vessels shall be designed and specified with a minimum of 1/16" [1.6 mm]
corrosion allowance.
12.1.8 It shall be determined that the pressure vessel is piped for the pressure and temperature
limitations as specified on the name plate data.
12.1.9 Alteration(s) to pressure vessels shall be allowed only as directed by the authority having
jurisdiction (AHJ). The alteration(s) shall only be performed by a qualified service in
accordance with the authority having jurisdiction (AHJ). A re-stamping shall be applied as
directed by the authority having jurisdiction (AHJ) when the modification is completed, if
required.
12.2 Procedures/Testing
12.2.1 Pressure vessels shall be tested per the provisions of Section VIII, Division 1, 2013, ASME
Boiler and Pressure Vessel Code [ref.3.2.1], if applicable, but at a minimum, shall be strength
tested hydrostatically to a minimum of 1.3 times the design pressure or air tested to a
minimum of 1.1 times the design pressure, subsequently leak tested, and proven tight at a
pressure not less than design.
12.3 Equipment Identification
12.3.1 Manufacturers producing pressure vessels shall provide data in accordance with the
requirements of the relevant “UG” sections of Section VIII, Division 1, 2013, ASME Boiler
and Pressure Vessel Code [ref. 3.2.1], but in any case shall provide the following minimum
data on a nameplate affixed to the equipment as specified in Section 12.3.2:
12.3.1.1 ASME stamp (where applicable)
12.3.1.2 National Board Number (where applicable)
12.3.1.3 Manufacturer’s name (preceded by the words “certified by,” if the vessel is ASME
stamped)
12.3.1.4 Maximum allowable working pressure (MAWP) _____ at _____ temperature
12.3.1.5 Minimum design metal temperature (MDMT) _____ at _____ pressure
12.3.1.6 Manufacturer’s serial number
12.3.1.7 Year of manufacture
12.3.1.8 Manufacturer’s model number (where applicable)
12.3.1.9 Type of construction (in accordance with Section VIII, Division 1, 2013, ASME Boiler
and Pressure Vessel Code [ref.3.2.1], where applicable)
12.3.1.10 A stamp shall be affixed to the equipment that includes the minimum design metal
temperature (MDMT) that it is operated at in accordance with Section VIII, Division 1,
2013, ASME Boiler and Pressure Vessel Code, [ref.3.2.1].
12.3.2 Nameplate Mounting
12.3.2.1 See Section 5.10.7.
12.3.2.2 If any pressure vessel is insulated, the name plate shall be mounted on an approved
stand-off so it is not covered or the insulation at the nameplate location on the pressure
vessel shall be removable to allow for name plate inspection.
12.4 Pressure Vessel Installation Considerations
The following considerations, in addition to the Section 7.1 Common Considerations and Section 7.1
Locations, must be addressed when designing for the installation of pressure vessels:
12.4.1 Consideration shall be given for proper clearance for maintenance and physical protection.
See Section 7.1.1.
12.4.2 Pressure vessels supported from the ground shall rest on a concrete or other foundation
and/or shall come with a support for sitting directly on and anchoring to the foundation.
12.5 Alarms and Detection
12.5.1 Pressure vessels located indoors in areas outside the machinery room shall use at a minimum,
level 3 detection. See Section 17.6.
Chapter 13 Piping
This chapter applies to piping for use in closed-circuit stationary ammonia refrigeration systems.
13.1 The design, fabrication, examination, and testing of the piping, whether fabricated in a shop or as
a field erection, shall comply with ASME B31.5-2013, Refrigeration Piping and Heat Transfer
Components [ref.3.2.2], except where noted.
13.2 Pipe, Tubing, Fittings, and Flanges
13.2.1 Material
13.2.1.1 The piping materials, whether fabricated in a shop or as a field erection, shall comply
with ASME B31.5-2013, Refrigeration Piping and Heat Transfer Components
[ref.3.2.2], except where noted.
EXCEPTION:
Other materials shall be acceptable if the material properties are suitable for the
intended duty and meet the specifications noted. See: Applicability Section 1.3.2
Alternative Materials and Methods.
13.2.1.2 ASTM A120, A53/A120, or A53-Type F pipe and cast iron or wrought iron pipe
(ref.3.1.4.2 and ref.3.1.4.1) shall not be used for close-circuit ammonia refrigeration
systems.
13.2.1.3 Zinc, copper, and copper alloys shall not be used in contact with or for containment of
ammonia. Copper-containing anti-seize and/or lubricating compounds shall not be used
in ammonia piping joints.
13.2.2 Minimum Pipe Wall Thickness
13.2.2.1 Minimum pipe wall thickness shall be based on the properties of the selected pipe
material, the design working pressure and shall comply with the requirements of ASME
B31.5-2013 (ref. 3.2.2).
EXCEPTION 1:
All carbon and stainless steel threaded pipe shall be minimum Schedule 80 for all sizes.
EXCEPTION 2:
All carbon steel pipe 1-1⁄2 inch and smaller shall be minimum Schedule 80.
EXCEPTION 3:
All stainless steel pipe 1-1⁄2 inch and smaller shall be minimum Schedule 40.
NOTE: Refer to Appendix L Pipe, Fittings, Flanges, and Bolting (informative) criteria
historically applied to ammonia piping in closed circuit ammonia refrigeration
systems.
13.2.3 Minimum Tubing Wall Thickness
NOTE: Tubing is used for compressor lubrication lines; small bore pressure sensing lines;
hydrostatic relief lines; etc.
13.2.3.1 Minimum tubing wall thickness shall be based on the properties of the selected material
and the greater of the design working pressure or the requirement specified by the
manufacturer of the compression ferrule used for the fitting connection.
13.2.3.2 The use of carbon steel tubing and compression fittings shall be limited to compressor
and compressor package lubricant lines.
13.2.4 Pipe Fittings
13.2.4.1 All butt weld (BW) fittings shall match pipe schedules.
EXCEPTION:
The schedule of BW fittings joining pipe at a wall thickness change shall match the
schedule of the thicker wall pipe. The internal diameter of the end of the fitting
connecting to the thinner wall pipe shall be machined and/or ground to match.
13.2.4.2 All socket weld (SW) and screwed fittings shall be minimum class 3000 and
manufactured from forged or cast steel.
13.2.4.3 Threaded joints shall not be used for refrigerant piping larger than 2”.
13.2.4.4 All threaded piping shall be minimum of Schedule 80.
13.2.5 Pipe Flanges
13.2.5.1 Flanges in accordance with ANSI ASME Standard B16.5 shall comply with the
requirements of ASME B31.5-2013 (ref. 3.2.2), be raised face type and the flange class
shall be based on the design working pressure (DWP) and the maximum working
temperature at DWP.
13.2.5.2 Gaskets shall be correctly dimensioned for the flange set.
13.3 Refrigerant Valves and Strainers
This section applies to the equipment and system design requirements for valves used in the ammonia-
containing and the lubricant-containing parts of closed-circuit ammonia refrigeration systems.
EXCEPTION 1:
Valves within the refrigerant-containing envelope of other equipment such as slide valves in screw
compressors.
EXCEPTION 2:
Safety relief valves.
Refer to Standard IIAR 3-2012 (ref.3.5.2) for the manufacturing, design and performance requirements
of ammonia refrigeration valves and strainers.
13.3.1 Valves in Equipment and System Design
13.3.1.1 Valves shall be oriented in accordance with the manufacturer’s specification.
EXCEPTION 1:
The equipment and system design drawing(s) shall clearly show the required valve
orientation in all cases where normal fluid flow through the valve is opposite to the flow
direction marking on the valve.
EXCEPTION 2:
The equipment and system design drawing(s) shall clearly show the required valve
spindle/stem orientation where a specific orientation is necessary for proper operation of
the system.
13.3.1.2 Valve gasket materials shall match valve manufacturer’s specifications and be of the
thickness specified.
13.3.2 Check valves installed upstream of other automatic valves have the potential to trap liquid.
Provision shall be made for overpressure relief. Provision for liquid removal to facilitate
maintenance shall be located downstream of the check valve. See Section 15.5.
13.3.3 Strainers shall be fitted with provision for refrigerant removal to facilitate maintenance.
13.3.4 Shut-off (Stop) valves used to isolate equipment, control valves, controls or other
components from other parts of the system for the purpose of maintenance or repair shall be
capable of being locked out. See Section 13.5.7 for locations where shut-off (stop) valves
shall be installed in the refrigerant piping.
13.3.4.1 Control valves and other valves without a manually operable and lockable actuating
element intended to stop flow for isolation purposes are not shut-off valves.
EXAMPLE: Solenoid valves, check valves.
13.3.5 Shut-off (Stop) valves connecting refrigerant-containing parts to atmosphere shall be capped,
plugged, blanked, or locked closed during shipping, testing, operating, servicing, or standby
conditions if they are not in use. See Standard IIAR 5-2013 (ref.3.5.4).
13.3.6 Valves required for system emergency shutdown procedure(s) shall be readily accessible and
appropriately identified – See Section 5.10.4 Valve Tagging.
13.4 Piping Hangers and Supports
13.4.1 Piping hangers and supports shall carry the weight of the piping, as well as any other
expected loads.
EXAMPLE: refrigerant weight; insulation; frost/ice; seismic/wind, thermal loads; etc.
13.4.2 Sway bracing shall be included where necessary.
13.4.3 Threaded hot rolled steel hanger rods are a permissible material. When used, they shall meet
or exceed ASTM A575-96 [ref.3.3.4]).
13.4.4 Anchors, their attachment points and methods shall be sufficient to bear all loads.
13.4.5 Mechanically expanded concrete anchor bodies shall not be adjusted (e.g. axially spun) after
being set.
NOTES:
a. ASME B31.5-2013 [ref.3.2.2] provides guidance for certain pipe support and hanger
components, protective coatings, etc.
b. See Appendix F (Informative) - Pipe Hanger Spacing, Hanger Rod Sizing, and Loading
for additional information.
13.4.6 For piping that is insulated, supports shall be designed and/or the insulation shall be selected
to avoid damage to the insulation from compression.
13.5 Location of Refrigerant Piping
13.5.1 Refrigerant piping crossing an open space that affords passageway in any building shall not
be less than 7.25 feet (2.2 m) above the floor unless the piping is located against the ceiling
of such space and is permitted by the authority having jurisdiction (AHJ).
13.5.2 Refrigerant piping shall not obstruct passages to means of egress.
13.5.3 Refrigerant piping shall not be placed in any elevator, dumbwaiter, or other shaft containing
a moving object.
13.5.4 Refrigerant piping shall not be installed in an enclosed public stair, landing, or means of
egress.
13.5.5 Refrigerant piping shall be isolated and supported to prevent damage from vibration, stress,
corrosion and physical impact.
13.5.6 Installing refrigerant piping underground is not prohibited. Any such piping installed
underground shall be protected against corrosion. Refrigerant piping installed in concrete
floors shall be encased in pipe duct.
13.5.7 Shut-off (Stop) valves shall be installed in the refrigerant piping of a refrigeration system at
the following locations:
13.5.7.1 At the inlet and outlet of a positive-displacement-type compressor, compressor unit, or
condensing unit.
13.5.7.2 At the main feed inlet(s) and outlet(s) of individual refrigeration equipment loads.
13.5.7.3 At the refrigerant inlet and outlet of a pressure vessel containing liquid refrigerant and
having an internal gross volume exceeding three (3) cubic feet (0.085 cubic meters).
EXCEPTION 1:
In lieu of providing shut-off (stop) valves at each serviceable component, packaged systems
or portions of built-up systems are permitted to have pump-down arrangements that permit the
safe removal or isolation of refrigerant for servicing one or more components.
EXCEPTION 2:
Shut-off (Stop) valves are not mandatory between a refrigeration equipment load and a
pressure vessel containing liquid refrigerant where a single load is piped into a single
pressure vessel (e.g. surge-fed evaporator piped into a surge drum).
Chapter 14 Packaged Systems and Components
This chapter applies to the design and fabrication of packaged closed-circuit ammonia refrigeration
systems and/or components of a system. These packages may or may not be enclosed. See Chapter 2
Definitions - Equipment Enclosure and Section 5.11.
14.1 General
14.1.1 Packaged systems and components shall be designed, constructed and installed in accordance
with the applicable chapters of Part 2 Design Considerations Affecting Construction.
14.1.2 The equipment and components shall be laid out on the package to provide clearances for
the safe and efficient service, maintenance, component replacement and operation per
manufacturer’s requirements.
14.1.3 Equipment, components and piping installed as part of a package shall be located in such a
manner as to allow safe egress from any part of the package in the event of an emergency.
14.1.4 Packages that are enclosed at point of fabrication or after installation shall be vented for the
proper operation of the equipment and for emergency ventilation in case of an ammonia leak.
Refer to Section 7.18 Ventilation.
14.1.5 Packages enclosed or not enclosed shall take into account installation considerations in
regards to location. See Section 7.2 Locations.
14.1.6 Equipment and components incorporated into packaged systems shall comply with the
applicable chapters of Part 3 Equipment and Components.
14.2 Design
14.2.1 The structure of the package shall be properly designed to hold the operating weight of all the
equipment and components.
14.2.2 The structure of the package shall be designed for the stresses caused by shipping and
rigging. Temporary supports and bracing may be used. Rigging instructions shall be
provided to accommodate the install of the structure.
14.2.3 The structure of the package shall be designed to allow for any loads and/or stresses that will
be imposed on the package after installation and start-up, including environmental factors
such as snow, ice, wind, and seismic forces.
14.2.4 Packaged equipment shall have valved pump out connections for removal of ammonia.
14.2.5 The package shall be designed for use in the lowest ambient temperatures expected in which
it will operate.
14.2.6 The package shall be designed for use in the highest ambient temperatures expected in which
it will operate.
14.2.7 The package shall be designed for the environment it is installed to maintain its integrity
during its working life.
14.2.8 All manually operated valves shall be accessible. Isolation valve(s) identified as being part
of a system emergency shutdown procedure(s) shall be directly operable or chain-operated
from a permanent work surface. See Section 5.10.4 for Valve Tagging.
14.2.9 Enclosed packages that require entrance for service, maintenance, inspection or operation
shall be equipped with ventilation in accordance with the applicable chapters of Part 2
Design Considerations Affecting Construction.
14.2.10 Pipes (where applicable) shall be labeled. See Section 5.10.5 Pipe Marking.
14.2.11 Equipment shall be labeled. See Section 5.10.6 Equipment Labeling.
14.2.12 Packages shall be equipped with lighting or installed in locations with light fixtures that
provide a minimum of 30 foot-candles [320 lumens/m2] at the working level of 36 in [0.9
m] above the floor or platform.
14.2.13 Enclosed packages that require entrance for service, maintenance, inspection or operation
shall have lighting control located at entrances. If continuous lighting exists, the lighting
control does not need to be located at the entrances.
14.2.14 Enclosed packages that require entrance for service, maintenance, inspection or operation
shall be equipped with ammonia detection in accordance with Chapter 17.
14.3 Fabrication
14.3.1 All equipment shall be set on the package to meet manufacturer’s recommendations
including proper support and clearances.
14.3.2 All components and piping shall be properly supported to allow for transporting and rigging.
Temporary supports and bracing may be used.
14.3.3 Stationary or temporary rigging points shall be provided as required to position the package.
14.3.4 All ammonia piping materials and installation shall meet the requirements of this and
referenced standards.
14.3.5 Piping shall be properly pressure tested after fabrication and any leaks repaired. The package
shall be shipped with a holding charge of dry nitrogen.
14.3.6 Electrical equipment and wiring shall be installed in accordance with the National Electric
Code (NEC) and the authority having jurisdiction (AHJ).
14.3.7 Gas fuel devices and equipment used with refrigeration systems in the package shall be
installed in accordance with approved safety standards and the requirements of the AHJ.
14.4 Alarms and Detection
14.4.1 Packaged systems and components located indoors in areas outside the machinery room shall
use the minimum ammonia refrigerant alarms and detection level per the applicable chapters
of Part 3 Equipment and Components (e.g. minimum level 3 is required if the system or
component is or includes a compressor, pressure vessel, and/or refrigerant pump, minimum
of level 2 is required if the system or component is, or includes, a condenser and/or an
evaporator).
Chapter 15 Overpressure Protection Devices
This chapter applies to pressure relief devices installed on stationary closed-circuit ammonia
refrigeration systems for the purpose of relieving excess pressure due to fire or other abnormal
conditions.
NOTE: Informative Appendix I provides additional information for overpressure protection.
15.1 Pressure Relief Devices
15.1.1 Every closed-circuit ammonia refrigeration system shall be protected by a pressure relief
device in accordance with Section VIII, Division 1, 2013, ASME Boiler and Pressure Vessel
Code [ref.3.2.1] and specific requirements set forth in this Standard.
15.1.2 The system design shall provide for all pressure relief devices to be installed as nearly as
practicable directly to the pressure vessel or other parts of the system protected thereby, so
that they are accessible for inspection and repair.
15.1.3 All pressure relief devices intended for vapor service shall be connected at the highest
practical point on the pressure vessel or other parts of the system protected thereby, but in
any case above the highest anticipated liquid refrigerant level.
EXCEPTIONS:
For hydrostatic overpressure relief protection, see Section 15.5.
For oil drain pot vessels and similar applications, connect at the highest point on the
oil drain pot vessel or the similar application.
15.1.4 Relief valves shall not be located in refrigerated spaces unless precautions (e.g. rupture disc)
are taken to prevent moisture migration into the valve body or relief vent line.
15.1.5 The seats and discs of pressure-relief devices shall be constructed of suitable material to
resist refrigerant corrosion or other chemical action caused by the refrigerant. Seats and discs
shall be limited in distortion, by pressure or other cause, to a set pressure change of not more
than 5% from the set pressure relief.
15.1.6 Setting of Pressure Relief Devices
15.1.6.1 Pressure Relief Valve Setting. The set pressure for pressure relief valves shall not
exceed the design pressure of the component it is protecting.
15.1.6.2 Rupture Member Setting. All rupture members used in series with a relief valve shall
have a nominal rated rupture pressure not to exceed the design pressure of the parts of
the system protected. The conditions of application shall conform to the requirements of
Section VIII, Division 1, 2013, ASME Boiler and Pressure Vessel Code [ref.3.2.1].
15.1.6.3 Provision shall be made to detect pressure build up (e.g. pressure gage, pressure switch,
telltale indicator) between the rupture member and the relief valve due to leakage
through the upstream relief device [ref.3.2.1 Section UG-127].
15.1.7 Marking of Relief Devices
15.1.7.1 All pressure relief valves for refrigerant-containing components shall be set and sealed
by the manufacturer. Each pressure relief valve shall be marked by the manufacturer
with the data required in Section VIII, Division 1, 2013, ASME Boiler and Pressure
Vessel Code [ref.3.2.1]. If a pressure relief valve requires resetting, this shall be
undertaken by the manufacturer or a company holding a valid testing certificate for this
work.
15.1.7.2 Each rupture member for refrigerant containing pressure vessels shall be marked with
the data required in Section VIII, Division 1, 2013, ASME Boiler and Pressure Vessel
Code [ref.3.2.1].
15.1.7.3 The capacity in SCFM [m3/s] or in lb air/min [kg air/min] shall be stamped on the valve
or available on request.
15.2 Pressure Relief Protection
15.2.1 Pressure vessels and other types of equipment built and stamped in accordance with Section
VIII, Division 1, 2013, ASME Boiler and Pressure Vessel Code [ref.3.2.1] shall be provided
with pressure relief protection in accordance with code.
15.2.2 Pressure vessels intended to operate completely filled with liquid refrigerant and are capable
of being isolated by stop valves from other parts of a closed-circuit ammonia refrigeration
system shall be protected with a certified hydrostatic service relief device (ref.3.2.1). See also
Section 15.5.
15.2.3 Pressure relief devices shall be sized in accordance with Section 15.2.7.
15.2.4 Pressure vessels less than 10 ft3 [0.3 m3] internal gross volume shall be protected by one or
more pressure relief devices.
15.2.5 Pressure vessels of 10 ft3 [0.3 m3] or more internal gross volume shall be protected by at least
one of the following options:
15.2.5.1 One or more dual pressure relief device(s). Dual pressure relief valves shall be installed
with a three-way valve to allow testing or repair. When dual relief valves are used, each
valve must meet the requirements of Section 15.2.7. When multiple dual relief valve
assemblies are used the following shall apply:
15.2.5.1.1 The sum of the capacities of the pressure relief devices actively protecting the
vessel must equal or exceed the requirements of Section 15.2.7, and
15.2.5.1.2 The dual relief valve(s) shall be set to a fully seated position (one side open and
one side closed).
15.2.5.2 A single pressure relief device, provided that: the vessel can be isolated and pumped
out; the relief valves are located on the low side of the system; and other pressure
vessels in the system are separately protected in accordance with Section 15.2.7.
15.2.6 When pressure relief valves are discharged into other parts of the closed-circuit ammonia
refrigeration system, the system shall be equipped with pressure relief devices capable of
discharging the increased capacity in accordance with Section 15.2.7 and the pressure relief
valves discharging into the system shall be either:
15.2.6.1 A pressure relief valve not appreciably affected by back pressure, or
15.2.6.2 A pressure relief valve affected by back pressure, in which case its set pressure added
to the set pressure of the system pressure relief device shall not exceed the maximum
allowable working pressure of any component being protected and shall comply with
the following:
15.2.6.2.1 The pressure relief valve that protects the higher pressure vessel shall be selected
to deliver capacity in accordance with Section 15.2.7 without exceeding the
minimum design pressure of the higher pressure vessel accounting
for the change in mass flow capacity due to the elevated back pressure.
15.2.6.2.2 The capacity of the pressure relief valve protecting the part of the system
receiving a discharge from a pressure relief valve protecting a higher pressure
vessel shall be at least the sum of the capacity required in Section 15.2.7 plus
the mass flow capacity of the pressure relief valve discharging into that part of
the system.
15.2.6.2.3 The design pressure of the body of the relief valve used on the higher pressure
vessel shall be rated for operation at the design pressure of the higher pressure
vessel in both pressure containing areas of the valve.
EXCEPTION:
Where hydrostatic overpressure protection relief devices are discharged into other parts of a
refrigeration system that are protected by pressure relief devices design to relieve vapor in
accordance with Section 15.2, the capacity of the hydrostatic overpressure protection relief
devices are not required to be summed with the vapor capacity required in Section 15.2.7.
15.2.7 Pressure Relief Device Capacity Determination
15.2.7.1 Pressure Relief devices shall have sufficient mass flow carrying capability (capacity)
to limit the pressure rise in a protected component to prevent its catastrophic failure.
The minimum required relief capacity shall depend on the component being
protected and the scenarios under which overpressure is being created.
NOTE: SCFM x 0.0764 = lb/min of dry air
15.2.7.2 The following scenarios shall be considered when determining the pressure relief
device capacity for refrigerant containing components. It is permissible to use
manufacturer’s data when determining relief requirements. All applicable scenarios
shall be considered and the capacity of the pressure relief device shall be based on the
scenario with the largest capacity requirements:
a. Overpressure due to External Fire
i. Pressure Vessels:
The required discharge capacity of a pressure relief device for each pressure vessel shall
be determined by the following equation:
C = ƒ ∙D∙L (lbm/min)
[C = ƒ∙ D∙L [kg/s]]
where
C = required discharge capacity of the relief device, lbm air/min [kg/s]
ƒ = capacity factor of the relief device which is 0.5 [0.04] for ammonia
[0.5 is in inch-pounds (IP), 0.04 is in International System of Units (SI)]
D = outside diameter of vessel, ft [m]
L = length of vessel, ft [m].
When one pressure relief device is used to protect more than one pressure vessel, the required
capacity shall be the sum of the capacities required for each pressure vessel.
ii. Oil Separators:
The required discharge capacity for each oil separator shall be determined by the
following equation:
Cr,os = ƒ·D∙L (lbm/min)
[Cr,os = ƒ∙ D∙L [kg/s]]
where
Cr,os = required discharge capacity of the relief device, lbm air/min [kg/s]
ƒ = capacity factor of the relief device which is 0.5 [0.04] for ammonia
D = outside diameter of the oil separator, ft (m)
L = length of the oil separator, ft (m)
iii. Plate Heat Exchangers
The capacity of the pressure relief device for plate heat exchangers shall be based on the
largest projected area of the exchanger using the following equation:
Cr,plate HX = ƒ · √𝐿2 + 𝑊2 ∙ H (lbm/min)
[Cr,plate HX = ƒ · √𝐿2 + 𝑊2 ∙ H, [kg/s]]
where
Cr,plate HX = Minimum required relief device capacity for plate heat exchanger (lbm/min of
air)[kg/s]
ƒ = relief device capacity factor which is 0.5 [0.04] for ammonia
L = length of the plate pack (ft) [m]
W = width of the plate pack (ft) [m]
H = Height of the plate pack (ft) [m]
iv. Shell and Tube Heat Exchangers
The capacity of the pressure relief device for shell and tube heat exchangers shall be based on
the sum of the capacities required for the heat exchanger and the surge drum (if fitted) as
follows:
C = ƒ∙(Dv ∙ Lv + Ds ∙ Ls) (lb/min)
[C = ƒ∙(Dv ∙ Lv + Ds ∙ Ls) [kg/s]]
where
C = required discharge capacity of the relief device, lb air/min [kg/s]
ƒ = capacity factor of the relief device which is 0.5 [0.04] for ammonia
Dv = outside diameter of the main vessel portion of the
shell and tube heat exchanger, ft [m]
Lv = length of main vessel portion of the shell and tube heat exchanger, ft [m].
Ds = outside diameter of the surge drum, ft [m]
Ls = length of the surge drum, ft [m].
v. Product Storage Tanks
For product storage tanks with cooling jackets, the capacity of the pressure relief
device shall be based on the diameter of the storage tank and the height of the cooling
jacket as follows:
Cr,tank = ƒ · D ∙ H (lbm/min)
[Cr,tank = ƒ · D ∙ H [kg/s]]
where
Cr,tank = required discharge capacity of the relief device, lb air/min [kg/s]
ƒ = capacity factor of the relief device which is 0.5 [0.04] for ammonia
D = outside diameter of the tank, ft (m)
H = height of the active portion of the heat exchanger (distance between refrigerant
supply and return) ft (m)
b. Potential for Overpressure due to Blocked Outlet
i. Positive Displacement Compressor Protection
See Section 8.2.1 for pressure relief protection for
positive displacement compressors.
ii. Oil Cooling Heat Exchangers
Informative Appendix B provides a method for
determining capacity for safety relief valves to
relieve overpressure due to blocked outlets.
iii. Hydrostatic Overpressure Relief Protection
Section 15.5 describes the situations where
hydrostatic overpressure relief is required for closed
refrigerant circuits. Informative Appendix G
provides a method for determining the size of
hydrostatic overpressure-relief valves.
c. Potential for Overpressure due to Internal Heat Load
i. Informative Appendix B provides a method for
determining the capacity for safety relief valves to
relieve pressure due to internal heat loads in heat
exchangers.
d. Other Potential Overpressure Scenarios
i. Evaluate other potential overpressure scenarios as
applicable to the specific component being
protected.
15.2.8 Combustible materials shall be stored at least 20 feet (6.1 m) from a pressure vessel. If a
combustible material is used within 20 feet (6.1 m) of a pressure vessel, the relief device
capacity factor, f, in the formulas above becomes f = 1.25 [f = 0.1].
15.2.9 The rated discharge capacity of a pressure relief valve shall be determined in accordance
with Section VIII, Division 1, 2013, ASME Boiler and Pressure Vessel Code [ref.3.2.1].
The capacity marked on the nameplate shall be in lb/min air or in standard
ft3/min (SCFM) of air at 60°F (SCFM x 0.0764 = lb/min of dry air).
15.2.10 The rated discharge capacity of a rupture member discharging under critical flow conditions
shall be determined by the following equations:
C = 0.64 P1d2 (lb/min)
d = 1.25 (C/P1)0.5 (in)
[C = 1.1 x 10-6 P1d2 (kg/s)]
[d = 959 (C/P1)0.5 (mm)]
where
C = rated discharge capacity in lb/min [kg/s] of air
d = smallest of the internal diameter of the inlet pipe, retaining flanges or
rupture member in inches [mm]
P1 = rated pressure (psig) x 1.1 + 14.7 psi
[P1 = rated pressure [kPa gage] x 1.1 + 101.3 kPa]
There shall be provisions to prevent plugging the piping in the event the rupture member
relieves.
15.3 Pressure Relief Device Piping
Relief valve piping that discharges external to the closed-circuit ammonia refrigeration system is
not part of the closed-circuit ammonia refrigeration system.
15.3.1 No stop valves shall be installed in the inlet or outlet piping of pressure relief devices unless
procedures specified in Appendix M, Section VIII, Division 1, 2013, ASME Boiler and
Pressure Vessel Code [ref.3.2.1] are followed. When applied, the pressure drop effects of full
area stop valves shall be taken into account in the engineering of the relief vent piping system.
Where used, stop valves shall be locked open whenever any relief device upstream is in
service.
15.3.2 The opening through all pipe, fittings, and pressure relief devices (if installed), including 3-
way valves, between a pressure vessel connection, which is a minimum of ¾”, and its
pressure relief valve shall have at least the area of the pressure relief valve inlet. This
upstream system shall be such that the pressure drop will not reduce the relieving capacity
below that required or adversely affect the operation of the pressure relief valve. For
compressor vessel connections, see Section 8.2.1.
15.3.3 The discharge piping from pressure relief devices shall be steel pipe minimum schedule 40
for pipe sizes up to 6” and minimum schedule 20 for pipe sizes 8” and larger. The relief
piping shall comply with the ferrous material requirements of ASME B31.5 (ref.3.2.2).
EXCEPTION:
Relief piping is permitted to be galvanized or un-galvanized ASTM A120, A53/A120, or
A53-Type F (ref.3.3.1 and ref.3.3.2). When these grades of un-galvanized pipe are used, the
pipe shall be clearly identified (e.g. with paint striping) or segregated to prevent their use in
the closed-circuit refrigeration system.
EXCEPTION:
Malleable iron ASTM A197 (ref.3.3.3) fittings are an acceptable material for discharge relief
piping.
15.3.4 The size of the discharge pipe from a pressure relief device shall not be less than the outlet
size of the pressure relief device. The size and total equivalent length of common discharge
piping downstream from each of two or more relief devices shall be governed by the sum of
the discharge capacities of all the relief devices that are expected to discharge simultaneously,
at the lowest pressure setting of any relief device that is discharging into the piping, with due
allowance for the pressure drop in all downstream sections.
15.3.5 Where piping in the system and other components required to comply with this section may
contain liquid refrigerant that can be isolated from the system during operation or service,
Section 15.4 shall apply.
15.3.6 Relief piping is intended for relieving only vapor from refrigerant relief valves. It is not
permitted to use the relief piping system for the discharge of hydrostatic overpressure-relief
devices and any other fluid discharges (e.g. secondary coolants, oil, etc.).
15.3.7 Discharge piping shall be supported per the provisions of Section 13.4 Piping Hangers and
Supports.
15.4 Discharge from Pressure Relief Devices
15.4.1 Atmospheric Discharge
Pressure relief devices shall discharge vapor directly to the atmosphere (outdoors) when the
relief vent meets the provisions of Sections 15.4.1.1 through 15.4.1.7. In lieu of relieving
directly to atmosphere, the following methods of discharging ammonia from pressure relief
devices shall be permitted where approved by the authority having jurisdiction (AHJ):
● Discharge through a treatment system.
● Discharge through a flaring system (See Section 15.4.1.7).
● Discharge through a water diffusion system in accordance with Section 15.4.2.
● Discharge using other approved means.
15.4.1.1 The maximum length of the discharge piping installed on the outlet of pressure relief
devices and fusible plugs discharging to the atmosphere shall be determined by the
method in Appendix A (Normative).
15.4.1.2 The extremity of the pressure relief device(s) discharge piping relieved to atmosphere
shall be at least 15 feet [4.6 m] above the grade and at least 20 feet [6.1 m] from any
window, ventilation intake, or personnel exit.
15.4.1.3 The discharge termination from pressure relief devices relieved to atmosphere shall not be
less 7.25 feet [2.2 m] above the roof. Where there is a higher adjacent roof level that is
within 20 feet [6.1 m] horizontal distance from the relief discharge, the discharge
termination shall not be less than 7.25 feet [2.2 m] above the height of the higher adjacent
roof.
15.4.1.4 Discharge piping is permitted to be terminated 7.25 feet [2.2 m] above platform surfaces
(e.g. upper condenser catwalks) and roofs that are occupied only during service and
inspection.
15.4.1.5 The termination of the discharge shall be directed vertically upward and arranged to avoid
the spraying of refrigerant on persons in the vicinity.
15.4.1.6 The termination point of the vent discharge line shall have a provision to minimize foreign
material or debris from entering the discharge piping.
15.4.1.7 Discharge piping from pressure relief devices piped to atmosphere shall have a provision
for draining moisture from the piping.
15.4.1.7 Flaring systems, if installed, shall be tested to demonstrate their safety and effectiveness
meets the design requirements as intended.
15.4.2 Discharge Through a Water Diffusion System (Tank of Water)
15.4.2.1 When relieving ammonia to a water tank, the tank shall be sized for containing one gallon
of water for each pound of ammonia (8.3 liters of water for each kilogram of ammonia)
that would be released in one hour from the largest relief device connected to the
discharge pipe or sized for the entire system if the entire system charge is less than the
amount that would be released in one hour from the largest relief device. The water shall
be prevented from freezing. The discharge pipe from the pressure-relief device shall
distribute ammonia in the bottom of the tank but no lower than 33 feet (10 m) below the
maximum liquid level. The tank shall contain the volume of water and ammonia without
overflowing.
If the relief discharge termination is over 30 feet (9.1 m) above the adjacent grade, or roof
level, the discharge through a water diffusion system (tank of water) is not required.
15.5 Equipment and Piping Hydrostatic Overpressure Protection
15.5.1 The manual isolation for any purpose of equipment and piping sub-section(s) shall be
undertaken by trained technician(s) taking all necessary precautions to protect against
overpressure due to thermal hydrostatic expansion of trapped liquid refrigerant.
15.5.1.1 Where a Lockout/Tagout is required for the energy control, the procedure and training
shall be in compliance with OSHA 29 CFR 1910.147 [Appendix O ref.1.9.4].
15.5.2 Equipment and piping sub-section(s) that can be isolated and can trap liquid refrigerant in the
isolated section (1) automatically during normal operation, (2) automatically during shut-
down (by any means, including alarm or power failure), (3) during planned isolation for
standby or seasonal conditions (e.g. situations when the valves in the ammonia lines
to/from evaporative condensers are closed during cold weather conditions), or (4) by
equipment or component fault, shall be protected against overpressure due to thermal
hydrostatic expansion of trapped liquid refrigerant by either:
● a static relief device or check valve relieving to another part of the close-circuit
system, or
● an expansion compensation device.
15.5.3 If trapping of liquid with subsequent thermal hydrostatic expansion can occur only during
maintenance - i.e., when personnel are performing maintenance tasks – either engineering or
administrative controls shall be used to relieve or prevent the overpressure.
15.5.4 Static pressure relief valves shall not be used as shut off valves (See Section 13.3.4.)
Chapter 16 Instrumentation and Controls
This chapter applies to instrumentation and controls installed on closed-circuit ammonia refrigeration
systems and components.
16.1 General
16.1.1 Instruments and controls shall be provided to indicate operating parameters of the
refrigeration system and components and provide the ability to manually or automatically
control the starting, stopping and operation of the system or components. The instruments
and controls shall provide notice if the system’s critical operating parameters as determined
by the owner/operator are exceeded.
16.1.2 The function, sequence and operating design parameters of each control (if applicable) shall
be obtained and/or documented by the owner/operator. The owner/operator shall maintain
control documentation in a readily-accessible location.
16.1.3 During a power failure, a means to monitor the status of the ammonia concentration levels
shall be available.
16.1.4 If the basic control system is intended to control safety functions of the system (e.g.
emergency exhaust, equipment shutdown), it shall be designed to be separate and
independent to the extent that its functional integrity is not compromised during normal
operations. For example, changing set points for system operation (e.g. temperature,
pressure, flow, vessel levels) shall not affect alarm and/or cutout levels.
16.1.5 All electrical control systems must be in compliance with the NFPA Standard 70: National
Electrical Code (NEC) (ref.3.7).
16.2 Visual Liquid Level Indicators: Bull’s- Eyes, tubular glass and flat “armored glass” linear
sight glasses/sight columns, Pressure Gauges
16.2.1 Design
16.2.1.1 Design of refrigerant containing parts shall meet the requirements of at least one of the
following:
16.2.1.1.1 Be listed either individually or as part of an assembly or a system;
16.2.1.1.2 Prove satisfactory by successful performance under comparable service
conditions;
16.2.1.1.3 Have a pressure-containment design based on an analysis consistent with the
general design philosophy embodied in ASME B31.5-2013 [ref.3.2.2] and
substantiated by one of the following:
16.2.1.1.3.1 Proof tests as described in UG-101 of Section VIII, Division 1, 2013, ASME
Boiler and Pressure Vessel Code [ref.3.2.1];
16.2.1.1.3.2 Experimental stress analysis.
16.2.1.2 For minimum design pressure, see Section 5.1.2.
16.2.2 All visual liquid level indicators used to observe the refrigerant level, such as in a vessel or
heat exchanger, shall be designed for installation in such a manner that they are protected
from physical damage.
16.2.3 To protect compressors from liquid slugging, vessels that are directly connected to
compressor(s) suction lines shall be equipped with high level indicator switches which
actuate a high level alarm, and where practical, cause the associated compressor(s) to shut
down when a high refrigerant level is detected.
16.2.4 Linear liquid level indicators (sight columns) shall be fitted with internal check-type shutoff
valves. This type of sight glass shall also have robust protection against accidental breakage
360 degrees around the glass tube, over the full length of the tube.
EXCEPTION:
Liquid-level-gauge columns using bull's-eye type sight glasses.
NOTE:
It is recommended that linear visual liquid indicators (sight columns) be of the flat “armored
glass” type in preference to the tubular glass type.
16.2.5 Bull’s eye sight glasses shall be verified compatible for use with ammonia, and shall be an
appropriate thickness for the diameter and type of glass that is used.
16.2.5.1 Bull’s eye sight glasses shall be traceable through a serial number or other form of
identification in a manner that does not compromise the glass structure or integrity.
16.2.5.2 Sight glasses and linear liquid level indicators shall not be installed in areas subject
to repeated thermal expansion or liquid hammer.
16.3 Controls, Electric and Pneumatic
This section applies to sensing devices which initiate control pulses or signals applied for use in
ammonia closed-circuit refrigeration systems.
Relay switches, contactors, and starters are not included in this section.
16.3.1 Design
16.3.1.1 Design of refrigerant containing parts shall meet the requirements of at least one of the
following:
16.3.1.1.1 Be listed either individually or as part of an assembly or a system;
16.3.1.1.2 Prove satisfactory by successful performance under comparable service
conditions;
16.3.1.1.3 Have a pressure-containment design based on an analysis consistent with the
general design philosophy embodied in ASME B31.5-2013 [ref.3.2.2] and
substantiated by one of the following:
16.3.1.1.3.1 Proof tests as described in UG-101 of Section VIII, Division 1, 2013,
ASME Boiler and Pressure Vessel Code [ref.3.2.1];
16.3.1.1.3.2 Experimental stress analysis.
16.3.1.2 For minimum design pressure, see Section 5.1.2.
16.3.2 Procedures/Testing
16.3.2.1 Each sensor shall be strength tested to a minimum of 1.1 times the design pressure,
subsequently leak tested, and proven tight at a pressure not less than design.
16.3.3 Equipment Identification
16.3.3.1 Manufacturers producing electrical and/or pneumatic controls shall provide the
following minimum nameplate data:
16.3.3.1.1 Manufacturer’s name
16.3.3.1.2 Manufacturer’s serial number (where applicable)
16.3.3.1.3 Manufacturer’s model number
16.3.3.1.4 Electric supply: volts, full load amps, frequency (Hz), phase (where applicable)
16.3.3.1.5 Pneumatic system: control range: maximum supply air pressure, minimum
supply air pressure, required ACFM (where applicable)
16.3.3.1.6 Flow direction (where applicable)
16.3.3.1.7 Any special characteristics of a control device shall be noted either on the name
tag or in the accompanying literature.
Chapter 17 Ammonia Detection and Alarms
This chapter applies to ammonia detection and alarms installed on closed-circuit ammonia refrigeration
systems.
17.1 Scope
17.1.1 The scope of this section applies to detection in areas containing refrigeration equipment.
This section does not include detection outdoors, within piping or other system components.
17.2 Power for Detectors and Alarms
17.2.1 The power supply for the refrigerant gas detectors shall be on a dedicated branch circuit. If
the area refrigeration equipment power shuts down, the refrigerant gas detection system shall
remain on. A trouble signal indicating fault in the refrigerant gas detection power system
shall be monitored so that corrective action can be taken.
17.3 Testing
17.3.1 The facility shall establish a time schedule for testing of the ammonia detectors and the
alarm system. The manufacturer’s recommendations shall be followed or modified based on
documented experience.
17.3.2 Where no recommendations are provided, these devices shall be scheduled for functional
testing on an annual basis.
17.4 Detector Placement and Alarms
17.4.1 The detection sensors, or sampling tubes that draw air to the detection sensors, shall be
located with consideration for personnel safety and maintenance access. If the room is
equipped with an exhaust system, the detection sensors shall be located inside the room
within the airflow to the inlet of the ventilation system.
17.4.2 The audible alarm(s) shall be loud enough to be heard over the ambient sound pressure level
of the area in which it is installed.
17.4.3 The meaning of each alarm shall be clearly marked by signage near the visual and audible
alarms.
17.5 Machinery Rooms
17.5.1 See Chapter 6 Section 6.13 for Refrigerant Detection in Machinery Rooms.
17.6 Other Areas
Areas other than machinery rooms that require refrigerant detection per this Standard shall adhere to
the following requirements:
17.6.1 Level 1 Ammonia detection required
17.6.1.1 At least one ammonia detector in the room is required. The detector shall actuate an
alarm that reports to a monitored location so that corrective action can be taken at a
level no higher than 25 ppm.
17.6.2 Level 2 Ammonia detection required
17.6.2.1 At least one ammonia detector in the room is required. The detector shall actuate an
alarm that reports to a monitored location so that corrective action can be taken at a
level no higher than 25 ppm.
17.6.2.2 There shall be audible and visual alarms inside the room for the room to warn that when
the alarm is activated, access to the room is restricted to authorized, trained
operators/technicians and/or trained emergency responders only.
17.6.3 Level 3 Ammonia Detection required
17.6.3.1 At least one ammonia detector in the room is required. The detector shall actuate an
alarm that reports to a monitored location so that corrective action can be taken at a
level no higher than 25 ppm.
17.6.3.2 There shall be audible and visual alarms inside the room for the room to warn that when
the alarm is activated, access to the room is restricted to authorized, trained
operators/technicians and/or trained emergency responders only.
17.6.3.3 Upon alarm, control valves feeding liquid and hot gas to equipment in the affected area
shall be closed, and any pumps, fans, or other motors associated with the ammonia
refrigeration equipment in the room shall be de-energized.
17.6.4 Level 4 Ammonia detection required
17.6.4.1 At least one ammonia detector in the room is required. The detector shall actuate an
alarm that reports to a monitored location so that corrective action can be taken at a
level no higher than 25 ppm.
17.6.4.2 There shall be audible and visual alarms inside the room for the room to warn that when
the alarm is activated, access to the room is restricted to authorized, trained
operators/technicians and/or trained emergency responders only.
17.6.4.3 Upon alarm, control valves feeding liquid and hot gas to equipment in the affected area
shall be closed, and any pumps, fans, or other motors associated with the ammonia
refrigeration equipment in the room shall be de-energized.
17.6.4.4 Upon alarm, the emergency exhaust system, if applicable, shall be activated. Refer to
Section 6.14.7 and Section 6.14.8.
Part 4 Appendices
Appendix A (Normative) Allowable Equivalent Length of Discharge Piping
(This is a normative appendix and is part of this standard.)
The design back pressure due to flow in the discharge piping at the outlet of pressure relief devices and
fusible plugs, discharging to atmosphere, shall be limited by the allowable equivalent length of piping
determined by Equation 1 or Equation 2.
f
PP
d
fC
PPdL
o
r 6
ln2146.0 2
2
2
2
2
0
5
Equation 1: Allowable relief discharge piping length, English units
f
PP
d
fC
PPdL
o
r 500
ln104381.7 2
2
2
2
2
0
515
Equation 2: Allowable relief discharge piping length, SI units
where
L = equivalent length of discharge piping, ft [m];
Cr = rated capacity as stamped on the relief device in lb/min [kg/s], or in SCFM multiplied by 0.0764,
or as calculated in ANSI/ASHRAE 15-2010 (Appendix O ref.1.3), Section 9.7.7 for a rupture
member or fusible plug, or as adjusted for reduced capacity due to piping as specified by the
manufacturer of the device, or as adjusted for reduced capacity due to piping as estimated by
an approved method;
ƒ = Moody friction factor in fully turbulent flow (see typical values below);
d = inside diameter of pipe or tube, in [mm];
ln = natural logarithm;
P2 = absolute pressure at outlet of discharge piping, psi [kPa];
P0 = allowed back pressure (absolute) at the outlet of pressure relief device, psi [kPa].
For the allowed back pressure (P0), use the percent of set pressure specified by the manufacturer, or,
when the allowed back pressure is not specified, use the following values, where
P is the set pressure:
a. for conventional relief valves, 15% of set pressure, P0 = (0.15 P) + atmospheric pressure;
b. for balanced relief valves, 25% of set pressure, P0 = (0.25 P) + atmospheric pressure;
c. for rupture members, fusible plugs, and pilot operated relief valves, 50% of set pressure,
P0 = (0.50 P) + atmospheric pressure.
NOTE:
For fusible plugs, P is the saturated absolute pressure for the stamped temperature melting
point of the fusible plug or the critical pressure of the refrigerant used, whichever is smaller, psi
[kPa] and atmospheric pressure is at the elevation of the installation above sea level. A default
value is the atmospheric pressure at sea level, 14.7 psi [101.325 kPa].
Typical Moody friction factors (ƒ) for fully turbulent flow:
Tubing
OD (in.)
DN ID (in.) ƒ
3⁄8 8 0.315 0.0136
1⁄2 10 0.430 0.0128
5⁄8 13 0.545 0.0122
3⁄4 16 0.666 0.0117
7⁄8 20 0.785 0.0114
11⁄8 25 1.025 0.0108
13⁄8 32 1.265 0.0104
15⁄8 40 1.505 0.0101
A.1: Typical Moody Friction Factors, Steel Tubing
Piping
NPS
DN ID (in.) ƒ
1⁄2 15 0.622 0.0259
3⁄4 20 0.824 0.0240
1 25 1.049 0.0225
11⁄4 32 1.380 0.0209
11⁄2 40 1.610 0.0202
2 50 2.067 0.0190
21⁄2 65 2.469 0.0182
3 80 3.068 0.0173
4 100 4.026 0.0163
5 125 5.047 0.0155
6 150 6.065 0.0149
A.2: Typical Moody Friction Factors, Steel Piping
Appendix B (Informative) Methods for Calculating Relief Valve Capacity for Heat Exchanger Internal Loads
INTRODUCTION This informative appendix presents approaches for determining the capacity of relief valves for overpressure scenarios not
explicitly covered in Chapter 15. This information can be used to document a basis for relief device capacity determination
for heat exchangers that may be subject to overpressure due to internal heat loads or blocked valves that can lead to high
refrigerant pressures. Pressure relief devices need to have sufficient mass flow carrying capability (capacity) to limit the
pressure rise in a protected component to prevent its catastrophic failure. The minimum required relief device capacity will
depend on the specific component being protected and the scenarios under which overpressure is being created. The
maximum relief device capacity is not limited by codes and standards. However, over-sizing relief valves shall be avoided to
prevent unstable relief device operation.
Although the methods presented in this informative appendix are intended to apply across a wide range of refrigeration
equipment and operating conditions, it is not possible to neatly prescribe relief device sizing and selection criteria to cover all
situations. The approach presented here is intended to be illustrative of the process that can be followed in establishing
pressure relief requirements for specific situations. As such, the use of sound engineering principles and the application of
engineering judgment are expected.
It is important to emphasize that for all of the cases considered, the rate of refrigerant vapor production needs to be converted
to an air mass flow since all of the relief devices are rated on an air basis. In the sections that follow are methods for relief
capacity determination for different types of heat exchangers based on internal heat addition.
NOMENCLATURE
cp,fluid - secondary fluid heat capacity (Btu/lbm-°F)
cpfluid,CIP- clean-in-place fluid heat capacity (Btu/lbm-ºF)
Cr - minimum required discharge capacity of the relief device for a vessel (lbm/min of air)
Cr,plate HX - minimum required relief device capacity for plate heat exchanger (lbm/min of air)
Cr,OS - minimum required discharge capacity of the relief device protecting an oil separator (lbm/min of air)
Cr,tank - minimum required discharge capacity of the relief device protecting a product tank heat exchanger (lbm/min of
air)
D - outside diameter of vessel or product tank (ft)
Ds - outside diameter of surge drum (ft)
Dv - outside diameter of the main vessel portion of the shell-and-tube heat exchanger (ft)
f - relief device capacity factor that depends on refrigerant type and whether combustible materials are in close
proximity to the pressure vessel (see ASHRAE 15 2007 for capacity factor values)
H - height of the plate pack or tank heat exchanger (ft)
hvapor,sat - saturated vapor refrigerant enthalpy at the fully accumulated relief device set pressure (Btu/lbm)
hliquid,sat - saturated liquid refrigerant enthalpy at fully accumulated relief device set pressure (Btu/lbm)
L - length of the vessel or plate pack (ft)
LMTD - Log mean temperature difference (°F)
Ls - length of surge drum (ft)
Lv - length of the main vessel portion of the shell-and-tube heat exchanger (ft)
brinem - secondary fluid mass flow rate (lbm/min)
,fluid CIPm - clean-in-place fluid mass flow rate (lbm/min)
refrigerantm - refrigerant vapor generation rate (lbm/min)
,refrigerant OCm - mass flow rate of refrigerant vapor generated by the oil cooler (lbm/min)
,refrigerant tankm - mass flow rate of refrigerant vapor generated in a tank heat exchanger (lbm/min)
Pr - Prandtl number for fluid used to establish the nominal UA (-)
Pr' - Prandtl number for fluid used to establish the modified UA' (-)
Q - heat exchanger heat flux (Btu/min)
QOC - oil cooling heat exchanger heat load (Btu/min)
Tfluid,CIP,supply - maximum fluid supply temperature during CIP (ºF)
Trefrigerant - refrigerant saturation temperature (°F)
Tref,sat - refrigerant’s saturation temperature at the relief valve set pressure (ºF)
Treturn - load-side heat exchanger secondary fluid return temperature (°F)
Tsupply - load-side heat exchanger secondary fluid supply temperature (°F)
UA - overall heat transfer coefficient-area product (Btu/min-°F)
UA' - modified overall heat transfer coefficient-area product (Btu/min-°F)
W - width of the plate pack (ft)
- refrigerant-to-product tank effectiveness (estimated as 0.2 for bulk tanks)
APPLICATION
If a heat exchanger is built to the requirements of the ASME Boiler and Pressure Vessel Code [Section VIII, Division 1,
2013 (ref.3.2.1)] and is physically stamped as such, it requires pressure relief protection per Section UG-125 of the B&PV
Code. In cases where conventional pressure relief protection is not required, it is often desirable to size a suitable “process”
relief that will prevent overpressuring the heat exchanger during abnormal operation. The first step in determining the
minimum required mass flow for relief protection is defining the scenarios likely to cause the overpressure situation. Heat
exchangers are susceptible to over-pressure by internal heat loads from either product or other secondary fluid flow streams
(e.g. clean-in-place systems). In either situation, the key consideration for relief device sizing is determining the rate of
refrigerant vapor production by evaporation which will be dependent on the heat load and the refrigerant properties
(saturation pressure-temperature relationship and heat of vaporization).
Shell-and-Tube, Plate and Frame, and Scraped (Swept) Surface Heat Exchangers
Most scenarios involve alternate means of thermal energy input to the heat exchanger when the refrigerant side of
the chiller has been isolated from the refrigeration system but the secondary fluid side remains active. Examples of
thermal loads that could generate excessive pressure in a shell-and-tube or plate-and-frame heat exchanger may include
but are not limited to product loads and clean-in-place (CIP) loads.
Of primary concern are those thermal energy sources whose temperatures that exceed the saturation temperature
corresponding to the heat exchanger’s maximum allowable working pressure (MAWP) or pressure relief device set
pressure. If the maximum fluid-side supply temperature is less than the saturation temperature corresponding to the heat
exchanger’s MAWP, the pressure relief capacity can be determined by Section 15 of Standard IIAR 2. If the maximum
fluid-side temperature is greater than the saturation temperature corresponding to the heat exchanger’s MAWP, vapor
generation rates based on the “internal loads” shall be estimated to determine if a larger relief device capacity requirement
results.
The first step in the process of considering an internal heat load scenario that could generate an overpressure
situation is to evaluate the normal capacity of the heat exchanger. The next step is to estimate the heat exchanger’s
capacity under the adverse load condition and determine the corresponding rate of refrigerant vapor generation. Lastly,
the predicted rate of refrigerant vapor generation is converted to an equivalent air mass flow rate to allow relief device
selection.
Determining the rate of refrigerant vapor production can be accomplished by solving a system of equations that
characterize the equipment heat transfer performance, as given by Equation (1), and the balance of both refrigerant-side
and fluid-side energy flows as given by Equations (2) and (3), respectively. The system of governing equations is as
follows:
Q UA LMTD (1)
ln
return supply
return refrigerant
supply refrigerant
T TLMTD
T T
T T
(2)
,fluid p fluid return supplyQ m c T T (3)
, ,refrigerant vapor sat liquid satQ m h h (4)
where:
Q = heat exchanger heat flux (Btu/min)
UA = overall heat transfer coefficient-area product (Btu/min-°F)
LMTD = Log mean temperature difference (°F)
Treturn = load-side heat exchanger secondary fluid return temperature (°F)
Tsupply = load-side heat exchanger secondary fluid supply temperature (°F)
Trefrigerant = refrigerant saturation temperature (°F)
brinem = secondary fluid mass flow rate (lbm/min)
cp,fluid = secondary fluid heat capacity (Btu/lbm-°F)
refrigerantm = refrigerant vapor generation rate (lbm/min)
hvapor,sat = saturated vapor refrigerant enthalpy at the fully accumulated relief device set pressure (Btu/lbm)
hliquid,sat = saturated liquid refrigerant enthalpy at fully accumulated relief device set pressure (Btu/lbm)
In a liquid-containing heat exchanger, the refrigerant temperature (Trefrigerant) is assumed to be the saturation
temperature corresponding to the pressure relief device set (opening) pressure. The enthalpy of vaporization (hvapor,sat –
hliquid,sat) for the refrigerant-side energy balance is evaluated at the pressure relief device set pressure as well. The return
fluid temperature to the heat exchanger (Treturn) is estimated based on the load which is a function of the fluid flow rate
and return fluid from process, CIP set temperature, etc. The mass flow rate of fluid on the load-side of the heat exchanger
( fluidm ) is required as well as the load-side fluid heat capacity (cp, fluid).
The nominal value of the heat exchanger’s overall heat transfer-area product (UA) is based on design operating
conditions. Equation (1) is used to estimate a nominal or design UA. Once a nominal or design UA is established, it can
be adjusted or corrected for use in estimating the refrigerant vapor production rate arising in an overpressure situation.
For example, if the fluid-side flow rate would be expected to vary from the design condition, the following relationship
based on the Dittus-Boelter turbulent heat transfer correlation could be used to predict a modified UA based on an
alternative fluid-side flow rate.
0.80.4
Pr
Pr
fluid
fluid
mUA UA
m
(5)
where:
UA = nominal overall heat transfer coefficient-area product (Btu/min-°F)
UA = modified overall heat transfer coefficient-area product (Btu/min-°F)
Pr = Prandtl number for fluid used to establish the nominal UA (-)
Pr = Prandtl number for fluid used to establish the modified UA (-)
In addition, Equation (5) accommodates changes in working fluids when transitioning from a design load condition
to a different working fluid that may arise and create an overpressure situation (e.g. changing from a fluid beverage during
load conditions to a CIP solution during clean-up) that forms the basis for sizing pressure relief protection for the heat
exchanger.
The above-mentioned known information (Trefrigerant, hvapor,sat, hliquid,sat, Treturn, fluidm , cp,fluid, and UA) can be used to
simultaneously solve Equations (1), (3), and (4) to find the remaining three unknown variables: refrigerantm , Tsupply, and Q.
The quantity of interest is the refrigerant vapor flow rate, refrigerantm , which represents the mass flow of vapor generated
during the overpressure scenario. Once obtained, the resulting refrigerant mass flow rate must then be converted to an
equivalent mass flow rate for air using the following relationship (ASHRAE 15 2007 Appendix F):
refrigerant airair
r refrigerant
refrigerant air refrigerant
T MCC m
C T M
(6)
Appendix F of ASHRAE 15 (2007) assumes a refrigerant temperature of 510°R [283 K] and an air temperature of
520°R [289 K]. Appendix F lists values of the constants, Cair and Crefrigerant, for a number of different refrigerants. The
calculated air mass flow based on the estimated refrigerant vapor mass flow represents the minimum required relief
capacity for the internal load scenario.
Example: Scraped (Swept) Surface Heat Exchanger
Heat Exchanger Characteristics for one manufacturer’s scraped (swept) surface heat exchanger:
U ≅ 300 𝐵𝑡𝑢/ℎ𝑟 ∙ 𝑓𝑡2 ∙ ℉
6 𝑓𝑡2 ≤ 𝐴 ≤ 14.5 𝑓𝑡2
150 𝑝𝑠𝑖𝑔 ≤ 𝑀𝐴𝑊𝑃 ≤ 250 𝑝𝑠𝑖𝑔
Heat Load Assumption
Internal Load is created by 160°F CIP fluid
Q UA LMTD ≅ U ∙ 𝐴 ∙ (𝑇𝐶𝐼𝑃 - 𝑇𝑠𝑎𝑡,𝑟𝑒𝑓)
, ,refrigerant vapor sat liquid satQ m h h
hr
minhh
TTAUm
liquidvapor
refsatCIP
ref
60
,
Heat Exchanger Characteristics
U = 300 Btu/hr-ft2-°F
A = 14.5 ft2
MAWP = 150 psig [h = 488 Btu/lbm, Tsat,ref = 89.6°F]
TCIP = 160°F
Heat Exchanger characteristics
U = 300 Btu/hr-ft2-°F
A = 14.5 ft2
MAWP = 250 psig [h = 453 Btu/lbm, Tsat,ref = 120.8°F]
TCIP = 160°F
Oil Cooling Heat Exchangers
Over-pressurization can occur when a thermosiphon oil-cooled screw compressor package is started while the
refrigerant-side of the oil cooler is isolated (valved-out). In this case, the compressor will operate and reject heat to the oil
cooler resulting in an increasing supply oil temperature back to the compressor over time. As the compressor continues to
)(5.10
60488
6.891605.14300 2
2
ammoniamin
lbm
hr
min
lbm
Btu
FftFfthr
Btu
mref
air
airmin
lbmm
8.135.10314.1
)(3.6
60453
8.1201605.14300 2
2
ammoniamin
lbm
hr
min
lbm
Btu
FftFfthr
Btu
mref
air
airmin
lbmm
3.83.6324.1
operate and reject a portion of its heat of compression through its oil to the oil cooling heat exchanger, a point will be
reached when the on-board compressor safeties shutdown the unit on high oil temperature. A typical screw compressor
package high oil temperature cut-out is approximately 205°F [96°C]. The saturation pressure corresponding to a
refrigerant temperature equal to the oil at its high temperature cut-out of 205°F [96°C] is 825 psig for ammonia. Since
this pressure is significantly greater than the oil cooling heat exchanger’s maximum allowable working pressure, the oil
cooler will be subject to overpressure under this scenario.
The mass flow rate of refrigerant vapor generated on the refrigerant-side of an oil cooler in an overpressure situation
is given by:
,
, ,
ocrefrigerant OC
vapor sat liquid sat
Qm
h h
(7)
where:
QOC = oil cooling heat load generated by the compressor operating at design suction pressure and discharge
pressures with a corresponding supply oil temperature at the compressor high temperature cut-out limit (Btu/min)
,refrigerant OCm = mass flow rate of refrigerant vapor generated by the oil cooler (lbm/min)
hvapor,sat = saturated vapor refrigerant enthalpy at the fully accumulated relief device opening pressure (Btu/lbm)
hliquid,sat = saturated liquid refrigerant enthalpy at the fully accumulated relief device opening pressure (Btu/lbm)
The best source for determining the overpressure condition oil cooling loads, QOC, is by information provided from
the compressor manufacturers. Some compressor manufacturers’ computerized selection programs provide this
information based on users inputting the design suction and discharge pressures along with oil supply temperatures. The
programs return the resulting oil cooling load under the modified (high oil supply temperature) conditions. The oil
cooling load imposed on the oil coolers can be evaluated at these modified conditions or alternatively, the full oil cooling
load can be taken for sizing the relief device.
The resulting oil cooling load at the elevated operating condition (Qoc) can then be used to estimate the refrigerant
mass flow rate using Equation (7). The refrigerant mass flow rate is then converted to an air basis using Equation (9);
thereby permitting the selection of a relief device.
Product Storage Tanks
The scenario for refrigerant vapor generation in the heat exchanger due to internal loads arises during clean-in-place.
The rate of refrigerant vapor generation during clean-in-place can be estimated as follows:
, , , , ,
,
, ,
fluid CIP fluid CIP fluid CIP supply ref sat
refrigerant tank
vapor sat liquid sat
m cp T Tm
h h
(8)
where:
,refrigerant tankm = mass flow rate of refrigerant vapor generated in the heat exchanger (lbm/min)
= refrigerant to product tank effectiveness (estimated as 0.2)
,fluid CIPm = CIP fluid mass flow rate (lbm/min)
cpfluid,CIP = CIP fluid heat capacity (approximated as 1 Btu/lbm-ºF)
Tfluid,CIP,supply = maximum fluid supply temperature during CIP (ºF)
Tref,sat = refrigerant’s saturation temperature at the relief valve set pressure (ºF)
hvapor,sat = saturated vapor refrigerant enthalpy at fully accumulated relief device set pressure (Btu/lbm)
hliquid,sat = saturated liquid refrigerant enthalpy at fully accumulated relief device set pressure (Btu/lbm)
After determining the refrigerant mass flow rate, the relief device capacity (on an air-equivalent basis) is found by
using Equation (6). The greater of these two capacities forms the basis for relief device selection for a product tank.
References
ASHRAE Transactions, “Pressure Relief Device Capacity Determination” Reindl, Douglas T. and Jekel, Todd B.,. Industrial Refrigeration Consortium. University of Wisconsin-Madison, Madison, WI and American Society of Heating, Refrigerating, and Air conditioning Engineers, Atlanta, GA, (2009). ASHRAE Standard 15, “Safety Standard for Refrigerating Systems”, American Society of Heating, Refrigerating, and Air conditioning Engineers, Atlanta, GA, (2007).
Appendix C (Informative) Ammonia Characteristics and Properties
This appendix is not part of this standard. It is merely informative and does not contain
requirements necessary for conformance to the standard. It has not been processed according to
the ANSI requirements for a standard and may contain material that has not been subject to
public review or a consensus process.
C.1 Ammonia Characteristics
The term ammonia, as used in this standard, refers to the compound formed by combination of
nitrogen and hydrogen, having the chemical formula NH3. It is not to be confused with aqua
ammonia, which is a solution of ammonia gas in water. Whenever the term ammonia appears in
this standard, it means refrigerant-grade anhydrous ammonia.
Experience has shown that ammonia is difficult to ignite and, under normal conditions, is a very
stable compound. It requires temperatures of 840-930°F [450-500°C][723.2-773.2K] to cause it to
dissociate slightly at atmospheric pressure. The flammable limits at atmospheric pressure are
15.5% to 27% by volume of ammonia in air. An ammonia-air mixture in an iron flask does not
ignite below 1204°F [651.1°C][925.3K].
Since ammonia is self-alarming, it serves as its own warning agent so that a person is not likely to
voluntarily remain in concentrations which are hazardous.
C.2 Physical Properties of Ammonia
English Common
Metric
SI
Molecular symbol NH3 NH3 NH3
Molecular weight 17.031 lb/lb-
mol
17.031 g/mol 17.031 g/mol
Boiling point at one atmosphere* -27.99°F -33.33°C 239.82K
Freezing point at one atmosphere* -107.78°F -77.66°C 195.5K
Critical temperature 269.99°F 132.22°C 405.37K
Critical pressure 1644 psig 115.6 kg/cm2
(gage)
11.34 MPa
(gage)
Latent heat at -28°F (-33°C)(240.15K) and one
atmosphere
588.8 Btu/lb 327.1 cal/g 1.369 MJ/kg
Relative density of vapor compared to dry air at 32°F
(0°C)(273.15K) and one atmosphere
0.5967 0.5967 0.5967
Vapor density at -28°F (-33°C)(240.15K) and one
atmosphere
0.05554 lb/ft3 0.8896 kg/m3 0.8896 kg/m3
Specific gravity of liquid at -28°F (-33°C)(240.15K)
compared to water at 39.4°F (4.0°C) (277.1K)
0.6816 0.6816 0.6816
Liquid density at -28°F (-33°C)(240.15K) and one
atmosphere*
42.55 lb/ft3 681.6 kg/m3 681.6 kg/m3
Specific volume of vapor at 32°F (0°C)(273.15K) and
one atmosphere*
20.80 ft3/lb 1.299 m3/kg 1.299 m3/kg
Flammable limits by volume in air at atmospheric
pressure
15.5% to
27%
15.5% to
27%
15.5% to
27%
Ignition temperature 1204°F 651.1°C 924.13K
Specific heat, gas at 59°F (15°C)(288.15K) and one atmosphere*
At constant pressure (cp )
At constant volume (cv )
0.5184
Btu/lb°F
0.3928
Btu/lb°F
0.5184
cal/g°C
0.3928
cal/g°C
2.1706 kJ/kg
K
1.6444 kJ/kg
K
Ratio of specific heats k(cp/cv, also ) at 50°F
(15°C)(288.15K) and one atmosphere*
1.320 1.320 1.320
NOTE:
*One standard atmosphere = 14.696 psia [1.0333 kg/cm2 absolute][101.33 kPa absolute]
Appendix D (Informative) Duplicate Nameplates on Pressure Vessels
This appendix is not part of this standard. It is merely informative and does not contain
requirements necessary for conformance to the standard. It has not been processed according to
the ANSI requirements for a standard and may contain material that has not been subject to
public review or a consensus process.
Duplicate Nameplates on Pressure Vessels
The ASME Boiler and Pressure Vessel Code, Section VIII, Division 1, 2013, [ref.3.2.1] permits duplicate
(or secondary) nameplates on pressure vessels. Duplicate nameplates may be desirable in certain
circumstances, especially where the original nameplate may be obscured by insulation.
Experience has shown that attempting to access the original nameplate for inspection through
windows, removable insulation sections, stanchion mounting, etc. tends to compromise the integrity of
the insulation system. Moisture ingress into the insulation system follows, with possible damage to the
pressure vessel. The use of duplicate nameplates helps prevent vessel damage from inspection ports
and other deliberate damage to insulation.
Unfortunately, using duplicate nameplates creates the possibility that the wrong (duplicate) nameplate
will be applied to a vessel. The ASME Boiler and Pressure Vessel Code, Section VIII, Division 1, 2013,
[ref.3.2.1] specifies that the vessel manufacturer must ensure that the duplicate nameplate is properly
applied. While the easiest way to accomplish this is for the manufacturer to weld the nameplate to a
support or other permanent vessel appurtenance that will not be insulated, field installation is also
permitted. (Some inspection authorities consider the insulation jacket as a permanent attachment to the
vessel, and therefore the duplicate nameplate may be applied to the jacket.) The manufacturer’s
procedures for ensuring a proper match of duplicate to original must be rigorously followed. It is
advisable to record the location of the original nameplate should inspection be necessary.
Various inspection authorities such as State vessel inspectors may demand to inspect and/or
approve the duplicate and original nameplates before insulation is applied. While many inspection
bodies will accept a duplicate nameplate as evidence of ASME Boiler and Pressure Vessel Code,
Section VIII, Division 1, 2013 [ref.3.2.1] compliance for an insulated vessel, authorized inspectors
may always demand to inspect the original vessel, including its nameplate. In particular, when the
inspector is concerned about the physical condition of the vessel or questions the provenance of
the duplicate nameplate, he or she may require the entire insulation system or any part to be
removed to permit inspection. Damage to the insulation system must be promptly and
professionally repaired, and due allowance should be made for the shorter service life of the
repaired insulation system.
Appendix E (Informative) Method for Calculating Discharge Capacity of a Positive Displacement Compressor Pressure Relief Device
This appendix is not part of this standard. It is merely informative and does not contain
requirements necessary for conformance to the standard. It has have not been processed
according to the ANSI requirements for a standard and may contain material that has not been
subject to public review or a consensus process.
Reprinted by permission of The American Society of Heating, Refrigerating and Air-conditioning Engineers (ASHRAE).
The following calculation method provides the required discharge capacity of the compressor pressure
relief device in Section 8.2.1.
g
v
r v
PLQW
where
Wr = mass flow of refrigerant, lbm/min [kg/s]
Q = swept volume flow rate of compressor, ft3/min [m3/s]
PL = fraction of compressor capacity at minimum regulated flow
v = volumetric efficiency (assume 0.9 actual volumetric efficiency at relieving pressure is known)
vg = specific volume of refrigerant vapor (rated at 50°F [10°C] saturated suction temperature), ft3/lbm
[m3/kg]
Next, find the relieving capacity in mass flow of air, Wa, for an ASME-rated [ref.3.1.2] pressure relief
device:
wra rWW (E.2)
r
a
a
r
r
aw
M
M
T
T
c
cr
(E.3)
where
rw = refrigerant-to-standard-air-mass-flow conversion factor
Mr = molar mass of refrigerant (17.0 for ammonia)
Ma = molar mass of air = 28.97
Ta = absolute temperature of the air = 520 R (289 K)
ca = constant for air = 356
cr = constant for refrigerant (as determined from Equation E.4)
Tr = absolute temperature of refrigerant = 510 R (283 K)
1k
1k
r1k
2k520c
(E.4)
where
k = ratio of specific heats cp/cv
cp = constant-pressure specific heat of refrigerant at a refrigerant quality of 1 at 50°F (10°C).
cv = constant-volume specific heat of refrigerant at a refrigerant quality of 1 at 50°F (10°C).
Constants for ammonia are listed below:
k = 1.422
Mr = 17.0
cr = 358.0
rw = 1.28
EXAMPLE:
Determine the flow capacity of a relief device for an ammonia screw compressor with a swept volume,
Q, of 1665 ft3/min (0.7858 m3/s). The compressor is equipped with capacity control that is actuated at
90% of the pressure relief device set pressure to its minimum regulated flow of 10%.
Q=1665 ft3/min (0.7858 m3/s)
v=0.90 (assumed) PL=0.1
vg =3.2997 ft3/lbm (0.206 m3/kg)
min4.45
2997.3
9.01.0min
1665
3
3
m
m
r
lb
lb
ft
ft
W
s
kg
kg
m
s
m
Wr 343.0
206.0
9.01.07858.0
3
3
min1.5828.14.45 m
wra
lbrWW
of air
air
s
kgrWW wra 439.028.1343.0
Converting to standard cubic feet/minute (SCFM), where Va= specific volume of air = 13.1 ft3/lbm
(0.818 m3/kg) for dry air at 60°F (15.6°C),
SCFM = 13.1(58.1) = 761 ft3/min
[SCFM = 0.818(0.439) = 0.359 m3/s].
Appendix F (Informative) Pipe Hanger Spacing, Hanger Rod Sizing, and Loading
This appendix is not part of this standard. It is merely informative and does not contain
requirements necessary for conformance to the standard. It has not been processed according to
the ANSI requirements for a standard and may contain material that has not been subject to
public review or a consensus process.
F.1 Recommended maximum spacing of hangers and minimum hanger rod size for steel pipe,
adapted from MSS SP-69 [Appendix 0 ref.1.8] is shown below. Spacing does not apply where span
calculations are made or where concentrated loads such as flanges, valves, specialties, etc. are placed
between supports. These tables do not account for seismic, thermal, or other dynamic load
considerations.
Table F.1
Nominal
Pipe Size
(in)
Maximum
Span (ft)
Minimum
Rod Diameter
(in)
Up to 1 7 3⁄8
11⁄4 –11⁄2 9 3⁄8
2 10 3⁄8
21⁄2 10 1⁄2
3 12 1⁄2
4 14 5⁄8
5 16 5⁄8
6 17 3⁄4
8 19 7⁄8
10 22 7⁄8
12 23 7⁄8
14 25 1
16 27 1
18 28 11⁄4
20 30 11⁄4
F.2 The maximum recommended hanger rod loading based on threaded hot rolled steel conforming
to ASTM A575-96 [Appendix O ref.1.8] is shown.
Table F.2
Rod
Diameter
(in)
Maximum
Load
(lb)
Rod
Diameter
(in)
Maximum
Load
(lb)
3⁄8 610 11⁄2 11 630
1⁄2 1 130 13⁄4 15 700
5⁄8 1 810 2 20 700
3⁄4 2 710 21⁄4 27 200
7⁄8 3 770 21⁄2 33 500
1 4 960 23⁄4 41 600
11⁄8 6 230 3 50 600
11⁄4 8 000 31⁄4 60 500
Adapted from MSS SP-69 [Appendix O ref.1.8].
Appendix G (Informative) Hydrostatic Overpressure Relief
This appendix is not part of this standard. It is merely informative and does not contain
requirements necessary for conformance to the standard. It has not been processed according to
the ANSI requirements for a standard and may contain material that has not been subject to
public review or a consensus process.
NOTE:
This Appendix is presented entirely in the English engineering unit system.
G.1 Background
Hydrostatic overpressures can occur when liquids become confined within enclosed volumes with
no gases present. For this to occur, the temperatures of such liquids must be below their boiling
points.
Liquids such as oil, secondary refrigerants, and subcooled primary refrigerants can become
entrapped when certain components of a closed-circuit ammonia refrigeration system are isolated
from other parts of the system by valves or other means. If there is an increase in temperature in
such confined liquids, rapidly rising pressures can occur that are functions of the bulk moduli of
elasticity of the liquids. While such increases in temperature and pressure can be very rapid, the
corresponding rates of volume increase of the liquids are relatively low. Therefore, relief devices
installed to relieve the resulting pressure need not have the flow capacity of vapor relief devices.
Practitioners have found that very small relief devices satisfy most requirements for hydrostatic
overpressure relief found in refrigeration service. The technical literature available that quantifies
such requirements, based on empirical test data, is found almost exclusively in areas of practice
that are much more severe than refrigeration service. However, many authorities having
jurisdiction require calculations or other evidence to justify selection and sizing of hydrostatic
overpressure-relief devices. In those cases, it is acceptable good engineering practice to
demonstrate that a relief device having adequate capacity for an extremely severe application will
certainly be adequate for less severe circumstances typically encountered in refrigeration
applications. To that end, applicable methodology borrowed from more severe applications such
as those found in the oil and gas industries provide a safe and conservative basis for hydrostatic
overpressure-relief protection in refrigeration applications. The objective is to provide adequate
relief, not necessarily to determine exactly how much liquid expansion will occur. In most, if not all
cases, the smallest relief valves manufactured for such purposes will have greater flow capacities
than the requirements found by calculation for extremely severe circumstances.
To address the sizing of orifices needed to relieve hydrostatic pressure as defined above, an
equation for determining the discharge areas of such orifices is stated below:
2138 PP
G
KKK
QA
vwd
where
A = required effective discharge area, in square inches
Q = flow rate, in US gallons per minute
Kd = effective coefficient of discharge (0.65 for hydrostatic overpressure-relief purposes)
Kw = correction factor due to back pressure (1.0 if back pressure is atmosphere or valve responds
only to pressure differential across its seat)
Kv = correction factor due to viscosity
G = specific gravity of the liquid at the flowing temperature
P1 = upstream relieving pressure in psig
P2 = total back pressure in psig (zero for discharge to atmosphere)
Q is determined by the relation:
GC
BHQ
500
where
B = cubical expansion coefficient per degree Fahrenheit for the liquid at the expected temperature
H = total heat of absorption to the wetted bare surface of a vessel, pipe or container in BTU per hour
(H = 21,000 A0.82, where A = total wetted surface in square feet)
G = specific gravity of the liquid at the flowing temperature
C = specific heat of the trapped fluid in BTU per lb-°F
Kv is determined as follows:
Refer to Figure G1 below to find Kv as a function of the Reynolds number (R), which is defined by the
following equation:
AU
QR
12,700
where
Q = flow rate at the flowing temperature in US GPM
U = viscosity at the flowing temperature in Saybolt Universal Seconds
A = effective discharge area, in square inches (from manufacturers’ standard orifice areas)
Figure G1: Capacity Correction Factor K Due to Viscosity
Figure G1 was reprinted by permission from Oil and Gas Journal, November 20, 1978 edition. Copyright 1978, Oil and Gas
Journal.
http://ogj.pennnet.com/home.cfm.
G.2 Hydrostatic Overpressure Relief of ASME Pressure Vessels
This section pertains to vessels covered by Section VIII, Division 1, 2013 of the ASME Boiler and
Pressure Vessel Code [ref.3.2.1], herein referred to as ASME pressure vessels.
When ASME pressure vessels contain liquid refrigerant and can be isolated from the other parts
of a closed-circuit ammonia refrigeration system, the rules of Section 15.5 apply. However, when
ASME pressure vessels contain a non-boiling liquid (i.e., a liquid whose vapor pressure at
maximum normal operational, maintenance or standby conditions is less than the relief valve
setting), specific requirements of the ASME Boiler and Pressure Vessel Code, Section VIII,
Division 1, 2013 [ref.3.2.1] for hydrostatic overpressure-relief valves apply:
a. Hydrostatic overpressure- relief valves protecting ASME
pressure vessels must bear an ASME UV Code Symbol Stamp. (Code Case BC94-620)
b. Hydrostatic overpressure-relief valves protecting ASME pressure vessels must be certified
and rated for liquid flow. (Code Case BC94-620)
c. Any liquid pressure relief valve used shall be at least NPS 1/2. (UG-128)
d. The opening through all pipe, fittings, and non-reclosing pressure relief devices (if installed)
between a pressure vessel and its pressure relief valve shall have at least the area of the
pressure relief valve inlet. In this upstream system, the pressure drop shall not reduce the
relieving capacity below that required or adversely affect the proper operation of the pressure
relief valve. (UG-135 (b) (1))
e. The size of the discharge lines leaving a hydrostatic overpressure-relief valve shall be such
that any pressure that may exist or develop will not reduce the relieving capacity of the pressure
relief valve below that required to properly protect the vessel. (UG-135 (f))
f. The hydrostatic overpressure-relief valve shall be capable of preventing the pressure from
rising more than 10% above the maximum allowable working pressure during normal service or
standby conditions.
G.3 Sample calculations
To illustrate how to apply these concepts and requirements, two examples of sizing hydrostatic
overpressure-relief valves for pressure-containing components are provided below.
NOTE:
These examples are for oil in the oilside of oil coolers rather than ammonia on the refrigerant side.
EXAMPLE 1: Sizing a Hydrostatic Overpressure-relief Valve for an ASME Pressure Vessel
Determine the hydrostatic overpressure-relief valve required to protect an oil cooler of
diameter 10" and length 12 feet with MAWP 400 psig.
Assume that the oil temperature is 100°F and that the oil viscosity (U) is 300 Saybolt Universal
Seconds at 100°F. From the oil manufacturer’s data, the cubical expansion coefficient (B) is
0.00043/°F, specific gravity (G) is 0.87 and specific heat (C) is 0.5.
First, determine the bare wetted external area (A) of the oil cooler, in square feet:
2ft 33.81212
10.75 dlA
Next, determine total heat absorption (H) of the wetted bare surface of the oil cooler when
exposed to maximum normal conditions:
H = 21,000 A0.82
H = 21,000 × (33.8)0.82 = 376,644 Btu/Hr.
Next, determine rate of increase of the oil volume from the relation below:
GC
BHQ
500
𝑄 = 0.00043 𝑥 376,644/500 𝑥 0.87 𝑥 0.5 = 0.74 gpm
This is the volume flow of oil due to heat input. Hydrostatic overpressure relief valves are
commonly rated on water, so this value can be used, along with the design pressure differential
and specific gravity, to determine a required Cv for the relief based on the definition Cv.
DeltaP
avitySpecificGrQCv
Assume the relief valve will discharge into another part of the system having relief protection set
at 300 psig. To prevent the pressure in the oil cooler from exceeding 400 psig under all
conditions, the hydrostatic overpressure-relief valve must be selected for 100 psi differential.
The required relief valve Cv is therefore:
100
87.074.0Cv = 0.069
A hydrostatic overpressure relief valve must therefore be selected with a minimum Cv of 0.069.
Note that this does not account for reduction in capacity due to inlet losses.
The equivalent GPM of water would then be 0.69 GPM (determined by solving the Cv equation for
Q using the required Cv, a 100 psi differential, and a specific gravity of 1).
A liquid-rated ASME certified relief valve is commercially available with 1/2" NPT inlet and 3/4"
NPT outlet. The valve’s capacity at 100 psi pressure differential is 25.9 gal per min, 37.5 times the
water equivalent oil volume rate of increase. The valve therefore meets ASME capacity
requirements. Per the ASME code, inlet and outlet pressure losses may total 40 psi and still meet
code requirements.
EXAMPLE 2: Sizing a Hydrostatic Overpressure-relief Valve for a non-ASME component
Determine the orifice area required to protect an oil cooler with diameter 5" and length 12 feet with
MAWP 400 psig.
Assume that the oil temperature is 100°F and oil viscosity (U) is 300 Saybolt Universal Seconds
at 100°F. From the oil manufacturer’s data, the cubical expansion coefficient (B) is 0.00043/°F,
specific gravity (G) is 0.87 and specific heat (C) is 0.5.
First, determine the bare wetted external area of the oil cooler, in square feet:
2ft 17.481212
5.563 dlA
Next, determine total heat absorption of the wetted bare surface of the oil cooler when exposed to
maximum normal conditions from the relation:
H = 21,000 A0.82, outlined above.
H = 21,000 × (17.48)0.82 = 219,298 Btu/hr.
Next, determine rate of increase of the oil volume from the relation:
GC
BHQ
500
GC
BHQ
500
Next, determine the viscosity correction factor (Kv) from Figure G1 and the Reynolds number (R)
from the formula below:
AU
QR
12,700
To calculate R in this equation requires a value for A, which represents the orifice area.
Interestingly, to calculate A using the primary equation requires a value for R. To solve this
problem, an iterative method (trial and error) must be used. First, an approximate starting value of
A must be estimated to obtain an initial estimate of R, which can then be used in the primary
equation to calculate a new value for A. Comparing this calculated value of A to the initial
approximation for A will enable a even better approximation for A for the next iteration. This
iterative process will converge on a calculated value for A that is reasonably close to the final
approximation for A. If it does not, more sophisticated mathematical methods are required to solve
the equations.
Try a 1/16" orifice having an area of 0.003068 in2.
3310.003068300
0.43312,700
R
From Figure G1, Kv = 0.825
2138 PP
G
KKK
QA
vwd
Assume the pressure differential to another part of the system (P1-P2) is 100 psi.
200198.0
100
87.0
825.0165.038
433.0inA
The required flow area is much smaller (0.00198 in2) than the area assumed in estimating the
Reynolds number (0.003068 in2). Therefore, a relief valve having a 1/16" diameter orifice is more
than adequate.
For a second iteration, assume a 3/64" orifice with 0.0017 in2 cross-sectional area. R would then
become
4450.0017300
0.43312,700
R
Kv = 0.85
200192.0100
87.0
85.0165.038
433.0inA
This area requirement is approximately 13% greater than that of the 3/64" orifice. Therefore, we
can conclude that an orifice between a diameter of 1/16" and 3/64" would be ideal. A 1/16" orifice
will be more than adequate.
G.4 Inlet and Outlet Piping
The ASME Boiler and Pressure Vessel (B & PV) Code, Section VIII, Division 1, 2013 [ref.3.2.1]
requires that hydrostatic overpressure-relief valve inlet piping for ASME pressure vessels must
have at least the area of the overpressure-relief valve inlet. Since the same code requires a
minimum NPS 1/2" valve, the minimum inlet piping is established. Inlet piping requirements on
larger hydrostatic overpressure-relief valves would follow suit.
On outlet piping, the B & PV Code simply requires that the relief valve discharge lines are large
enough to avoid reducing the relieving capacity of the pressure relief device below that required to
properly protect the vessel.
For normal over-pressure protection, ASME permits overpressurization of a vessel to 10% above
its MAWP.
In the previous examples, the flows of liquid created by thermal expansion were very low.
Consequently, outlet piping from commercially available certified ASME liquid relief valves could
usually be much smaller than the nominal outlets of the valves themselves. For instance, consider
the ASME vessel example with a 0.74 gpm relief requirement. The relief valve suggested for this
application has a 3/4" NPT connection on the outlet. If, for example, the discharge piping is
reduced to 1/2” in stainless steel tubing, the Reynolds number for oil having a nominal viscosity of
68 centistokes at 100° F is less than 60 (57.9). In laminar flow, which by definition is flow at or
below Reynolds numbers of 2000, pressure loss to friction in psi per 100 feet of smooth pipe is
given as:
RD
GVh
2
f
43.3
where
V = fluid velocity in ft/sec
G = specific gravity of fluid
R = Reynolds Number of fluid
D = I.D. of pipe in ft
From the previous example, oil flow due to thermal expansion is 0.74 gpm or 0.1 cfm. The 1/2"
stainless steel tubing has a cross-sectional flow area of 1.0085 x 10-3 ft2. Fluid velocity is
therefore:
ft/sec 1.65101.008560
0.1ft/sec
60 3-
A
cfmV
Discharge piping pressure drop through the 1/2" stainless tubing would therefore be:
ft 100 / psi 49.30.035857.9
0.8671.6543.343.3 2
RD
GVh
2
f
For a typical relief valve discharge pipe run of 6 feet, pressure drop due to friction would be less
than 3 psi. Because ASME permits overpressurization of 10% above the MAWP of a pressure
vessel, inlet and outlet losses could total 40 psi and meet ASME requirements. Therefore,
hydrostatic overpressure-relief valve outlet piping can be greatly reduced below the nominal outlet
size of the relief valve selected in many cases.
Inlet and outlet piping for hydrostatic overpressure-relief valves protecting non-ASME components
containing incompressible non-refrigerants can be sized using identical techniques. In providing
overpressure protection against ambient warming, 10% overpressurization above MAWP is
permitted, providing the relief valve is selected at MAWP.
Hydrostatic overpressure-relief devices may be located anywhere on the protected component.
When used to protect an ASME vessel, they must bear a UV Code Symbol. When used to protect
a non-ASME component, they must be listed by an approved nationally recognized testing
laboratory or bear a UV Code Symbol.
Appendix H (Informative) Stress Corrosion Cracking
This appendix is not part of this standard. It is merely informative and does not contain
requirements necessary for conformance to the standard. It has not been processed according to
the ANSI requirements for a standard and may contain material that has not been subject to
public review or a consensus process.
H.1 Background
Stress corrosion cracking (SCC) is a generic term describing the initiation and propagation of
cracks that can occur in metals when subjected to stress in the presence of an enabling chemical
environment. The stress can originate from an externally applied force, thermal stress, or residual
stress from welding or forming.
H.2 Carbon steel is susceptible to SCC when stressed in the presence of ammonia and oxygen.
Ammonia SCC has been recognized as a problem in the agricultural, chemical, and transport
industries for many years. Studies have shown that the following factors contribute to the
likelihood of SCC:
• Material yield strength greater than 50 ksi
• Oxygen contamination
• Residual or applied stress
• Water content less than 0.2%
H.3 SCC in Ammonia Refrigeration Systems
SCC in ammonia refrigeration systems is less common, but there have been reports of SCC in
vessels and piping. Vessels seem to be more susceptible to SCC because of their higher material
yield strengths and residual fabrication stresses. High pressure receivers are particularly
vulnerable due to their potential for higher oxygen content (noncondensibles) and lower water
content but SCC has also been found in low pressure vessels and piping.
Propagation of cracks via SCC is usually a gradual process. In ammonia refrigeration applications
using carbon steel materials, stress corrosion cracks typically propagate from surface or
subsurface discontinuities at the interior wall of a susceptible vessel or pipe. Sufficiently high
stresses can propagate crack(s) through the material to emerge as a “pinhole leak” on the
external surface. Discovery of a “pinhole leak” on a vessel is indicative of SCC and it is likely that
additional cracks will be present in the same vessel. Repair of stress corrosion cracks
is difficult and often not cost-effective.
H.4 Recommendations to Inhibit SCC in Ammonia Refrigeration Systems
The following recommendations are intended to minimize the likelihood of SCC for vessels
constructed from carbon steel for use in ammonia refrigeration systems.
• The presence of noncondensible gases (specifically, oxygen) increases the probability of
SCC. As such, purging of air from the system during both initial start-up and during operation and
maintenance is important.
• Post-weld heat treat (PWHT) all high temperature vessels, especially vessels such as high
pressure receivers, and intermediate and low temperature water chillers, intercoolers and
economizers, to relieve the residual stress of welding and forming. Where low temperature
vessels are critical to the process, or may be held at temperatures above 23°F (-5°C) for long
periods of time, consideration should be given to PWHT.
EXCEPTIONS:
a. compressor oil separators
b. specialized vessels, such as plate heat exchangers, containing internal components that could
be damaged, e.g. internal bushings, gaskets.
NOTE: PWHT may produce significant scale, which could cause operating problems in the
system.
H.5 Refrigerant-grade anhydrous ammonia shall meet or exceed the requirements of the
Compressed Gas Association CGA G-2, 1995, Eight Edition, (ref.3.4).
Appendix I (Informative) Emergency Pressure Control Systems
This appendix is not part of this standard. It is merely informative and does not contain
requirements necessary for conformance to the standard. It has not been processed according to
the ANSI requirements for a standard and may contain material that has not been subject to
public review or a consensus process.
Emergency Pressure Control System Design and Installation Guidelines
I.1 General
I.1.1 Purpose. This technical guideline describes requirements for Emergency Pressure Control
Systems (EPCS), which provide a means of internally mitigating an overpressure event in a
refrigeration system that is independent of other required safety features and functions prior to
operation of a pressure relief device.
I.1.2 Scope. Emergency Pressure Control Systems used as a means to mitigate an overpressure
event involving an ammonia refrigeration system should comply with this technical guideline.
I.1.3 Limitations. An EPCS does not reduce or eliminate requirements for pressure relief devices
set forth in other codes and standards.
I.2 Definitions
crossover valve is a valve that allows interconnection of two different portions of a refrigeration
system that normally operate at different pressures.
emergency pressure control system (EPCS) is a system consisting of pressure sensors,
independent compressor cut-off controls and automatically controlled crossover valves that will
permit a high-pressure portion of a system to connect to a lower pressure portion of a system
when opened.
header is a pipe to which other pipes or tubes are connected.
high-side consists of those parts of a mechanical refrigeration system that are subjected to
approximate condenser pressure.
low-side consists of those parts of a mechanical refrigeration system that are subjected to
approximate evaporator pressure.
pressure sensor is a mechanical or electronic device that measures ammonia pressure.
seep is a nuisance loss of refrigerant from a relief valve that can occur when the vessel pressure
approaches the relief pressure setting, or a nuisance loss of refrigerant from a relief valve that can
occur after the valve discharges
if the valve does not fully re-seat.
zone is a general term used to identify a pressure level or temperature level of a refrigeration
system. A zone will be associated with a compressor or group of compressors and the associated
vessels serving a common pressure level. The term does not pertain to individual temperature
controlled areas or rooms served by one or more compressor.
I.3 Referenced Standards
I.3.1 International Fire Code (IFC), Section 606.10, 2012 (Appendix O ref.1.6)
I.4 EPCS Recommended. Each zone should be provided with an EPCS. Each EPCS, other than
the lowest pressure zone, should include a crossover valve to allow an abnormally high pressure
to be discharged to a lower pressure zone.
I.4.1 Design and Installation Recommendations
I.4.2 Crossover Valve Connections.
I.4.2.1 Crossover valves should be connected to locations that will allow pressure in each
high pressure zone to discharge to a lower pressure zone. Connections between pressure
zones should continue in the above-described manner until all major pressure zones in a
system are connected with the EPCS, always with the intended flow traveling from a high
pressure to a lower pressure.
I.4.2.2 Where multiple low-pressure zones are present, low-pressure zones with the highest
pressure should be connected to the next lowest pressure zone.
I.4.2.3 Crossover valve connections should not be to pipes or tubes conveying liquid
refrigerant.
I.4.2.4 High pressure crossover valve connections should come from the top of a dry suction
header, compressor discharge header or other main gas header.
I.4.2.5 Low pressure crossover valve connections should discharge to the vapor space in a
receiving vessel or to a common vapor header serving multiple receiving vessels.
I.4.2.6 The designer of a refrigeration system should consider the ability of the low pressure
portion of the system to receive the high pressure discharge from the EPCS crossover valve.
Operation of the crossover valve should not cause a release of refrigerant from pressure relief
devices on the low pressure portion of the system.
I.4.2.7 Crossover valves and connecting piping and valves should have a minimum nominal
size of 1-inch.
I.4.2.8 Piping and tubing associated with a crossover valve should be independent of any
other connections. The connection should not be in the same pipe or tube where a pressure
relief device is connected.
I.4.3 Crossover Valve Type. The crossover valve should be of a type that fully opens when
activated.
I.4.4 Isolation Valves
I.4.4.1 Each crossover valve should be provided with a stop valve on either side to allow
isolation of the crossover valve for maintenance.
I.4.4.2 Isolation valves should be locked in the open position during normal operations.
I.4.5 System Operation
I.4.5.1 The EPCS should be arranged for automatic operation.
I.4.5.2 Where required by the fire department, the EPCS should be provided with a remote
switch for manual activation.
I.4.5.3 An EPCS should be arranged to activate at a pressure not greater than 90 percent of
the pressure relief device setting.
I.4.5.4 A dedicated, independent mechanical pressure switch or a combination of a
mechanical and electronic pressure-sensing device dedicated to the EPCS should be
provided to activate each EPCS.
I.4.5.5 Pressure sensing equipment should continuously monitor pressure in the refrigeration
system adjacent to each crossover valve.
I.4.5.6 When a pressure sensor reaches the EPCS activation pressure, all of the following
should occur:
1) All compressors supplying the pressure zone that is in an over-pressure condition
should be stopped by a means that is independent of all other safety controls,
2) Associated crossover valves should open, and
3) Condenser fans and pumps should be stopped if the system pressure falls below 90
psig.
I.4.5.7 A means should be provided to signal personnel responsible for refrigeration system
maintenance that an EPCS has been activated.
I.4.5.8 Once an EPCS has been activated, it should remain active until manually reset.
I.4.6 Inspection and Maintenance
K.4.6.1 General. EPCS crossover valves and isolation valves should be inspected and tested
on an annual basis to verify proper operation.
I.4.7 Written Procedures
I.4.7.1 General. Written procedures should be in place to describe the operation of the
EPCS. Procedures should address the importance of maintaining isolation valves in the full
open position unless maintenance is being performed on the crossover valve.
Considerations for Pressure Set Points
Seep through a relief valve is nuisance refrigerant loss due to pressure differential conditions across the
valve or dirt and debris located at the seat. Seep is measured in bubbles per minute and can vary from
manufacturer, design, type of seat material, pressure differential across relief, amount of dirt that is
trapped after a relief discharges, and age of the relief valve. Relief valves are set with a tolerance of +/-
3%, but when these reliefs are stored or left in operation for a long period of time, the reliefs can begin to
seep at larger tolerances. In some cases, seep has occurred when pressure increases to within 10% of
relief set pressure.
One method to prevent seep, is to maintain a pressure on the relief valve of 90% or less of the rated
relief valve pressure setting. When pressures higher than 90% of rated relief valve pressure setting are
anticipated, it is possible to select soft seats that are bubble tight at higher pressures. Rupture disks in
combination with a relief valve will result in tighter tolerances.
The following tables show examples of typical tolerances and pressures associated with relief valves
and the EPCS.
TABLE I-1
Typical Set Point Values and Tolerances
for a 300 psig System
Relief Full Open (+10%) 330 psig
+3% tolerance 309 psig
Relief Valve Set Point 300 psig
-3% tolerance 291 psig
Potential seep point (-10%) 270 psig
EPCS set point 250 psig to 270 psig
(EPCS set point is equal or below the seep point)
Design System Operating Pressure (-25%)225 psig
(system operating pressure should be
25% lower than the relief valve setting
when selecting relief valves)
Compressor off set point 225 psig
TABLE I-2
Typical Set Point Values and Tolerances
for a 250 psig System
Relief Full Open (+10%) 275 psig
+3% tolerance 257.5 psig
Relief Valve Set Point 250 psig
-3% tolerance 242.5 psig
Potential seep point (-10%) 225 psig
(EPCS set point is equal or below the seep point)
EPCS set point 210 psig to 225 psig
Design System Operating Pressure (-25%)200 psig
(system operating pressure should be
25% lower than the relief valve setting
when selecting relief valves)
Compressor off set point 200 psig
Appendix J (Informative) Machine Room Signs
This appendix is not part of this standard. It is merely informative and does not contain
requirements necessary for conformance to the standard. It has not been processed according to
the ANSI requirements for a standard and may contain material that has not been subject to
public review or a consensus process.
The following example of the Principal and Auxiliary Machinery Room doors are provided for reference
only.
Key to door signage:
J.1 Refrigeration Machinery Room – Authorized Personnel Only
Color: Black Text, Yellow Background
Location: All entrances to Machinery Room
J.2 Caution – Ammonia R-717
Color: Black Text, Yellow Background
Location: All entrances to Machinery Room
J.3 Caution – Eye and Ear protection must be worn in this area
Color: Black Text, Yellow Background
Location: All entrances to Machinery Room
J.4 Warning – When alarms are activated ammonia has been detected
1. Leave room immediately when alarms are activated
2. Do not enter except by emergency trained personnel only
3. Do not enter without personal protective equipment
Location: All entrances to Machinery Room
J.5 Refrigeration Machinery Shutdown, Emergency use only
Color: Black Text, Orange Background
Location: Designated principal exterior machinery room door.
J.6 Refrigeration Machinery Room: Refrigeration Ventilation, Emergency use only
Color: Black Text, Orange Background
Location: Designated Principal Exterior Machinery Room Door, also can be used for remote On /
OFF / AUTO ventilation switch.
J.7. NFPA 704 – Ammonia Fire Diamond
Color: Black Text, White, Blue, Red & Yellow Background
Location: All entrances to Machinery Room
4
5
6
EMERGENCY USE
ONLY BREAK GLASS TO PUSH BUTTON
EMERGENCY USE
ONLY
REFRIGERATION MACHINERY
ROOM
AUTHORIZED PERSONNEL ONLY
2 3
AMMONIA R-717
EYE AND EAR
PROTECTION REQUIRED
IN THIS AREA
7 3 0
3
1
WHEN ALARMS ARE ACTIVATED
AMMONIA HAS BEEN DETECTED: 1. LEAVE ROOM IMMEDIATELY
2. DO NOT ENTER EXCEPT
BY TRAINED & AUTHORIZED PERSONNEL.
3. DO NOT ENTER WITHOUT PERSONAL
PROTECTIVE EQUIPMENT.
Principal Machinery Room Door
REFRIGERATION MACHINERY
ROOM
AUTHORIZED PERSONNEL ONLY
AMMONIA R-717
EYE AND EAR
PROTECTION REQUIRED
IN THIS AREA
3 0
3
WHEN ALARMS ARE ACTIVATED
AMMONIA HAS BEEN DETECTED:
Auxiliary Machinery Room Door
Appendix K (Informative) Alternative Ventilation Calculation Methods
This appendix is not part of this standard. It is merely informative and does not contain
requirements necessary for conformance to the standard. It has not been processed according to
the ANSI requirements for a standard and may contain material that has not been subject to
public review or a consensus process.
K.1 General
Section 6.14.8 describes alternative ventilation methods which are available for ammonia (NH₃)
refrigeration systems. This appendix (informative) contains sample calculations for the design
of alternative ventilation methods.
K.2 Sample Calculations: 30 ACH for Emergency and 20 ACH Normal Ventilation Rates
K.2.1 Design the ventilation system for an ammonia refrigeration skid package which contains 450
pounds of anhydrous ammonia (G) and is located in a machinery room which has a volume (V)
of 100,000 cubic feet (ft3).
K.2.2 The emergency ventilation rate equation (30 ACH = 0.5 air changes/minute):
Q = V x 0.5 (changes/min)
Where
Q = airflow in ft3/min
V = room volume in ft3
For this example:
Q = (100,000 ft3) x 0.5 (changes/min) = 50,000 ft3/min
K.3 Sample Calculations: Demonstrate that ammonia concentrations will never exceed 40,000 ppm
[25% of the Lower Flammability Limit (LFL)].
K.3.1 Demonstrate that the ammonia concentrations would never exceed 40,000 ppm if 100 pounds
of anhydrous ammonia (G) were released from an ammonia refrigeration skid package located
in a machinery room which has a volume (V) of 100,000 cubic feet (ft3).
K.3.2 The following equation can be used to demonstrate that the ammonia concentrations would
never exceed 40,000 ppm:
C = G x (Vapor Sp. Vol.) x (100%) / V
Where
C = volumetric concentration of ammonia in %
G = amount of ammonia released in the room in pounds (lbs). For the purposes of these
calculations it is assumed that the entire ammonia inventory is released and vaporized inside
the machinery room.
Vapor Sp. Vol. = the vapor specific volume for anhydrous ammonia in ft3/lb
V = room volume in ft3
@ 15 psia ______
Temperature (°F) Specific Volume (ft3/lb)
40°F 20.6880
60°F 21.5641
80°F 22.4338
100°F 23.2985
For this example:
C = (100 lbs) x (22.4338 ft3/lb. at 80oF) x (100%) / (100,000 ft3) = 2.24%
The LFL for anhydrous ammonia is typically considered to be to 16% (160,000 ppm). 25% of the
LFL is 4% (40,000 ppm). Thus, under steady state conditions, the ammonia concentration inside
the machinery room (2.24%) would not exceed 40,000 ppm, even if the entire ammonia charge
were released and vaporized within the machinery room.
K.3.3 Even though the calculations demonstrate that under steady-state conditions the ammonia
concentrations would never exceed 40,000 ppm, it is recommended that an emergency
ventilation system be provided in the machinery room in this example. The emergency
ventilation rate used would be at the discretion of the designer(s).
K.4 Sample Calculations: Provide Localized (Spot) Ventilation designed to maintain ammonia
concentrations below 40,000 ppm.
K4.1 Design a localized (spot) ventilation system for an ammonia refrigeration skid package which
contains 250 pounds of anhydrous ammonia (G) and is located in a machinery room which has a
volume (V) of 100,000 cubic feet (ft3) which will maintain the ammonia concentrations below
40,000 ppm. Assume temperature to be 60°F.
K4.2 The following equation can be used to calculate the ventilation rate for a localized (spot)
ventilation system which will maintain the ammonia concentrations below 40,000 ppm. The
derivation of this equation and an explanation of its use can be found in Chapter 4, Section 4.5
(General Industrial Ventilation) from ACGIH®, Industrial Ventilation: A Manual of Recommended
Practice for Design, 27th Edition. Copyright 2010. Reprinted with permission (Appendix O
ref.1.1).
Q = [403 x SG x 100% x ER x Sf] / [MW x LFL x B]
Where
Q = airflow in ft3/min
SG = specific gravity of ammonia liquid (SG = 0.62 @ 60°F per IIAR Ammonia Data Book)
ER = evaporation rate of liquid in pounds per minute (lbs/min). For the purposes of these
calculations it is assumed that the entire ammonia inventory is released and vaporized inside
the machinery room over a 10 minute period, i.e. 250 pounds over a 10 minute period (25
lbs/min).
Convert 25 lbs/min to pints/min
1 pint = 0.01671 ft³
NH₃ liquid @ 60°F = 38.54 lb/ft³
ER = 25 lb/min x ft³/38.5416 x pint/0.01671 ft³ = 38.82 pints/min
Sf = a safety coefficient that depends on the percentage of the LFL necessary for safe
conditions. Since it has been found desirable to maintain vapor concentrations of not more
than 40,000 ppm, a Sf coefficient of 4 (25% of the LFL) will be used for these calculations.
MW = the molecular weight of ammonia liquid (MW = 17.03 per IIAR Ammonia Data Book)
LFL = the lower flammability limit for ammonia (LFL = 16% per IIAR Ammonia Data Book)
B = a constant that takes into account the fact that the LFL decreases at elevated temperatures.
B = 1 for temperatures up to 250oF; B = 0.70 for temperatures above to 250oF, though it is
unlikely that temperatures above 250oF would ever be applicable for an ammonia refrigeration
system.
For this example:
B = 1
Q = [(403) x (0.62 @ 60oF) x (100%) x (38.82 pints/min) x (4)] / [(17.03) x (16%) x (1)]
Q = 14,238.9 ft3/min
K.4.3 Chapter 4 of Industrial Ventilation – A Manual of Recommended Practice for Design provides
guidance dilution ventilation principles that should be followed when designing localized (spot)
ventilation systems. These principles include:
K.4.3.1 Locate the exhaust openings near the sources of contamination, if possible, in order to
obtain the benefit of “spot ventilation.”
K.4.3.2 Locate the air supply and exhaust outlets such that the air passes through the zone of
contamination. The operator should remain between the air supply and the sources of the
contaminant.
K.4.3.3 Replace the exhausted air by use of a replacement air system.
K.4.3.4 Avoid re-entry of the exhausted air by discharging the exhaust high above the roof line
and by ensuring that no window, outdoor air intakes, or other such openings are located near
the exhaust discharge.
Appendix L Pipe, Fittings, Flanges, and Bolting (informative)
The following Materials and Minimum Pipe Wall Thickness criteria have historically been
commonly used in the ammonia refrigeration industry for ammonia Pipe, Fittings, Flanges and
Bolting:
A. Materials:
1) Pipe
Carbon steel: ASTM A53 — Grade A or B, Type E or S [Appendix O ref.1.4.1]
Carbon steel: ASTM A106 — Grade A or B [Appendix O ref.1.4.3]
Stainless steel: ASTM A312 — Type 304, 304L, 316, or 316L [Appendix O ref.1.4.9]
Carbon steel (low temperature): ASTM A333 — Grade 1 or 6 [Appendix O ref.1.4.11].
Carbon steel pipe, ASTM A53 or A106 may be used below -20°F if it meets ASME B31.5-
2013 Refrigeration Piping and Heat Transfer Components [ref.3.2.2].
2) Fittings
Carbon steel: ASTM A105 [Appendix O ref.1.4.2]
Carbon steel: ASTM A234 [Appendix O ref.1.4.7]
Stainless steel: ASTM A403 [Appendix O ref.1.4.12]
Carbon steel (low temperature): ASTM A420 [Appendix O ref. 1.4.13].
3) Flanges
Carbon steel: ASTM A105 [Appendix O ref.1.4.2]
Carbon steel: ASTM A181 [Appendix O ref.1.4.4]
Stainless steel: ASTM A403 [Appendix O ref.1.4.12]
Carbon steel (low temperature): ASTM A707 [Appendix O ref1.4.15].
4) Bolting
Cast Iron flanges when used with ring gaskets, or when coupled to a raised-face flange:
ASTM A307 Grade B [Appendix O ref.1.4.8]
Carbon or Stainless Steel Flanges down to -55°F: ASTM A193 Grade B7 [Appendix O
ref.1.4.5]
Low-temperature applications (-55°F to -150°F): ASTM A320 Grade L7 [Appendix O
ref.1.4.10]
Nuts for above materials: ASTM A194 [Appendix O ref.1.4.6], in accordance with the
bolting material requirements listed in the standards referenced above.
NOTE: The above materials refer to those common materials in joining piping flanges
only. These materials or other commonly used qualifying materials selected for a
safe design are permitted for bolts and studs for equipment closures, valve bonnet-
body connection, etc.
B. Minimum Pipe Wall Thickness:
1) Carbon Steel: Welded.
1.1) 1 ½ inch and smaller - schedule 80
1.2) 2 inch through 6 inch - schedule 40 or Perform Engineering Analysis for
Requirement
1.3) 8 inch and larger - Perform Engineering Analysis for Requirement
2) Stainless Steel: Welded.
2.1) 1 ½ inch and smaller - schedule 40
2.2) 2 inch through 6 inch - schedule 40 or Perform Engineering Analysis for
Requirement
2.3) 8 inch and larger - Perform Engineering Analysis for Requirement
3) Carbon and Stainless Steel: Threaded.
3.1) Minimum schedule 80 for all sizes
Appendix M Operational Containment (Informative)
Operational Containment is a rare strategy as an alternative ventilation method where there are sensitive
off site receptors, such as densely-populated areas, nursing homes, or schools. The design should be
handled on a case-by-case basis for definition of appropriate criteria for application and design as a
variance to the standard practices defined in IIAR 2.
A refrigerant detection system meeting the requirements of Chapter 17 and a ventilation system meeting
the requirements of Section 7.6 should be provided, at a minimum.
An Operational Containment includes at a detection level determined by the site refrigeration
management designee, emergency responders, and/or owner. A pre-determined procedure should be
developed to ensure that personnel are not located within the machinery room before Operational
Containment is initiated. The procedure should include the following at a minimum:
A. Provide an “ON / OFF / AUTO” override for emergency ventilation at a secured remote
location that can be used for Operational containment shutdown of the ventilation system.
B. Automatically de-energize all unclassified electrical equipment at the detection of
ammonia vapor concentrations that exceeds the detector’s upper detection limit or
40,000 ppm (25% LFL), whichever is higher or upon stopping ventilation using manual
controls.
C. Equipment or controls that must remain energized for monitoring or controlling
equipment should be designed for operation in a hazardous location.
D. Airflow dampers on fans, air inlets and air outlets should close when an Operational
Containment is actuated.
Appendix N Site Considerations (Informative)
The following site considerations may be considered during the design review where a refrigerated
facility is to be constructed or expanded:
1) Proximity to Surface Waters: Topography of the site should prevent any possibility of an ammonia
spill from reaching surface waters such as creeks, streams, rivers, lakes, or ponds per all state and
federal regulations. A site drainage plan should be prepared for this purpose.
2) Proximity to Off-Site and Major Traffic Thoroughfares: Machinery rooms should be located on the
site with due consideration for proximity to off-site major traffic thoroughfares, nearby neighbors,
and prevailing winds. Machinery room location considerations should include safety, noise hazards,
and off-site effects. Refer to state and local codes and ordinances for any requirements.
3) Proximity to Sensitive Receptors: Machinery rooms should be located to minimize the impact on
nearby sensitive receptors such as schools and nursing homes. Refer to state and local codes and
ordinances for any requirements.
4) Arrangement of Machinery Room to Overall Facility: The machinery room location relative to the
rest of the refrigerated facility is important. Following are lists of preferred locations and least
desirable locations and others may also be identified:
Preferred Locations:
a. Ground level.
b. Separate Building (or sharing a building with another utility system).
c. Peninsular part of main building with three exposed walls and exposed roof, remote
from heavily occupied areas.
d. Along exterior of main building having one or two exposed walls and exposed roof,
remote from heavily occupied areas.
Least Desirable Locations:
a. Inner areas of building with no exterior wall exposure.
b. Adjacent to (horizontally or vertically) heavily occupied areas such as office and
employee welfare facilities or areas.
c. Basement of building.
d. Building floors above ground level.
Appendix 0 Informative References and Sources of References (Informative) 1.0 Informative References
1.1 American Conference of Governmental Industrial Hygienists (ACGIH), Industrial Ventilation,
A Manual of Recommended Practice for Design, 27th Edition (February 2010), Chapter 4,
Section 4.5 (General Industrial Ventilation).
1.2 American Petroleum Institute (API), API Standard 520, Sizing, Selection, and Installation of
Pressure-relieving Devices in Refineries, Part I – Sizing and Selection, Eighth Edition,
December 2008.
1.3 American Society of Heating, Refrigerating and Air Conditioning Engineers, Inc. (ASHRAE),
ANSI/ASHRAE Standard 15-2013, Safety Standard for Refrigeration Systems.
1.4 American Society of Testing and Materials (ASTM), editions as shown below:
1.4.1 ASTM A53/A53M-12, Standard Specification for Pipe, Steel, Black and Hot-Dipped,
Zinc-Coated, Welded and Seamless;
1.4.2 ASTM A105/A105M-13, Standard Specification for Carbon Steel Forgings for Piping
Applications;
1.4.3 ASTM A106/A106M-13, Standard Specification for Seamless Carbon Steel Pipe for
High-Temperature Service;
1.4.4 ASTM A181/A181M-13, Standard Specification for Carbon Steel Forgings, for General-
Purpose Piping;
1.4.5 ASTM A193/A193M-12b, Standard Specification for Alloy-Steel and Stainless Steel
Bolting Materials for High-Temperature Service;
1.4.6 ASTM A194/A194M-13, Standard Specification for Carbon and Alloy Steel Nuts for Bolts
for High-Pressure and High-Temperature Service, or Both;
1.4.7 ASTM A234/A234M-11a, Standard Specification for Piping Fittings of Wrought Carbon
Steel and Alloy Steel for Moderate and High Temperature Service;
1.4.8 ASTM A307-12, Standard Specification for Carbon Steel Bolts, Studs, and Threaded Rod
60,000 PSI Tensile Strength;
1.4.9 ASTM A312/A312M-13b, Standard Specification for Seamless, Welded, and Heavily
Cold Worked Austenitic Stainless Steel Pipes;
1.4.10 ASTM A320/A320M-11a, Standard Specification for Alloy-Steel and Stainless Steel
Bolting for Low-Temperature Service;
1.4.11 ASTM A333/A333M-11, Standard Specification for Seamless and Welded Steel Pipe for
Low-Temperature Service;
1.4.12 ASTM A403/A403M-13a, Standard Specification for Wrought Austenitic Stainless Steel
Piping Fittings;
1.4.13 ASTM A420/A420M-13, Standard Specification for Piping Fittings of Wrought Carbon
Steel and Alloy Steel for Low-Temperature Service;
1.4.14 ASTM A575-96 (2013), Standard Specification of Steel Bars, Carbon, Merchant
Quality, M Grades;
1.4.15 ASTM A707/A707M-13, Standard Specification for Forged Carbon and Alloy Steel
Flanges for Low-Temperature Service.
1.5 Environmental Protection Agency, 40 CFR Part 68, Accidental Release Prevention
Requirements: Risk Management Programs Under Clean Air Act, 2004.
1.6 International Fire Code (IFC), Section 606.10, Emergency Pressure Control System, 2012.
1.7 International Institute of Ammonia Refrigeration (IIAR):
1.7.1 Process Safety Management & Risk Management Program Guidelines, 2012;
1.7.2 The Ammonia Refrigeration Management Program (ARM), 2005;
1.7.3 IIAR Piping Handbook, Insulation for Refrigeration Systems, Chapter 7, 2004.
1.7.4 IIAR Bulletin No. 114 Identification of Ammonia Piping and System Components, 2014.
1.8 Manufacturers Standardization Society of the Valve and Fittings Industry (MSS), ANSI/MSS
Standard Practice SP 69-2003, Pipe Hangers and Supports, Selection and Application.
1.9 Occupational Safety and Health Administration (OSHA), U.S. Department of Labor, 2012:
1.9.1 29 CFR 1910.119, Process Safety Management of Highly Hazardous Chemicals;
1.9.2 29 CFR 1910 subpart D, Walking-Working Surfaces;
1.9.3 29 CFR 1910.27, ladders;
1.9.4 29 CFR 1910.147, Control of Hazardous Energy, (“Lockout/Tagout”);
1.9.5 29 CFR 1910.37(b), Maintenance, Safeguards, and Operational Features for Exit Routes.
2.0 Sources of References (Informative)
2.1 American Conference of Governmental Industrial Hygienists (ACGIH).
1330 Kemper Meadow Drive, Suite 600
Cincinnati, OH 45240
www.acgih.org
2.2 American National Standards Institute (ANSI).
25 West 43rd Street, 4th Floor
New York, NY 10036
www.ansi.org
2.3 American Petroleum Institute (API).
1220 L Street NW
Washington, DC 20005-4070
www.api.org
2.4 American Society of Heating, Refrigerating and Air Conditioning Engineers, Inc. (ASHRAE).
1791 Tullie Circle, N.E.
Atlanta, GA 30329
www.ashrae.org
2.5 American Society of Mechanical Engineers (ASME).
ASME International
Three Park Avenue
New York, NY 10016-5990
www.asme.org
2.6 American Society of Testing and Materials (ASTM).
ASTM International
100 Barr Harbor Drive
P.O. Box C700
West Conshohocken, PA 19428-2959
www.astm.org
2.7 International Institute of Ammonia Refrigeration (IIAR).
1001 North Fairfax Street, Suite 503
Alexandria, VA 22314
www.iiar.org
2.8 Manufacturers Standardization Society of the Valve and Fittings Industry (MSS).
127 Park Street, N.E.
Vienna, VA 22180
www.mss-hq.com
2.9 National Fire Protection Association (NFPA).
60 Batterymarch Park
Quincy, MA 02169-7471
www.nfpa.org
2.10 U. S. Department of Labor/OSHA.
Publications Department
200 Constitution Avenue, NW, Room N3101
Washington, DC 20210
www.osha.gov
2.11 U. S. Department of Transportation (US DoT).
Research and Special Programs Administration
Office of Hazardous Materials Safety
400 7th Street, S.W.
Washington, DC 20590
www.dot.gov