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PDH Course M398

ASME Section I & Section VIIIFundamentals

Jurandir Primo, PE

2011

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1.0 - INTRODUCTION:

The ASME Code design criteria consist of basic rules specifying the design method, design loads,allowable stress, acceptable materials, fabrication, testing, certification and inspection requirements.

The design method known as "design by rule" uses design pressure, allowable stress and a designformula compatible with the geometry to calculate the minimum required thickness of pressurized tanks,

vessels and pipes.

The ASME - American Society of Mechanical Engineers - International Boiler and Pressure VesselCode is made of 12 sections and contains over 15 divisions and subsections.

1.1 - Code Sections

I. Power BoilersII. MaterialsIII. Rules for Construction of Nuclear Facility ComponentsIV. Heating BoilersV. Nondestructive Examination

VI. Recommended Rules for the Care and Operation of Heating BoilersVII. Recommended Guidelines for the Care of Power BoilersVIII. Pressure VesselsIX. Welding and Brazing QualificationsX. Fiber-Reinforced Plastic Pressure VesselsXI. Rules for In-service Inspection of Nuclear Power Plant ComponentsXII. Rules for Construction and Continued Service of Transport Tanks

SECTION I. Power Boilers

This Section provides requirements for all methods of construction of power, electric, and miniatureboilers; high temperature water boilers used in stationary service; and power boilers used in locomotive,

portable, and traction service.

SECTION II. Materials

• Part A - Ferrous Material Specifications• Part B - Nonferrous Material Specifications• Part C - Specifications for Welding Rods, Electrodes, and Filler Metals• Part D - Properties

SECTION III. Rules for Construction of Nuclear Facility Components

• Subsection NCA - General Requirements for Divisions 1 and 2

DIVISION 1

• Subsection NB- Class 1 Components• Subsection NC- Class 2 Components• Subsection ND- Class 3 Components• Subsection NE- Class MC Components• Subsection NF - Supports• Subsection NG - Core Support Structures• Subsection NH - Class 1 Components in Elevated Temperature Service





DIVISION 2

• Code for Concrete Containments

DIVISION 3

• Containments for Transportation and Storage

SECTION IV. Heating Boilers

Requirements for design, fabrication, installation and inspection of steam generating boilers, and hotwater boilers intended for low pressure service that are directly fired by oil, gas, electricity, or coal. Itcontains appendices which cover approval of new material, methods of checking safety valve, safetyrelief valve capacity, definitions relating to boiler design and welding and quality control systems.

SECTION V. Nondestructive Examination

Requirements and methods for nondestructive examination which are referenced and required by othercode Sections. It also includes manufacturer's examination responsibilities, duties of authorized

inspectors and requirements for qualification of personnel, inspection and examination.

SECTION VI. Recommended Rules for the Care and Operation of Heating Boilers

It defines general descriptions, terminology and guidelines applicable to steel and cast iron boilerslimited to the operating ranges of Section IV Heating Boilers. It includes guidelines for associatedcontrols and automatic fuel burning equipment.

SECTION VII. Recommended Guidelines for the Care of Power Boilers

Guidelines to promote safety in the use of stationary, portable, and traction type heating boilers. Thesection provides guidelines to assist operators of power boilers in maintaining their plants as safely as

possible. Contains fuels for routine operation; Operating and maintaining boiler appliances; Inspectionand prevention of boiler failure; Design of installation; Operation of boiler auxiliaries; Control of internalchemical conditions

SECTION VIII. Pressure Vessels

Division 1 - Provides requirements applicable to the design, fabrication, inspection, testing, andcertification of pressure vessels operating at either internal or external pressures exceeding 15 psig.

Division 2 - Alternative rules, provides requirements to the design, fabrication, inspection, testing, andcertification of pressure vessels operating at either internal or external pressures exceeding 15 psig.

Division 3 - Alternative rules for Construction of High Pressure Vessels, provides requirementsapplicable to the design, fabrication, inspection, testing, and certification of pressure vessels operating ateither internal or external pressures generally above 10,000 psi.

SECTION IX. Welding and Brazing Qualifications

Rules relating to the qualification of welding and brazing procedures as required by other Code Sectionsfor component manufacture. Covers rules are related to the qualification and re-qualification of weldersand welding and brazing operators in order that they may perform welding or brazing as required byother Code Sections in the manufacture of components.





SECTION X. Fiber-Reinforced Plastic Pressure Vessels

Requirements for construction of FRP (Fiber-Reinforced Plastic) pressure vessels in conformance witha manufacturer's design report. It includes production, processing, fabrication, inspection and testingmethods required.

SECTION XI. Rules for In-service Inspection of Nuclear Power Plant Components

Requirements for the examination, in-service testing and inspection, and repair and replacement ofcomponents and systems in light-water cooled and liquid-metal cooled nuclear power plants.

SECTION XII. Rules for Construction and Continued Service of Transport Tanks

Requirements for construction and continued service of pressure vessels for the transportation ofdangerous goods via highway, rail, air or water at pressures from full vacuum to 3,000 psig and volumesgreater than 120 gallons.

1.2 - The ASME B31 Code

ASME B31 was earlier known as ANSI B31. The B31 Code for Pressure Piping, covers Power Piping,Fuel Gas Piping, Process Piping, Pipeline Transportation Systems for Liquid Hydrocarbons and OtherLiquids, Refrigeration Piping and Heat Transfer Components and Building Services Piping.

Piping consists of pipe, flanges, bolting, gaskets, valves, relief devices, fittings and the pressurecontaining parts of other piping components. It also includes hangers and supports, and other equipmentitems necessary to prevent overstressing the pressure containing parts. It does not include supportstructures such as frames of buildings, buildings stanchions or foundations.

B31.1 - 2001 - Power Piping

Required piping for industrial plants and marine applications. This code prescribes requirements for the

design, materials, fabrication, erection, test, and inspection of power and auxiliary service piping systemsfor electric generation stations, industrial institutional plants, central and district heating plants.

The code covers boiler external piping for power boilers and high temperature, high pressure waterboilers in which steam or vapor is generated at a pressure of more than 15 PSIG; and high temperaturewater is generated at pressures exceeding 160 PSIG and/or temperatures exceeding 250 degrees F.

B31.2 - 1968 - Fuel Gas Piping

This has been withdrawn as a National Standard and replaced by ANSI/NFPA Z223.1, but B31.2 is stillavailable from ASME and is a good reference for the design of gas piping systems (from the meter to theappliance).

B31.3 - 2002 - Process Piping

Code rules for design of chemical, petroleum plants, refineries, hydrocarbons, water and steam. ThisCode contains rules for piping typically found in petroleum refineries; chemical, pharmaceutical, textile,paper, semiconductor, and cryogenic plants; and related processing plants and terminals.

It prescribes requirements for materials and components, design, fabrication, assembly, erection,examination, inspection, and testing of piping. Also included is piping which interconnects pieces orstages within a packaged equipment assembly.





B31.4 - 2002 - Pipeline Transportation Systems for Liquid Hydrocarbons and Other Liquids

This Code prescribes requirements for the design, materials, construction, assembly, inspection, andtesting of piping transporting liquids such as crude oil, condensate, natural gasoline, natural gas liquids,liquefied petroleum gas, carbon dioxide, liquid alcohol, liquid anhydrous ammonia and liquid petroleumproducts between producers' lease facilities, tank farms, natural gas processing plants, refineries,stations, ammonia plants, terminals (marine, rail and truck) and other delivery and receiving points.

The requirements for offshore pipelines are found in Chapter IX. Also included within the scope of thisCode are:

• Primary and associated auxiliary liquid petroleum and liquid anhydrous ammonia piping atpipeline terminals (marine, rail and truck), tank farms, pump stations, pressure reducing stations andmetering stations, including scraper traps, strainers, and proper loops;• Storage and working tanks including pipe-type storage fabricated from pipe and fittings, andpiping interconnecting these facilities;• Liquid petroleum and liquid anhydrous ammonia piping located on property which has been setaside for such piping within petroleum refinery, natural gasoline, gas processing, ammonia, and bulkplants;• Those aspects of operation and maintenance of liquid pipeline systems relating to the safety andprotection of the general public, operating company personnel, environment, property and the pipingsystems.

B31.5 - 2001 - Refrigeration Piping and Heat Transfer Components

This Code prescribes requirements for the materials, design, fabrication, assembly, erection, test, andinspection of refrigerant, heat transfer components, and secondary coolant piping for temperatures aslow as -320 °F (-196 °C), whether erected on the premises or factory assembled, except as specificallyexcluded in the following paragraphs.

Users are advised that other piping Code Sections may provide requirements for refrigeration piping in

their respective jurisdictions.

This Code shall not apply to:• Any self- contained or unit systems subject to the requirements of Underwriters Laboratories orother nationally recognized testing laboratory:• Water piping and piping designed for external or internal gage pressure not exceeding 15 psi(105 kPa) regardless of size; or• Pressure vessels, compressors, or pumps, but does include all connecting refrigerant andsecondary coolant piping starting at the first joint adjacent to such apparatus.

B31.8 - 2003 - Gas Transmission and Distribution Piping Systems

This Code covers the design, fabrication, installation, inspection, and testing of pipeline facilities used forthe transportation of gas. This Code also covers safety aspects of the operation and maintenance ofthose facilities.

B31.8S-2001 - 2002 - Managing System Integrity of Gas Pipelines

This Standard applies to on-shore pipeline systems constructed with ferrous materials and that transportgas. Pipeline system means all parts of physical facilities through which gas is transported, includingpipe, valves, appurtenances attached to pipe, compressor units, metering stations, regulator stations,delivery stations, holders and fabricated assemblies.





The principles and processes are applicable to all pipeline systems. This Standard is specificallydesigned to provide the operator (as defined in section 13) with the information necessary to developand implement an effective integrity management program utilizing proven industry practices andprocesses.

The processes and approaches within this Standard are applicable to the entire pipeline system.

B31.9 - 1996 - Building Services Piping

This Code Section has rules for the piping in industrial, institutional, commercial and public buildings,and multi-unit residences, which does not require the range of sizes, pressures, and temperaturescovered in B31.1.

This Code prescribes requirements for the design, materials, fabrication, installation, inspection,examination and testing of piping systems for building services. It includes piping systems in the buildingor within the property limits.

B31.11 - 2002 - Slurry Transportation Piping Systems

Rule for design, construction, inspection and security requirements of slurry piping systems. This codecovers piping systems that transport aqueous slurries of no hazardous materials, such as coal, mineralores and other solids between a slurry processing plant and the receiving plant.

B31G - 1991 - Manual for Determining Remaining Strength of Corroded Pipelines

The scope of this Manual includes all pipelines within the scope of the pipeline codes that are part of ASME B31 Code for Pressure Piping, ASME B31.4, Liquid Transportation Systems for Hydrocarbons,Liquid Petroleum Gas, Anhydrous Ammonia, and Alcohols; ASME B31.8, Gas Transmission andDistribution Piping Systems; and ASME B31.11, Slurry Transportation Piping Systems. Parts 2, 3, and 4are based on material included in ASME Guide for Gas Transmission and Distribution Piping Systems,1983 Edition.

1.3 - ASME Certification and Inspection Procedures:

The symbols "A", "S", "U", "PP" and "H" Stamps covers the fabrication and alteration ofhigh pressure boilers, unfired pressure vessels, power piping and heating boilers.

Once any ASME Stamped Pressure Vessel is manufactured, it is checked, tested and approved by theASME Authorized Inspector, who review all the procedures and all the documentation and sign the DataReport Form before to procedure to Stamp the name plate with the “U” or “UM” symbols, which meansthat the Pressure Vessel fully complies with the ASME Code rules for construction of Pressure Vessels.

The National Board of Boiler & Pressure Vessel Inspectors uses the “NB” Symbol as well the “R”

Symbol to repair or to alter any previous Stamped Pressure Vessel.

All material used in manufacture must be documented. All welders must be certified. Manufacturershave an Authorized Inspector , who is the judge of code acceptability. The quality of weld is thenchecked for lack of weld penetration, slag inclusion, overlap and excessive reinforcement. At the finalinspection the units are hydrostatically tested at 1.5 times working pressure and observed for leaks.

1.4 – Imperial and Metric Values:

Professionals and students should be well versed in conversion practice. Many US customary unitvalues presented in the ASME codes do not convert directly into metric values in the ASME editions.





2.0 – SECTION I & SECTION VIII – Fundamentals:

The formulae in ASME Section I and Section VIII are used to determine the minimum requiredthickness and design pressure of piping, tubes, drums and headers using the Maximum AllowableWorking Pressure (MAWP).

However, Paragraph UG-31 states, that these formulae may be also used for calculating wall

thickness of tubes and pipes under internal pressure.

2.1 – Design:

The ASME Boiler Code Section I, as well as Section VIII, requires longitudinal and circumferential butt joints to be examined by full radiograph.

When the vessel design is required fully radiographed longitudinal butt-welded joint, the cylindricalshell will have a joint efficiency factor (E) of 1.0. This factor corresponds to a safety factor (or materialquality factor) of 3.5 in the parent metal.

When the vessel design is required non radiographed longitudinal butt-welded joints the vessel will

have a joint efficiency factor (E) of 0.7, which corresponds to a safety factor of 0.5 in., resulting in anincrease of 43% in the thickness of the plates.

2.2 – Pressure Vessels Maximum Allowable Stress Values

The maximum allowable stress values to be used in the calculation of the vessel’s wall thickness aregiven in the ASME Code for many different materials. These stress values are a function of temperature.

Grade 55 13,800 18,300

Grade 60 15,000 20,000

Grade 65 16,300 21,700

Grade 70 17,500 23,300

Grade A 11,300 15,000

Grade B 12,500 16,700

Grade C 13,800 18,300

SA - 36 12,700 16,900

Grade A 16,300 21,700

Grade B 17,500 23,300

Grade D 16,300 21,700

Grade E 17,500 23,300

Grade 304 11,200 20,000

Grade 304L - 16,700

Grade 316 12,300 20,000

Grade 316L 10,200 16,700

Maximum Allowable Stress Value for Common Steels

Material Spec. Nbr Grade

DIVISION 1

-20°F to

650°F

DIVISION 2

-20°F to

650°F

Carbon Steel

Plates and

Sheets

High Alloy

Steel Plates

SA - 516

SA - 285

SA - 203

SA - 240

Division 1 governs the design by Rules, is less stringent from the standpoint of certain design detailsand inspection procedures, and thus incorporates a higher safety factor of 4. For example, if a 60,000psi tensile strength material is used, the Maximum Allowable Stress Value is 15,000 psi.

Division 2 governs the design by Analysis and incorporates a lower safety factor of 3. Thus, themaximum allowable stress value for a 60,000 psi tensile strength material will become 20,000 psi.





Many companies require that all their pressure vessels be constructed in accordance with Division 2because of the more exacting standards. Others find that they can purchase less expensive vesselsby allowing manufacturers the choice of either Division 1 or Division 2.

Normally, manufacturers will choose Division 1 for low-pressure vessels and Division 2 for high-pressure vessels. The maximum allowable stress values at normal temperature range for the steelplates most commonly used in the fabrication of pressure vessels are given in Table above.

3.0 – ASME SECTION I Power Boilers – Types, Design, Fabrication, Inspection & Repair

Provides requirements for construction of power, electric, and miniature boilers; high temperature waterboilers used in stationary service; and power boilers used in locomotive, portable, and traction service.

Rules allow the use of the V, A, M, PP, S and E symbol stamps. The rules are applicable to boilers inwhich steam is generated at pressures exceeding 15 psig, and high temperature water boilers foroperation at pressures exceeding 160 psig and/or temperatures exceeding 250 °F.

This code covers power boiler superheaters, economizers, and other pressure parts connecteddirectly to the boiler without intervening valves are considered as part of the scope of Section 1.

3.1 – SECTION I – Boiler Tubes up to and including 5 inches O.D. (125 mm):

4. To calculate the minimum required thickness, according to paragraph PG-27.2.1, use equationbelow:

b) To calculate the Maximum Allowable Working Pressure (MAWP):

Where:

t = Minimum Design Wall Thickness (in)P = Design Pressure (psi)D = Tube Outside Diameter (in)e = Thickness Factor (0.04 for expanded tubes; 0 = for strength welded tubes)S = Maximum Allowable Stress According to ASME Section II, Table 1A

Example 1 - Boiler Tube:

Calculate the minimum required wall thickness of a water tube boiler 2.75 in O.D., strength welded (e =0) into place in a boiler. The tube has an average wall temperature of 650°F. The Maximum AllowableWorking Pressure (MAWP) is 580 psi gauge. Material is carbon steel SA-192.

Note: Before starting calculations check the correct stress table in ASME Section II, Table 1A:

SA-192 = 11,800 psi – allowable stress – Div. 1.

Solution:

For tubing up to and including 5 in O.D., use equation 1.1 above.





P = [580 psi]D = [2.75 in]e = 0 (strength welded)S = [11,800 psi] at [650°F])

t = 2.75 x 580 + 0.005 (2.75) + 0

2 (11,800) + 580

t = 0.079 in.

Note: Where the manufacturing process produces only standard plate thickness, so should be used 1/8in (3.2 mm) minimum.

3.2 – SECTION I – Piping, Drums, and Headers:

The following formulae are found in ASME Section I, paragraph PG-27.2.2. The information for piping,drums, or headers may be given with either the inside I or outside (D) measurement.

4. Using the outside diameter :

b) Using the inside radius:

Where:

t = Minimum Design Wall Thickness (in)P = Design Pressure (psi)D = Tube Outside Diameter (in)R = Tube Radius (in)E = Tube Welding Factor (1.0 for seamless pipe; 0.85 = for welded pipe)y = Wall Thickness Welding Factor (0.4 for 900°F & lower; 0.7 for 950°F & up)C = Corrosion Allowance (0 for no corrosion; 0.0625 in. commonly used; 0.125 in. maximum)S = Maximum Allowable Stress According to ASME Section II, Table 1A

Example 2 – Steam Piping:

Calculate the required minimum thickness of a seamless steam piping which carries steam at a pressureof 900 psi gauge and a temperature of 700°F. The piping is 10.77 in O.D., (10 inches nominal) plainend; the material is SA-335 – P1, alloy steel. Allow a manufacturer’s tolerance allowance of 12.5%.





Note: Before starting calculations check the material stress table in ASME Section II, Table 1A:

SA-335 – P1 = 13,800 psi – allowable stress – Div.1. Use equation 2.1:

P = [900 psi]D = [10.77 in]C = 0S = [13,800] – (SA-335 – P1 alloy steel at 700°F)E = 1.0y = 0.4 (Ferritic steel less than 900°F)

t = 900 x 10.77………. + 0 =2(13,800)(1.0) + 2(0.4)(900)

t = 0.34 in.

Therefore, including a manufacturer’s allowance of 12.5%; - 0.34 × 1.125 = 0.38 in.

Example 3 – Maximum Allowable Working Pressure (MAWP):

Calculate the Maximum Allowable Working Pressure (MAWP) for a seamless steel pipe of material SA-209-T1. The outside pipe diameter is 12.75 in. (nominal diam. 12 in.) with a wall thickness of 0.46 in.The operating temperature is 850°F. The pipe is plain ended.

D = 12.75 in (outside diameter)t = 0.46 inC = 0 (3 to 4 inches nominal and larger)

S = 13,100 psi (Section II, Table 1A, Div.1, SA-209-T1 at 850°F)E = 1.0 (seamless pipe as per PG-9.1)y = 0.4 (austenitic steel at 850°F)

Use equation 2.2:

P = 2SE (t – C) =D – (2y) (t – C)

P = 2 (13,100) (1.0) x (0.46 – 0) =12.75 – (2 x 0.4) (0.46 – 0)

P = 26,200 x 0.46 =12.75 – 0.368

P = 973 psi

Example 4 – Welded Tube Boiler Drum:

A welded water tube boiler drum of SA-515-60 material is fabricated to an inside radius of 18.70 in. onthe tube sheet and 19.68 in on the drum. The plate thickness of the tube sheet and drum are 2.34in. and 1.49 in., respectively.





The longitudinal joint efficiency is 100%, and the ligament efficiencies are 56% horizontal and 30%circumferential. The operating temperature is not to exceed 500°F. Determine the Maximum AllowableWorking Pressure (MAWP) based on:

Welded Water Tube Boiler Drum:DRUM &

TUBESHEET

Note: This is a common example of a water tube drum fabricated from two plates of different thickness.Thicker material is required where the boiler tubes enter the drum than is required for a plain drum.

This example has two parts:a) The drum – consider the drum to be plain with no penetrations.b) The tube sheet – consider the drum to have penetrations for boiler tubes.

(a) Drum. Use equation 2.4 (inside radius R):

Drum – P = SE (t – C)…. =R + (1 – y (t – C)

Where:

S = 15,000 psi (Section II, Table 1A, Div.1, SA-515-60 at 500°F) E = 1.0t = 1.49 inC = 0R = 19.68 in

y = 0.4 (Ferritic steel less than 900°F)

Drum – P = (15,000) (1.0) (1.49 – 0).. =19.68 + (1 – 0.4) (1.49 – 0)

Drum – P = 15,000 x 1.4919.68 + 0.894

Drum – P = 1,086 psi

(b) Tube Sheet. Use equation 2.4 (inside radius R):

Tube Sheet – P = SE (t – C)…. =R + (1 – y (t – C)

Where:

S = 15,000 psiE = 0.56 (circumferential stress = 30% and longitudinal stress = 56%; therefore = 0.56 < 2 x 0.30)t = 2.34 inC = 0 (3 to 4 inches nominal and larger)R = 18.70 iny = 0.4 (Ferritic steel less than 900°F)





Tube Sheet – P = (15,000) (1.0) (2.34 – 0)… =18.70 + (1 – 0.4) (2.34 – 0)

Tube Sheet – P = 15,000 x 2.3418.70 + 1.404

Tube Sheet – P = 1,746 psi

Note: Consider the Maximum Allowable Working Pressure (MAWP) = 1,086 psi (lowest number).

4.0 – ASME SECTION VIII – Division 1, Division 2, Division 3:

The ASME Section VIII, rules for fired or unfired pressure vessels, is divided into three divisions toprovide requirements applicable to the design, fabrication, inspection, testing, and certification. Theformulae and allowable stresses presented in this sketch are only for Division 1, the main code.

It contains mandatory and non-mandatory appendices detailing supplementary design criteria,nondestructive examination and inspection acceptance standards. Rules pertaining to the use of the U,UM and UV Code symbol stamps are also included.

4.1 – SECTION VIII – Thin Cylindrical Shells:

The formulae in ASME Section VIII, Division 1, paragraph UG-27, used for calculating the wallthickness and design pressure of pressure vessels, are:

a) Circumferential Stress (longitudinal welds):

• When, P < 0.385SE:

b) Longitudinal Stress (circumferential welds):

• When, P < 1.25SE

4.2 – SECTION VIII – Thick Cylindrical Shells:

For internal pressures higher than 3,000 psi, special considerations must be given as specified inparagraph U-1 (d). As the ratio of t/R increases beyond 0.5, a more accurate equation is required todetermine the thickness.





The formulae in ASME Appendix 1, Supplementary Design Formulas used for calculating thick walland design pressure, are:

a) For longitudinal stress (longitudinal welds):

When, P > 0.385SE:

And,

b) For longitudinal stress (circumferential welds):

When, P > 1.25SE:

And,

Where:

R = Design Radius (in.)Z = Dimensionless Factor

4.3 – SECTION VIII – Tube Spherical Shells:

The standard design method uses an increased wall thickness at the equator line of the vessel tosupport the additional stresses caused by the attachment of the legs. The formula for calculation the wallthickness of a segmented plate of a sphere to be welded in a heat exchanger tube is:

t = PL…… + C 2SE – 0.2P

L = Di/2

Where:

t = Minimum Design Wall Thickness (in);P = Design Pressure (psi);Di = Inside Diameter of Sphere (in);L = Sphere Radius (in);E = Tube Welding Factor (1.0 for seamless pipe; 0.85 = for welded pipe);C = Corrosion Allowance (0 for no corrosion; 0.0625 in. commonly used; 0.125 in. maximum);S = Maximum Allowable Stress According to ASME Section II, Table 1A.





Example 5 – Thin Cylindrical Shells:

A vertical boiler is constructed of SA-515-60 according to Section VIII-1. It has an inside diameter of 96in. and an internal design pressure of 1,000 psi at 450 F°. The corrosion allowance is 0.125 in., and joint efficiency is E = 0.85. Calculate the required thickness of the shell.

SA-515-60 = 15,000 psi – allowable stress, ASME Section II, Table 1A, Div.1.

Since P < 0.385SE (6,545 psi) as 1,000 psi < 6,545 psi, use equation 1.3:

t = PR… + CSE – 0.6P

Considering the external radius = 48 in. + 0.125 in. Corrosion allowance = 0.125 in.

t = 1,000 x (48 in. + 0.125).. + 0.125 =2(15,000)(0.85) – 0.8(1,000)

t = 2.07 in.

Example 6 – Thick Cylindrical Shells:

a) When P > 0.385SE:

Calculate the required shell thickness of an accumulator with P = 10,000 psi, R = 18 in., S = 20,000 psi,and E = 1.0. Assume a corrosion allowance of 0.25 in.

For P > 0.385SE (7,700 psi) as 10,000 psi > 7,700 psi, use equation 1.7:

t = R (Z½

- 1) =

Z = (20,000)(1.0) + 10,000 = 30,000 = 3 (20,000)(1.0) – 10,000 10,000

t = (18 + 0.25) (3½

– 1) = 13.36 in.

Example 7 – Thick Cylindrical Shells:

b) When P < 0.385SE:

Calculate the required shell thickness of an accumulator with P = 7,650 psi, R = 18 in, S = 20,000 psi,and E = 1.0. Assume corrosion allowance = 0.

For P< 0.385SE (7,700 psi) as 7,650 psi < 7,700 psi, use equation 1.3:

t = PR… + CSE – 0.6P

t = 7,650 x 18………… + 0(20,000)(1.0) – 0.6(7,650)

t = 8.9 in.





Example 8 – Comparison between Equation 1.3 and Equation 1.7:

Calculate the shell thickness, comparing the equation 1.3 with another answer using equation 1.7.

t = R (Z½

- 1) =

Z = (20,000)(1.0) + 7,650 = 27,650 = 2.24 (20,000)(1.0) – 7,650 12,350

t = (18 + 0) (2.24½

- 1) =

t = 8.9 in.

This shows that the “simple use” of equation (1.3) is accurate over a wide range of R/t ratios.

5.0 – SECTION I: Dished Heads Formulae:

Flanged and dished heads can be formed from carbon steel, stainless steel, and other ferrous and non-

ferrous metals and alloys. Flanged and dished heads can be formed in a size range from 4 in to 300 indiameter and in thickness range of 14 Gauge to 1-1/2” thick.

Pressure vessel heads and dished ends are essentially the same – the end caps of a pressure vesseltank or an industrial boiler. They are supplied with a flanged edge to make it easier for the fabricator toweld the head to the main body of the tank.

Dished heads can be manufactured using a combination of processes, spinning & flanging, where thespherical radius is made via the spinning process and the knuckle is created under the flanging method.

5.1 – Blank, Unstayed Dished Heads:

Paragraph PG-29.1 states that the thickness of a blank, unstayed dished head with the pressure on theconcave side, when it is a segment of a sphere, shall be calculated by the following formula:

Where:

t = Minimum thickness of head (in)P = maximum allowable working pressure (psi)L = Concave side radius (in)S = Maximum Allowable Working Stress (psi)

Paragraph PG-29.2 states: “The radius to which the head is dished shall be not greater than theoutside diameter of the flanged portion of the head. Where two radii are used, the longer shall betaken as the value of L in the formula.”

Example 9 – Segment of a Spherical Dished Head:

Calculate the thickness of a seamless, blank unstayed dished head having pressure on the concaveside. The head has an inside diameter of 42.7 in. with a dish radius of 36.0 in. The Maximum Allowable Working Pressure (MAWP) is 360 psi and the material is SA-285 A. The temperature doesnot exceed 480°F. State if this thickness meets Code.





Solution: Use equation 1.11

P = 360 psiL = 36.0 in

S = 11,300 psi – SA-285 A at 480°F

t = 5 (360 x 36) =4.8 (11,300)

t = 1.19 in.

PG-29.6 states: “No head, except a full-hemispherical head, shall be of a lesser thickness than thatrequired for a seamless shell of the same diameter.” Then, the minimum thickness of piping is:

Where:

P = 360 psiD = 42.7 iny = 0.4 (Ferritic steel less than 900°F)E = 1.0 (welded)

t = 360 x 42.7 =2(11,300)(1.0) + 2 (0.4)(360)

t = 0.67 in.

Therefore, the calculated head thickness meets the code requirements, since 1.19 > 0.67.

Example 10 - Segment of a Spherical Dished Head with a Flanged-in Manhole:

Calculate the thickness of a seamless, unstayed dished head with pressure on the concave side, havinga flanged-in manhole 6.0 in x 16 in. Diameter head is 47.5 in with a dish radius of 45 in. The MAWP is225 psi, the material is SA-285-C, and temperature does not exceed 428°F.

First thing to check: is the radius of the dish at least 80% of the diameter of the shell?

Dish Radius = 45

Shell Diameter 47.5

0.947 > 0.8 - The radius of the dish meets the criteria. Then, use equation 1.11:

P = 225 psiL = 45 inS = 13,800 psi (450°F - use the next higher temperature).





t = 5 (225 x 45) =4.8 (13,800)

t = 0.764 in.

This thickness is for a blank head. PG-29.3 requires this thickness to be increased by 15% or 0.125in., whichever is greater. As 0.764 × 0.15 = 0.114 in., that is less than 0.125 in., then, the thicknessmust be increased by 0.125 in.

Then, the required head thickness is, t = 0.764 + 0.125 = ~0.90 in.

5.2 - Seamless or Full-Hemispherical Head:

The thickness of a blank, unstayed, full-hemispherical head with the pressure on the concave sideshall be calculated by the following formula:

t = Minimum thickness of head (in)P = Maximum Allowable Working Pressure (psi)L = Radius to which the head was formed (in)S = Maximum Allowable Working Stress (psi)

The above formula shall not be used when the required thickness of the head given by the formulaexceeds 35.6% of the inside radius. Instead, use the following formula:

Example 11 - Seamless or Full-Hemispherical Head:

Calculate the minimum required thickness for a blank, unstayed, full-hemispherical head. The radiusto which the head is dished is 7.5 in. The MAWP is 900 psi and the head material is SA 285-C. Theaverage temperature of the header is 570°F.

Solution: Use equation 1.13.

P = 900 psiL = 7.5 in.S = 13,800 psi - (SA 285-C at 600°F).

t = 900 x 7.5 =2 (13,800) – 0.2 (900)

t = 0.24 in.

Check if this thickness exceeds 35.6% of the inside radius = 7.5 x 0.356 = 2.67 in. It does not exceed35.6%, therefore the calculated thickness of the head meets the code requirements.





6.0 - SECTION VIII-1: Dished Heads Formulae:

The Section VIII-1 determines the rules for dished heads. The most common configurations arespherical, hemispherical, elliptical (or ellipsoidal) and torispherical shapes.

How the shapes are, make some confusion for beginners and even professionals users of ASMEVIII. To cast a little light on these subjects see the resume below:

Spherical or Hemispherical Heads

Semi-Elliptical Heads (2:1)

Elliptical or Ellipsoidal Heads (1.9:1)

Torispherical Heads

Flanged and Dished Heads

Flat Dished HeadsNon Standard 80-10 Dished Heads Dished Discs Toriconical Heads

6.1 - Spherical or Hemispherical Heads:

a) When t < 0.356R or P < 0.665SE:

Or,

b) When t > 0.356R or P > 0.665SE:

Or,





Example 12 - Spherical or Hemispherical Head:

A pressure vessel is built of SA-516-70 material and has an inside diameter of 96 in. The internal designpressure is 100 psi at 450°F. Corrosion allowance is 0.125 in. and joint efficiency is E = 0.85. What isthe required thickness of the hemispherical head if “S” is 20000 psi?

Solution: Since 0.665SE > P = 11305 psi > 100 psi, use equation 2.1.

The inside radius in a corroded condition is equal to, R = 48 + 0.125 = 48.125 in.

t = PR =2SE – 0.2P

t = 100 x 48.125 =2(20,000) (0.85) – 0.2(100)

t = 0.14 in.

Example: Spherical Shell:

A spherical pressure vessel with an internal diameter of 120 in has a head thickness of 1 in.Determine the design pressure if the allowable stress is 16300 psi. Assume joint efficiency E = 0.85. Nocorrosion allowance is stated to the design pressure.

Solution: Since t < 0.356R use equation 2.2.

P = 2SEt =R + 0.2t

P = 2(16,300)(0.85)(1) =60 + 0.2(1)

P = 460 psi

The calculated pressure 460 psi is < 0.665SE (9213 psi); therefore, equation 2.2 is acceptable.

Example 13 - Thick Hemispherical Head:

Calculate the required hemispherical head thickness of an accumulator with P = 10000 psi, R = 18.0 in,S = 15,000 psi, and E = 1.0. Corrosion allowance is 0.125 in.

Solution: As 0.665SE < P = 9975 psi < 10000 psi, use equation 2.3.

Y = 2(15,000)(1.0) + 15,000 =2(15,000)(1.0) – 15,000

Y = 45,000 = 3 15,000

t = R (Y1/3 – 1) = 18.0 + 0.25 (31/3 – 1) = 8.0 in.





This is the minimum thickness for fully corroded state. Total head thickness is 8.0 + 0.125 in (corrosion

allowance), t = 8.125.

6.2 – Elliptical or Ellipsoidal Heads:

The commonly used semi-ellipsoidal head has a ratio of base radius to depth of 2:1 (shown in Fig. 2a).The actual shape can be approximated by a spherical radius of 0.9D and a knuckle radius of 0.17D.The required thickness of 2:1 heads with pressure on the concave side is given below:

Semi-Elliptical or Semi-Ellipsoidal Heads – 2:1:

Example 14 - Elliptical or Ellipsoidal Heads:

Calculate the head thickness considering the dimensions given below:

Inside Diameter of Head (Di): 18.0 in Inside Crown Radius (L): (18.0 x 0.9Di) in Inside Knuckle Radius (ri): (18.0 x 0.17Di) in Straight Skirt Length (h): 1.500 in Radius L - (18.0 x 0.9Di) = 16.20 in Radius ri - (18.0 x 0.17Di) = 3.06 in





Material and Conditions:

Material: SA-202 Gr. B (Room Temperature)Internal Pressure: 200 psi Allowable Stress: 20,000 psiHead Longitudinal Joint Efficiency: 0.85 Corrosion Allowance: 0.010 in

Variable:

L/r = L/ri = 16.20/3.06 = 5.29 in

a) Required Thickness:

t = PD + corrosion allowance2SE – 0.2P

t = 200 x 18.0 + 0.0102(20,000)(0.85) – 0.2(200)

t = 0.116 in.

b) Maximum Pressure:

P = 2SEt =D + 0.2t

P = 2(20,000)(0.85)(0.116) =18 + 0.2 (0.116)

P = 219 psi.

Note: Ellipsoidal heads and all torispherical heads made of materials having a specified minimumtensile strength > 80 000 psi shall be designed using a value of S = 20,000 psi at room temperature(see UG-23).

6.3 - Torispherical Heads:

Shallow heads, commonly referred to as flanged and dished heads (F&D heads), are according toparagraph UG-32 (e), with a spherical radius L of 1.0D and a knuckle radius r of 0.06D.

• a) Flanged & Dished Head (F&D heads):

The dish radius of a Flanged and Dished Head is 1.0 D and the knuckle radius is 0.06% D. The requiredthickness of a Torispherical F&D Head with r/L = 0.06 and L = Di, is:

or





P = Pressure on the concave side of the headS = Allowable stresst = Thickness of the headL = Inside spherical radiusE = Joint efficiency factor

Example 15 - Torispherical Heads:

A drum is to operate at 500°F and 350 psi and to hold5000 gallons of water . Dished Torispherical Headsinside radius is 78 in. The material is SA 285 Grade A. Assume “S” = 11200 psi and “E” = 0.85.

Solution: Dished Torispherical Heads with L = Di andr/L = 0.06, use equation 2.7.

t = 0.885 PL =SE – 0.1P

t = 0.885 (350) (78) =(11200)(0.85) – 0.1(350)

t = 2.54 in.

• b) Non Standard 80-10 Flanged & Dished Head:

On an 80-10 the inside radius (L) is 0.8 Di and the knuckle radius (ri) is 10% of the head diameter.For the required thickness of a Non Standard 80-10 Head, use equations 2.7 and 2.8.

Designing 80-10 Torispherical Heads rather than standard shapes can be achieved by lowering thematerial costs. The 80-10 is typically only 66% the thickness of the standard Torispherical Heads.

6.4 – Conical or Toriconical Heads:

The required thickness of the Conical or Toriconical Head (knuckle radius > 6%OD) shall be determined by formula using internal diameter of shell, α ≤ 30º.

t = PD 2.92 (SE - 0.6P) cos α

L = Di / (2 cos α)Di = Internal Diameter (conical portion) = D - 2 r (1 - cos α)r = Inside Knuckle Radius





Toriconical Heads Definitions:

6.5 – Resume of Pressure Vessels Formulae – ASME Section I & ASME Section VIII:

Item Thickness - t (in)Pressure - P

(in)Stress - S (in) Notes

PR SEt P(R + 0.6t) t ≤ 0.25 D; P ≤ 0.385 SE

SE - 0.6P R + 0.6t t

PR 2.SEt P(R + 0.2t) t ≤ 0.178D; P ≤ 0.685 SE

2SE - 0.2P R + 0.2t 2t

Flat Flanged HeadD√0.3P/S t²S/0.3D² 0.3D² P/t²

0.885PL SEt P(0.885L + 0.1t) r/L = 0.06; L ≤ D + 2t

SE - 0.1P 0.885L + 0.1t t

PLM 2.SEt P(LM + 0.2t) M = 3 + (L/r)1/2

/ 4

2SE - 0.2P LM + 0.2t 2t

PD 2.SEt P(D + 0.2t) h/D = 4

2SE - 0.2P D + 0.2t 2t

PDK 2.SEt P(DK + 0.2t) K = [2 + (D/2h)²] / 6; 2 ≤ D/h ≤ 6

2SE - 0.2P DK + 0.2t 2Et

PD 2.SEt cos α P(D + 1.2t cos α) α ≤ 30°

2(SE - 0.6P) cos α D + 1.2t cos α 2t cos α

Cylindrical Shell

Torispherical Head (a)

Torispherical Head (b)

2:1 Semi-Elliptical Head

(a)

Toriconical Head

Ellipsoidal Head (b)

Hemispherical Shell (or

Head)

OBS.:

D = Shell / Head Inside Diameter, E = Weld Joint Efficiency (0.7 -1.0), L = Crown Radius, P = Internal Pressure, h = InsideDepth of Head, r = Knuckle Radius, R = Shell/Head Inside Radius, S = Allowable Stress, t = Shell / Head Thickness.

6.6 - Scope of ASME Section VIII:





• Objective: Minimum requirements for safe construction and operation, Division 1, 2, and 3.

• Section VIII Division 1:

15 psig < P ≤ 3000 psig

• Other exclusions:

– Internals (except for attachment weld to vessel) – Fired process heaters – Pressure containers integral with machinery – Piping systems

• Section VIII, Division 2, Alternative Rules:

15 psig < P ≤ 3000 psig - identical to Division 1, but the different requirements are:

– Allowable stress – Stress calculations – Design – Quality control – Fabrication and inspection

The choice between Divisions 1 and 2 is based mainly on economics of materials.

• Division 3, Alternative Rules - High Pressure Vessels:

Applications over 10,000 psi;Pressure from external source, process reaction, application of heat, combination of these;Does not establish maximum pressure limits of Division 1 or 2 or minimum limits for Division 3.

• Structure of Section VIII, Divis ion 1:

Subsection A: Part UG applies to all vessels;

Subsection B: Requirements based on fabrication method, Parts UW, UF, UB;

Subsection C: Requirements based on material class, Parts UCS, UNF, UHA, UCI, UCL, UCD, UHT,ULW, ULT. Mandatory and Nonmandatory Appendices

• Determination of Material Thickness:

• Yield Strength, Ultimate Tensile Strength, Creep Strength, Rupture Strength and Corrosion Resistance.

• Resistance to Hydrogen Attack:

-Temperature at 300 - 400°F, monatomic hydrogen forms molecular hydrogen in voids;- Pressure buildup can cause steel to crack;- Above 600°F, hydrogen attack causes irreparable damage through component thickness.

• Brittle Fracture and Fracture Toughness:

The conditions that could cause brittle fracture are:





– Typically at “low” temperature – Can occur below design pressure – No yielding before complete failure – High enough stress for crack initiation and growth – Low enough material fracture toughness at temperature – Critical size defect to act as stress concentration

• Factors That Influence Fracture Toughness:

- Temperature- Type and chemistry of steel- Manufacturing and fabrication processes- Arc strikes, especially if over repaired area- Stress raisers or scratches in cold formed thick plate

• Material Groups – The Most Common Used Materials:

Curve A:

SA-216 Gr. WCB & WCC, normalized and tempered;SA-217 Gr. WC6, normalized and tempered.

Curve B:

SA-216 Gr. WCA, normalized and tempered or water-quenched and tempered;SA-216 Gr. WCB & WCC for maximum thickness of 2 in. (water-quenched and tempered);SA-285 Gr. A & B;SA-414 Gr. A;SA-515 Gr. 60;SA-516 Gr. 65 & 70, not normalized.

Curve C:

SA-182 Gr. 21& 22, normalized and temperedSA-302 Gr. C & DSA-336 Gr. F21 & F22, normalized and temperedS A-3 8 7 G r. 21 & 22, normalized and temperedS A-5 1 6 G r. 55 & 60, not normalizedSA-533 Gr. B & CSA-662 Gr. A

Curve D:

SA-203SA-537 Cl. 1, 2 & 3SA-508 Cl. 1SA-612, normalizedSA-516, normalizedSA 662, normalizedSA-524 Cl. 1 & 2SA-738 Gr. A

Common Materials - Temperature Limits:





• Bolting:

• See the ASME Code Section VIII, Div. 1, for impact and nuts test for specified material specifications.

• Addi tional ASME Code Impact Test Requ irements :

• For welded construction over 4 in. thick, or non welded construction over 6 in. thick, if MDMT < 120°F• Not required for flanges if temperature -20°F• Required if SMYS > 65 ksi unless specifically exempt.

• Weld Joint Efficiencies, E

7.0 - Shell Nozzles – Fundamentals:





Vessel components are weakened when material is removed to provide openings for nozzles or accessopenings. To avoid failure in the opening area, compensation or reinforcement is required.

The Code procedure is to relocate the removed material to an area within an effective boundary aroundthe opening. Figure bellow shows the steps necessary to reinforce an opening in a pressure vessel.

• Definitions:

• Diameter of Circular Opening, d:

d = Diameter of Opening – 2 (Tn + Corrosion Allowance)

• Required wall thickness of the nozzle (min):

tn = PR...... SE – 0.6P

• Area of Required Reinforcement, Ar :





Ar = d.ts.F (in²)

Where:

d =Diameter of circular opening, or finished dimension of opening in plane under consideration, in.

ts = Minimum required thickness of shell when E = 1.0, in.

F = Correction factor, normally 1.0

Example 16 – Basic Pipe Nozzle:

Design Pressure = 300 psigDesign Temperature = 200° FShell Material is SA-516 Gr. 60Nozzle Diameter 8 in, Sch. 40Nozzle Material is SA-53 Gr. B, Seamless

Corrosion Allowance = 0.0625"Vessel is 100% RadiographedNozzle does not pass through Vessel Weld Seam

Wall thickness of the nozzle (min):

tn = PR...... = SE – 0.6P

tn = 300 x 4.312”…….. + 0.0625 (Corrosion Allowance)

12,000(1.0) – 0.6(300)

tn = 0.11” + 0.0625” = 0.17 in (min) – Pipe Sch. 40 is t = 0.32 in.

Circular Opening, d:

d = Diameter of Opening – 2 (Tn + Corrosion Allowance)

d = 8.625 – 2(0.32 + 0.0625) =

d = 8.625 – 2 (0.3825) = 7.86 in

Area of Required Reinforcement, Ar :





Ar = d.ts.F (in²)

Ar = 7.86 x 0.487 x 1.0 = 3.82 in²

• Available reinforcement area in shell, Ar , as larger of As or An:

• As = Larger of: d (Ts – ts) - 2 Tn (Ts – ts) =

As = 7.86 (0.5625 – 0,487) – 2x 0,5625 (0.5625 – 0,487) = 0.50 in²

• An = Smaller of: 2 [2.5 (Ts) (Tn – tn)]

An = 2 [2.5 (0.5625) (0.32 – 0.17)] = 0.42 in²

• Ar < (As + An) =

Ar < (0.50 + 0.42) = 0.92 in² < 3.82 in² (Reqd.)

Therefore, it´s necessary to increase Ts and / or Tn to attend the premise Ar < (As + An).

Example 17 – Basic Shell & Nozzle:

Design Pressure = 700 psiDesign temperature = 700 °FNozzle Diameter = 8 in. (8.625 OD)Material:

• Shell – SA 516 Gr.70

• Head – SA 516 Gr. 70

• Nozzle – SA 106 Gr. B

• E = 1.0 (weld efficiency)

Required Shell Thickness:

ts = PR… SE – 0.6P

ts = 700 x 30……..... = 1.30 (Use Ts = 1.50”) 16,600(1.0) – 0.6(700)

Required Head Thickness:

th = PR…… 2SE – 0.2P

th = 700 x 30…….......... = 0.64 (Use Th = 1.0”)

2(16,600)(1.0) – 0.2(700)

Required Nozzle Thickness:

tn = PR… SE – 0.6P

tn = 700 x 4.312”……..... = 0.21 (Use Tn = 1.0”) 14,400(1.0) – 0.6(700)

Opening Reinforcement:

Ar (Reqd.) = d.ts = 8.625 x 1.3 = 11.2 in²

As = Larger of: d (Ts – ts) - 2 Tn (Ts – ts) =

As = 8.625 (1.5 – 1.3) – 2 (1.0) (1.5 – 1.3) = 1.325 in²

An = Smaller of: 2[2.5 (Ts) (Tn – tn)]

An = 2[2.5 (1.5) (1.0 – 0.21)] = 5.925 in²

Ar < (As + An) =

Ar < (1.325 + 5.925) = 7.25 in² < 11.2 (Reqd.)

OBS.: Necessary to increase Ts and / or Tn to attendthe premise (As + An) > Ar.

Example 18 – Nozzle Design:





8.2 - Low Alloy Steels:





8.1 – MAWP – Maximum Allowable Stress Values:

The Section II, Part D contains properties of ferrous and nonferrous materials adopted by the Code forthe design of boiler, pressure-vessel, and nuclear-power-plant components including tables of themaximum allowable stresses and design-stress intensities for the materials adopted by variousCodebook sections.

The tables below are an extract from ASME for the most common ferrous materials for a basic designpurpose. The student must always consult the original tables.





9.0 – Suplementary ASME Allowable Stress for General Design at Atmospheric Pressure:





1. Stress values for fusion-welded pipes include a welded-joint efficiecy factor of 0.80. Only straight-seam pipe shallbe used; the use of spiral-seam pipe is prohibited.

2. Stress values for castings include a factor of 0.80.

3. Allowable stress based on Section VIII of the ASME multiplied by the ratio of the design stress factors in thisstandard.





9.0 – Extract ASME Section VIII – Division 1 - Suplementary Design Formulas:





Example 19 – MAWP (Maximum Allowable Working Pressure:

Example 20 – Thickness of a Cylindrical Shell Considering Internal Pressure:





Example 21 – Design of a Standard Torispherical Head:





Example 22 – Design of a Non-Standard Torispherical Head

pressure-vessel-design-asme-section-1-viii.pdf

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