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09/9/2014
Products Solutions Services
CT287
Hazardous Area Classifications and Protection Systems
Slide 1 Craig McIntyre
09/9/2014
CT287 - Hazardous Area Classifications and Protection Systems
Topics covered
• Types of Hazardous Area classifications with focus on North America • Types of hazardous protection systems • Overview of Recognized National Testing Laboratories (NRTL), the
National Electrical Code and OSHA • Documentation and labeling • Questions
Slide 2 Craig McIntyre
09/9/2014
CT287 - Hazardous Area Classifications and Protection Systems
Types of Hazardous Area classifications with focus on North America
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What constitutes a Hazardous Location?
• In electrical engineering, a hazardous location is defined as a place where concentrations of flammable gases, vapors, or dusts occur. Electrical equipment that must be installed in such locations is especially designed and tested to ensure it does not initiate an explosion, due to arcing contacts or high surface temperature of equipment.
• In some cases the gas, ignitable vapor or dust is present all the time or for long periods; other areas would have a dangerous concentration of flammable substances only during process upsets, equipment deterioration between maintenance periods, or during an incident. These are then divided into areas of risk of release of gas, vapor or dust. The process of determining the type and size of these hazardous areas is called area classification.
CT287 - Hazardous Area Classifications and Protection Systems
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Solvent Recovery Tank
CT287 - Hazardous Area Classifications and Protection Systems
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Coal Conveyor
CT287 - Hazardous Area Classifications and Protection Systems
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Industrial Fire
CT287 - Hazardous Area Classifications and Protection Systems
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History
• Began with mine safety in the U.K.
• Low voltage concepts began early
• By 1913 a deadly explosion proved low voltage was not enough
CT287 - Hazardous Area Classifications and Protection Systems
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CT287 - Hazardous Area Classifications and Protection Systems
Ignition Triangle
• Three components are required to permit combustion, ignition, fire or explosion
Fuel
Oxygen
Energy
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Sources of Ignition
CT287 - Hazardous Area Classifications and Protection Systems
• Flame • Spark • Heat • Electrical energy
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Sources of Ignition
• Flame • Spark • Heat • Electrical energy
CT287 - Hazardous Area Classifications and Protection Systems
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Classification
• Instrumentation specifications often designate the classification of the area where instrument will be used.
• We will address the Area classification system
• The Zone classification system is in place but is not common
CT287 - Hazardous Area Classifications and Protection Systems
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Area Classification hierarchy
CT287 - Hazardous Area Classifications and Protection Systems
• Class • Division • Group
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CT287 - Hazardous Area Classifications and Protection Systems
Area Classes
• Class I - Ignitable gases or vapors • Class II - Ignitable dust • Class III - Ignitable textile fibers
NOTE: always in Roman numerals
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Three “Classes” Means Three Types of Materials
CT287 - Hazardous Area Classifications and Protection Systems
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Area Divisions
CT287 - Hazardous Area Classifications and Protection Systems
• Division 1 - Hazard constantly present, or occasionally present under normal operating conditions.
• Division 2 - Hazard present only under abnormal conditions.
NOTE: always in Arabic numerals
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Abnormal Tank Conditions
CT287 - Hazardous Area Classifications and Protection Systems
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Dike
Grade Sump or trench
Vent Hatch
Vent
Flammable Liquid
Boundaries • Division Method – Boundaries (Designated Areas)
Division 1
Division 2
Key
CT287 - Hazardous Area Classifications and Protection Systems
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Gases and Vapors
CT287 - Hazardous Area Classifications and Protection Systems
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CT287 - Hazardous Area Classifications and Protection Systems
Area Groups: Gases
• Group • A - Acetylene only • B - Hydrogen + few select gases • C - Ethylene, UDMH, etc. • D - Hydrocarbons, alcohols, etc.
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Dusts
CT287 - Hazardous Area Classifications and Protection Systems
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CT287 - Hazardous Area Classifications and Protection Systems
Area Groups: Dusts
• Group • E - Metal dusts • F - Coal dusts (carbonaceous dusts) • G - Non-conductive dusts
• Agricultural • Plastics
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Another consideration is Temperature: • Temperature Class, or T-Class
• Definition: • The temperature classes are used to
designate the maximum operating temperatures on the surface of the equipment which should not exceed the ignition temperature of the surrounding atmosphere. Ignition temperature is the minimum temperature required, at normal atmospheric pressure and in the absence of a spark or flame, to set afire or cause self-sustained combustion independently of the heating or heated element.
Typical North American Standard:
CT287 - Hazardous Area Classifications and Protection Systems
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Temperature (T) Class Values:
Typical North American Standard:
CT287 - Hazardous Area Classifications and Protection Systems
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CT287 - Hazardous Area Classifications and Protection Systems
Types of hazardous protection systems
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Achieving Safety
CT287 - Hazardous Area Classifications and Protection Systems
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CT287 - Hazardous Area Classifications and Protection Systems
Safety Approach: Terms
• Explosionproof • Dust ignitionproof • Intrinsically safe • Non-incendive • Associated apparatus • Purged
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CT287 - Hazardous Area Classifications and Protection Systems
Explosionproof
• Applies to Class I Only (Gases) • Containment Strategy - Assume gas will enter enclosure and the
contained circuitry is capable of igniting it. BUT the system is sufficiently sealed and of sufficient strength to prevent ignition of outside atmosphere.
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Explosionproof enclosures
CT287 - Hazardous Area Classifications and Protection Systems
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“Exploded” Explosion-Proof Housing
CT287 - Hazardous Area Classifications and Protection Systems
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CT287 - Hazardous Area Classifications and Protection Systems
Dust Ignitionproof
• Applies to Class II and III Only (Dusts/Fibers) • Containment Strategy - Assumes contained circuitry is capable of
igniting dust. BUT enclosure is sufficiently sealed against entry of dust, and surface temperatures are too low to ignite settled dust on enclosure.
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CT287 - Hazardous Area Classifications and Protection Systems
Intrinsically Safe
• Applies to all Division 1 Areas (i.e. in all Classes and Groups) • Circuitry Strategy - Circuits are designed to be incapable of an energy
release sufficient to ignite the specified atmosphere, even with specific instances of circuitry failures.
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Intrinsically Safe System
CT287 - Hazardous Area Classifications and Protection Systems
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CT287 - Hazardous Area Classifications and Protection Systems
How is a Circuit Made “Intrinsically Safe?”
• First must define what atmospheres will be involved • Refer to published ignition curves
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CT287 - Hazardous Area Classifications and Protection Systems
How is a Circuit Made “Intrinsically Safe?”
• First must define what atmospheres will be involved • Refer to published ignition curves
Max Allowable
Current
Max Operating Voltage
Group C
Group B
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CT287 - Hazardous Area Classifications and Protection Systems
How is a Circuit Made “Intrinsically Safe?”
• First must define what atmospheres will be involved • Refer to published ignition curves • Implement voltage and current limiting
L1
L2
device
hazardous safe
Slide 36 Craig McIntyre
09/9/2014
CT287 - Hazardous Area Classifications and Protection Systems
How is a Circuit Made “Intrinsically Safe?”
• First must define what atmospheres will be involved • Refer to published ignition curves • Implement voltage and current limiting
L1
L2
device
hazardous safe
Slide 37 Craig McIntyre
09/9/2014
CT287 - Hazardous Area Classifications and Protection Systems
How is a Circuit Made “Intrinsically Safe?”
• First must define what atmospheres will be involved • Refer to published ignition curves • Implement voltage and current limiting
L1
L2
device
hazardous safe
Slide 38 Craig McIntyre
09/9/2014
CT287 - Hazardous Area Classifications and Protection Systems
How is a Circuit Made “Intrinsically Safe?”
• First must define what atmospheres will be involved • Refer to published ignition curves • Implement voltage and current limiting
L1
L2
device
hazardous safe
Slide 39 Craig McIntyre
09/9/2014
CT287 - Hazardous Area Classifications and Protection Systems
How is a Circuit Made “Intrinsically Safe?”
• First must define what atmospheres will be involved • Refer to published ignition curves • Implement voltage and current limiting
L1
L2
device
hazardous safe
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09/9/2014
How is a Circuit Made “Intrinsically Safe”?
CT287 - Hazardous Area Classifications and Protection Systems
• First must define what atmospheres will be involved
• Refer to published ignition curves
• Implement voltage and current limiting • What are the practical
limitations?
Max Allowable
Current
Max Operating Voltage
Group C
Group B
Slide 41 Craig McIntyre
09/9/2014
CT287 - Hazardous Area Classifications and Protection Systems
How is a Circuit Made “Intrinsically Safe”?
• First must define what atmospheres will be involved • Refer to published ignition curves • Implement voltage and current limiting
• What are the practical limitations?
• Installation Requirements • Proper wiring connections • Proper cable routing • Attention to “entity parameters”
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09/9/2014
CT287 - Hazardous Area Classifications and Protection Systems
Non-Incendive
• Applies to all Division 2 Areas • Circuitry Strategy - Circuits are incapable of an energy release
sufficient to ignite the specified atmosphere, under normal circuit operation. In this context “normal” includes user mis-wiring.
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Div. 2 Non-Incendive Installation
CT287 - Hazardous Area Classifications and Protection Systems
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CT287 - Hazardous Area Classifications and Protection Systems
Associated Apparatus
• Normally “safe area” equipment which affects the energy levels of intrinsically safe equipment in the hazardous area.
• Examples - Intrinsic Safety Barrier or I.S. Power Supply
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CT287 - Hazardous Area Classifications and Protection Systems
Purged
• Systems or devices are under positive pressure, to exclude hazardous atmospheres from the equipment interior. Extensive controls, interlocks may be required, depending upon specific areas involved.
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CT287 - Hazardous Area Classifications and Protection Systems
Purged
• Systems or devices are under positive pressure, to exclude hazardous atmospheres from equipment interior. Extensive controls, interlocks may be required, depending upon specific areas involved.
Type X purging: reduces classification within enclosure from Div 1 to non-hazardous Type Y purging: reduces classification within enclosure from Div 1 to Div 2 Type Z purging: reduces classification within enclosure from Div 2 to non-hazardous
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09/9/2014
CT287 - Hazardous Area Classifications and Protection Systems
Purged
• Systems or devices are under positive pressure, to exclude hazardous atmospheres from equipment interior. Extensive controls, interlocks may be required, depending upon specific areas involved.
Type X purging: reduces classification within enclosure from Div 1 to non-hazardous Type Y purging: reduces classification within enclosure from Div 1 to Div 2 Type Z purging: reduces classification within enclosure from Div 2 to non-hazardous
Escalating Severity
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Common Purge Systems
CT287 - Hazardous Area Classifications and Protection Systems
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Overview: Safety Techniques
CT287 - Hazardous Area Classifications and Protection Systems
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CT287 - Hazardous Area Classifications and Protection Systems
NEMA Ratings
• NEMA 4 = Outdoor, Weatherproof • NEMA 4x = NEMA 4 + Corrosion Resistance • NEMA 6 and 6P: Submersible • NEMA 7 = Explosionproof • NEMA 9 = Dust Ignitionproof
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Wiring containment Techniques: NEC
Conduit Seals: Process seals:
CT287 - Hazardous Area Classifications and Protection Systems
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CT287 - Hazardous Area Classifications and Protection Systems
Overview of Recognized National Testing Laboratories (NRTL),
the National Electrical Code and OSHA
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NRTL = Nationally Recognized Testing Laboratory…
• The US Occupational Safety and Health Act (OSHA) accredits Nationally Recognized Testing Laboratories (NRTL).
• Canadian Standards Council of Canada (SCC) accredits Testing Organization and Certification Bodies (TOCB)
• Individual States are allowed to implement State Occupational Safety and Health Plans. OSHA approves and monitors State plans.
What’s an NRTL?
CT287 - Hazardous Area Classifications and Protection Systems
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09/9/2014
NRTL = Nationally Recognized Testing Laboratory…
• A “Scope of recognition” defines the
specific safety test standards for which an NRTL applies for recognition, and that OSHA approves. OSHA does not specify which test standards an NRTL must use. Instead, when an organization applies for recognition, it submits a list of test standards for which it seeks recognition, and OSHA determines if these standards are "appropriate" as defined in 29 CFR 1910.7. An NRTL may only certify products to the specific product safety test standards included in its scope of recognition.
What’s an NRTL?
CT287 - Hazardous Area Classifications and Protection Systems
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CT287 - Hazardous Area Classifications and Protection Systems
National Electrical Code (NEC) and NRTL test standards
• The National Electrical Code (NEC) is the “bible" of the Electrical Industry, and the primary source of reference for hazardous locations. The NEC is also the basis for OSHA standard 1926.407, Hazardous (Classified) Locations.
• The NEC is approved as an American National Standard by the American National Standards Institute (ANSI) and formally identified as ANSI/NFPA 70
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CT287 - Hazardous Area Classifications and Protection Systems
National Electrical Code (NEC) and NRTL test standards
• The National Fire Protection Association NFPA 70: National Electrical Code (NEC) publishes the “Bible” with the most recent the 2011 Edition (available Sept 24 2010) which is adopted in all 50 states
• NRTLs use safety test standards that OSHA determines are "appropriate" as defined in 29 CFR 1910.7 developed to assess that a device has been designed, manufactured, tested or inspected, and marked in accordance with requirements of the listing agency as recognized by the United States Department of Labor, Occupational Safety and Health Administration (OSHA) under the requirements of 29CFR1910.7.
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CT287 - Hazardous Area Classifications and Protection Systems
Some NRTL History
• When first adopted, OSHA regulations gave two examples of approval organizations: Underwriters Laboratories (UL) and Factory Mutual Research Corporation (FMRC)
• In 1983, OSHA was ordered by a court to remove the specific references to UL and FMRC in a successful lawsuit brought by a private lab
• In 1988, OSHA revised its regulations to remove the references, and established the NRTL Program to recognize other organizations as NRTLs
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CT287 - Hazardous Area Classifications and Protection Systems
Some additional background on FM and UL • Underwriters Laboratory (UL) is not only an NRTL but a function
within the company also develops testing standards. Underwriters Laboratories is an independent, not-for-profit product safety certification organization that has been writing Standards for Safety, testing products and involved in conformity assessment for well over a century. Many of these standards are now open ANSI standards as well used by other organizations
• FM not only is an NRTL but a function within the company also develops testing standards. Many of these standards are now open ANSI standards as well used by other organizations. Another portion of FM has grown to be the largest independent insurance provider to industry.
• Each of the NRTL, standards setting and insurance portions of these organization are separate functions and are not supposed to be combined to the exclusion of others
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CT287 - Hazardous Area Classifications and Protection Systems
Documentation and labeling
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Documentation
• Certificates are issued by the cognizant NRTL • Many Labs can issue combined certifications, such as for both US and
Canada, as well as issuing separate certificates for multiple schemes simultaneously (such as ATEX and IECEx).
• Multiple certificates typically exist for any given device or model family, for multiple protection techniques as well as from multiple entities, in multiple countries.
• Copies of most certifications are available though the equipment vendor or via lifecycle management tools like the Endress+Hauser Web Asset Management (W@M) system.
CT287 - Hazardous Area Classifications and Protection Systems
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Typical Equipment Marking
• In the US, we’ll typically see a layout like this: Cl I Div 1 ABCD T4, Cl II Div1 EFG, Cl III • So, what’s it all mean? • And what can we use for a given location?
CT287 - Hazardous Area Classifications and Protection Systems
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Typical Equipment Marking
• Let’s break it down:
CT287 - Hazardous Area Classifications and Protection Systems
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Typical Equipment Marking
• Let’s break it down: Cl I Div 1 ABCD T4, Cl II Div 1 EFG, Cl III
CT287 - Hazardous Area Classifications and Protection Systems
NRTL (FM, for both US and Canada)
Hazard Class (Class I = Gas) Area Classification (Division 1)
Gas Groups (All)
Temperature Class (T4: 135C)
Hazard Class (Class II = Dust)
Dust Groups (All)
Hazard Class (Class III = Flyings)
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