Fisher Hazardous Area Classifications Bulletin February 2010

8/6/2019 Fisher Hazardous Area Classifications Bulletin February 2010

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www.Fisher.com

Hazardous Area Classifications and

ProtectionsThe intent of this document is to provide a broadoverview of hazardous area classifications and thetypes of protection techniques involved. Theinformation provided in this bulletin is for educationalpurposes and should not be used in place of anyother source or governing documents.

Not all approvals are covered in this bulletin. Contactyour Emerson Process Management sales office forinformation on approvals not covered in this bulletin.

Contact your Emerson Process Management salesoffice for product specific hazardous area approvalinformation or visit our website at www.Fisher.com.

Hazardous Area Classifications

When electrical equipment is used in, around, ornear an atmosphere that has flammable gases orvapors, flammable liquids, combustible dusts,ignitable fibers or flyings, there is always a possibilityor risk that a fire or explosion might occur. Those

areas where the possibility or risk of fire or explosionmight occur due to an explosive atmosphere and/ormixture is often called a hazardous (or classified)location/area. Currently there are two systems usedto classify these hazardous areas; the Class/Divisionsystem and the Zone system. The Class/Divisionsystem is used predominately in the United Statesand Canada, whereas the rest of the world generallyuses the Zone system.

Class/Division System

Hazardous locations per the Class/Division systemare classified according to the Class, Division, andGroup.

1. ClassThe Class defines the general nature (orproperties) of the hazardous material in the

surrounding atmosphere which may or may not be insufficient quantities.

a. Class ILocations in which flammable gasesor vapors may or may not be in sufficientquantities to produce explosive or ignitablemixtures.

b. Class IILocations in which combustibledusts (either in suspension, intermittently, orperiodically) may or may not be in sufficientquantities to produce explosive or ignitable

mixtures.

c. Class IIILocations in which ignitable fibersmay or may not be in sufficient quantities toproduce explosive or ignitable mixtures.

2. DivisionThe Division defines the probability ofthe hazardous material being able to produce anexplosive or ignitable mixture based upon itspresence.

a. Division 1 indicates that the hazardousmaterial has a high probability of producing anexplosive or ignitable mixture due to it being

present continuously, intermittently, orperiodically or from the equipment itself undernormal operating conditions.

b. Division 2 indicates that the hazardousmaterial has a low probability of producing anexplosive or ignitable mixture and is present onlyduring abnormal conditions for a short period oftime.

3. GroupThe Group defines the type of hazardousmaterial in the surrounding atmosphere. Groups A,B, C, and D are for gases (Class I only) while groupsE, F, and G are for dusts and flyings (Class II or III).

a. Group AAtmospheres containing acetylene.

b. Group BAtmospheres containing aflammable gas, flammable liquidproducedvapor, or combustible liquidproduced vapor

Product Bulletin9.2:001D103222X012February 2010 Hazardous Area Classifications


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Hazardous Area ClassificationsProduct Bulletin

9.2:001February 2010

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whose MESG is less than 0.45 mm or MIC ratiois less than 0.40. Typical gases includehydrogen, butadiene, ethylene oxide, propyleneoxide, and acrolein.

c. Group CAtmospheres containing aflammable gas, flammable liquidproducedvapor, or combustible liquidproduced vaporwhose MESG is greater than 0.45 mm but lessthan 0.75 mm or MIC ratio is greater than 0.40but less than 0.80. Typical gases include ethyleither, ethylene, acetaldehyde, andcyclopropane.

d. Group DAtmospheres containing aflammable gas, flammable liquidproducedvapor, or combustible liquidproduced vaporwhose MESE is greater than 0.75 mm or MIC

ration is greater than 0.80. Typical gases includeacetone, ammonia, benzene, butane, ethanol,gasoline, methane, natural gas, naphtha, andpropane.

e. Group EAtmospheres containingcombustible metal dusts such as aluminum,magnesium, and their commercial alloys.

f. Group FAtmospheres containingcombustible carbonaceous dusts with 8% ormore trapped volatiles such as carbon black,coal, or coke dust.

g. Group GAtmospheres containingcombustible dusts not included in Group E orGroup F. Typical dusts include flour, starch,grain, wood, plastic, and chemicals.

Zone System

Hazardous locations per the Zone system areclassified according to its Zone which can be gas ordust. For gas atmospheres electrical equipment isfurther divided into Groups and Subgroups.

ZoneThe Zone defines the probability of thehazardous material, gas or dust, being present insufficient quantities to produce explosive or ignitablemixtures.

1. Gas

a. Zone 0Ignitable concentrations offlammable gases or vapors which are presentcontinuously or for long periods of time.

b. Zone 1Ignitable concentrations offlammable gases or vapors which are likely tooccur under normal operating conditions.

c. Zone 2Ignitable concentrations of flammablegases or vapors which are not likely to occurunder normal operating conditions and do so onlyfor a short period of time.

GroupElectrical equipment used in gasatmospheres is divided into two groups.

D Group IEquipment used in mines withatmospheres containing methane or gases andvapors of equivalent hazard.

D Group IIAll other equipment; which isfurther subdivided into three subgroups.

Group IIAAtmospheres containing

propane, or gases and vapors of equivalenthazard.

Group IIBAtmospheres containingethylene, or gases and vapors of equivalenthazard.

Group IICAtmospheres containingacetylene or hydrogen, or gases and vaporsof equivalent hazard.

2. Dust

a. Zone 20An area where combustible dusts orignitable fibers and flyings are presentcontinuously or for long periods of time.

b. Zone 21An area where combustible dusts orignitable fibers and flyings are likely to occurunder normal operating conditions.

c. Zone 22An area where combustible dusts orignitable fibers and flyings are not likely to occurunder normal operating conditions and do so onlyfor a short period of time.

Protection Techniques andMethods

Various protection techniques and methods havebeen developed and employed, thus reducing orminimizing the potential risks of explosion or firefrom electrical equipment located in hazardouslocations. Not all methods are listed.


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Product Bulletin9.2:001February 2010

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Class/Division system

D ExplosionproofA type of protection thatutilizes an enclosure that is capable of withstanding

an explosive gas or vapor within it and or preventingthe ignition of an explosive gas or vapor that maysurround it and that operates at such an externaltemperature that a surrounding explosive gas orvapor will not be ignited thereby.

D Intrinsically SafeA type of protection in whichthe electrical equipment under normal or abnormalconditions is incapable of releasing sufficientelectrical or thermal energy to cause ignition of aspecific hazardous atmospheric mixture in its mosteasily ignitable concentration.

D Dust IgnitionproofA type of protection that

excludes ignitable amounts of dust or amounts thatmight affect performance or rating and that, wheninstalled and protected in accordance with theoriginal design intent, will not allow arcs, sparks orheat otherwise generated or liberated inside theenclosure to cause ignition of exterior accumulationsor atmospheric suspensions of a specified dust.

D NonincendiveA type of protection in whichthe equipment is incapable, under normal conditions,of causing ignition of a specified flammable gas orvaporinair mixture due to arcing or thermal effect.

Zone system

D FlameproofA type of protection in which anenclosure can withstand the pressure developedduring an internal explosion of an explosive mixtureand that prevents the transmission of the explosionto the explosive atmosphere surrounding theenclosure and that operates at such an externaltemperature that a surrounding explosive gas orvapor will not be ignited there. This type of protectionis referred to as Ex d.

D Intrinsically SafeA type of protection in whichthe electrical equipment under normal or abnormalconditions is incapable of releasing sufficientelectrical or thermal energy to cause ignition of aspecific hazardous atmospheric mixture in its mosteasily ignitable concentrations. This type ofprotection is referred to as Ex i.

D Increase SafetyA type of protection in whichvarious measures are applied to reduce theprobability of excessive temperatures and theoccurrence of arcs or sparks in the interior and onthe external parts of electrical apparatus that do notproduce them in normal service. Increased safetymay be used with flameproof type of protection.This type of protection is referred to as Ex e.

D Type nA type of protection applied toelectrical equipment such that in normal operation itis not capable of igniting a surrounding explosiveatmosphere. This type of protection is referred to asEx n.

Temperature Code (T Code)

A mixture of hazardous gases and air may be ignitedby coming into contact with a hot surface. The

conditions under which a hot surface will ignite a gasdepends on surface area, temperature, and theconcentration of the gas. The same can be saidabout combustible dusts. The T code of a productdenotes the maximum surface temperature that agiven product will not exceed under a specifiedambient temperature. For example, a product with aT code of T3 means that its maximum surfacetemperature will not exceed 200_C provided it isoperated in a ambient temperature defined by themanufacturer.


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Table 1. Approval Agencies

Approvals(1) Approval Agencies Used(2) Approvals Accepted

FM FMFactory Mutual North America

CSA CSACanadian Standards Association North America

ATEXBaseefaBritish Approvals Service for Electrical Equipment in Flammable AtmospheresKEMANV tot Keuring van Elektrotechnische MaterialenLCIELaboratorie Central des Industries Electriques

European Union

IECExCSACanadian Standards AssociationBaseefaBritish Approvals Service for Electrical Equipment in Flammable Atmospheres

International

SAA SAAStandards Association of Australia Australia

NEPSINEPSINational Supervision and Inspection Centre for Explosion Protection and Safetyof Instrumentation

China

TIIS TIISTechnology Institution of Industrial Safety Japan

INMETRO INMETRONational Institute of Metrology, Standardization and Industrial Quality Brazil

GOSTR GOSTGOSSTANDART Russia

1. Fisherr products may carry additional approvals. Contact your Emerson Process Management sales office for additional approval information.2. Fisher product approvals may be certified by other agencies. Contact your Emerson Process Management sales office for additional information.

Nomenclature

Class/Division system

Approved equipment is marked according to whichClass (I, II, or III), Division (1 or 2), Group (A, B, C,D, E, F, or G), and temperature code (T1 throughT6) that it is rated for. For intrinsically safeequipment the words Intrinsically Safe or IS willprecede the actual approval marking to indicate it asbeing intrinsically safe. Examples are listed below:

Class I Division 1 Group B,C,D T5CL I Div 2 GP ABCD T5IS CL I,II,III Div 1 GP ABCDEFGCL II,III Div 1,2 GP EFG T4

Zone system

Approved equipment is marked according to theprotection concept for which it has been designed(Ex i, Ex d, Ex n, and etc.), the gas group (I, IIA, IIB,or IIC), and temperature code (T1 through T6) that itis rated for. For the United States it will be precededby which Class and Zone it is approved for.Examples are listed below:

Ex ia IIC T5Ex d IIB+H2 T6Ex nA IIC T6Class I Zone 2 AEx nC IIC T5

Additional TerminologyAlthough the following terminology is not permittedfor markings it is commonly used to describe thevarious types of approvals or when speaking ofthem.

XPFlameproof approval for Class I Division 1EXPFlameproof approval for Class I Division 1NINonincendive approval for Class I Division 2DIPDust Ignition Proof approval for Class II

Division 1SSuitable For for Class II Division 2ISIntrinsically Safe

Approval AgenciesGenerally speaking, most countries require thatproducts intended for installation in a hazardouslocation be approved by a recognized authority orapproval agency (governmental or independent)which that country has established by various laws,regulations, or codes. See table 1 for an overview ofapprovals and approval agencies.

North American Approvals

Of the 15 national testing laboratories (NRTLs) in

the United States, only a few are qualified toapprove products for use in hazardous locations.Two such agencies are; Factory Mutual (FM) andUnderwriters Laboratories (UL). In Canada, productsare approved by the Canadian StandardsAssociation (CSA).

European Approvals

Each country belonging to the European Union hasestablished one or more Notified Bodies for


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product approval. Notified Bodies not only approveproducts for use within their own country, commonlycalled national certifications/approvals, but also forany other country within the union, known asCENELEC certifications/approvals. CENELEC is theacronym for European Committee forElectrotechnical Standardization. A product whichhas been CENELEC certified or approved by any ofthe Notified Bodies is automatically accepted for usewithin all of the participating union countries. In July2003 a European Directive, called the ATEXDirective, which pertains to equipment for explosiveatmospheres, was adopted. All equipment intendedfor use in explosive atmospheres must comply withthe ATEX Directive in order to be sold into theEuropean Union.

International Approvals

Countries participating in the IECEx Scheme(International Electrotechnical Commission onexplosion protected equipment, known as Ex) canissue either an international certification or a nationalcertification of explosion protected equipment. Eachcountry within the IECEx scheme establishes anExCB (Ex Certification Body) which can approveproducts. ExCBs can issue the national certificationfor their country based upon the IECEx standards(including any national deviations) and theinternational certification. Currently, Australia is theonly country accepting international certifications foruse in their country.


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Vmax = 30 VDC

Imax = 226 mA

Pi = 1.4 WCi = 5 nF

Li = 0.55 mH

Vmax = 30 VDC

Imax = 200 mAPi = 1 WCi = 0 F

Li = 0 mH

Voc = 1.9 VDCIsc = 32 APo = 61 W

Ca = 100 FLa = 5600 mH

FIELD COMMUNICATOR

DVC6010 I.S. BARRIER

Voc = ?

Isc = ?Ca = ?La = ?

HAZARDOUS AREA NONHAZARDOUS AREA

Figure 1. Typical I.S Installation

Guidelines for Selecting IntrinsicSafety Barriers Using EntityRatings

Selecting an intrinsic safety barrier with the requiredentity ratings depends upon the combined effects ofthe instrument, its cabling, and any instrumentaccessories such as the 475 Field Communicator.Determine the barrier entity ratings using thefollowing guidelines:

Voc Vmax

Isc ImaxCa Ci + CcableLa Li + Lcable

where:

Voc = Barrier open circuit voltage

Vmax = Instrument Vmax

Isc= Barrier short circuit current

Imax = Instrument Imax

Ca= Barrier acceptable connected capacitance

Ci = Instrument total unprotected internalcapacitance

Ccable = Signal cable total capacitance

La = Barrier acceptable connected inductance

Li = Instrument total unprotected internal inductance

Lcable = Signal cable total inductance

The values Voc, Isc, Ca, and La are specified by thebarrier manufacturer for any given barrier. Thevalues of Ccable and Lcable for the signal cable mustbe determined for the specific cable used.

Example barrier entity ratings calculation.

A system is comprised of a FIELDVUEr DVC6010digital valve controller (FM approved), a FieldCommunicator (FM approved), and 1000 feet ofcable with 60 pF/ft capacitance and 0.2 H/ft

inductance. Calculate the barrier entity ratings.

Figure 1 shows a typical I.S. installation.

Calculate Ccable and Lcable

Ccable = 60 pF/ft x 1000 ft

= 60 nF

Lcable = 0.2 H/ft x 1000 ft

= 0.2 mH

Determine Ca and La for the barrier

Caw Ci(DVC6010)+ Ci(475) + Ccable

w 5 nF + 0 nF + 60 nF

Caw65 nF

Law Li(DVC6010)+Li(475) + Lcable

w 0.55 mH + 0 mH + 0.2 mH

Law0.75 mH


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Determine Voc and Isc of the barrier. Note that in thisexample the output of the 475 (Voc(475) and Isc(475))must also be considered because it can also addenergy to the loop besides just the barrier itself. Vocof the barrier plus any additional voltage that couldbe added to the loop from each device must besubtracted from Vmax for each device. Isc of thebarrier plus any additional current that could beadded to the loop from each device must not exceedImax for each device.

Voc of the barrier must meet all of the followingconditional requirements.

1) Vocv Vmax(DVC6010) Voc(375)! 30 VDC 1.9 Vdc! 28.1 VDC

2) Vocv Vmax(DVC6010)! 30 VDC

3) Vocv

Vmax(475)!

30 VDCVocv28.1 VDC

Isc of the barrier must meet all of the followingconditional requirements.

1) Iscv Imax(DVC6010) + Isc(475)! 226 mA +0.032 mA! 226.032 mA

2) Iscv Imax(DVC6010)! 226 mA

3) Iscv Imax(475)! 200 mA

Iscv200 mA

Note

Neither Emerson, Emerson ProcessManagement nor any of their affiliatedentities assumes responsibility for theselection, use, or maintenance of anyproduct. Responsibility for theselection, use, and maintenance of any

product remains with the purchaserand end user.


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Emerson Process ManagementMarshalltown, Iowa 50158 USASorocaba, 18087 BrazilChatham, Kent ME4 4QZ UKDubai, United Arab EmiratesSingapore 128461 Singapore

EFisher Controls International LLC 2006, 2010; All Rights Reserved

www.Fisher.com

The contents of this publication are presented for informational purposes only, and while every effort has been made to ensure their accuracy, theyare not to be construed as warranties or guarantees, express or implied, regarding the products or services described herein or their use orapplicability. All sales are governed by our terms and conditions, which are available upon request. We reserve the right to modify or improve thedesigns or specifications of such products at any time without notice. Neither Emerson, Emerson Process Management, nor any of their affiliatedentities assumes responsibility for the selection, use or maintenance of any product. Responsibility for proper selection, use, and maintenance ofany product remains solely with the purchaser and end user.

Fisher and FIELDVUE are marks owned by one of the companies in the Emerson Process Management business division of Emerson Electric Co.Emerson Process Management, Emerson, and the Emerson logo are trademarks and service marks of Emerson Electric Co. All other marks arethe property of their respective owners.

Fisher Hazardous Area Classifications Bulletin February 2010

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