BSI en 50016 1996 Elect Apparatus for Potentially Explosive

7/30/2019 BSI en 50016 1996 Elect Apparatus for Potentially Explosive

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BRITISH STANDARD

Electrical apparatus orpotentially explosiveatmospheres-Pressurized apparatus p9

The EuropeanStandardEN 50016 : 995 has the status of aBritish Standard

ICs29.260.20

BS EN50016 : 996

NO COPYING WITHOUT BSI PERMISSION EXCEPTAS PERMITTED BY COPYRIGm LAW

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B$ EN 60016 :1996

Committees responsible for thisBritish StandardThe preparation f this British standard was entrustedo Technical CommitteeGELC31, Electrical apparatus for explosive atmospheres, upon which theollowingbodieswere represented:

British CableMakers ConfederationBritishGas plcBritish Lighting Association or the Preparationf Standards (BRITLAPS)Confederation of United Kingdom Coal roducersCouncil for Electrical Equipment for Flammable AtmospheresBEAMA)Electxical "ace Heating Industrial Council (ETHIC)Electrical Contractors' AssociationElectroheat Manufacturers' Association ofEAMA(Em)Energy Industries CouncilEngineering Equipment andMaterials Users' AssociationERA TechnologyLM.GAMBICA (BEAMA Ltd.)Gland ManufacturersTechnicalCommitteeHealth and Safety ExecutiveM t u t e of PetroleumLightmg Industry Federation td.Loss Prevention CouncilNational Inspection Council for Electricalstahtion ContractingRotatingElectrical Machines AssociationBEAMA Ltd.)S m td."ades Union CongressUnited Kmgdom Ofhhore Operators AssociationDeparhnent of ?kade and Industry standardsPolicyUnit)Marine Safety AgencyMinistry of DefenceCo-opted members

ThisBritish Standard, havingbeen prepared under hedirection of the ElectrotechnicalSector Board,was publishedunder the authorityof theStandards Board and comesntoeffect on16 November 1996QBSI 1996 Amendments issued since publication

Amd. No. Text affectedate

The following BSI referencesrelate to he work on thisstandardCommittee reference GEIL31Draft for comment 1B1014DC I IISBN O 680 268408 I I



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BSI B S * E N * 5 0 0 2 b 9 b W Lb24bb9 05b9LBO 324 W B$ EN 50016 :1996

Contentspage

Committees responsiblenside front coverNational foreword ii

2Text of EN 50016 3

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National forewordThis British Standardasbeen prepared by Technical CommitteeEM 1 and is theEnglish language version ofN 50016Electrical apparatus o r potentially explosivea&nosphmes- e.smdzed apparatus @,ublished by he European Committee forElectrotechnical S t a n d a r a o n CENELEC). It supersedes BS 5501 :Part 3 :1977,which iswithdrawn.This Standard shouldbe read n conjunction withBS EN 50014:1993Electricalapparatus o r potentially explosive a t m o s p h- eneml equirements,which itsupplements.Product certification. Users of this British Standardsre advised to consider thedesirability of thirdparty certificationof product conformity with this British Standardbased on testi ngand continuing product surveillance, which maye coupled withassessment of a suppliersquality systemsagainst the appropriateart ofBS EN IS09OOOEnquiries as o the availability of third party certification schemesre forwarded byBSI to he Association of British Certification Bodies.f a third party certificationscheme does notlready exist, users should consider approachingn appropriatebody&om the list of association members.Cross-referencesPublication referred oEN 50014 :1992EN 50015: 1994EN 50017 : 1994

EN 50018 : 1994

EN 50019 :1994

EN 50020 : 1994

EN 50028 : 1987

EN 50033 : 1991

EN 50039 :1980EN 60034-5 :1986

EN 60529 :1991HD 53.1S2:1985HD 214 S2 :1980

Corresponding British StandardBS EN 50014:1993Elect?-icaLapparatus orpotentiallyq lo s iv e a tmospheres- eneml requirementsBS EN 50015:1994Elect?-ical apparatus orpotentiallyexplosive atmospheresoil immersion oBS EN 50017:1994Electrical apparatus orpotentiallyexplosive atmospheresBS EN 50018:1995Elect?-iccd apparatus o r potentiallyexplosive atmospheresf i m q m o f aclosure dBSEN 50019:1994ElecWaL apparatus o r potentiallyexplosive atmospheresIn cr m ed safety eBS EN 50020:1995ElecWaL apparatus orpotentiallyex pb siw atmospheresIntrinsic safety i BS 5501:Part 8 : 1988Elect?-icdapparatusfor potentiallyexplosive atmospheresEncapsulation mBS EN 50033:1991Sp&&ation fo r const ruc t ion andtesting of miners caplamps in relation to the rislc ofexplosion, or mi ne susceptible to iredampBS 5501:Part 9:1982Specification or intrinsicauy sclfeBS 4999 Geneml requirementsfor rotating elSctricalmachinesPart 105:1988CEassification of egreesof protectionprovided by enclosures o r rotating machineryBS EN 60529:1992Spec&ficationo r degrees of protecth npvided b y enclosum {P ode)BS EN 60034Rota ting elextrical mach inesPart 1:1995Rating and per.$omnceBS 5901:1980Method fo r determ ining ULe comprat ive andtheproof tmlcin g indices of solid insulating materialsundermoist conditions

Powder iuing q

elSccrical systems i

Compliance with a British Standard does notf itself confer immunityfrom legal obligations.

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EN 50016Ckt~ber995

ICs 29.260.20 Supersedes EN 60016 : 1977 and its amendmentDescriptors:Electricalapparatus,potentiallyexplosiveatmosphere,explosiveatmosphere,explosionproofmg,specificrequirement,pressurized apparatusP

Wriel&ctrique pour ahnosphres explosibles Elektrische Bettiebsmittelfr explosionsgefhrdeteSurpression inteme p Bereichebedruckkapselung P

This European Standard was approved by CENELEC on 199509-20. CENELECmembers are bound to comply with the CENKENELEC Internal Regulahons whichstipulate the conditions forgiving this European Standard the status of a nationalstandardwithout anyal terati on.Uptodate lists and bibliographical references concerning such national standardsmay be obtained on application to the Central Secretariat or to any CENELECmember.This European Standard existsn three official versions (English, French, German).A version in any other language made by translation under the responsibility of aCENELEC memberinto its own language and notifiedo the Central Secretariatasthe same status as the official versions.CENELECmembers are he national electrotechnid committees of Austria,Belgium, Denmark, Finland, France, Ge-, Greece,celand,reland,taly,Luxembourg,Netherlands,Norwax Portugal, Spain, Sweden,Switzerland ndUnited Kingdom.

CENEXECEuropean Committee for Electrotechnical Standardization

Comit Europen de Normahation ElectmtechniqueEuropisches Komiteefr Elektrotechnische Normung

Central Secretariat: ruede St a s s a r t 36, B-1060 Brussels

O 1995Copyright reservedto CEN members Ref. No. EN 50016 : 1995 E



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Page 2EN 60016:1995

ForewordThis European Standard was prepared bySC 31-7,Pressurization and other techniques,fkhncaCommittee CENELEC TC 31, Electrical apparatus forexplosive atmospheres.The textof the draft was submitted to the formal voteand was approved by CENELECas EN 50016 on199509-20.This second edition ofEN 50016 is based on the firstedition but extendedo also include pressurizedenclosures with an internal sourcef release offlammable substances andtatic pressurizaton.This European standardis to be read in conjunctionwith EN 50014 :1992,Elec&al apparatus f o rpotentially explosive ahrwsphem- eneralrequirements,and with the second editionf theEuropean Standards for the specificypes of protectionlisted in the scope of EN 50014 :1992. This Europeanshould not be considered in conjunctionith any ofthe first edition standards and their amendments,published in 1977 or thereafter, listed inEN 50014.The followingdates were fixed:- atest date by which the ENhas to be implementedatnational level by publication ofan identical national standard rbydop) 1996-09-01- atest date by which thewith the EN have to benational standards conflictingwithdrawn 1996-09-01

Annexes designated normativere part of the body ofthe standardAnnexes designated informativere given forinformationonlyIn this standard annexD is normative andmexesA,B andC are informative.

ContentsGeneral1 Scope2 DefjnitionsRequirements for pressurizedenclosures3 Enclosuresnducting4 Tkrnperaturelimits6 Safetyprovisionsandsafetydevices(except for static pressurization)6 Safetyprovisionsandsafetydevicesfor static pressurization7 Supplyofprotective gasAdditional requirements orpressurized enclosures withcontainment systems8 Introduction9 Releaseonditions10 Designrequirementsfor the11 ProtectivegasandpressUrizig12 Ignitioncapable apparatus13 Intend hot surfacesVerification and e s t s14 Typeverificationand tests16 Routine testsMarking16 MarkingAnnexesA (iiormative) Ducting of protective gasB (iormative) Infallbility test for aC (iiormative) Function test ofD (normative)Purging anddilution tests

containment systemtechnique

containmentsystemE surveillancecircuits

33

45677

7889

101010131314181920

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1 scope1.1 This European Standard contains the specificrequirements for the construction and testingfelectrical a p p W with type of protectionpressurizat;ionp, intended foruse in poten*explosive atmospheres.This European standard supplements EuropeanStandardEN 50014, the requirements of which applytoelectrical apparatus withype of protectionp.1.2 This European Standard includes the requirementsfor the constructionof the enclosure and its s s o c i a t e dcomponents, including,f anx the inlet and outlet ductsfor the protective a s , and for the safety provisions anddevices necessary for the typef protectionpremwizationp.1.3 This European Standard specifies therequirementsfor pressurized enclosures with rwithout an internal source f release, with heexceptions given in1.6 and 1.6.1.4 This European Standard specifies requirement forpressurized enclosures containing an unlimited sourceof release of flammable gas or vapour onlywhere theunlimited sourceof release is from the surface of aliquid.1.6 This European Standard does not containrequirements for pressurized rooms or analyser houses.1.6 This European Standard does not contain therequirements for pressurized enclosures where, incontainmentsystem with limited or unlimitd releasethere is:a) air with an oxygen content greaterhan normal;b) or oxygen in combination with inert as in aproportion greaterthan21%.

1.7 Due to the safety factors incorporated in thetypeof protection the uncertain@f measurement inherentin good quali@, regularly calibrated measurementequipment is considered to have no significantdetrimental effect and need not be taken into accountwhen making the measurements necessaryo verifycompliance of the apparatus with the requirementsfthis standard.1.8 PublicationsEuropean Standards:EN 50014 : 1992

EN 50015 : 1994

EN 50017 : 1994

Electrical apparatus for potentiallyexplosive atmspheres. Generalrequi?vmentsElectrical apparatus forp o t e n t i d yexplosive atnwspheres. Oilimmersion oElectrical apparatus fo r potentiallyexplosive atmospheres.PowderfUing 4

EN 50018: 1994

EN 50019: 1994

EN 50020 : 1994

EN 50028: 1987

EN 50033 : 1991

EN 50039: 1980

EN 954l)

Page 3EN 60016:1995

Electrical apparatusfor potentiallyexplosive atm ospheres. l ? h m o fenclosures dElectrical apparatus forpotentiallyexplosive atmospheres. Increclsedsafety eElectrical apparatus forp otentiallyexplosive atmospheres. Intrinsicsafety iE l e c W apparatus forpotentiallyexplosive atmospheres.Encapsulation mElectrical apparatusforpotentiallyexplosive atnwspheres. Caplishts formines susct.ptible to f iredampElectrical apparatus forpotentiallyexplosive atnwspheres. I d r i m ysafe systems iSafety of machinery- afetyrelated parts of control systems

EN 60034-5 1986Rotatirw electrical nuxhines.

EN 60529 : 1991HD 53.1S2:1985

HD 214 S2 :1980

2 Deinitions

part 5.&sv*atbn of degrees ofprotectionprovided by enclosures orrotating machines IEC 34-5 :1981)Degrees of protectionprovided byenclosures (IF Code) (IEC 529:1989)Rota ting electrical machinesRating and perfirnaunce(IEC 34-1:1983)Method fo r d etermining Wcomparative and the proof tmlcingundermoist conditions(IEC 112 :1979)i n d k e s of solid insulating mater&

The following defjnitions specifico type of protectionpressurization p,are applicable in this EuropeanStan- they supplement the definitions which aregiven in EN 50014.2.1 type ofprotection pressurization PThe technique of applyinga protective gas to anenclosure in order to prevent the formation f anexplosive atmosphere inside the enclosure bymaintainingan overpressure agajnst the surroundingatmosphere, and where necessary bysing dilution.2.2 pressurized enclosureAn enclosure inwhich a protective gas is maintainedat a pressure greater hanthat of the externalatmosphere.

1~nreparation.



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Page 4EN 60016: 1996

2.3 protective gasAir or inertgas used for purging and maintaining anoverpressure and, f required, dilution.NOTE. For the purpose of th is standard inert gas means nitrogen,carbon dioxideargon or any gas which, when mixedwith oxygenin the ratio41 as found in air, does not make the ignition andflammability properties, suchas explosive limits,more onerous.2.4 purgingThe operationof passing a quantity of protective gasthrough he pressurized enclosure and ducts,o that

a) when the protective gass air, any explosiveatmosphere in the pressurized enclosures reducedto a safe concentration;b) or when the protectivegas is inert theconcentration of oxygen in the pressurized enclosureis reduced to a safe level.2.6 static pressurization

The maintenance of an overpressurewithin apressurized enclosure without he addition ofprotective gas in ahazardousarea.2.6 pressurization with leakage compensationThe maintenanceof an overpressurewithin apressurized enclosureso that, when the outletapertures are closed, the supplyof protective gas issufficient to compensatefor any leakage from hepressurized enclosure and ts ducts.2.7 pressurization with continuous low of theprotective gasThe maintenance of an overpressurewithinapressurized enclosurewith continuousflow of theprotective gas hrough the enclosure.2.8 internal sourceof releaseA point or location from whicha flammable substancein the form of a flammablegas orvapour or liquid maybe released into the pressurized enclosure suchhat inthe presenceof air an explosivegas atmosphere couldbe formed2.9 containment systemThe partof the apparatus containing he flammableg a s , vapour or liquid that may constitute an ntendsource of release.2.10 infallible containment systemThe constructionof an infallible containment system isof such integrity hat the possibilityof a leak is soremotethat it can be ignored2.11 dilutionThe continuoussupply of a protective gas, afterp u r m , at such a rate that the concentrationof aflammable mixture inside the pressurized enclosuresmaintained at a value outside the explosivelimitsexcept in a dilution areaNOTE.Dilution of oxygen by inert gas may result in aconcentrationof flammable gas above the UEL

2.12 ignition capable apparatusApparatus which in normal operation constitutessource of ignition for a specified explosive ahnosphere.This includes electrical apparatus not protected bytype of protection listedin 1.8.1 of this standard2.13 dilution areaA n area in the vicinityof a source of release where theconcentration of flammable gas or vapour is notdiluted to a safe concentration.2.14 limited releaseA release of flammable gas or vapour the maximumflow rate of which can be predicted2.16 unlimited releaseA release of flammable gas or vapour the maximumflow rate of which cannot bepredictedNOTE. This refers to liquids which can evolve flammablegas orvapour where therate of release cannot be predicted.2.16 lower explosive limit(LEL)Volume ratio of flammable gas or vapour in air belowwhich an explosive gas atmospherewnot be formed.2.17 upper explosive limit(UEL)Volume ratio of flammable gas or vapour n air abovewhich an explosive gas atmospherewnot be formed.2.18 volume ratio (vh)Ratio of the volume of a component to the volume ofthe gasmixtureunder specified conditions ftemperature and pressure.Requirementsfor pressurized enclosures3 Enclosures and ducting3.1 GeneralThe pressurized enclosure, including any pertures formoving parts butexcluding apertures for the inlet andoutlet of the protective gas, shall have a degree ofprotection in accordance with t least IP 40 ofEN 60529, or in the caseof a rotating electricalmachine, EN 60034-5.NOTE. The degree of protection of IF 44may be required onacoal face under humid and dusty conditions.3.2 Spark and particle barriersThe pressurized enclosure and he ducting, if any, forthe protective gas shall guardgainst the ejection ofignition capablesparks or particles into the hazardousarea (see annexA.2).3.3 Mechanical strengthThe pressurized enclosure, ductsf any, and theirConnectingparts shall withstand a pressure equal o1,5 times the maximum overpressure specified by themanufacturer for normal service withll outlets closedwith aminimum of 200PaIfapress~ecanoccurinservicethatcancauseadeformation of the enclosure, ducts f any, orconnecting parts,a safety deviceshall be fitted by themanufacturer to limit the maximum internaloverpressure to a level below that which couldadversely affect he type of protection.



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3.4 Apertures3.4.1 In the case of static pressurization the enclosureshallhave one or more apertures.After filling and pressurizational l apertures shall beclosed.3.4.2 In the case of pressurizationwith leakagecompensation the enclosureshallhave one or moreinlet apertures. It hallalso have one or more outletapertures constructedso hat theym e closedafterPurging.3.4.3 In the case of pressurizationwith continuousflow of protective g a s , the enclosureshall have one ormore inlet apertures and one or more outlet aperturesfor the connectionof the inlet and outlet ducts for theprotective gas.NOTE. The location,size and number of apertures should besuitable for effective purging. The numberof apertures should bechosen with regardto the design and dispositionof the apparatus,particular consideration being given o the needs ofsubcomparhnents into whichhe apparatus might be divided.3.6 MaterialsThe materialsused for the enclosure, ducts andconnectingarts shallnotedversely afectedby the. specifiedrotective gas.I 3.6 Doornd covers3.6.1 Group I apparatus

x. shall either:-have special fasteners complying with9.2 ofEN 50014.- or, except for thease of static pressurization beinterlockedso hat the electrical supply o apparatusnot protectedby a type of protection listed in 1.8.1of this standard is disconnected automatidly whenthey are opened andso that the supply cannot berestored until they are closed The requirementsof 6.6 of thi s standard shall also applyIn the caseof static pressurization, doors and coversshall carry the following warning:

I

* For Group I pressurized enclosures, doors and covers

Do not open in hazardous area.3.6.2 Group II apparatusThe requirements for fasteners for doors and coversin 9.1,paragraph1,of EN 50014 need not applyoGroup II pressurized enclosures.Doors and covers,except for those whichan be openedonly by the useof a tool or kex shall be interlockedso that theelectrical supply o electrical apparatus not protectedby a type of protection listed in1.8.1 of thi s standardis disconnected automatically when they re openedand so that the supply cannot be restoredntil theyare closed The requirementsof 6.6 of thi s standardshall also WPb

Page 5EN 50016: 995

In the case of static pressurization, doors and coversshall only be opened by the use of a tool, andshallcarry the following warning:Do not open in hazardous area.3.6.3 When doors and coversare provided to permitinspection in service, theyhall cany he followingwarning:

Do not open when energized.except where provision s made for austment duringoperation, in which ase the warning shall be

See instructions before opening.3.7 Insulating materialsFor Group I apparatus,nsulaljng materials subjectedto electrical stresses capable of causing arcs in air andwhich result fromrated currents of more than 16Ashall have a comparative tracking indexqual o orgreater thanCTI400M accordingto IECPublication112.4 kmperature l imts4.1 The pressurized enclosureshall be classied inaccordance with the temperature classiicationrequirementsof EN 50014.The maximum surface temperaturehall bedetermined:

a) either by the temperatureof the hottest pointofthe external surface f the enclosure.b) or by the temperature of the hottest point f thesurface of the internal parts whichreprotected byany of the typesof protection listed in EN 50014,and which remain energized even whenhe supplyof protective gas is removed (e.g. electrical heaters).

4.2 If during normal service the temperature f anysurface within the pressurized enclosure exceeds themaximumvalue permitted inEN 50014 for thetemperature class, appropriatemeasures shallbe takento prevent, if pressurization ceases, any explosiveatmosphere which may exist making contact withhatsurface before it as cooled below the permittedmaximum value. This may be achieved either by hedesign and construction f the jointsof the pressurizedenclosure and ductsor by other means, e.g. by bringingauxilmy ventilation systems into operation or byarranging that the hot surface within the enclosuresin a gasbght or encapsulated housing.When determining the temperahre for rotatingelectrical machines he duty type accordingopublication IEC 34-1 as specified by the manufacturershall be considered.



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6 Safety provisions and safety devices 6.7 Where theprotective gas is air, theconcentration(except for static pressurization) of flammable gasafter purging shallnot exceed25% ofthe LEL6.1 All safety devices used to prevent electricalapparatus protected by pressurization from causingnexplosion shall hemselves not be capableof causingan explosion or shall be mounted outside thehazardous area.6.2 The safety devices required by his standard formsafety related parts of a control system. It is theresponsibility of the manufacturer o assess hat thesafety and integrity f the control system s consistentwith the level of safety required byhi s standard.NOTE. EN 964, afety of machinery- afety related parts of acontrol sys tem, is in preparation.6.3 The safety devices shallbe provided by themanufacturer of the apparatusor by the user. In thelatter case the apparatusshall be marked 'X' and thedescription documents hall contain all necessaryinformation required by he user to ensure conformitywith the requirementsof thi s standard.NOTE. An example of the information to be supplied by themanufacturer is given inannexC.6.4 Where the safety related controlystem formspart of the apparatusa functional sequencedi agramshall be provided by the manufacturer, for exampletruth table,state di a gr am flow chart, etc., o define theaction of the control system. The sequenceiagramshall clearly identify and show the operational states ofthe safety devices and ensuing actions. Functionalestsshall be required to verify conformity o the di agramThese tests need only be carried out under normalatmospheric conditions unless otherwise specified bythe manufacturer.6.6 The manufacturer shall specify the maximum andminimum action levels and tolerances ofhe safetydevices. The safety devicesshall be used within then o d perationallimitsas specified by themanufacturertaking due account of the most onerousconditions specified for normal service.6.6 Safety devices, suchas ime delay relays anddevices for monitoring the flowf protective gas shallbe provided to prevent electricalapparatus within apressurized enclosure becoming energized until purginghas been completed.The sequence of operations of he safety devicesshallbe as follows:- ollowing the initiation of he sequence, thepurging flow though and the overpressure in heenclosure shall be monitored in accordance withhisstandasd,-when the minimum flowrate of protective gasisachieved and the overpressureis within the specified

l i m i t s the purge timer can betarted;- after the expiryof the time the a p p w s thenavailable to be energized.

In the event of failure of any step in the sequence thecircuit shall be arranged to reset to the beginning.

Where the protective gass other than&, theconcentration of oxygen after purging shall notexceed2 %by volume.The minimum flow rate of protective gas required forpurging is the rate specified by he manufacturer andverified by the type tests in 14.3 and 14.4.Theminimum purging durationis the durationalsospecified by the manufacturer and verifiedy the typetests.The purging flow ate shall be monitored at the outletof the pressurized enclosure.NOTE. To determine the free spaceof the associated ducts and toset up the additional purging time or the givenminimum flowrateis the responsibility of the user. The purge duration shall beincreased by the time necessaryto purge the free volume of thoseassociated ductswhich are not part of the certified apparatus byat least five times th& volume at the minimum flowate specifiedby the manufadurer.6.8 One or more automatic safety deviceshall beprovided to operate when the overpressure falls belowthe minimumvalue specified by the manufacturer. Itshall be posible to check the correct operationf thesafety devices. Their location and settinghall takeinto account the requirementsf 6.9.When a minimum rate of flow of protective gas isspecified by the manufacturer one r more automaticsafety device(s)shall be provided to operate when theflow rate of protective gas at the outlet allsbelow thespecified minimum value.NOTE. The purpose(s) forwhich the automatic safety device(s)are used (i.e. to disconnect power or to sound analarmorotherwise ensure he safety of the installation) is the responsibilityof the user.6.9 A minimum overpresure of 50Pa shall bemaintained relativeto the external pressure t everypoint within the enclosure and itsssociated ducts, atwhich leakage can obcur.The manufacturershall specify the minimum andmaximum overpressure in service and the maximumleakage rate at the maximum overpressure.The distribution of pressure in differentystems andducts is illw4xat.d in figuresA l toA.4.NOTE. It is essential for the safety of an nstallation ofpressurized enclosures hat the installation of the associated ductsand of the compressor or fan does not introduce a hazard. Thebasic requirements for he installation of ducting systems aregiven inannexA.6.10 When a source of protective gas is common to anumber of separate, enclosures, the safety device ordevices may be common to several of these, providedthat theresulting control takes account of the mostunfavourable conditions in he group of enclosures.When a common safety device is fitte4 the opening ofa door or cover need not switchoff all the electr idapparatus in the enclosuresor initiate the alarmprovided that the following three conditions are met.



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a) The opening of the door or cover s preceded bydisconnecting the supply to the electrid apparatusin the particular pressurized enclosure, exceptelectrical apparatus protected by ny of the types ofprotection listed in 1.8.1 of this standardb) The common safety device continueso monitorthe overpressure in, and where necessary the flowthrough, all the other pressurized enclosures f theSOUP.c) The subsequent connecting f the supply o theelec tr id apparatus in the particular pressurizedenclosure is preceded by the purging procedurespecified in 6.6.

6.11 Electrid apparatuswithin the pressurizedenclosure that may be energized when ype ofprotection presfllrizationp, s not in operation, shallbe protectedby a type of prokction listed in1.8.1 ofthis standard6 Safety provisions and safety devicesfor static pressurization6.1 All safety devices used o preventelectridapparatus protected byressurizationromausing anexplosion shall themselvesoteapablefausinganxplosion or shall be mountedutside theI hazardousarea.6.2 The protective gas shall bein& Thebe lessthan1%by volume.6.3 Internal sources of release of flammablesubstances are not permitted6.4 The pressurized enclosure shallbe filled with inertgas ina non-hazardous area using the procedurespecified by he manufacturer.6.6 W o utomatic safety devices hall be provided toopemte when the overpressurealls below theminimum value specified byhe manufacturer. Itshallbe possible o check the correct operation of thedevices when the apparatus s in service.The automatic safety deviceshall only be capable ofbeing reset by the use of a tool ora kW.NOTE. The purpose for which the automatic safety devices reused (i.e. to disconnect power or to sound an al armor otherwiseensure safetyof the installation)is the responsibility of the user.6.6 Electr id apparatuswithin the p d e denclosure that may be energized when type ofprotection pressurizationp is not in operation, shallbe protectedby a type of protection listed in 1.8.1 ofthis standard.

** concentration ofxygen after fillingwithnertas shall

Page 7EN 50016: 995

6.7 The minimum level of overpressure shall begreamthanthe maximum pressure loss in normalservice measured overa period not less than100timesthe time necessary for the coolingf enclosedcomponents according o 6.2 of EN 50014with aminimum of 1 h. The minimum level of overpressureshall not be less than 50Pa above the externalpressure under the most onerous conditions specifiedfor normal service.NOTE. If he overpressure falls below the minimum specified, it isthe users responsibilityto ensure that the pressurized enclosureis removed to a non-hazardous area before refilling.7 Supply of protective gas7.1 The protective gasshall be non-flammable. Themanufacturershall specify the protective as and anyalternative permitted.NOTE 1.The protectivegas should not, by reason of its chemicalcharacteristics or the impurities that it may contain, reduce heeffectivenessof the type of protection pressurization P, oradversely affect he satisfactory operation and integrity f theenclosed apparatus.NOTE 2. When an inert gas is used and a risk of asphyxiationexists, a suitable warning label should be fixed mthe enclosure.Normally the temperatureof the protectivegas o betaken into consideration is 40 C at the inletto thepressurized enclosure.In special circumstances ahigher temperaturemay be permitted or a lowertemperature may be required, or example for coolingpurposes, in which case the maximum inlettemperature of the protective gashall be marked onthe pressurized enclosure and stated in themanufacturers documentation.7.2 The manufacturershall specify the density limitsof the range of flammable gases for which hepressurized enclosure s designed except where thepressurized enclosure s designed forall flammablegases or for a specific flammablegas.Addit iod requirements for pressurizedenclosures with containment systems8 IntroductionThis section specifies he additional requirements forpressurized enclosures with containment system.The choiceof protective gas for pressurized enclosuresdepends upon the probability, quantity and constituentsof the release from the containment system. Therelease conditions, containment system designrequirements, categoryof internal release and theappropriate pressurization techniquesre given in theNOTE. Consideration should be given by the usero the possibleformation of flammable mixture due to the possibility of airpenetrationinto the Containment system and the resultingadditional precautions hat may be necessary.

following paragraphs.



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Page 8EN 50016 : 995

9 Release conditions9.1 No releaseThere is no intemal release when the containmentsystem is infallible. See10.1.9.1.1 No internal release is deemed to exist when theflammable substances insidehe containment systemare in the gas or vapour phase when operatingbetween the specifiedemperatwe limits and either- he gas mixturewithin the containment system salways belowLEL. The conditions to be met in th ssubclause require the apparatus o marked 'F,

or- he minimum pressure specified for hepressurized enclosure s at least 50 Pa higher thanthe maximum pressure specified for the containmentsystem and an automatic safety devices provided tooperate if the pressure difference falls below0 Pa

NOTE. The purpose(s) for which the automatic safety devicesused (i.e. to disconnect poweror to sound an alarm or otherwisemaintain the safety of the installation) is the responsibility of theuser.9.2 Limited releaseThe rate of release of the hnmable substance into thepressurized enclosureshall be predictable in llconditions of containment system failure. See0.2.9.3 Unlimited releaseThe rate of release of the flammable substance into thepressurized enclosure s not predictable.This conditionrefers to liquidswhich can evolve flammablegas orvapour. See10.3.If there may be, together with theiquid, entrainedoxygen, the maximum flowrate of oxygen shallbepredictable.10 Design requirementsfor thecontainment systemThe design and construction of the containmentsystem, whichwill determine whether leakage s likelyto occur or not, should be based on the most onerousconditionsof service specified by the manufacturer.The manufacturer shall specify he maximuminletpressure to the containmentsystem.Details of the design and construction f thecontainment system, the types and operatingconditions of flammable substances itmay contain andthe expected release ate or rates at given locations,shallbe provided by the manufacturer, in order hatthe containmentsystem can be classified in onef thefollowing categories:

10.1 Infallible containment systemAn infalible containmentsystem shall not have anyintentional leakage into the pressurized enclosure.hisconditionis satided when the containment systemcomprises metallic, ceramicor g l a s s , pipes, tubes orvessels which have no moving joints. Jointshall bemade by welding, brazing,glass to metal sealmg oreutectic methods2).Low temperature solderalloys such as l e ecompositesare not acceptable.NOTE. The manufacturer should consider carefullyherequirements of clause 6 of EN 50014 n relation to a potentiallyfragile infallible Containment system. Adverse operating conditionsto be agreed between manufacturer and user ay includevibration, thermal shock and damage o the infallible containmentsystem during maintenance operations when doors oraccesscovers of the pressurized enclosuremay be open.Goodengineering practice inafety matters must be observed.10.2Containment system with limited releaseThe designof a containment system with limitedrelease shallbe such hat the rate of release of theflammable substanceis predictable in all conditions ofcontainment system failure. The quantityf flammablesubstance released into the pressurized enclosureincludes the quantity f ihnmable substance in thecontainmentsystem and the flowof the flammablesubstance entering he containment system for theprocess. The flowshall be limitedto a predictable rateby appropriate flow limiting devices,itted outside thepressurized enclosure.However, if that part of the containmentsystem fromthe entry point i nto the pressurized enclosure upoand including the inleto the flow limiting deviceconforms to 10.1,he flow limiting device may beinstalled inside the pressurized enclosure,n whichcase the flow limiting device shall be permanentlysecured and have no movable parts.If the flow limiting device s not includedas part of theapparatus, the pressurized enclosurehall bemarked 'X.The process flow into he containment system neednot be limited f the maximum release rate from thecontainment system into the pressurized enclosureanbe predictedThis conditioncan be met when thematerialwithin the containment systems entirely inthe gaseous phase and- he containment system comprises connected partswhich individually meet he requirements of 10.1and the joints between the parts areo constructedthat the maximumrelease rate can be predicted andthe joints are permanently secured,and/or- he containment system includes nozzles ororifices for the purposef release in normaloperation (e.g. flames) but otherwise meets therequirements of 10.1.

'1 A method of joining two or more components, normally metallic, employing a binary or ternary alloy system which solidifiest aconstant temperaturewhich is lower than the beginning of solidification of an y of the components being joined.



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Pressurized enclosures containinga flame shall beassessedas hough the flame had been extinguishedThe maximum quantity of he fuel/& mixture whichsupplies the flame hall be added to the quantity ofrelease fiom the containment system.NOTE 1. Elastometric seals, windows and other non-metallic partsof the containment systemare permissible. Pipe threads andflanged joints are also permissible.NOTE 2. It is the responsibility of the user to ensure that hemaxjmumpressure and flowof the flammable substanceinto thecontainment system do not exceed the ratings specified by themufacturer10.3 Containment system with unlimited releaseContainmentsystems conforming to 10.2 containingliquids from whichcan evolve flammablegases orvapoum shall be designatedas containmentsystemswith unlimited release.NOTE. Other conditionsof unl imted release are outside the scopeof this standard, see 1.4. Consideration shall be given to thepossible accumulationof liquid inside the pressurized enclosuresand the consequences thereof.11 Protective gas and pressurizingtechniqueThe design of the pressurized enclosure withcontainment system and limtedor unlimited releaseshallbe suchthat no explosive gas atmosphere an beformed inside he pressurized enclosure, except indilution areaWhere inert gasis used as the protective gas, labelwith the following wordinghall be fixed to theenclosure:WARNING. This enclosure normally contains inertgas and may release flammable substance.

The applicable pressurizing techniques depend uponthe category and on the constituents f the releaseasfollows.ll.1 Pressurization with leakage compensation11.1.1No releaseThe protectivegas may be air or inert gas.11.1.2 Limited releaseThe protectivegas shall be inert gas.The concentsation of oxygen in the containmentsystem shallnot exceed2 % (vh).Leakage compendjon with inertgas cannot be usedwhen thereis adeliberate release of flammablematerial from the containment,aspart of its normalfunction, into the pressurized enclosure.When the flammable substance release from thecontainment systemhas a UEL greater than80% (vh),leakage compensations not permittedNOTE. I t is difficult or impossible to protect with leakagecompensation using inert gas for apparatus which contains arelease of gases or vapours which re capable of reactingexothermically evenwith little or no oxygen present, e.g. an UELgreater than80%Only dilution in accordance with 11.2.2a) is suitable.

Page 9EN 50016: 1995

11.1.3 Unlimited releaseThe protectivegas shall be inert gas.Where oxygenis entrained with flammable substancein the containment system, the concentrationfoxygen in the gas phase of the containmentsystemshall not exceed2% (vh).Leakage compensation with inertas cannot beusedwhen there is adeliberate releaseof flammablematerial from the containment into the pressurizedenclosureas part of it s normal function.NOTE. It is difficult or impossible to protect with leakagecompensation using inert gas or apparatus which contains arelease of gases or vapours which are capable of reactinggreater than80%.exothermically even with littleor no oxygen present, e.g. an UEL11.2 Pressurization with continuous low of theprotective gasWhere the technique of continuous flow of theprotective gas is applied, the flow rate must besufficient to maintain the minimum i n t e doverpressure of the pressurized enclosure andoachieve the dilution where appropriate.11.2.1 No releaseThe protectivegas may be air or inert gas.11.2.2 Limited releaseThe flow rat^of protective gas after purging hall besufficient, undera l l conditions of containment systemfailure, to dilute themaxjmum release into thepressurized enclosureas follows:a) when the protective gas is air, the flammablesubstance in the releaseshall be dilutedto aconcentration not exceeding5% of theEL;

b) when the protective gas s inert any oxygen in therelease shallbe dilutedto a concentsation notexceeding2% (v&)at the outlet aperture andt any place within thepressurized enclosure except in he dilution areaWhere the protectivegas is inert, and there s not morethan2% (v&) oxygen in he containment system, theflow rate after purgingmay be reduced to thatnecessary to maintain the minimum overpressurespecified by the manufacturer.When the flammable substance released from hecontainment systemhas a UEL greater than 80ohairshall be used to dilute any releaseof flammablesubstance to a concentration not exceeding5% ofthe LEL.NOTE. It is difficult or impossible to protect with continuous flowusing inert gas for apparatus which contains a release f gases orvapours which are capable of reacting exothermically even withlittle or no oxygen present, e.g. an UEL greater than 80%.Only dilution in accordance with 11.2.2as suitable.11.2.3 Unlimited releaseThe protectivegas shall be inertgas. he flow rate ofprotective gas after purging shall be sufficient, underall conditions of containment Mure, to dilute themaximum release of entrained oxygen to aconcentraction not exceeding % (v&) at the outletaperture andat any place within he pressurizedenclosure except in the dilution rea

0 BSI 1996PYRIGHT British Standards Institute on ERC Specs and Standardscensed by Information Handling Services


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Where there is not morethan2% (vh) oxygen in thegas phase within the containment system, the flow rateafter purging may be reduced o that necessary omaintain the minimum overpressure specified byhemanufacturer.Dilutionwith the inertgas cannot be used when thereis a deliberate release of flammable material from thecontainment system, into the pressurized enclosurespart of its normal function.12 Ignition capable apparatusIgnition capable apparatushall not be located n thedilution area Electrical apparatus in he dilutionareashall be protectedby a type of protection l istedin 1.8.1 of this standard.Exceptions from hi srequirement are flames, ignitors or other similarapparatus intended o ignite a flame. The dilution areaemanatjng rom the flame shall not overlap any otherdilution area.NOTE 1. Generally any source of release should be nearo theoutlet and any ignition capable apparatus nearo the inlet of theprotective gas, o allow the shortest possible way for releasedflammable materials to leave the pressurized enclosure, withoutpassing ignition capable apparalxs.NOTE 2. To avoid ignition from an gnition source withh thecontainment system backinto the plant the use of a flamearrestorcan be necessary, Such measures re not covered by thisstandard.13 Internal hot surfacesIf the pressurized enclosure contains any surfacehaving a temperature which exceeds he ignitiontemperatwe of the flammable substance released fromthe containment system, he sample flow into thecontainment systemshallbe cutoff automaticallyfollowing the operation of the safety devices specifiedin 6.8 and 9.1.2.Additionallya) if the protectivegas is air, the release of theremaining flammable substance in he containment

system shall not form a concentration greaterthan50% of the LEL n the vicinity of the hot surface(s);orb) if the protective gas is inert, the design andconstruction of the joints f the pressurizedenclosureshallbe suchas o prevent significantmixing of external air with the internal inert gas (orinternal flammable gas) during the cooling eriodThe ingress of external air shall not increase theconcentration of oxygen to a value greaterthan2% (vh).Awarning labelshall also be fitted o the pressurizedenclosure stating the delayo be observedbetween theremoval of the source of heat within the pressurizedenclosure and he opening of any doors or covers.Thisdelay shall be the longerof the time taken for the hot

surface to cool below the ignition temperaturef theflammable substance released from he containmentsystem or the temperature lass of the pressurizedenclosure.

Verihication and es t s14m e erification and estsThe apparatusshall be subjected o the following estsapplicable and in the following sequence.-all relevant testsof EN 50014;- overpressure test;- eakagete$- urging test, orfilling procedure test for taticpresswkatioq-dilution test;- erification of minitnum overpressure;- test for infallible containment system;-overpressure test for containment systems withlimited release.

14.1 Overpressure testA pressure equal to 1,5 i mes the maximumoverpressure specified for normal Service withminimum of 200 Pa shall be applied to the pressurizedenclosure and, where theyre an integral partof theenclosure, the associated ducts and their connectingP-The test pressureshall be applied fora period of2minf10s.The test is considered to be satisfactory if nopermanent deformation occurs which would invalidatethe type of protection.14.2 Leakage test14.2.1 The pressure in the pressurized enclosureshallbe adjusted to the maximum overpressure specified bythe manufacturer for normal service.With the outletaperture closed, the leakage flowate shall bemeasured at the nlet aperture.The measured flow ate shall be not greater han themaximum leakage flow ate specified by themanufacturer.14.2.2 In the c a e of static pressurization the pressurein the pressurized enclosurehall beausted to themaximum overpressurethatcan occur in normalservice. With the aperture(s) closed, the internalpressure shall be monitored for period of time,according to 6.7 of thi s standard The change ofpressure shall be not greater han the minimumoverpressure specified for o d ervice.14.3 Purging test for pressurized enclosureswith no internal sourceof release(pressurization technique may be leakagecompensation or continuousflow) and fillingprocedure test for static pressurization14.3.1 Pressurized enclosure where the protectivegas is airThe pressurized enclosure shall be prepared forest asdescribed in annexD.The pressurized enclosureshallbe filled with the testgas to a concentration of not less than70% at anypoint.



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As soon as he pressurized enclosure s filled the testgas supplyshall be turnedoff and the protective gassupply turned onat the minimum purging ratespecified by the manufacturer. The time taken untilthere is no sample point where here is a test gasconcentration in excess of that specified inD.2 shallbe measured and notedas the purging time.If a second test is required, the pressurized enclosureshallbe filled witha second test gas, representing theother endof the densi@ range,o a concentrationofnot less han 70% at any point and the purging timefor the secondest shallbe gas measuredThe minimum purging duration specified by hemanufacturershall be not less han the measuredpurging time or the longer of the two measuredpurging times where wo tests are carried out.14.3.2Pressurized enclosure where the protectivegas is inert gasThe pressmized enclosureshallbe prepared for est asdescribed in annexD. The enclosureshall be fdledinitially with air at normal atmospheric pressure. Theenclosureshall then be purged with the inertasspecified by the manufacture^The time takenntil there is no sample point wherethere is an oxygen concentration exceedinghatspecified inD.3, shall be measured and notedas hepurging time.The minimum purging duration specified byhemanufacturershall be not less han the measuredpurging time.14.3.3Pressurized enclosure where the protectivegas may be either air or an inert gas with adensity equal to air*10%Where air and inert gas are permitteds alternativeprotective gases with the same purging time, thepurging timeshall be measured by the methodspecified in 14.3.1.14.3.4 RUing procedure test fo r pressurizedenclosures protected by static pressurizationIn the case of static pressurization the enclosurehallbe filled withair.The apparatusshall hen be filledwith inertgas in accordance with the manufacturer'sspecifications. Itshall then be verified that there is nosample point where here is an oxygen concentrationexceeding 1% (vh), referredto atmospheric conditions.14.4 Purging and dilution ests for pressurizedenclosures with an internal source of releaseThe choiceof test gas or gases shall take accountfboth the external gases and thenternally releasedflammable materials .

14.4.1Pressurized enclosures with limited orunlimited release, pressurization by leakagecompensation or continuous jlow, containmentsystem with less han 2%(vh> xygen andwhere the protective gas is inert gas14.4.1.1PuTging testThe test shall be carried out using theest procedurespecified in14.3.2. The minimum purge flow rateshallnot be less han the maximum release rateh m hecontainmentsystem. Tb make allowance for oxygenthat could be released from the containment systemduring purging, the purging time confnned inhe testshall be increased by 50%.The minimumpurging time specified byhemanufacturershall be not lesshan 1,5 times themeasured purging time.14.4.1.2Dilution testA dilution test is not required because he containmentsystem does not contain morehan 2%(vh)xygen.14.4.2 Pressurized enclosures with limited orunlimited release pressurizationby continuousjlow, containment system with less han21 % (vh> xygen and the protective gas is inert14.4.2.1Purging testThe enclosureshall be filled withair.Air shall also beiqjected into the enclosure through the containmentsystem at a flow ratecorresponding to the maximumrelease rate in a manner representing the most onerousconditions of release, takinginto account the position,number andnature of the releases and their proximityto ignition capable apparatus.The supply ofhe protectivegas shall then be turnedon at the minimum purging flowrate specified by hemanufacturer.The time taken until theres no sample point wherethere is an oxygen concentration exceedingthatspecified inD.3 shallbe measured and notedas thepurging time. The minimum purging time specified bythe manufkturer shall be not less han the measuredpurging time.14.4.2.2Dilution testImmediately after thepurging test specified in 14.4.2.1the supply of the protective gas shall be adjusted tothe minimumflow rate specified by the manufacturer,the oxygen flow rate from the containment systembeing maintainedat that specified n 14.4.2.1.The oxygen concentration measuredover a period oftime not less han 30minshall not exceed theconcentration as specifiedinD.3.A quantity of air containing an equivalent quantityfoxygen to that within the containment system hallthen be releasedinto the pressurized enclosure fromthe containment system together with release of airin accordance with 10.2.



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Page 12EN 60016:1995

Duringthe periodof release the concentrationofoxygen in the vicinity of ignition capable apparatusshall not exceed 1,6times the oxygen concentrationspecified inD.3 and shall,in a time not greater than30minutes, be reduced belowhe specifiedconcentration.14.4.3Pressurized enclosures with limitedrelease, pressurization bu continuousflow andthe protective gas is air14.4.3.1Puryng testThe test shall be carried outusing the test procedurespecified in 14.3.1.In addition during the est, the test gas shall beinjected into the pressurized enclosure through thecontainmentsystem at the maximum release rate in amanner representing the most onerous conditionsfrelease taking into account the position, number andnature of the releases and their proximityo ignitioncapable apparatus.The time takenuntil there is no Sample point wherethere is a test gas concentration exceeding hatspecified in D.2 shallbe measured.Ifa second testis required the est shall be repeatedusingthe second est gas and the purging timemeasured and notedas he purging time.The minimum purging time specified by hemanufacturershall be not less han the measuredpurging time or the longer of the two measuredpurging times where wo tests are carried out14.43.2Dilution testImmediately after he purging test specified 14.4.3.1the supply of protective gas shallbe adjusted, ifnecessary, to theminimumdilution flowrate specifiedby the mufacturer, the test gas flow rate from thecontainmentsystem being maintainedat that specifiedin 14.4.3.1.The test gas concentration measured during timeperiod of not lessthan30minutes shall not exceedthat specified in D.2.A Quantity of test ga s equivalentto the volume offlammable gas within the containment systemhallthen be releasedinto the pressurized enclosure fromthe containment system together withflow of testgas equivalent to the maximumrelease of Dammablegas in accordance with10.2.During the period of release the concentrationof a testgas in the vicinity of ignition capable apparatushallnot exceed twice the value specifiedn D.2 and shallwithin 30min be reduced below the specified value.If a second test is required the est shall be repeatedusing the second testgas.

14.6 Verification of minimum overpressureA test shall be made to verify that the pressurizationsystem is capable of operating and maintaininganoverpressure complying with .9 under normal serviceconditions.The pressure n the enclosureshall be measured atpoints where leakages likely to occur, and especiallywhere the lowest pressurewill occur. Protective gasshall be supplied o the pressurized enclosure t thelowest pressure, andf nece- at the minimum flowrate, specified by the manufacturer. For rotatingelectrical machines theests shall be carried out withthe machine stopped andunning at itsmaximumrated speed14.6 Tests for infallible containment sytemsThese tests are carried out on containmentyst~msdesigned to be infallible.14.6.1 Overpressure testA test pressure of at least five times the maximuminternaloverpressure specified for normal service witha minimum of lo00 Pa shall be appliedto thecontainment system for period of 2 min f 10 s. Thecontainment system hall be tested under the mostonerous conditionsof rated temperature.The increase of the test pressure should achieve themaximum pressure within5 s.The test is considered to be satisfactow f nopermanent deformation occm and the test specifiedin 14.6.2 ispassed14.6.2 I@dlibili& test

a) The containment systemshallbe surrounded byhelium at a pressure equalto the maximum pressurespecified for normal service. The containmentsystem shall be evacuated down o a pressure of0, lPa or better.b) Atemalively the containmentystem shall belocated in a vacuum chamber and be connectedo ahelium supply at the maximum pressure specifiedfor normal service. The vacuum chamberhall beevacuated down o a pressure of 0,l Pa or better.

The test is considered satisfactory if a pressure of0,l Pa can be maintainedNOTE. A schematic diagramof an infallibilitytest asdescribedin 14.6.2ais given in annexB.14.7 Overpressure test for containment systemswith limited releaseThis test is carried out on containmentystems whichhave a limited release during normal operation.A test pressureof at least 1,5 times the maximuminternal overpressure specified for normal service, witha minimumof 200 Pa shallbe applied o thecontainment system and maintained fortime of2minf 10s. The test is considered to be satjsfactory ifno permanent deformation CCUIS.



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15 Routine testsThe followingtests shall be carried out after thecompletion of the relevant tests of EN 50014.16.1 Overpressure testA routine test shallbe carried outas specified in14.1.16.2 Leakage testA routine test shallbe carried outas specified in14.2.16.3 Tests for infallible containmentystemsInfa3lible containmentsystemstests shall be carriedout as specified in14.6.16.4 Test for containment systems with limitedreleaseContainmentsystems with limited releaseshall betested as specified in14.7.Marking16 MarkingPressurized enclosuresshallbe marked in accordancewith the requirementsof EN 50014.The followingsupplementary informationhall also be marked asapProPriat.16.1 Pressurized enclosures other than thoseprotected by static pressurizationa) The internalfreevolume, including ducts wherethey are an ntegral partof the enclosure.

b) Qpe of protective gas (where his is not air>.c ) Minimum quantity of protective gas required topurge the enclosure specified y-minimum purging flow rate of protective gas;-minimum purging duration;-minimum additionalpurging duration perunitvolume of additional ducting (where appropriate).

NOTE. t is the responsibilityof the user to increase the quantityof protective gas to ensure purging of the ducts.d) The minimum and maximum overpressure.e) The maximum leakage ate fiom the pressurizedenclosure.f) A special temperatweor range of temperaturesfor the protective as at the inlet o the pressurizedenclosure when specified by the manufacturer.g) The point or pointst which the pressure s to bemonitoredunless this is indicated in the relevantdocumentation.

16.2 Pressurized enclosures with containmentsystemIn addition to the above, enclosures withacontainmentsystem shallbe marked with the followingwhere appropriate:

a) the categoryof internal release;b) the minimum flow rate of protective g a s , ifnecessary;c ) the maximum inlet pressure o the containmentsystem;d) the maximum flow rate into the containmentsystem;e) the maximum oxygen concentsation in thecontainment system;f) the maximum permittedUEL in the containmentsystem.

16.3 Pressurized enclosures protectedby staticpressurizationAwarning label (or labels)shallbe fitted with thefollowing wording:

a) TH SENCLOSURE IS PROTECTED BY STATICPRESSURIZATION.b) THISENCLOSURE SHALL BE FILLED O W NMANUFACTURERS INSTRUCTIONS.

16.4 Safety related control systemsIf certified, the afely r e m ontrol system andassociated safety deviceshall be marked [EExp].16.6 Any other marking required.

A NON-HAZARDOUSAREA ACCORDING TO THE



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Annex A (informative)Ducting ofprotective gasA.l Except for cylinder supplied gases and someGroup I applications the pointsat which the protectivegas enters the supply duct(s) should be situated in anon-hazardousareaFor Group applications where the protectiveasenters the supply ducts rom a hazardous area thefollowing precautions shoulde taken.

a) Two independent firedamp detectors should befitted at the discharge sideof the fan or compressor,each arrangedto disconnect automatically theelectricity supply o the pressurized enclosuref theconcentration of firedamp exceeds 10% of the lowerexplosive limitb) The time takeno achieve automaticdisconnection should not be greaterhan one halfthe transit time for the protective gaso flow fromthe detection pointo the pressurized enclosure.c) In the eventof automatic disconnection thepressurized enclosure should be repurged before theelectricity supplys restored The purging timeshould notstart until the firedamp concentmiiontthe source of protective gas falls below0% of thelower explosivelimit

Any compressor or fan and the associated ductingshould be designed and installed in such way thatthe surroundingatmosphere cannot enter theenclosure and duct(s).A.2 Ducts for exhausting he protedive gas shouldpreferably have their outlets in anreawhich would,apartfrom the area in close proximity o the outlets,be a non-hazardousarea Consideration shouldotherwise be given to the fitting of spark and particlebaniem (that is devicesto guard against the ejectionofignition capable spa& or particle) as shown incolumns3 and 4 in tableAl.

FIGURESExamples of the changes in pressure n ducts andenclosuresKey to figures A.l toA.4NOTE. In the figures, examples are shown where the overpressureismaintainedby a fan. This can however, also be provided byother means, e.g. by feedingair from compressedair cylinders,compressors etc. n such cases there would be different pressuredrops up the enclosed enw.

Pl .

P2.P3.

P4.

P5.1.2.3.4.5.6.7.8.

hure of the protective gas (determined bythe flow resistancehrough the ducting, theparts within the enclosure andn certain casesthrough a choke or spark and particle barrier)Pressure of the protectivegas (almostconstant)Pressure of the protective gas (determined bythe flow resistanceof the internal parts, andinfluenced betweenA, B andC by the i n t e dcoolingfan)Pressure of protective gas (determined by theflow resistance of the internal parts andy theuppermost valueof pressure of the externalair>Pressure of the externalair, caused by theextend cooling fanProtective gas inlet (in non-hazardous area)DuctingFanEnclosureChoke (where requiredomaintain theoverpresure)Outlet valveProtective gas outletSpark and particle barrier

ITable A.l Use of spark and particlearriers II *OUP IZone of purge 1 Enclosedpparatus A I Enclosedpparatus Bexhaust INon hazardous Not required Not required

Hazardous Required')equired,II I Non hazardous I Notequired I Notequired ~-1

Zone 2Required')equired',one 1 Not requiredequired

A Apparatus which may produce ignition capable sparksor particles in normal service.B Apparatus which doesnot produce ignition capable sparks r particles in normal service.'1 If th e temperature of the enclosed apparatus constitutes a hazard uponailure of pressurization, a suitable device should preventherapid enW of the surrounding atmomhere intohe Dressurized enclosure. See4.2.

~ ~



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OverpressurePa mbar P l

Case a: protectivegas outletwithout asparkandparticlebarrier

Caseb protectivegas outletwitha markandwuticle barrierFigure A.1 Pressurized enclosures with continuousflow of protective gas



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OverpressurePa mbar

-7 "-" _

I

Figure A.2 Pressurized enclosures with leakage compensation, enclosureswithout moving parts

-

-" _

AOverpressurePa mbar I I

50 LL

"

\3 3Figure A.3 Pressurized enclosures with leakage compensation, rotatingelectricalmachine with an internal cooling fan. Pressure t every point where leakage can occuris above the minimum of 60 Pa



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OverpressurePa mbar

OL o -

I /Internalressure I I I I

External pressure ? 50 Pa0,5 mbarFigure A.4 Pressurized enclosures with leakage compensation, rotating lectricalmachine with an external cooling fan



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Annex B (informative)Infallbility test for a containment system

a) The volumeV2 >the volumeV1 of the systemunder test.b) The crosssectional area of the critical orificediameter D0 c the cross-sectional area of theconnecting orificeDXc) The pressuremonitoring device P shall becorrected to take accountof the propertiesof theleak testing gas (e.g.helium).d) Thetest is satisfactory f a pressureof I 0 , l Pacan be maintained inV2 with both valves open IV1and IV2).e) The leakate (if any) can be determined withN1open andN2 closed

Helium filledchamber+nSystem under testDX+nectingorificediameter

Pressuremonitoringdevice

v2"""-Evacuating'"2 system+

D0 CriticalorificediameterFigure B.l. Schematic diagramof infallibility test described in clause 14.6.2a)



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Annex C (inormtiv)Function test ofE urveillance circuitsThe following is an example of informationto be provided by the manufacturer fora simple controlsystem for apressurized enclosure with leakage compensation.

SO I S1 I S2 I S3 I MOP IXOP I PFLO IPTIM I1 I o l o I oo I l I o I l I1 0 0 0 0

10 0 0 1O0 0 0 11

1 0 0 0 1

O0 0 0 110 0 0 0 10 0 0 01

1 0 0 0 0

O0 0 0 0O0 0 0 0O

1 0 0 0 0

10 0 1 1O0 1 0 1O1 0 0 1O

o I o I o I l I l I o I ll IILeakage compensation logical definitionsExcess over pressure = [XOP]Over pressure >50pascals = [MOP]Purge flow >minimum = [PFIO]Purgeime = NOT[PTIM]Purgeime = [PTIM]Initial state>[MOP]&NOT[XOP]&NOT[PF'LO]&NOT[PTIM] = so= S1Minimum conditionsto start purge[MOP]&NOT[XOP]&[PFLO]&NOT[Fl'IM] = SZPUrging[MOP]&NOT[XOP]&[PTIM] = S3 purging complete,oweronnectedState diagram and truth tableof a eakage compensationpurge control systemEach STATE of the system is defined in response to the inputs of the monitoring devices. The tates are unique."ansitions between states are only allowed alongpaths defined by the mows and in the directionof the arrows.The logical conditions for the occupation f each state are uniquely defined by BOOLEAN ogical expressions.Allpossible combinationsof input conditionsase shown in the table. Othersystems with moremonitoring devicescan be described bythismethod provided eachoperationalstate is uniquely defined byits inputs.O BSI 1996



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Annex D (normative)Purging and dilution testsD.1 GeneralThe internal &nosphere of the pressurized enclosureshallbe testedat Merent points where itsconsidered that the gasis most likely to persist duringthe tests except the dilution areas where no testhallbe made.The gas concentration at the test points shall beanalysed or measured throughout the periodf thetest@). If the test consists of taking samples, thequantities taken should not ignificantly influence thetest.For example, the pressurized enclosure may e fittedwith a number of small bore tubes, the open endsfwhich shallbe located inside he pressurized enclosureat sampling points where its considered that the testgas is most likelyto persist during the ests. Where theenclosure contains an internal sourcef release, someof the test points sha3l be located in he vicinity ofignition capable apparatus.If necessary aperturesn the pressurized enclosuremay be closed to enable the pressurized enclosureobe f i l ledwith the specified est gasprovided that theyare reopened for the purging and dilutionests.Where air is used as he protective g a s , the testmethod shall be as follows.-When required for specific applicationsestsmaybe canied out fora specific range of flammablegases andvapours. In this case the potentiallyhazardous gases shallbe specified and est gaseschosen having densities similar to the upper andlowerboundaries of the stated hazardousgases sothat the tests coverallgases in the stated densityrange.- n the case of a single specifiedgas, a single testsha,ll beded out with a test gas having a densitysimilar to that of the specifiedgas.-When it is required to cover all flammablegasestwo tests shall be&edout, one to cover lighterthanair gases, where the testgasshallbe helium,the other test to cover heavierthanair gases, wherethe test gas shallbe either argonor carbon dioxide.

NOTE. Generally test gases should be non-flammable andnon-toxic.

D.2 Criteria for compliance where theprotective gas is airThe concenlxaiionof test gasat the sample pointsafterpurging, and where applicable dilution,hall notexceed:- a value equivalent o 25 %of the more onerousLEL where two ksts are carriedout to cover aspecific rangeof flammable gases;- a value equivalent o 25 % of the LEL where onespecific flammablegas is covered;- 1% for the helium test and,25% for the argon orcarbon dioxide test to cover all flammable gas.NOTE.These values correspond approximatelyto 25% of LEL orth e lighter thanair gases and heavier than ir gases respectively.D.3 Criteria for compliance where theprotective gas is inert gasWhere the protectivegas is inert gas, the concentrationof oxygen after purging, and where applicable dilution,shall not exceed2 % (vh).



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List of referencesSee national foreword.

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BS EN50016:1996

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BSI en 50016 1996 Elect Apparatus for Potentially Explosive