By Authority Of THE UNITED STATES OF AMERICA Legally Binding Document

Transcription

1 By Authrity Of THE UNITED STATES OF AMERICA Legally Binding Dcument By the Authrity Vested By Part 5 f the United States Cde 552(a) and Part 1 f the Cde f Regulatins 51 the attached dcument has been duly INCORPORATED BY REFERENCE and shall be cnsidered legally binding upn all citizens and residents f the United States f America. HEED THIS NOTICE: Criminal penalties may apply fr nncmpliance. e Dcument Name: UL 913: Intrinsically Safe Apparatus and Assciated CFR Sectin(s): Standards Bdy: Apparatus fr Use in Class I, II, and III Divisin 1, Hazardus (Classified) Lcatins 46 CFR (a) Underwriters Labratries Official Incrpratr: THE EXECUTIVE DIRECTOR OFFICE OF THE FEDERAL REGISTER WASHINGTON, D.C.

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3 ,! '-. UL 913. i INTRINSICALL Y SAFE APPARATUS-AND ASSOCIATED APPARATUS FOR USE IN CLASS I, II, AND III, DIVISION I, HAZARDOUS (CLASSIFIED) LOCATIONS,.

4 UNDERWRITERS LABORATORIES an independent, nt-tr-prfit rganizatin testing fr public safety July 29, Labratry Drive, Relearch Triangle Park, NC Walt Whitman Rad, Melville, L.I., NY Sctt Bulevard, Santa Clara, CA Pfingsten Rad, Nrthbrk, IL STANDARD FOR INTRINSICALLY SAFE APPARATUS AND ASSOCIA TED APPARATUS FOR USE IN CLASS I, II, AND III, DIVISION 1, HAZARDOUS (CLASSIFIED) LOCATIONS UL 913, FOURTH EDITION Accmpanying this transmittal ntice is a cpy f the furth editin f UL 913. THIS EDITION OF THE STANDARD IS NOW IN EFFECT EXCEPT FOR PARAGRAPHS, ITEMS, AND FIGURE, WHICH BECOME EFFECTIVE SEPTEMBER 13, 1991 AS INDICATED IN THE SMALL PRINT NOTE FOLLOWING THE AFFECTED ITEM,S. New prduct submittals made prir t a specified future effective date will be judged under all f the requirements in this standard unless the applicant specifically requests that the prduct be judged under the current requirements. Hwever, shuld the applicant elect this ptin, it shuld be nted that cmpliance with all the requirements in this standard will be required as a cnditin f cntinued Listing r Recgnitin and Fllw-Up Services after the effective date and understanding f this shuld be signified in writing. As indicated n the title page, this UL Standard fr Safety is an American Natinal Standard. Revised and/r additinal pages may be issued frm time t time. Subscribers t UL's services in the area cvered by this standard will receive these revised and/r additinal pages autmatically. Others may receive such pages by subscribing t UL's subscriptin service fr revisins. See UL's CATALOG OF STANDARDS FOR SAFETY fr a descriptin f the revisins subscriptin service, the cst f the service fr this standard, and rdering infrmatin. A PRODUCT INDEX f UL Standards fr Safety is als available. The index prvides mre than 3,000 examples frm the mre than 12,000 specific prducts that are cvered by UL's Services and Standards fr Safety. The index als includes an alphabetical listing f keywrds f each title f each standard. A STANDARDS GLOSSARY is als available. The glssary is a cmpilatin f terms and their definitins taken frm the glssaries f ver 500 UL Standards fr Safety. T btain a free cpy f UL's CATALOG OF STANDARDS FOR SAFETY cntact any f UL's Offices. Detailed pricing and rdering infrmatin fr the PRODUCT INDEX and/r the STAN DARDS GLOSSARY is included in UL's CATALOG OF STANDARDS FOR SAFETY. Telephne rders fr UL's publicatins may be charged t yur Visa r MasterCard accunt.

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6 =R~~ July 29, 1988, ANSIjUL UL 913 STANDARD FOR INTRINSICALLY SAFE APPARATUS AND ASSOCIA TED APPARATUS FOR USE IN CLASS I, II, AND III, DIVISION 1, HAZARDOUS (CLASSIFIED) LOCATIONS First Editin - Nvember, 1971 (First Editin titled Standard fr Intrinsically Safe Electrical Equipment fr Use in Hazardus Lcatins) Secnd Editin - January, 1976 (Secnd Editin titled Standard fr Intrinsically Safe Electrical Circuits and Apparatus fr Use in Hazardus Lcatins and its assciated Apparatus) Third Editin - July, 1979 FOURTH EDITION July 29, 1988 Apprval as an American Natinal Standard cvers the numbered paragraphs n pages dated July 29, These pages shuld nt be discarded when revised r additinal pages are issued if it is desired t retain the apprved text. Revisins f this standard will be made by issuing revised r additinal pages bearing their dates f issue. An effective date included as a nte immediately fllwing certain requirements is ne established by Underwriters Labratries Inc. Apprved as ANSIjUL/NFPA , Nvember 5, 1979 Apprved as ANSIjUL , May 20, 1988 Figures 2-4 and 8 are frm British Apprvals Service fr Electrical Equipment in Flammable Atmspheres Certificatin Standard SF A 3012: Intrinsic Safety. Permissin t use this Crwn Cpyright Material is gratefully acknwledged. Figures 5 and 6 are frm "Sme Aspects f the Design f Intrinsically Safe Circuits," Research Reprt 256 by D. W. Widgentn, Safety in Mines Research Establishment, Sheffield, England, (1-7/29/88) COPYRIGHT 1976, 1988 UNDERWRITERS LABORATORIES INC. UL's Standards fr Safety 1118 cpyrighted t prtect UL's publicatin rights, nt t restrict their use In prduct design r evaluatin, See paragraph E f the Frewrd. (~. ) ~I

7 2 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL 913 JULY 29, 1988 CONTENTS SECTION 1. General Scpe Purpse Applicability f Other Standards Definitins Cntrl Drawing Evaluatin f Intrinsic Safety Fundamental Requirements Evaluatin Prcedure Entity Evaluatin Assciated Apparatus Evaluatin Intrinsically Safe Apparatus Inductance and Capacitance Determinatin Intrinsically Safe Apparatus Cntrl Drawing Evaluatin Intrinsically Safe Apparatus Evaluatin Cnstructin Requirements Creepage and Clearance Distances Encapsulatin Field Wiring Cnnectins Internal Wiring Cnductrs Prtective Cmpnents Miscellaneus Cmpnents Prtable Apparatus Enclsures Cells and Batteries Additinal Requirements Maximum Temperature Marking Cmparisn Prcedure fr Determining Spark Ignitin Capability General Maximum Vltage and Current Levels Apparatus fr Class II and Class III Lcatins Applicability f Other Requirements f this Standard Specific Requirements fr Intrinsic Safety Dust-Tight Enclsures... 31

8 -~ ~ I -i JULY 29, 1988 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL Test Prcedures Prtective Transfrmer Tests Current-Limiting Resistr Test Shunt Dide Prtective Barrier Tests Optical Islatr Tests Temperature Tests Small Cmpnent Ignitin Test Dielectric Tests Mechanical Tests Drp Test Dust-Tight Enclsure Test Dust Blanketing Temperature Test Lamp Breakage Test Encapsulatin Tests Internal Capacitance r Inductance Test Spark Ignitin Test General Requirements Test Apparatus Gas Mixtures Verificatin f Spark Test Apparatus Test Prcedure Test Factrs Appendixes Appendix A Additinal Infrmatin... Al Appendix B Referenced Publicatins... B 1

9 4 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL 913 JULY 29, 1988 FOREWORD A. This Standard cntains basic requirements fr prducts cvered by Underwriters Labratries Inc. (UL) under its Fllw-Up Service fr this categry within the limitatins given belw and in the Scpe sectin f this Standard. These requirements are based upn sund engineering principles, research, recrds f tests and field experience, and an appreciatin f the prblems f manufacture, installatin, and use derived frm cnsultatin with and infrmatin btained frm manufacturers, users, inspectin authrities, and thers having specialized experience. They are subject t revisin as further experience and investigatin may shw is necessary r desirable. B. The bservance f the requirements f this Standard by a manufacturer is ne f the cnditins f the cntinued cverage f the manufacturer's prduct. C. A prduct which cmplies with the text f this Standard will nt necessarily be judged t cmply with the Standard if, when examined and tested, it is fund t have ther features which impair the level f safety cntemplated by these requirements. D. A prduct emplying materials r having frms f cnstructin differing frm thse detailed in the requirements f this Standard may be examined and tested accrding t the intent f the requirements and, if fund t be substantially equivalent, may be judged t cmply with the Standard. E. UL, in perfrming its functins in accrdance with its bjectives, des nt assume r undertake t discharge any respnsibility f the manufacturer r any ther party. The pinins and findings ful represent its prfessinal judgment given with due cnsideratin t the necessary limitatins f practical peratin and state f the art at the time the Standard is prcessed. UL shall nt be respnsible t anyne fr the use f r reliance upn this Standard by anyne. UL shall nt incur any bligatin r liability fr damages, including cnsequential damages, arising ut f r in cnnectin with the use, interpretatin f r reliance upn this Standard. F. Many tests required by the Standards f UL are inherently hazardus and adequate safeguards fr persnnel and prperty shall be emplyed in cnducting such tests.

10 --- l ~--~------~~ ~--- ~ ~ ~ ~ JUL Y 29, 1988 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL General NOTICE: The asterisk fllwing the subsectin number signifies that explanatry material n that paragraph appears in Appendix A. 1.1 Scpe This standard applies t: (1) Apparatus r parts f apparatus in Class I, II, r III, Divisin 1 lcatins I; (2) Thse parts f apparatus lcated utside f the Class I, II, r III, Divisin 1 lcatin having a design and cnstructin that may influence the intrinsic safety f an electrical circuit within the Class I, II, r III, Divisin 1 lcatin * These requirements are based n cnsideratin f ignitin in lcatins made hazardus by the presence f flammable r cmbustible material under nrmal atmspheric cnditins. l Fr the purpses f this standard, nrmal atmspheric cnditins are cnsidered t be: (1) An ambient temperature f 40 C (104 F); (2) An xygen cncentratin nt greater than 21 percent; and (3) A pressure f ne atmsphere This standard des nt cver mechanisms f ignitin frm external surces, such as static electricity r lightning, which are nt related t the electrical characteristics f the apparatus. This standard des nt cver apparatus based n high vltage electrstatic principles, such as electrstatic paint spraying apparatus. ISectin 500 3(a) f ANSI/NFPA , Natinal Electrical Cde, states that equipment that has been apprved fr a Divisin 1 lcatin shall be permitted in a Divisin 2 lcatin f the same class and grup. 1.2 Purpse The purpse f this standard is t prvide requirements fr the cnstructin and testing f electrical apparatus, r parts f such apparatus, having circuits that are nt capable f causing ignitin in Divisin 1 hazardus lcatins as defined ip Article 500 f the Natiunal Electrical Cde, ANSIjNFP A This standard is nt t be cnsidered an instructin manual fr untrained persns. It is intended t prmte unifrmity f practice amng thse skilled in the field f intrinsic safety. 1.3 Applicability f Other Standards Except where mdified by the requirements f this standard, intrinsically safe and assciated apparatus shall cmply with the applicable requirements fr rdinary lcatins. I Assciated apparatus and circuits shall cnfrm t the requirements f the lcatin in which the apparatus and circuits are installed Definitins Assciated Apparatus. Apparatus in which the circuits are nt necessarily intrinsically safe themselves, but which affect the energy in the intrinsically safe circuits and are relied upn t maintain intrinsic safety. Assciated electrical apparatus may be either: (1) Electrical apparatus that has an alternative type f prtectin fr use in the apprpriate ptentially flammable atmsphere; r (2) Electrical apparatus nt s prtected that shall nt be used within a ptentially flammable atmsphere. 1 As an example f requirements fr rdinary lcatins, see ANSI C39.5, Safety Requirements fr Electrical and Electrnic Measuring and Cntrlling Instrumentatin, available frm the American Natinal Standards Institute, 1430 Bradway, New Yrk, NY Fr guidance n installatin, see ANSI/ISA RPI2.6, Installatin f Intrinsically Safe Systems fr Class I Hazardus (Classified) Lcatins, available frm the Instrument Sciety f America, 67 Alexander Drive, Research Triangle Park, Nrth Carlina,

11 6 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL 913 JUL Y 29, Cntrl Drawing. A drawing r ther dcument prvided by the manufacturer f the intrinsically safe r assciated apparatus that details the allwed intercnnectins between the intrinsically safe and assciated apparatus * Entity Evaluatin. A methd used t determine acceptable cmbinatins f intrinsically safe apparatus and cnnected assciated apparatus that have nt been investigated in such cmbinatins External Inductance-t-Resistance Rati. The rati f inductance t resistance f the intrinsically safe circuit cnnected t the assciated apparatus Fault. A defect r electrical breakdwn f any cmpnent, spacing, r insulatin that alne r in cmbinatin with ther faults may adversely affect the electrical r thermal characteristics f the intrinsically safe circuit. If a defect r breakdwn leads t defects r breakdwns in ther cmpnents, the primary and subsequent defects and breakdwns are cnsidered t be a single fault Internal Inductance-t-Resistance Rati. The rati f inductance t resistance f the intrinsically safe apparatus Internal Wiring. Wiring and electrical cnnectins that are made within the apparatus by the manufacturer. Within racks r panels, intercnnectins between separate pieces f apparatus made in accrdance with detailed instructins frm the apparatus' manufacturer are cnsidered t be internal wiring Intrinsically Safe Apparatus. Apparatus in which all the circuits are intrinsically safe Intrinsically Safe Circuit. A circuit in which any spark r thermal effect, prduced either nrmally r in specified fault cnditins, is incapable, under the test cnditins prescribed in this standard, f causing ignitin f a mixture f flammable r cmbustible material in air in the mixture's mst easily ignitable cncentratin Linear Output Assciated Apparatus. Assciated apparatus in which the utput current is limited by a resistr such that the utput vltage-current plt is a straight line drawn between pen circuit vltage and shrtcircuit current Maximum Allwed Capacitance. The maximum value f capacitance that may be cnnected t the intrinsically safe circuit f the assciated apparatus Maximum Allwed Inductance. The maximum value f inductance that may be cnnected t the intrinsically safe circuit f the assciated apparatus Maximum Input Current. The maximum dc r peak ac current that can be safely applied t the terminals f the intrinsically safe apparatus. The maximum input current may be different fr different terminals Maximum Input Vltage. The maximum dc r peak ac vltage that can be safely applied t the terminals f an intrinsically safe apparatus. The maximum input vltage may be different fr different terminals Maximum Internal Capacitance. The ttal equivalent internal capacitance f the intrinsically safe apparatus that must be cnsidered as appearing acrss the terminals f the intrinsically safe apparatus Maximum Internal Inductance. The ttal equivalent internal inductance f the intrinsically safe apparatus that must be cnsidered as appearing acrss the terminals f the intrinsically safe apparatus Maximum Nnhazardus Lcatin Vltage. The maximum vltage that may be applied t each f the nnintrinsically safe terminals f assciated apparatus withut affecting intrinsic safety Maximum Output Current. The maximum dc r peak ac current that may be extracted frm the intrinsically safe cnnectins f the assciated apparatus.

12 JULY 29,1988 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL c) Maximum Output Vltage. The maximum dc r peak ac pen circuit vltage that can appear at the intrinsically safe cnnectins f the assciated apparatus Nrmal Operatin. Intrinsically safe apparatus r assciated apparatus cnfrming electrically and mechanically with its design specificatin Prtective Cmpnent r Assembly. A cmpnent r assembly that is s unlikely t becme defective in a manner that will lwer the intrinsic safety f the circuit that it may be cnsidered nt subject t fault when analysis r tests fr intrinsic safety are cnducted Shunt Dide Barrier. A fuse- r resistr-prtected dide barrier Fuse-Prtected Shunt Dide Barrier. A netwrk designed t limit current and vltage that cnsists f a series fuse, vltagelimiting shunt dides, and a current-limiting resistr r ther current-limiting cmpnents. The fuse is intended t prtect the dides frm pen-circuiting when high fault currents flw Resistr-Prtected Shunt Dide Barrier. A netwrk identical t a fuseprtected shunt dide barrier, except that the fuse is replaced by a resistr. 1.5 Cntrl Drawing A cntrl drawing shall be prvided fr all intrinsically safe apparatus r assciated apparatus that requires intercnnectin t ther circuits r apparatus. Paragraph effective September 13, An intrinsically safe system culd cnsist f apparatus investigated as a system r apparatus investigated under the entity cncept. If the intrinsically safe and assciated apparatus are investigated as a system, the cntrl drawing shall prvide infrmatin fr prper cnnectin and installatin. If the intrinsically safe r assciated apparatus is investigated under the entity cncept, the cntrl drawing shall include applicable electrical parameters t permit selectin f apparatus fr intercnnectin. Paragraph effective September 13, Evaluatin f Intrinsic Safety 2.1 Fundamental Requirements. Intrinsically safe apparatus and circuits shall cmply with the tw basic requirements specified in and The energy available in the hazardus lcatin shall nt be capable f igniting the flammable mixture specified in thrugh due t arcing r ht surfaces during nrmal peratin Fr evaluatin purpses, nrmal peratin is t include all f the fllwing: (1) Supply vltage at maximum rated value; (2) Envirnmental cnditins within the ratings given fr the intrinsically safe apparatus r assciated apparatus; (3) Tlerances f all cmpnents in the cmbinatin that represents the mst unfavrable cnditin; (4) Adjustments at the mst unfavrahle settings; (5) Opening f anyne f the field wires, shrting f any tw field wires, r grunding f anyne f the field wires f the intrinsically safe circuit being evaluated.

13 8 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL 913 JUL Y 29, * Fr test purpses, nrmal peratin is t include an additinal test factr f 1.5 applied t energy. This factr is t be achieved accrding t the prcedures utlined in 8.6 thrugh The energy available in the hazardus lcatin shall nt be capable f igniting the flammable mixture specified in thrugh due t arcing r ht surfaces under fault cnditins. Befre faults are intrduced, the apparatus is t be in nrmal peratin as specified in Fault cnditins are t include the fllwing: (1) The mst unfavrable single fault and any subsequent related defects and breakdwns, with an additinal test factr f 1.5 applied t energy; (2) The mst unfavrable cmbinatin f tw faults and any subsequent related defects and breakdwns, with n additinal test factr. Such test factrs are t be achieved accrding t the prcedures utlined in 8.6 thrugh Apparatus in which n fault r nly ne fault can ccur shall be cnsidered acceptable if it cmplies with (1) the test requirements fr nrmal peratin as described in with an additinal test factr f 1.5 applied t energy, (2) the test requirements fr any fault that can ccur with an additinal test factr f 1.5 applied t energy, and (3) the requirements f this standard All intrinsically safe and assciated apparatus and circuits shall cmply with the requirements in Sectins 3 and Evaluatin Prcedure. Circuits are t be evaluated fr intrinsic safety as specified in thrugh * The circuits are t be analyzed t determine circuit parameters under the nrmal and fault cnditins specified in 2.1 thrugh Fr intrinsically safe apparatus, each pssible ignitin pint where circuit interruptin, shrt circuit, r grund fault may ccur is t be cnsidered Cnstructin details and temperatures are t be reviewed fr cmpliance with Sectins 3 and 4. The apparatus shall cmply with the applicable test prcedures f Sectin The pssibility f arc ignitin under nrmal and fault cnditins is t be determined by either f the fllwing tw prcedures: (1) Testing the circuit accrding t the test requirements f Sectin 8; r (2) Cmparing the calculated r measured values f current, vltage, and assciated inductances and capacitances t the apprpriate figures in Sectin 5 t establish that the current and vltage levels are belw the specified values in thrugh In evaluating circuits fr intrinsic safety, ignitin surces such as the fllwing are t be cnsidered: (1) Surces f spark ignitin: (a) (b) Discharge f a capacitive circuit; Interruptin f an inductive circuit; (c) Intermittent making and breaking f a resistive circuit; (d) Ht wire fusing. (2) Surces f thermal ignitin: (a) (b) Heating f small gage wire strand; Glwing f a filament; (c) High surface temperature f cmpnents.

14 J JULY 29,1988 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL I~ \~ 2.3* Entity Evaluatin. The requirements in 2.4 thrugh are intended fr entity evaluatins. These requirements may als be used fr system evaluatins. Only assciated apparatus with linear utputs having each utput referenced t grund are presently cnsidered in Sectins 2.4 thrugh Paragraph 2.3 effective September 13, * Assciated Apparatus Evaluatin. Assciated apparatus is t be evaluated t determine that the utput is intrinsically safe. Assciated apparatus shall cmply with 2.1 thrugh Paragraph 2.4 effective September 13, The maximum utput vltage is t be the highest utput vltage frm the fllwing: (1) N faults and the mst unfavrable nrmal perating cnditin. (2) The mst unfavrable ne fault cnditin. (3) The mst unfavrable tw fault cnditin. Paragraph effective September 13, The maximum utput current is t be the highest shrt-circuit current btainable under the cnditins specified in Paragraph effective September 13, The maximum allwed capacitance is determined by test r by cmparisn and is the lwer value btained frm the fllwing: (1) The maximum capacitance that des nt cause ignitin at 1.22 times the maximum utput vltage if this vltage was determined with less than tw faults. (2) The maximum capacitance that des nt cause ignitin at the maximum utput vltage if this vltage was determined with tw faults. Paragraph effective September 13, The maximum allwed inductance is determined by test r by cmparisn and is the lwer value btained frm the fllwing: (1) The maximum inductance that des nt cause ignitin at 1.22 times the maximum utput current if this current was determined with less than tw faults. (2) The maximum inductance that des nt cause ignitin at the maximum utput current if this current was determined with tw faults. Paragraph effective September 13, * Intrinsically Safe Apparatus Inductance and Capacitance Determinatin. The intrinsically safe apparatus maximum internal capacitance r inductance is t be determined cnsidering bth nrmal and fault cnditins by ne f the fllwing methds: (1) Inspectin r analytical cmputatin; r (2) Cnfirmatin f the value by testing in accrdance with thrugh , if the apparatus manufacturer declares a maximum internal capacitance r maximum internal inductance value; r (3) Derivatin f the value f maximum internal capacitance r maximum internal inductance using the prcedure specified in thrugh Paragraph 2.5 effective September 13, * Intrinsically Safe and Assciated Apparatus Cntrl Drawing. The cntrl drawing shall specify the allwed assciated apparatus that may be cnnected t each terminal n the intrinsically safe apparatus by a set r sets f maximum vltage and maximum current. The cntrl drawing shall explain which assciated apparatus nrmally prvides pwer. Paragraph 2.6 effective September 13, A cuntable fault is impsed fr evaluatins based upn the specified maximum vltage and current ratings. A maximum f ne fault is cunted even if all assciated apparatus cmmn t the lp are cnsidered t be at their maximum vltages and currents...paragraph effective September 13, 1991

15 10 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL 913 JUL Y 29, The shrting f any tw assciated apparatus utputs r the grunding f anyne assciated apparatus utput shall nt be a cuntable fault. The shrting f each additinal assciated apparatus utput is a cuntable fault. Paragraph effective September 13, If tw assciated apparatus utputs are shrted and then the cnnectin is grunded, the grunding is a cuntable fault. Paragraph effective September 13, The shrting and grunding specified in shall nt be cnsidered if the assciated apparatus are cnnected t separate circuits and the cntrl drawing specifies cables in which shrting is nt expected t ccur. (Reference ISA RPI2.6) Paragraph effective September 13, The shrting and grunding specified in shall nt be a cuntable fault if cnnectin is cnsidered because f inadequate spacing within the intrinsically safe apparatus. Paragraph effective September 13, The shrting and grunding specified in shall nt be a cuntable fault if cnnectin can be cnsidered thrugh internal resistance within the intrinsically safe apparatus. The evaluatin will be dne using the mst unfavrable internal resistance. Paragraph effective September 13, * The cntrl drawing shall cntain ntes t explain the fllwing if applicable: (1) The plarity requirements fr assciated apparatus. (2) That assciated apparatus must nt be cnnected in parallel unless this is permitted by the assciated apparatus apprval. (3) Hw t calculate the allwed capacitance and inductance values fr field wiring used in the intrinsically safe circuit. Paragraph effective September 13, Intrinsically Safe Apparatus Evaluatin. Intrinsically safe apparatus is t be evaluated fr the pssibility f arc ignitin r ht surface ignitin using 2.1 thrugh The assciated apparatus cnnected t each terminal is determined frm the cntrl drawing. The number f faults cunted when cnnecting varius allwed cmbinatins f the assciated apparatus is described in 2.6 thrugh Paragraph 2.7 effective September 13, The determinatin f temperature rise f a cmpnent in an entity evaluatin is t be made using a pwer surce having parameters that are within the stated entity parameters at a vltage and current that is n the relevant ignitin curve and that results in maximum pwer transfer. Paragraph effective September 13, Capacitive discharge evaluatin f the intrinsically safe apparatus is dne using the highest specified maximum utput vltage frm any set f parameters adjusted by the test factr described in , cnsidering current drawn frm the surce during discharge. Paragraph effective September 13, Inductive discharge evaluatin f the intrinsically safe apparatus is t be dne using an equivalent pwer surce that has parameters within the stated entity parameters at a vltage and current that lie n the relevant ignitin curve. The surce is t be chsen that causes maximum current flw in the inductr. The current is adjusted using the test factr described in Paragraph effective September 13, Cnstructin Requirements 3.1 * Creepage and Clearance Distances. Creepage and clearance distances between uninsulated cnductive parts shall be cnsidered nt subject t fault if, taking int cnsideratin likely mvement f cmpnents, they cmply with the values given in Table 1, except as nted in thrugh Paragraph 3.1 effective September 13, 1991

16 n (j "---_/ (-) ~...r (TS-410) 1. Nminal Vltage C TABLE 1 CLEARANCES, CREEPAGE DISTANCES, AND DISTANCES THROUGH CASTING COMPOUND AND INSULATIONSa,b '-< e t"' 0< ~ "" -< Kv 4.7Kv 9.5Kv 15.6Kv 2. Creepage Distance mm (in.) Creepage Distance Under Cating mm (in.) Minimum Cmparative Tracking Index d 5. Clearance mm (in.) Distance Thrugh Casting Cmpund mm (in.) Distance Thrugh Slid Insulatin mm C 16.5 (in.) acreepage distance is t be assessed n the basis f the maximum cntinuing nminal rms vltage. Clearance is t be assessed n the basis f the maximum nrmal peak vltage. bfr circuits 1500V r greater and with high pwer capability the danger due t pwer arcing in the circuit is t be taken int accunt. cthe value f the vltage is the nminal rms vltage fr assessing creepage distance and nminal peak vltage fr assessing clearance distance, tlerance nt cnsidered. The vltages are t be the sum f the nrmal perating vltages fthe circuits being cnsidered, except ifthe nrmal perating vltage f ne circuit is less than 20 percent f the vltage f the ther circuit, the vltage is t be the greater. z -,l ~ Z en > t"" t"' 0< en -C") > "!l t>1 > '" > ~ > -,l C! en "!l ~ e en t>1 -z ::z: > N > ~ t::l e en t"" C") > -,l (5 Z en e t"' <0 -'-'> dsee Standard Test Methd fr Cmparative Tracking Index f Electrical Insulating Materials, ASTM Table 1 effective September 13, 1991

17 12 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL 913 JULY 29, Clearances, creepage distances, and distances thrugh casting cmpund and insulatins that are at least ne third f the relevant values but less than the relevant values specified in Table 1 are t be cnsidered cnnected if cnnectin results in the mst severe cnditin. Each such cnnectin is t be cunted as a fault subject t the requirements in 2.2 thrugh If the separatin between tw cnductrs is less than ne third f that specified in Table 1, the cnductrs are t be cnsidered cnnected if cnnectin results in the mst severe cnditin * If mre than tw cnductrs are invlved and the spacing between adjacent cnductrs is less than ne third the applicable value in Table 1, the sum f the individual spacings is t be added until the ttal spacing equals r exceeds ne third the applicable value. Only that number f cnductrs is t be cnsidered cnnected. A single fault is t be cunted. Within a ttal dimensin equal t the applicable table value, nly ne such grup f cnductrs is t be cnsidered cnnected * The requirements in 3.1 als apply where breakdwn between intrinsically safe circuits culd increase the energy in the circuit s that it is n lnger intrinsically safe The requirements in d nt apply where grunded metal (e.g., printed wiring r a partitin) separates an intrinsically safe circuit frm ther circuits and ther parts f the same circuit, prvided breakdwn t grund des nt adversely affect intrinsic safety and the grunded cnductr can carry the maximum current which wuld flw under fault cnditins A grunded metal partitin shall have strength and rigidity s that it is unlikely t be damaged and shall be f sufficient thickness and shall have current-carrying capacity t prevent burn-thrugh r lss f grund under fault cnditins. A partitin at least 0.25 mm (0.01 in.)l thick, attached t a rigid, grunded metal prtin f the apparatus and cmplying with the test requirements in is presumed t cmply with the requirements f this subsectin The clearance between tw terminals fr cnnectin f field wiring f different intrinsically safe circuits shall be at least 6 millimeters (1/4 in.) unless n hazard results frm cnnectin. Paragraph effective September 13, Printed Wiring Bards. Printed wiring bards shall cmp!y with the creepage distances specified in Table 1. The creepage distances under cating apply t printed wiring bards that are prtected by an adherent insulating cating that is: (1) At least tw layers thick f materials (such as slder resist and varnish, r tw cats f varnish) that have a minimum dielectric vltage rating f 200 vlts per mm (0.001 in.) f thickness; r (2) A single layer nt less than 0.7 mm (0.028 in.) thick; r (3) A single layer, and the printed wiring bard cmplies with the dielectric vltagewithstand test in The 0.25 mm (0.01 in.) minimum thickness cmplies frm the standpint f current-carrying capacity.

18 ----~---- -~-~~~ JULY 29,1988 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL * Encapsulatin. If encapsulatin is used t separate cnductrs and cmpnents f an intrinsically safe circuit frm (1) nnintrinsically safe circuits, (2) ther intrinsically safe circuits, (3) ther parts f the same circuit, r (4) grunded metal, the encapsulant shall: (1) Cmply with the Distance Thrugh Casting Cmpund values in line 6 f Table 1. (2) Be adherent t any emerging cnductrs r cmpnents, including printed wiring bard substrates, (3) Have sufficient rigidity t cmply with the test requirements specified in thrugh if the encapsulated enclsure is intended fr use withut additinal enclsure, such as a partitin device. (4) Have a temperature rating at least equal t the maximum temperature f any encapsulated cmpnent r cnductr achieved under fault cnditins after encapsulatin, and (5) Have the cmparative tracking index as required in Table 1 if any un insulated cnductrs r cmpnents exit the encapsulant. Paragraph 3.2 effective September 13, If encapsulatin is used t reduce the risk f ignitin f a ptentially flammable atmsphere by the fllwing types f cmpnents, then the minimum thickness f the encapsulant between such cmpnents and the free surface shall be ne half f the Distance Thrugh Casting Cmpund values in line 6 f Table 1, but n less than 1 mm. (1) Piezelectric devices and their cnnectin t any suppressin devices. (2) Energy strage devices and their suppressin cmpnents where breakage f the cnnectin culd ccur. Paragraph effective September 13, If the surface f the encapsulant is in cntact with an enclsure f electrical insulating material, then the thickness requirement need nt be applied. Paragraph effective September 13, If encapsulatin is used t reduce surface temperatures, the vlume f encapsulant and its minimum thickness ver the ht cmpnent r cnductr shall be at least that necessary t reduce the encapsulant surface temperature t the desired level. The rated perating temperature f the encapsulant shall be at least equal t the httest surface that it cntacts. Paragraph effective September 13, The free surface f the encapsulant shall cmply with the test requirements in If the encapsulant is nt prtected frm shck by anther enclsure r partitin it shall cmply with Paragraph effective September 13, The encapsulant is t be identified by generic name, specific type designatin, and maximum temperature rating fr reprting purpses. Paragraph effective September 13, Field Wiring Cnnectins. Terminals fr intrinsically safe circuits shall be adequately separated frm terminals fr nn intrinsically safe circuits by ne r mre f the methds described in thrugh Separatin may be accmplished by distance. The distance between adjacent terminals shall be at least 50 mm (2 in.). Care shall be exercised in the layut f terminals s as t reduce the risk f unintended cntact between different circuits if a field wire becmes disldged. I Separatin may be accmplished by lcating intrinsically safe and nnintrinsically safe terminals in separate enclsures r by use f either an insulating partitin r a grunded metal partitin between terminals. 1 Additinal precautins, such as wiring tie dwns r special wiring methds, may be necessary t prvide adequate separatin. This is especially true when terminals are arranged ne abve the ther. In such cases, spacing alne will nt usually prvide adequate separatin.

19 14 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL 913 JULY 29, Separate enclsures r partitins within cmmn enclsures shall be arranged t prevent wiring f an intrinsically safe circuit frm cntacting the wiring f a nnintrinsically safe circuit, taking int cnsideratin stwage f excess wire in each cmpartment Partitins used t separate terminals shall extend t within 1.5 mm (0.06 in.) f enclsure walls t prvide adequate separatin. Paragraph effective September 13, Metal partitins shall be grunded and shall pssess sufficient strength and rigidity that they are nt likely t be damaged during field wiring. (See ) Paragraph effective September 13, Nnmetallic insulating partitins shall pssess sufficient thickness and shall be s supprted that they cannt be readily defrmed t defeat their purpse. See 7.S If plugs and receptacles are used fr external cnnectins, the plugs and receptacles used t cnnect intrinsically safe circuits shall be nninterchangeable with ther plugs and receptacles. Exceptin: This requirement des nt apply t circuits ther than branch circuits, if interchange des nt affect intrinsic safety, r t plugs and receptacles that are identified s that interchange is unlikely. 3.4 Internal Wiring Cnductrs. Internal wiring cnductrs that are nt rigidly supprted s as t maintain the spacings specified in Table 1 shall be insulated accrding t and 3.4.2, and separated accrding t Where breakdwn may adversely affect intrinsic safety f the same r separate intrinsically safe circuits, each circuit shall be wired with insulated cnductrs having a grade f insulatin capable f withstanding an ac test vltage f 500 vlts rms r twice the nrmal wrking vltage f the intrinsically safe circuit, whichever is the greater. Exceptin: A dc test vltage may be used as described in 7.7.1(1) Nnintrinsically safe circuits in the same enclsure with intrinsically safe circuits shall be wired with insulated cnductrs having a grade f insulatin capable f withstanding an ac test vltage f 2 U vlts, with a minimum f 1500 vlts rms, where U is the sum f the rms values f the vltages f the intrinsically safe circuit and the nnintrinsically safe circuit. (See thrugh fr dielectric vltage test prcedure.) Exceptin: A dc test vltage may be used as described in 7.7.1(1) * Separatin f the intrinsically safe and nnintrinsically safe wiring shall be accmplished by enclsing either type f wiring in a grunded shield capable f carrying the fault current which wuld flw if the nnintrinsically safe circuit were t becme cnnected t the shield. Exceptin: If the wiring f a nn intrinsically safe circuit is rated as a Natinal Electrical Cde Class 2 r 3 pwer-limited circuit, a shield is nt required. But, the wiring shall be insulated and sized s that verlad, including cnsideratin f faults and vercurrent prtectin, will nt damage insulatin t the extent that the nnintrinsically safe circuit becmes cnnected t the intrinsically safe circuit. 3.5* Prtective Cmpnents. In evaluating intrinsically safe and assciated apparatus, cmpnents cmplying with the requirements f the fllwing subsectins are t be cnsidered nt subject t fault Transfrmers. Transfrmers used as prtective cmpnents fr supplying intrinsically safe circuits shall cmply with the fllwing cnstructin requirements and the test requirements in thrugh

20 -----~----~----~ ~~~~~~~--~~~~~~- JULY 29, 1988 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL l.1 * The winding supplying the intrinsically safe circuit shall be electrically separated frm all ther windings by ne f the fllwing types f cnstructin. Type 1 (a) ~ The windings are side by side n ne leg f the cre and separated by an insulating partitin nt less than 0.71 mm (0.028 in.) thick. Type l(b) - The windings are n different legs f the cre.. Type 2(a) - The windings are wund ne ver anther, with high temperature insulatin such as mica, glass fiber, layers f plyamide film, r armatic plyamide paper between the winding supplying the intrinsically safe circuit and all ther windings. Type 2(b) - The input and utput windings are wund ne ver anther with a grunded shield f cpper fil r an equivalent wire winding between the input winding and all ther windings.' (See 3.5.l.2.) Type 3 - The transfrmer is either Type l(a), Type l(b), r Type 2(b) cnstructin, except that the shield f a Type 2(b) cnstructin may be prvided with a single lead t the grund cnnectin. N primary fuse is required. (See Appendix A3.4.1 and A l.) 3.5.l.2 A Type 2(b) cnstructin shall cmply with the fllwing: (2) The shield shall be prvided with tw independently cnnected leads t the grund cnnectin, each f which is capable f withstanding withut damage the current which flws befre the fuse r circuit breaker perates. The shield grunding leads are c.nsidered t cmply withut testing if each lead is at least equal in size t the primary leads f the transfrmer but nt less than N. 24 AWe (0.21 mm~). (3) A wire-wund shield shall cnsist f at least tw layers f windings If a fuse is used t prevent transfrmer burnut, its prspective current rating shall be specified by the apparatus manufacturer The cre f a pwer supply transfrmer shall be -prvided with a grund cnnectin, unless grunding is nt practicable, as with insulated tridal cre transfrmers used in dc-t-dc cnverters. 3.5.l.5 All transfrmers shall be impregnated r encapsulated in rder t cnslidate the windings Damping Windings. Damping windings are t be cnsidered nt subject t fault if they are f reliable mechanical cnstructin, such as seamless metal tubes, windings f bare wire cntinuusly shrt circuited by sldering, r the equivalent. (1) The thickness f the cpper fil shield r the diameter f the wire shield shall be such that in the event f a shrt circuit between any winding and the shield, the shield will be able t withstand withut breakdwn the current which flws until the fuse r circuit breaker functins. A shield made f cpper fil at least 0.13 mm (0.005 in.) thick is cnsidered t cmply with this requirement withut -test Current-Limiting Resistrs. Current-limiting resistrs are t be cnsidered nt subject t shrt-circuit faults, if (1) they are a film type, a wire-wund type with prtectin t prevent unwinding f the wire in the event f breakage, r similar cnstructin in which the resistance nrmally increases during failure and (2) if they cmply with the requirements in 7.2 and 7.2.l. 1 N type test is nrmally required fr Type 2(b) cnstructin.

21 16 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL 913 JULY 29, Blcking Capacitrs. Blcking capacitrs cnnected between an intrinsically safe circuit and a nnintrinsically safe circuit are t be cnsidered nt subject t fault if tw capacitrs are cnnected in series and each capacitr is rated t withstand an ac test vltage f twice the fault vltage acrss the capacitrs plus 1000 vlts rms. They shall be high-reliability types such as hermetically sealed r ceramic capacitrs. Electrlytic r tantalum capacitrs shall nt be used fr this purpse. Failure f a single capacitr is a cuntable fault. When analyzing r testing, the capacitance value t be used is the capacitance f ne capacitr. Exceptin: If the capacitrs are cnnected in a secndary circuit, they need nt withstand the test vltage specified if they are each rated fr three times the fault vltage acrss the assembly Shunt Prtective Cmpnents. Shunt prtective cmpnents, such as dides and vltage-limiting resistrs fitted t inductive elements, are nt cnsidered subject t fault if they are redundant. Bridge cnnected dides are accepted as redundant shunt dides. There shall be n unacceptable increase in energy in the intrinsically safe circuit if ne f the cmpnents becmes defective. They shall be cnnected clse t the prtected cmpnent in such a manner that btlt cannt becme discnnected due t a single fault, unless the discnnectin f either f the shunt cmpnents results in discnnectin f the prtected cmpnent. Breakdwn f the prtected cmpnent t grund is t be cnsidered Shunt Dide Barriers. Shunt dide barriers are t be cnsidered prtective assemblies, as defined in and , if they cmply with the requirements f thrugh Barrier cmpnent failures shall nt increase the energy f the intrinsically safe circuit t an unacceptable level upn the applicatin f up t the maximum nnhazardus lcatin vltage t the assembly. This maximum vltage is assumed t be less than r equal t 250 vlts rms, unless a higher value is specified. Applicatin f this vltage is cnsidered a fault Cnstructin f the shunt dide barrier shall be such that: (1) Resistr-prtected barrier dides cmply with the requirements in and (2) The fuse f a fuse-prtected barrier perates at least 10 times faster than the pen circuit time f the dide, as specified in 7.3.3; r the fuse time-current characteristic shall nt permit the steady state r surge current ratings f the prtected dide t be exceeded, r each dide used shall be rutinely tested with a series f rectangular 50uS current pulses at 60 hertz fr 5 secnds. The current shall be that which will flw upn applicatin f 250 vlts rms r the specified maximum vltage taking int accunt all resistance in series with the dide. (3) Barrier shunt dides are duplicated s that the assembly remains effective if ne f the dides pen circuits The design f shunt dide barriers shall be such that the assembly can readily be seen t be munted crrectly At least ne terminal r cnnectin shall be prvided n each barrier r barrier assembly fr cnnecting the barrier circuit t grund. The grunding terminal r cnnectin shall be sized t accmmdate a N. 12 AWG (3.3 mm 2 ) minimum grunding cnductr. The fllwing cnstructins r their equivalents cmply: (1) A N.8 (4.8 mm diameter) wire binding screw that engages the terminal plate by at least tw full threads. The terminal plate shall be n less than 1.25 mm (0.049 in.) thick, and shall be prvided with upturned lugs r the equivalent t hld the cnductr in place. (2) A pressure-type wire cnnectr cmplying with the requirements fr such cnnectrs. (Sldering lugs, push-in cnnectrs, quickcnnects, r similar frictin fit cnnectrs are unacceptable.) (3) Blting the barrier t a grunding bus.

22 JULY 29, 1988 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL (\ "- / The barrier cmpnents shall be s munted and physically arranged as t prevent ccurrence f a fault which culd impair the effective peratin f the barrier (fr example, a shrt circuit f a resistr r fuse r pen circuit f a dide) If cmpnents are nt encapsulated, the enclsure shall be cnstructed s as t prevent access t cmpnents ther than fuses and t prtect cmpnents If it is accessible fr replacement, the fuse n a fuse-prtected shunt dide barrier shall nt be replaceable by ne f higher rating Optical Islatrs. Optical islatrs are t be cnsidered nt subject t a shrt-circuit fault between the input and utput circuits if they cmply with the requirements in thrugh Miscellaneus Cmpnents Derating f Cmpnents * During nrmal peratin cnditins as defined in , all cmpnents affecting intrinsic safety shall perate at nt mre than tw thirds f their rated current, vltage, r pwer, as apprpriate. Exceptin: Transfrmers need nt cmply with this requirement Semicnductr devices used as shunt energy-limiting cmpnents shall nt fail in the pen cnditin when subjected t the current which wuld flw if the semicnductr device shrt-circuits and the fault cnditins in and are assumed, taking int accunt vercurrent prtectin devices Plug-In Bards and Cmpnents. Plug-in bards and cmpnents shall nt be interchangeable with nnidentical bards r cmpnents in the same apparatus. Exceptin: If intrinsic safety is nt affected frm interchange r if plug-in bards and cmpnents are identified s that interchange is unlikely, nn interchangeable plug-in bards and cmpnents are nt required * Relays. Where intrinsically safe and nnintrinsically safe circuits are cnnected t the same relay, the creepage and clearance distances shall cmply with 3.1. Except as specified in , the currents and vltages switched by the cntacts in the nn intrinsically safe circuits shall n"t exceed 5 amperes and 250 vlts, dc r rms, respectively, and the prduct f the current and vltage shall nt exceed 100 vltamperes. If the vltage exceeds 250 vlts and the current and vlt-amperes d nt exceed 10 amperes and 500 vlt-amperes, respectively, the creepage and clearance distances shall be twice the applicable values in Table With respect t the requirement in 3.6.3, fr higher values f current and vltage, the circuits shall be cnnected t the same relay nly if they are separated by a grunded metal partitin r an insulating partitin. A grunded metal partitin shall nt be used where breakdwn t grund wuld affect intrinsic safety. A metal partitin at least 0.25 mm (0.01 in.) thick, attached t a grunded metal part f the device, r an insulating partitin at least 0.7 mm (0.03 in.) thick cmplies with this requirement. Hwever, a thicker insulating partitin may be required t take int accunt inizatin due t peratin f the relay. 3.7 Prtable Apparatus Enclsures Expsed external surfaces f the external enclsure and parts shall be made f a nnsparking material, such as plastic r brass, unless the part is prtected by a recess r a guard. Exceptin: Such a surface may be f a sparking material if an investigatin indicates that percussin sparks capable f igniting a flammable atmsphere are unlikely. Paragraph effective September 13, 1991

23 18 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL 913 JUL Y 29, Cells and Batteries. These requirements apply t bth prtable and statinary batteryperated apparatus in which the entire apparatus, including batteries, is intended t be used in a Divisin 1 hazardus lcatin and is nt prvided with ther means f prtectin, such as an explsinprf r dust-ignitinprf enclsure. These requirements apply t bth primary (nnrechargeable) and secndary (rechargeable) cells and batteries Battery cells shall be f a type frm which there can be n spilling f electrlyte r shall be enclsed t prevent cntact between the electrlyte and circuits which affect intrinsic safety. Cmpartments cntaining batteries which emit flammable gas shall be ventilated t prevent accumulatins f ignitible cncentratins The battery shall be cnstructed t prevent shrting between internal cells, unless the shrting des nt result in an ignitin surce Fr the purpse f evaluatin and test, the battery vltage is t be the maximum pen circuit vltage attainable under nrmal cnditins, such as that vltage measured n a fresh primary battery r a secndary battery just after full charge Fr the purpse f evaluatin and test, the battery shrt-circuit current is t be the maximum initial current under shrt-circuit cnditins * When cnducting tests which require applying a factr f 1.5 applied t energy, in accrdance with 8.6 thrugh 8.6.4, ne f the fllwing methds, r its equivalent, is t be used: (1) Additinal individual cells identical t the cells used in a multi-cell battery pack are t be added in series r parallel, as apprpriate, t yield a simulated battery with at least 1.5 times the energy capacity f the battery used in the apparatus. (2) The battery vltage r current value, as apprpriate, is t be simulated with a suitable pwer supply, and the value increased s that the energy level is increased by a factr f 1.5. (3) The intended batteries are t be used, either tw in series fr duble vltage r tw in parallel fr duble current, as apprpriate, yielding an energy factr greater than If batteries are used fr spark ignitin tests, fur trials with fresh r fully charged batteries, tw fr each plarity, are t be cnducted Battery-perated apparatus in which the battery requires energy-limiting cmpnents fr intrinsic safety shall either have the energylimiting cmpnents as an integral part f the battery assembly, r use replaceable batteries with the energy-limiting cmpnents cntained separately within the apparatus If the energy-limiting cmpnents are cntained separately within the apparatus, the apparatus shall be cnstructed as fllws: (1) The energy limiting cmpnents shall be lcated as clse t the battery terminals as practical. All live parts f the nn intrinsically safe circuit except fr cnnectin pints shall be insulated and spaced by a minimum clearance distance specified in Table 1. (2) The battery husing r attachment shall be arranged s that batteries can be installed and replaced withut shrt-circuiting the battery utput and withut applying the battery utput t the lad side f the energy-limiting cmpnents. (3) Fr hand-held prtable apparatus, such as radi receivers and transceivers, the cnstructin shall prevent the ejectin r separatin f the batteries frm the apparatus even under rugh-use cnditins, as represented by the drp test described in (4) The apparatus shall be marked t warn against replacement f the batteries in a hazardus lcatin, as described in Item (1) f paragraph effective September 13, 1991

24 JULY 29, 1988 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL (~ If an energy-limiting cmpnent is necessary and is prvided as an integral part f the battery assembly, it shall frm a cmplete replaceable unit with the battery assembly. The assembly shall be cnstructed s that the energylimiting cmpnent is unlikely t be bypassed. The assembly shall be intrinsically safe under the rugh-use cnditins, as represented by the drp test described in * Apparatus r battery packs that are prvided with external cntacts fr recharging the batteries shall be prvided with means t prevent the batteries frm delivering ignitincapable energy t the cntacts when any pair f the cntacts is accidentally shrt-circuited. This may be accmplished by ne r mre f the fllwing: (1) Prviding blcking dides r series resistrs in the charging circuit. Unless these blcking dides r resistrs are prtective cmpnents, they are t be cnsidered subject t fault. (2) Recessing at least ne cntact f a pair f cntacts s that a circular disc prbe 1.2 mm (3/64 in.) thick and 18 mm (45/64 in.) in diameter will nt tuch the cntact. In this case, shrtcircuiting fthe pair f charging cntacts is t be cunted as ne fault. (3) Separately recessing each cntact f a pair f cntacts s that a circular disc prbe as defined in (2) abve cannt tuch either cntact. In this case, shrt-circuiting f the pair f charging cntacts is t be cunted as tw faults. (4) Separately recessing each cntact f a pair f cntacts at least 0.5 mm (0.02 in.) belw the plane f the surrunding surface and separating the t.w cntacts such that tw circular disc prbes as defined in (2) abve may tuch the cntacts but cannt be arranged in any way t simultaneusly tuch and cmplete a shrt circuit between the tw cntact.s. In this case, shrtcircuiting f the pair f charging cntacts is t be cunted as ne fault If the charging cntacts are nt arranged in accrdance with 3.8.9(2), 3.8.9(3), r 3.8.9(4), shrt-circuiting f the charging cntacts is t be cnsidered a cnditin f nrmal peratin If the charging cntacts are nt separated in accrdance with the minimum distances required in 3.1, shrt-circuiting f the charging cntacts is t be cnsidered a cnditin f nrmal peratin. 4. Additinal Requirements 4.1 * Maximum Temperature Intrinsically safe apparatus in the hazardus lcatin shall nt have, under nrmal r fault cnditins, any surface expsed t flammable r cmbustible materials that perates at a temperature exceeding the temperature rating marked n the apparatus. If the apparatus is nt marked with a temperature rating, the surface temperature shall nt exceed (212 F). Exceptin: Rather than measuring temperatures, the apparatus may be subjected t the test specified in 7.6 thrugh * If wiring ther than wund cils r transfrmer wiring f intrinsically safe apparatus is cpper and its current is in accrdance with the requirements in Table 2, r the fllwing equatin, temperature tests t determine its maximum surface temperature are nt necessary. j 1M2 t [1 + O.00393(T - t)] In which: I 1= is the current, amperes, 1M is the current at which the wire melts, amperes, T is the temperature at which cpper melts, 1083 C, t is the maximum acceptable wire temperature, 0c. T

25 20 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL 913 JULY 29, 1988 TABLE 2 CURRENTS IN COPPER WIREa {TC-7201 Minimum Cnductr Size b Maximum Cnductr Current, Area Amperes, fr Apparatus Diameter (Wire Rated T4, T5, r T6 mm 2 In. 2 Size, mm (Mils) x10-3 x10-5 AWG) T4 T5 T afr cnductrs n printed wiring bards, the current is 250 percent f that listed in the table. Fr flexible flat cnductrs, such as ribbn cable, the tabulated values apply. bfr stranded cnductrs, the crss sectinal area is the sum f the crss sectinal areas f each strand f the cnductr * Temperatures higher than that f the marked perating temperature per 4.2.1(3) shall be permitted fr small cmpnents, fr example, transistrs r resistrs, if it is shwn by the test prcedures described in 7.6 thrugh and thrugh that the temperature is insufficient t cause ignitin r charring. 4.2 Marking The minimum marking shall include the fllwing: (1) Identificatin f the apparatus, including manufacturer's name r trademark and type r mdel designatin; (2) Hazardus lcatin class and grup; (3) Maximum surface temperature r temperature identificatin number based n peratin at 40 C (104 F) ambient temper.ature (See Table 500-2(b) f NFPA , Natinal Electrical Cde); Exceptin: Apparatus having a maximum surface temperature n greater than 100 C (212 F) need nt have a marked maximum surface temperature r temperature identificatin number. (4) Fr shunt dide and similar prtective barrier assemblies which are intended fr field r panel installatin, the maximum nnhazardus lcatin vltage. (See ) (5) Cntrl drawing number, except fr apparatus nt intended t be cnnected t ther apparatus r circuits. Item (5) f paragraph effective September 13, 1991

26 , I I -1 JULY 29, 1988 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL I,~ / I f 4.2.2* In additin t the minimum marking specified in 4.2.1, the marking shall include the fllwing. As much infrmatin as pssible shall be prvided n the apparatus label. It is recgnized, hwever, that it is impractical t mark small pieces f apparatus with all the required infrmatin. If this infrmatin is nt n the apparatus, it shall be included In the accmpanying literature. (1) Fr intrinsically safe apparatus: (a) An indicatin that the apparatus is intrinsically safe; (b) If investigated using the entity evaluatin, the maximum input vltage, maximum input current, maximum internal capacitance and maximum internal inductance; (c) If repair is pssible, a warning label wrded "Warning - Substitutin f Cmpnents May Impair Intrinsic Safety;" and (d) A reference t accmpanying literature, that prvides special installatin, maintenance, r perating instructins. If this infrmatin is nt n the apparatus, it shall be included r referenced n the cntrl drawing. (2) Fr assciated apparatus: (a) If investigated using the entity evaluatin, the maximum utput vltage, maximum utput current, maximum allwed capacitance, and maximum allwed inductance; (b) If repair is pssible, a warning wrded "Warning - Substitutin f Cmpnents May Impair Intrinsic Safety;" (c) Any ther necessary infrmatin, in particular, an indicatin f any ther type f prtectin and its characteristics; and (d) A reference t accmpanying literature, that prvides special installatin, maintenance, r perating instructins. If this infrmatin is nt n the apparatus, it shall be included r referenced n the cntrl drawing. Subitem (b) in item (I) and Subitem (a) in item (2) f paragraph effective September 13, Terminals, terminal bxes, and plugs and receptacles fr cnnectin t intrinsically safe circuits shall be clearly identified and clearly distinguishable. If clr nly is used t cmply with this requirement, the clr shall be light blue Battery-pwered apparatus shall be marked with a cautin statement t (1) indicate the type, size, and vltage f batteries t be used r (2) indicate the specific battery by manufacturer and mdel number r eqllivalent t be used. If the batteries used are nt intrinsically safe, the apparatus shall be marked with the fllwing warning r equivalent: "Warning - t reduce the risk f ignitin f a flammable atmsphere, batteries must nly be changed in an area knwn t be nnflammable." 5. Cmparisn Prcedure fr Determining Spark Ignitin Capability 5.1 * General Apparatus may be cnsidered intrinsically safe withut spark ignitin testing if the circuits can be readily assessed. T be cnsidered intrinsically safe by the cmparisn prcedure, circuits and apparatus shall cmply with thrugh n. ~' 1 All figures, except Figures 5 and 6, are reprinted frm Certificatin Standard SFA 3012,1972 editin, with permissin f the. Department f Trade and Industry, British Apprvals Service fr Electrical Equipment in Flammable Atmspheres. Figures 5 and 6 are frm "Sme Aspects f the Design f Intrinsically Safe Circuits," Research Reprt 256, 1968, by D. W. Widgentn, Safety in Mines Research Establishment, Sheffield, England.

27 22 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL 913 JULY 29, Circuits that cannt be readily assessed in terms f elementary circuits represented by the ignitin curves shwn in the figures in this chapter, circuits in which the current r vltage values exceed thse indicated n the curves, and circuits that d nt cmply with thrugh are t be evaluated by the test prcedures in Sectin Resistance Circults. Figures 1 and 2 apply t resistance circuits nly and shw cmbinatins f vltage and current that will ignite gas and vaprs in air fr Grups A, B, C, D and fr methane. These figures apply nly t circuits having an utput vltage-current plt that is a straight line drawn between pen circuit vltage and shrt-circuit current Resistance-Inductance Circuits. Figures 3 and 4 apply t resistance-inductance circuits and shw the cmbinatins f inductance and current at 24 vlts which will ignite gases r vaprs in air fr Grups A, B, C, D and fr methane. Figures 5 and 6 apply t resistanceinductance circuits and shw cmbinatins f inductance and current at specific vltages which will ignite gases r vaprs in Grup Band methane, respectively Resistance-Capacitance Circuits. Figures 7 and 8 apply t resistancecapacitance circuits and shw cmbinatins f capacitance, vltage, and resistance which will ignite gases r vaprs in air fr Grups A and B and fr methane. These curves represent capacitr discharge nly. They d nt include the additinal current which may be available frm the assciated apparatus. 5.2 Maximum Vltage and Current Levels The circuit cnditins are t include all nrmal and fault cnditins described in this standard, excluding the 1.5 test factr Maximum vltage and current levels (dc r peak ac) in circuits determined t be intrinsically safe by the cmparisn prcedure shall nt exceed the values in and , fr given circuit cnstants Fr nrmal r single-fault peratin, the current shall nt exceed 80 percent f the value determined frm Figures 1 thrugh 6. The vltage shall nt exceed 80 percent f the value determined frm Figures 7 and Fr tw-fault cnditin, the current shall nt exceed 90 percent f the value determined frm Figures 1 thrugh 6. The vltage shall nt exceed 90 percent f the value determined frm Figures 7 and 8.

28 -~ JULY 29, 1988 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL f"'- ( \ -. ) ' _/ 2A II FIGURE 1 RESISTANCE CIRCUITS (L < 5 fh) Igniting currents applicable t all circuits cntaining aluminum, cadmium, magnesium, r zinc. ---, I 200m I-!,-++ j-t.:- I+H+Rl-!:f- GROUP A AND B "rt,;~ rf 20mA, CI lorna S V I I

29 24 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL 913 JULY 29,1988 5A~. flit".,--... t- IH+!" :t.:=i+ :: -;t ~ r -f- '-r. _~~' roo H+1t I :.! METHANE lj 1;1:1111 ' IIIIIIII!IIII I I I HIHIII!I!;: : +' IIIH I I tth i +I+hr ET G ::- [j..l.~~~ ~:;-. -;::; I:.:.:::-r.;:...,q,j". c=.. _.1::...::=..:;.;.:::..;.:: ~~~I-:-:s.-::;:-:= r-; -:;"'I:.;:ti-t- -= I 200mA -r-t- -H- FIGURE 2 RESISTANCE CIRCUITS (L -< 5)-lH) Igniting currents applicable t circuits where aluminum, cadmium, magnesium, and zinc can be excluded. _. "!i:: I I I I lorna 10 II : I IJ I I.1 II III II V 100 I I i I

30 JUL Y 29, 1988 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL t\ I, \ /./ FIGURE 3 INDUCTANCE CIRCUITS IGNITING CURRENTS AT 24 VOLTS APPLICABLE ONLY TO CIRCUITS WHERE ALUMINUM, CADMIUM, MAGNESIUM, OR ZINC MAY BE PRESENT. L lmh lorna S 2846 I

31 26 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL 913 JULY 29,1988 FIGURE 4 INDUCTANCE CIRCUITS IGNITING CURRENTS AT 24 VOLTS APPLICABLE ONLY TO CIRCUITS WHERE ALJMINUM, CADMIUM, MAGNESIUM AND ZINC CAN BE EXCLUDED. S2847 I

32 *DECEMBER 12, 1988 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL C) FIGURE 5 INDUCTANCE CIRCUITS IHi i 1 iii iii i,,;;: : ~ :::::!:: t:... il!flflll ~iii.:,:n':: :': '.. : :L:~:::::. '\ <: c:: 0 -c:: a -0 IGNITING CURRENTS FOR VARIOUS VOLTAGES IN GROUP B. APPLICABLE TO ALL CIRCUITS CONTAINING ALUMINUM, CADMIUM, MAGNESIUM, OR ZINC. : 0-0 u OIl Q,) ::> '" > E ::> E c::.- 2 -'-'.,-+-:-+,-":'+.. '+- +'4-+-'1-4 ~ -,...:... ~: -.' '\.'.. I'".... f-- lmtl...\....l.: :.. :...,... ;.;.. -.~.. : t I. '. :"'-, r -,.,, '1' '! f.:. i. 1 1,. :, ~ I::: 1""1:;;' :::,:::}:.. I:;:::~f~... :::::i::::~~:~~::.., I::: ::::1:::: '""fiji '-, '.' i I Open circuit vltage Vac v *Replaces page 27 dated July 29, 1988 COPYRIGHT 1976, 1988 UNDERWRITERS LABORATORIES INC.

33 28 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL 913 *DECEMBER 12, 1988 FIGURE 6 INDUCTANCE CIRCUITS «c: 0 IGNITING CURRENTS FOR VARIOUS VOLTAGES IN METHANE AND APPLICABLE TO ALL CIRCUITS CONTAINING ALUMINUM, CADMIUM, MAGNESIUM, OR ZINC. c: ClIO <:) u '" 0 c» ~ "' > E ~ E c: 0'1 ~ 2' S2848 Open circuit vltage Ve v *Replaces page 28 dated July 29, 1988 COPYRIGHT 1976, 1988 UNDERWRITERS LABORATORIES INC.

34 JUL Y 29, 1988 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL ,~ i' \ l '- FIGURE 7 CAPACITANCE CIRCUITS IGNITION VOLTAGES IN METHANE. THE CURVES CORRESPOND TO VALUES OF CURRENT LIMITING RESISTANCE AS INDICATED. THE CURVE MARKED Sn IS APPLICABLE ONLY WHERE ALUMINUM, CADMIUM, MAGNESIUM, AND ZINC CAN BE EXCLUDED. 0'03 FII v

35 30 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL 913 JULY 29, ! FIGURE 8 CAPACITANCE CIRCUITS IGNITION VOLTAGES IN GROUPS A AND B. THE CURVE~ CORRESPOND TO VALUES OF CURRENT-LIMITING RESISTANCE AS INDICATED. THE CURVE MARKED Sn IS APPLICABLE ONLY WHERE ALUMINUM, CADMIUM, MAGNESIUM, AND ZINC CAN BE EXCLUDED. c v

36 JULY 29, 1988 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL Apparatus fr Class II and Class III Lcatins 6.1 Applicability f Other Requirements in this Standard Intrinsically safe and assciated apparatus intended fr use in Class II and Class III, Divisin 1 hazardus lcatins shall cmply with all requirements in Sectins 1 thrugh 5 in this standard Except as specified in 6.2.4, intrinsically safe apparatus shall be enclsed in a dust-tight enclsure that cmplies with the requirements in thrugh The apparatus shall als cmply with the spark ignitin requirements fr Class I lcatins as fllws: Hazardus Lcatin Class II, Grups E and G; Class III Applicable Limits Class I, Grup D r Methane 6.2 Specific Requirements fr Intrinsic Safety Apparatus and assciated wiring that cmplies with the requirements in Sectins 1 thrugh 5 in this standard, as applicable, shall als be cnsidered t cmply with the requirements fr Class II and Class III lcatins if they cmply with and either r The temperature f expsed surfaces f apparatus shall nt exceed the fllwing values when tested accrding t the prcedures described in thrugh Fr this requirement, "expsed" means expsed t the flammable r cmbustible material r atmspheres. Parts within a dust-tight enclsure are nt cnsidered expsed; the utside surfaces f the enclsure are expsed. Class II, Grup E C (392 F); Class II, Grup G and Class III C (329 F). Class II, Carbnaceus Dusts (Grup E r G) C (392 F) Exceptin: Temperature excursins f small cmpnents under fault cnditins may exceed these limits if it is shwn by test that such higher temperatures will nt result in ignitin r charring. See thrugh * Intrinsically safe apparatus nt enclsed in a dust-tight enclsure cmplying with the requirements in thrugh shall cmply with the spark ignitin requirements specified in In this case, it is t be assumed that all spacings d nt cmply with the creepage and clearance distance requirements specified in 3.1 and that all cnnectins between live r grunded parts and cnductrs are in the mst unfavrable cnditin. The number f such cnnectins is unlimited. 6.3* Dust-Tight Enclsures Fr the purpses f this standard, an enclsure is cnsidered suitable if it (1) cmplies with the requirements in r , r (2) cmplies with the requirements in 7.10, r (3) is dust-ignitinprf. In additin, a prtable apparatus shall be dust-tight after the drp test described in An enclsure is cnsidered suitable if (1) it cnfrms t applicable requirements fr enclsures fr rdinary lcatins, (2) it has n penings, and (3) all jints are either threaded with a three full-thread minimum engagement r sealed by cntinuus welding, brazing, sldering r fusin f glass Parts f apparatus within an enclsure suitable fr rdinary lcatins that are encapsulated t a depth f at least 1 mm (0.04 in.) are t be cnsidered dust-tight.

37 32 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL 913 JULY 29, Test Prcedures 7.1 Prtective Transfrmers Tests Rutine Tests Transfrmers fr direct cnnectin t an external supply shall be capable f withstanding the fllwing test vltages. (See thrugh ) Where Applied Between input and utput windings. Between au the utput windings and the cre r shiefd. Between each winding supplying an intrinsically safe circuit and every ther utput winding. rms Test Vltages (Un = highest rated vltage f any winding) 4U n r 2500 V, whichever is the greater. 2U n r 1000 V, whichever is the greater. 2U n Vr 1500 V, whichever is the greater Fr transfrmers nt intended fr direct cnnectin t an external supply system, the test vltage between input and utput windings shall be reduced t 2U n vlts rms r 1500 vlts, whichever is greater Type Tests. The transfrmer is t be subjected t the apprpriate type tests described belw, fllwed by a vltage test f twice the highest rated vltage f any winding plus 1000 vlts rms r 1500 vlts, whichever is greater, between any windings used t supply the intrinsically safe system and all ther windings. (See thrugh ) Type l(a) and Type l(b) Transfrmers. (1) The transfrmer's secndary winding r windings are t be shrt-circuited r laded in such a way s that the highest primary winding current des nt exceed 1.5 times the fuse r circuit breaker rating. If 1.5 times the rating f the vercurrent device is nt reached, then the transfrmer's secndary winding r windings are t be shrt-circuited r laded t draw maximum primary current with the primary winding subjected t its wrst case rated input vltage. The prtective fuse r circuit breaker in the primary circuit is t be bypassed fr this test. (2) The temperature rise f the transfrmer shall at n pint exceed the permissible value fr the class f insulatin used during cntinuus peratin fr at least 6 hurs r up t the mment when the imbedded thermal trip device, if any, functins. (3) If an utput winding has a currentlimiting resistr arranged s that a shrt circuit is unlik~ly t ccur directly acrss the winding, the test IS t be cnducted with the resistr in the circuit Type 2(a) Transfrmer. (1) The test is t be cnducted by lading the secnda~y winding(s) s that maximum primary current IS dra~n while.the primary winding is cnnec~ed t ItS rated mput vltage. The primary wmding current is nt t be limited. (2) The transfrmer is t be tested fr 6 hurs r until failure, whichever ccurs first. Ei ~her the primary w:indi,ng r the secndary windmg(s) may shrt-circuit t the cre during this test, if shrting f the secndary winding(s) t the cre des nt result in unacceptable energies in the hazardus lcatin. (3) The transfrmer shall nt burst int flames during the test. An imbedded ne-time thermal fuse may be used t reduce the likelihd that a transfrmer will burst int flames Type 3 Transfrmer. The transfrmer is t be perated with any r all secnda~y windings shrt-circuited, depending n which represents the mre severe cnditin f he~ting, and with rated vltage applied t the primary winding until thermal equilibrium is established. All thermal fuses r ther current- r temperature-sensitive prtective devices are t be sh~rtcircuited during this test. The temperature rise f the transfrmer shall at n pint exceed the permissible value fr the class f insulatin emplyed.

38 JULY 29,1988 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL ,~, ') 7.2 Current-Limiting Resistr. As a result f being subjected t 1.5 times the maximum fault vltage appearing acrss a current-limiting resistr, it shall (1) pen circuit, (2) increase in resistance, r (3) decrease in resistance n mre than 33 percent during the test and n mre than 10 percent after the test. Exceptin N.1: If the resistr is prtected by a fuse, it is t be tested at (1) a current f 1.7 times the current rating f the fuse withut the fuse in the circuit, and (2) a vltage f 1.5 times the maximum fault vltage with the fuse cnnected in series with the resistr. Exceptin N.2: This requirement des nt apply t resistrs that are perated at n mre than tw thirds f their pwer rating during bth nrmal and fault cnditins The adequacy f a fuse in preventing an pen circuit f a Zener dide is t be determined by ne f the fllwing methds: (1) The barrier assembly fuse is t be substituted by a similar type fuse having a current rating 10 times greater. The substituted fuse shall perate prir t dide failure, upn applicatin f up t the maximum nnhazardus lcatin vltage. (2) A current flw f 200 percent f the fuse current rating is t be applied t the barrier assembly, withut the fuse, fr 10 times lnger than the perating time f the fuse. There shall be n dide failure that will render the barrier ineffective. The perating time f the fuse is t be determined by test r taken frm the manufacturer's perating time versus current curve at 200 percent f its current rating The test vltage is t be raised frm ze; t the required value in apprximately ne mmute. The test is t cntinue until the resistr temperature becmes stable r until it is evident that n further deteriratin will ccur. 7.3 Shunt Dide Prtective Barrier Tests Resistr-prtected barrier dides shall either (1) withstand withut damage r (2) fail withut rendering the barrier ineffective, as a result f being subjected t 1.5 times the maximum current that will flw cntinuusly thrugh the resistr when up t the maximum nnhazardus lcatin vltage is applied t the barrier The test is t cntinue until the temperatures becme stable r until it is evident that n further deteriratin will ccur Zener dide maximum vltage is t be the summatin f the nminal Zener vltage, plus maximum tlerance f the Zener Optical Islatr Tests An ptical islatr in a secndary circuit shall withstand the test vltage specified in An ptical islatr in a primary circuit shall be capable f withstanding a 4000 vlt rms test vltage initially and 1000 vlts plus twice the highest rated vltage f the circuit r 1500 vlts, whichever is greater, after the limited shrt circuit test prcedure described in The test vltage is t be applied between the intrinsically safe circuit and the nnintrinsically safe circuit. Three samples are t be used fr each test. See 7.7.1(1) thrugh 7.7.1(3) and With regard t 7.4.2, the pen circuit vltage f the test circuit is t be the nminal maximum rated nnhazardus lcatin vltage, fr example, 120 r 240 vlts. The available instantaneus shrt-circuit current capacity f the test circuit is t be at least 200 amperes. The test circuit is t be cnnected t the ptical islatr s that the test current flws thrugh the nn intrinsically safe circuit terminals f the ptical islatr. Prtective cmpnents r fuses are t be permitted in the circuit fr the test. I I'

39 34 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL 913 JUL Y 29, Temperature Tests All temperature data are t be referred t a base ambient temperature f 40 C (104 F). Tests t be based n an ambient temperature f 40 C (104 F) may be cnducted at any ambient temperature within the range f C ( F). The difference between the ambient temperature at which the test was cnducted and 40 C (104 F) is t then be added t the temperature measured. Exceptin: Temperatures ther than thse fr determining temperature marking n cmpnents f assciated apparatus, such as prtective transfrmers, shall be referred t a base ambient temperature f 25 C (77 F) r the maximum rated ambient temperature f the apparatus, whichever is higher Temperatures are t be measured either by thermcuples cnsistin& f wires nt larger than N. 24 AWe (0.21 mm-) r by equivalent means The thermcuples and related instruments are t be accurate and calibrated in accrdance with gd labratry practice. The thermcuple wire is t cnfrm with the requirements fr special thermcuples as listed in the table f limits f errr f thermcuples in ANSI C96.1, Temperature Measurement Thermcuples. ' A thermcuple junctin and adjacent thermcuple lead wires are t be securely held in gd thermal cntact with the surface f the material being measured. In mst cases, gd thermal cntact will result frm securely taping r cementing the thermcuple in place; but if a metal surface is invlved, brazing r sldering the thermcuple t the metal may be necessary The frmula fr btaining the temperature rise f a prtective transfrmer winding by the resistance methd is as fllws. The windings are t be at rm ambient temperature at the start f the test: Exceptin: Cil temperatures may be determined by the methd described in l\t R A thermcuple is t be used fr determining the temperature f a cil r winding f a prtective transfrmer if the thermcuple can be munted withut remval f encapsulating cmpund r similar material: (1) n the integrally applied insulatin f a cil withut a wrap, r (2) n the uter surface f a wrap that is nt mre than 0.8 mm (1/32 in.) thick and cnsists f cttn, paper, rayn, r similar material (but nt thermal insulatin). The change-f-resistance methd is t be used if the thermcuple measurement cannt be cnducted in accrdance with the freging cnsideratins Tests are t be cntinued until cnstant temperatures are attained, r until the maximum temperature has been attained, whichever ccurs first A temperature is t be cnsidered cnstant when three successive readings, taken at intervals f 10 percent f the previusly elapsed duratin f the test (but n less than 5-minute intervals) indicate n change. where At the temperature rise, C R = the resistance f the cil at the end f the test, hms r = the resistance f the cil at the beginning f the test, hms t, = the rm temperature, C, at the beginning f the test t2 = the rm temperature, C, at the end f the test k = fr cpper, fr aluminum electrical cnductr (EC grade). 1 Available frm the American Natinal Standards Institute, 1430 Bradway, New Yrk, NY

40 r JULY 29, 1988 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL Small Cmpnent Ignitin Test. Small cmpnents and small gage wire that either exceed the marked perating temperature f apparatus intended fr use in Class I lcatins r exceed 100 C (212 F) fr apparatus nt required t be marked with an perating temperature shall nt cause ignitin f the flammable mixture used when tested as described in thrugh The flammable mixture used is t be diethyl ether fr apparatus marked T The test is t be cnducted under the fault cnditin that prduces the maximum surface temperatures n the cmpnent The cmpnent may be munted in the apparatus as intended r the cmpnent may be tested in the mixture t determine the temperature at which ignitin ccurs. The temperature f the cmpnent in the apparatus being assessed may then be determined. The flammable mixture is t be intrduced int the apparatus enclsure s as t assure cntact between the mixture and the surface f the cmpnent being tested. If this is impractical, such a cnditin is t be simulated s as t assure representative test results, taking int cnsideratin ther parts f the apparatus in the vicini ty f the cmpnent being tested that culd affect the temperature f the mixture and the flw f the mixture arund the cmpnent due t ventilatin and thermal effects * The test is tb als be cnducted under the nrmal r fault cnditin that prduces the maximum release f thermal energy whenever such cnditin prduces maximum surface temperature that bth exceeds the marked perating temperature and is lwer than that prduced in 7.6.2, that is, the temperature rise f mre than ne cmpnent exceeds the marked perating temperature The tests are t cntinue until thermal equilibrium f the cmpnent under test and surrunding parts is attained r until the temperature f the cmpnent under test drps t a value equal t the marked perating temperature as a result f failure f the cmpnent, whichever ccurs first. If failure f the cmpnent terminates the test, five additinal samples are t be tested; nne f these shall ignite the mixture. Hn ignitin ccurs, the mixture is t be ignited by ther means t verify presence f a flammable mixture. 7.7 Dielectric Tests The fllwing test methd IS t be used: (1) The test is t be cnducted using alternating vltage f substantially sinusidal wave frm at a frequency between 48 Hz and 62 Hz. Alternatively, the test is t be cnducted using a dc vltage having n mre than 3 percent peakt-peak ripple and at a level f times the specified ac vltage. (2) The supply is t have sufficient vltampere capacity t maintain the test vltage, taking int accunt any leakage current that may ccur. (3) The vltage is t be increased steadily t the specified value in a perid nt less than 10 secnds and then maintained fr at least 60 secnds. (4) Fr rutine tests, the test vltage may be increased 20 percent and applied fr nt less than 1 secnd There shall be n breakdwn f the apparatus between the test pints Representative circuits n printed wiring bards cated with a single layer f adherent insulating cating that is less than 0.7 mm thick (0.028 inch) are t be subjected t a dielectric withstand test. See and fr the test methd. The test vltage is t be based n the perating vltages f the circuits being cnsidered in accrdance with nte c t Table 1 and the values specified in Table 3.,' i

41 36 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL 913 JULY 29,1988 (TV-110) TABLE 3 COATED BOARD WITHSTAND TEST VALUES Peak Circuit Operating Vltage, Vlts rms ~ Mechanical Tests. Withstand Test, kv, rms Partitins shall withstand a frce f 30 newtns (6. 75 lbs-frce), applied by a 6 mm (0.25 in.) diameter rigid test rd. The frce is t be applied at the apprximate center f the partitin fr 10 secnds. There shall be n defrmatin f the partitin that wuld defeat its purpse. 7.9 Drp Test Prtable apparatus is t be subjected t the fllwing drp test. Intrinsic safety shall nt be affected. (1) A sample f the apparatus is t be drpped six times, nt mre than nce n any ne surface, edge, r crner, frm a height f 1.00 meter (39.4 in.) nt a smth hrizntal cncrete flr. (2) If apprpriate, a nnrestrictive guide is t be used t btain free-fall drpping n the surface t be tested Dust-Tight Enclsure Test. A dusttight enclsure shall cmply with the requirements fr the Dust Test as specified in NEMA Publicatin N , Enclsures fr Electrical Equipment (1000 Vlts Maximum). I 7.11 Dust Blanketing Temperature Test The apparatus is t be munted in its nrmal psitin and cvered with the dust mixture specified in until n mre will stay n the enclsure r cmpnent (see 6.2.2) r t a depth f 12 mm (0.48 in.), whichever is less The dust used is t be ne f the fllwing: (1) Wheat r crn dust (r a mixture f bth); (2) Type 1, General Purpse Prtland Cement; r (3) Aluminum xide. The dust is t be fine enugh t pass thrugh a 1 OO-mesh screen. Alternatively, magnesium dust may be used fr Grup E The apparatus is t be perated under fault cnditins apprpriate t the apparatus until all temperatures becme cnstant. See thrugh The temperature f surfaces expsed t dust shall nt exceed the values in Temperatures are t be based n temperature rise abve ambient in the test chamber and 40 C (104 F). Exceptin: Higher temperatures are permitted fr tests using grain dust if the dust des nt char r ignite Lamp Breakage Test The heated filament f a tungstenfilament lamp shall nt ignite a surrunding explsive mixture when the glass envelpe is brken. Paragraph effective September I Available frm Natinal Electrical Manufacturers Assciatin., 2101 "L" Street, N.W., Washingtn, DC

42 I JUL Y 29, 1988 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL The lamp is t be munted in a test chamber cnnected t a nrmal (n fault) pwer supply. The chamber is t be filled with an explsive mixture specified in thrugh in accrdance with applicable fault prcedures in The lamp envelpe is t be brken quickly and cmpletely (nt just cracked) while the lamp is immersed in the mixture t expse the glwing filament t the explsive mixture. The filament is nt t be brken by the breakage f the envelpe. Six samples are t be tested. Paragraph effective September 13, Encapsulatin Tests Frce Test. An encapsulant shall withstand a frce f 30 newtns (6.74 lb) applied using the flat end f a 6 mm (0.24 in.) diameter slid test rd. The frce is t be applied fr at least 10 secnds in a directin perpendicular t the surface f the encapsulant. The encapsulant may transiently mve during the test, but shall nt permanently defrm r be damaged in a way that impairs the prtectin prvided. Paragraph effective September 13, Impact Test. Encapsulant that is nt prtected frm shck by anther enclsure r partitin is als t be subjected t an impact test f 2 jules (1.48 ft lb ). The encapsulant may transiently mve during the test, but shall nt permanently defrm r be damaged in a way that impairs the prtectin prvided. Paragraph effective September 13, The impact is t be applied by a 0.25 kg (0.55 lb) test mass having a hardened steel impact head 25 mm (0.98 in.) diameter falling thrugh a vertical <;listance f 0.8 meters (2.62 ft). Paragraph effective September 13, The apparatus is t be munted n a steel base having a mass f at least 20 kg (44 lb) r is t be munted n a steel base rigidly fixed t r inserted in the flr. The directin f the impact is t be nrmal t flat surfaces being tested, r nrmal t a tangent t the surface if the surface is nt flat. Paragraph effective September 13, Slvent Vapr Expsure. An encapsulant shall be cnstructed f materials suitable fr the intended envirnment including cnsideratin fr atmspheric cntaminants and fr crrsive cmpunds. There shall be n deteriratin that impairs the prtectin prvided. Paragraph effective September 13, Internal Capacitance r Inductance Test These requirements apply t apparatus t be investigated in accrdance with 2.5(2) r 2.5(3). The effective capacitance r inductance f the intrinsically safe apparatus is t be determined by the change in capacitance r inductance required t just prevent ignitin using the spark ignitin test apparatus and methds described in Sectin A variable capacitr is t be tested in accrdance with thrugh The capacitr is t be adjusted until ignitin just des nt ccur. The test surce vltage is t be 1.22 times the maximum input vltage. The value f the capacitr (C, in ) is t be recrded The intrinsically safe. apparatus is then t be cnnected in parallel with the variable capacitr using whatever terminals n the intrinsically safe apparatus are relevant. In sme cases, the test may have t be repeated using a different set f terminals The variable capacitr and intrinsically safe apparatus cmbinatin is t be tested in accrdance with thrugh The variable capacitr is again t be adjusted until ignitin just des nt ccur. The value f the variable capacitr (C 2 in ) is again recrded The maximum internal intrinsically safe apparatus capacitance, C j, fr thse terminals is the difference between the tw recrded capacitance values as fllws: C j = C,-C 2 A negative number is assumed t be zer.

43 38 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL 913 JUL Y 29, The prcedure described in thrugh is als used t determine the effective inductance. In this case, the terminals f the intrinsically safe apparatus are placed in series with a 95 millihenry inductr. The pwer surce is t be 24 vlts dc pen circuit. Hwever, the surce vltage and inductance may be altered t imprve sensitivity fr circuits that perate n currents higher than 100 milliamperes. The current is t be varied with nninductive series resistance until ignitin just des nt ccur. The difference in currents can then be related t the effective inductance utilizing the apprpriate curve in Figure Spark Ignitin Test 8.1 General Requirements All circuits requiring spark ignitin testing are t be tested t ensure that they are incapable f causing ignitin under the cnditins specified in Sectin 2, taking int accunt the apprpriate gas grup r grups specified in thrugh See als Nrmal and fault cnditins are t be simulated during the tests. Factrs shall be added as described in 8.6 thrugh Specialized test apparatus as described in and is t be used rather than the cntacts used in the field. The test apparatus cntacts are t be perated in a chamber filled with the mst readily ignited mixture f the test gas with air as determined by verificatin in accrdance with and * Test Apparatus The spark test apparatus is t cnsist f an explsin chamber f abut 250 cubic centimeters (15.25 cu. in.) vlume, in which circuitmaking-and-breaking sparks can be prduced in the presence f the prescribed test gas Cmpnents f the cntact arrangement are a cadmium disc with 2 slts and 4 tungsten wires f 0.2 mm (0.008 in.) diameter, which slide ver the disc. The free length f the tungsten wires is t be 11 mm (0.44 in.). The driving spindle, t which the tungsten wires are attached, is t make 80 revlutins a minute. The spindle n which the cadmium disc is munted is t revlve in the ppsite directin. The rati f the speeds f the driving spindle La the disc spindle is t be 50 t 12. The spindles are t be insulated frm ne anther and frm the husing. See Figure 9. The explsin chamber is t withstand pressures up t 1470 kpa (213.2 Ibf/in. 2 ) r be prvided with suitable pressure relief. When cadmium, zinc, r magnesium will nt be present, the cadmium disc may be replaced by a tin disc. 8.3 Gas Mixtures Fr Grup D, the test mixture is t be 5.25 ± 0.25 percent prpane in air Fr Grup C, the test mixture is t be 7.8 ± 0.5 percent ethylene in air Fr Grups A and B, the test mixture is t be 21 ± 2 percent hydrgen in air Fr Class II, Grups E, F, and G, the test mixture is t be percent prpane in air r 8.3 ± 0.3 percent methane in air Intrinsically safe apparatus that is intended fr use in a particular gas r vapr and that will be marked accrdingly is t be tested in the mst easily ignited cncentratin f that gas r vapr in air. 1 The purity f cmmercially available gases and vaprs is nrmally adequate fr these tests, but thse f purity less than 95 percent shuld nt be used. The effect f nrmal variatins in labratry temperature and pressure and f the humidity f the air in the gas mixture is als likely t be small. Any significant effects f these variables will becme apparent during the rutine verificatin f the spark test apparatus.

44 JULY 29, 1988 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL FIGURE 9 TEST APPARATUS FOR EVALUATING INTRINSICALLY SAFE CIRCUITS (Measurements are in millimeters) TUNGSTEN WIRES ~ I l"- ~ I I I ru I r.,... f'.. '" I " ~ 2~ J _Il0l

45 40 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL 913 JULY 29, Verificatin f Spark Test Apparatus The sensitivity f the spark test apparatus is t be checked befre and after each test series carried ut in accrdance with thrugh Fr this purpse, the test apparatus is t be perated in a 24 vlt dc circuit cntaining a H air-cre cil. The currents in these circuits are t be set at the values given in Tables 4 and 5 fr the apprpriate grup, and the spark test apparatus is t cmply with bth the "must ignite" and "must nt ignite" specificatins in the tables. TABLE 4 CURENT IN CALIBRATION CIRCUIT FOR CADMIUM DISC (TP-70B) Grup A&B C D a Inductive Circuit Currents, Milliamperes Must Nt Ignite afr tests using methane, see B.3.4. Must Ignite TABLE 5 CURENT IN CALIBRATION CIRCUIT FOR TIN DISC (TP-709) Inductive Circuit Currents, Milliamperes The spark test apparatus is t be run fr 400 revlutins (5 minutes) f the tungsten wire-hlder with the hlder at psitive plarity and is t be cnsidered t be satisfactry nly if at least ne ignitin f the test gas ccurs. 8.5 Test Prcedure After verificatin, the spark test apparatus is t be inserted in each circuit requiring test as determined in accrdance with 2.2 thrugh In additin t the cnditins described in 2.1 thrugh 2.1.4, fr line-cnnected apparatus the input vltage is t be increased t 110 percent f rated line vltage Each circuit is t be tested fr the fllwing number f revlutins f the tungsten wire hlder in the spark test apparatus: (1) Fr dc circuits, nt less than 400 revlutins (5 minutes), 200 revlutins at each plarity; (2) Fr ac circuits, nt less than 1,000 revlutins (12.5 minutes) After each circuit test, verificatin f the spark test apparatus is t be repeated as fllws: If the circuit test resulted in ignitin, the "must nt ignite" verificatin in and is t be repeated; if the circuit test did nt result in ignitin, the "must ignite" verificatin in and is t be repeated. If the verificatin des nt cmply with the applicable prtin f and 8.4.2, the spark test n the circuit under investigatin is t be cnsidered invalid. Grup A&B C D Must Nt Ignite Must Ignite Test Factrs. An additinal factr is t be used when applicable. Where an additinal factr f 1.5 is required by Sectin 2, it may be achieved by the methds given in 3.8.5, 8.6.1, 8.6.2~ r r by any methd f equivalent s~venty, fr example, the use f mre easily igmted test gases.

46 JULY 29, 1988 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL Inductive circuits: the energy is t be increased by a factr f 1.5 by first reducing the values f limiting resistance as much as practical, and then by increasing the vltage Resistive circuits having an inductance less than 5 uh: the energy is t be increased by a factr f 1.5 in rder f preference as fllws: (1) Decreasing the values f limiting resistance; (2) Increasing the line vltage; (3) Increasing ther supply vltages; (4) Increasing the setting f vltage limiting devices. 8,6,3 Capacitive circuits: the energy is t be increased by a factr f 1,5 by increasing the vltage by a factr f 1.22, 8,6.4 When the test series is being carried ut with a fault applied t the circuit, the additinal factr is t be applied as indicated in 8,6.1 thrugh 8,6,3 t the values f current and/r vltage that arise under fault cnditins. I' I '\ ~

47

48 JULY 29,1988 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL 913 Al 1\, I./ APPENDIXES (These appendixes are nt part f American Natinal Standard ANSI/UL ~) but are included fr infrmatin nly.), NOTICE: A number in parentheses fllwing a subsectin number in these appendixes is the subsectin number in the standard t which the explanatry material applies. APPENDIX A Additinal Infrmatin AI. General A 1.1 (l.1.1) Divisin 1 hazardus lcatins, as defined in NFPA , Natinal Electrical Cde, include lcatins defined in many ther cuntries and by the Internatinal Electrtechnical Cmmissin (lec) as Zne O. Zne 0 lcatins are hazardus because f the presence f flammable r cmbustible materials within the flammable range all r a large percentage f the time. In thse natins which recgnize Zne 0 as well as Zne 1, in which hazardus material may be present in nrmal peratin fr a lesser percentage f the time, tw sets f requirements fr intrinsically safe systems are recgnized: ia fr Zne 0 and ib fr Zne 1. Fr Zne 0 applicatin, systems must nt be capable f causing ignitin after cnsideratin f tw faults, as in this dcument. See als A1.2. Fr systems designed t be installed nly in Zne 1 lcatins, nly ne fault must be cnsidered. Because Zne 1 is nt recgnized in NFPA , Natinal Electrical Cde, intrinsically safe systems must be designed fr the mre hazardus Zne 0 lcatins. A1.2 (1.1.2) The experimental data n which the requirements f this dcument are based were determined under nrmal labratry atmspheric cnditins. Ignitin parameters are nt easy t extraplate frm nrmal labratry cnditins t ther cnditins (such as might exist in prcess vessels) withut careful engineering cnsideratin. Increasing the initial temperature f a flammable r cmbustible mixture will decrease the amunt f electrical energy required t cause ignitin s that, at the autignitin temperature f a gas r vapr, the electrical energy required fr ignitin will be zer. The nature f the energy variatin between these limits is nt well dcumented. Temperature variatins can als change the cncentratins f flammable materials in the mixture. A!. 2.1 (1.l. 2) Oxygen enrichment decreases the energy necessary fr ignitin. The minimum ignitin energy f mixtures f flammable materials with xygen may be ne percent f that required fr the same material mixed with air. A1.2.2 (1.1.2) As a general rule, the minimum ignitin energy is inversely prprtinal t pressure squared. When examining a situatin where the gas mixture is nt at atmspheric pressure, ne must cnsider whether a flammable mixture exists under higher pressure cnditins. When the mixture is at high pressure many flammable materials will cndense.

49 A2 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL 913 JULY 29,1988 A1.3 (1.4.3) The cncept f intrinsic safety depends upn assciated apparatus limiting energy t a safe level and then intercnnecting nly thse intrinsically safe apparatus which can nt stre ignitin capable amunts f energy. Traditinally, the examinatin was based n a cmbinatin f assciated and intrinsically safe apparatus, which were specified by manufacturer's name and type number. This traditinal methd created a serius prblem fr manufacturers and users in that nly a small prtin f pssible equipment cmbinatins were ever evaluated by a third party testing lab. A need existed fr a cnvenient methd f determining if apparatus f different manufacturers culd be intercnnected in intrinsically safe lps. The entity cncept was develped t satisfy this need. A2.2 (2.2.1) Fr evaluatin f intrinsic safety, the relevant circuit parameters are pen-circuit vltage, shrt-circuit current, capacitance and inductance. A2.3 (2.3) The entity cncept allws fr assciated apparatus and intrinsically safe apparatus t be evaluated as separate entities. Apparatus evaluated under the entity cncept must have a cntrl drawing that specifies the allwed apparatus and the terminals t which they may be cnnected. The descriptin is nt dne in terms f vendr name and type number, but rather by the specified maximum vltage and the specified maximum current. The values specified may be cmbinatins f vltage and current that are abve the ignitin curve. A2. Evaluatin f Intrinsic Safety A2.1 ( ) It is recgnized that the real margin f safety lies in the use f a test apparatus mre sensitive than any prbable accident cnditin, the use f the ideal gas mixture in testing, and the. extreme imprbability f the cincidence f multiple-circuit faults and external wiring failure at the precise time and place that the ideal gas mixture is present. A2.3.1 (2.3) At this time, the ignitin curves nly apply t assciated apparatus with linear utputs. Entity listing f intrinsically safe apparatus using assciated apparatus with nnlinear utputs must be the subject f special investigatin. The cntrl drawing must be explicit in identifying thse parameters applicable t linear utput assciated apparatus and thse applicable t nnlinear assciated apparatus. A2.1.2 ( ) It shuld be nted that the factrs given in this standard differ frm thse published in the Canadian and Eurpean standards. This standard bases the 1.5 factr n energy while ther standards base the 1.5 factr n current r vltage which can result in a 2.25 factr n energy. Thse using this standard intending t meet standards utside f the U.S. shuld acljust the factrs accrdingly. A2.3.2 (2.3) The evaluatin des nt cnsider pssible summing f maximum utput vltages which might be pssible with assciated apparatus having tw r mre utputs where the vltage is limited between the utputs, but nt between the utputs and grund.

50 r ~ ! JULY 29, 1988 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL 913 A3 r'\ A2.4 (2.4) The utput f the assciated apparatus is the terminal(s) cnnected t intrinsically safe field wiring. A2.5 (2.5) Intrinsically safe apparatus may have a large amunt f capacitance munted inside.. A methd f prtectin is t add series resistance. High capacitance with series resistance may be equivalent t a much lwer capacitance (but nt zer) with n series resistance. The test in thrugh is intended t determine the equivalence. If the equivalent capacitance must be determined, it may require several spark ignitin tests. The manufacturer may greatly reduce these tests by specifying what the equivalent capacitance might be. Then, after determinatin f Cl' ne test is run with the intrinsically safe apparatus cnnected in parallel with an adjustable capacitr set t a value f C]-G. If n ignitin ccurs, then the value is acceptable and must be marked n the unit as the internal capacitance. It is pssible that the value specified by the manufacturer may be cnsiderably higher than the actual equivalent capacitance which wuld have been determined frm the mre exhaustive series f tests. A2.6 (2.6) Figure A 1 is an example f infrmatin t be shwn n the cntrl drawing. The specified set(s) f parameters are evaluated t ascertain that permitted fault cnnectins f these assciated apparatus d nt create an ignitin capable circuit. A2.6.1 (2.6) The phrase "nrmally prvides pwer" means that if the wire t the intrinsically safe apparatus were discnnected, grunding f the wire wuld cause a spark when the unspecified apparatus is perating as intended. Fr example, if the assciated apparatus is cnnected t a 24 vlt pwer supply, grunding wuld cause a spark. A2.6.2 (2.6.7) Applicatin f maximum allwable cable capacitance and inductance. When cable parameters are knwn, the system designer adds the parameters fr lengths f cable t be used t the knwn parameters f the intrinsically safe apparatus. The sums are then cmpared t the allwable parameters mar.ked n the assciated apparatus. If the electrical parameters f the cable are unknwn, the fllwing values may be used: Capacitance - 60 pf 1ft Inductance uh/ft Based n a survey f manufacturer's data, few cables exceed either f these values. A3. Cnstructin Requirements A3.1 (3.1) The values in Table 1 represent assumptins f accumulatin f dust, dirt, and films and are quite cnservative. There is a substantial bdy f pinin that industrial apparatus f the type which can be made intrinsically safe will remain s with spacings even belw thse given in Table 1. A3.1.1 (3.1.3) Fr example, cnsider a 14 pin cmpnent that has a spacing between pins f 0.3 mm and vltage under 10 vlts. Any three pins may be shrted tgether with ne fault cunted. Within any grup f 6 pins nly ne such set f three pins will be shrted. In this case tw such grups f three can be shrted and cunted as tw faults. /'\ U

51 FIGURE A1 EXAMPLE CONTROL DRAWING :: POTEI SERVO 5 CIRCUIT 4 AP83 3 POSITIONER,... (, \ T 4-20 ma2,... FEEDBACK r ) CIRCUIT :::7 CKT 1 "C7CKT 2,... ( \ SERVO 5 CIRCUIT 4 AP83 \ T :::7 CKT 1 POSITIONER 4-20 ma2 FEEDBACK r ) CIRCUIT 1 '-/ CKT 2 HAZARDOUS AREA NilTES ON AP8J POSmONER 1. CIRCUIT 1 AND CIRCUIT 2 MUST BE IN SEP.~~TE CABLES OR Itl ONE CABLE WHICH HAS SUIT.ABLE ItiSULATION. REFER TO INSTRUMENT SOCIETY OF A!.IERICAN RECOMMENDED PRACnCE ISA RP12.6 FOR INST.AWtIG INTRINSICAUY SAFE LOOPS. I I --- ~~ DIOD< - SUPPLY B.lRRIER -=-- SIGNAl BIJIRlnl - DIODE - DIODE<lARRW'I<... - NON-HAZARDOUS AREA SIIPPI y Ql "R... NOTES ON BARRIERS,. MAY BE IN A DIVISION 2 LOCATION IF SO APPROVe:D. 2. OUTPUT CURRENT MUST BE LIMITED BY A RESISTOR SUCH THAT THE OUTPUT VOLTAGE-CURRENT PLOT IS A STRAIGHT LINE DR,AWN BElWEEN OPEN CIRCUIT VOLTAGE AND SHORT CIRCUIT CURRENT. 3. MUST BE INSTALLED IN ACCORDANCE WITH GUIDELINES PROVIDED BY THE MANUFACTURER. BARRIERS MAY NOT Be: CONNECTED IN PARALLEL UNLESS ALLOWED BY THE MANUFACTURER'S APPROVAL. 4. CABLE CAPACITANCE PLUS INTRINSICALLY SAFE EQUIPMENT CAPACITANCE MUST BE LESS THAN THE MARKED CAPACrrANCE (C) SHOWN ON ANY BARRIER USED. THE SAME APPLIES FOR INDUCTANCE. 5. SELECTED BARRIERS MUST HAVE Ve; NOT EXCEEDING Vmax AtlD Ise NOT EXCEEDING Imax AS SHOWN FOR EACH TYPE OF BARRIER IN THE TABLE BELOW. ALL BARRIERS MUST BE OF THE SAME POLARITY. Class 1,11,111 'SUPPLY' Barrier 'SIGNAL' Barrier 'DIODE' Barrier Haz Le Grup Vmax Imax Vmx Imax Vmax Imax A,B,C,D,F,G 40V 150 ma 13V 350 ma 40 V OmA A.B,C,D,F,G 40V 150 ma 40 V 0 ma 40V OmA C,D,F,G 35 V 250 ma 13 V 350 ma 40V InA +24 V l!'difjl~ SWITCH TO COUUON CONTROL +24 V EQUIPMENT 1-5 V r (4-20 mal +24 V SWITCH TO COUUON S'lI':TCfI TO COUUON +24 V and SIGNAl. CONTROL EQUIPII/1ENT NOTES ON CONTROL EQUIPMENT MAINS POWER MUST NOT EXCEED 250 VOLTS WITH RESPECT TO EARTH. I Z >-l ::ti Z c:ij... C'l 01>t"" t"" 0< CIl 01> "l t'l 01> "11 "11 01> ::ti 01> >-l c: c:ij "l ::ti c: c:ij t'l Z li: 01> N 01> ::ti t:i c: c:ij S C'l 01> >-l... z c:ij c: t"" CD... r '-0 c: t"" 0< N> ~... CD CD CD

52 r JULY 29,1988 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL 913 A5 A3.1.2 (3.1.4) Where tw identical intrinsically safe circuits are derived frm the same pwer supply, lack f apprpriate creepage and clearance may result in an increase in the circuit current s that it is n lnger intrinsically safe. If the external circuits are assumed t be shrted r grunded, twice the current will flw int the grund cnnectin, exceeding the current fr which the circuit is designed. If the tw intrinsically safe circuits are derived frm different pwer supplies, a cnnectin f the tw circuits, as wuld be assumed if the creepage and clearance distances are nt in accrdance with the requirements f Table 1, will in almst all cases subject ne f the circuits t vltages r currents higher than the design value. A3.2 (3.2) Adherence. The remval f creepage requirements frm encapsulated cmpnents is based upn the remval f the pssibility f cntaminatin. The measurement f cmparative tracking index, CTI, is, in effect, a measurement f the degree f cntaminatin needed t cause breakdwn f a separatin between cnducting parts. The fllwing facts emerge frm this basic cnsideratin: (1) If all electrical parts and substrates are ttally enclsed in that nthing emerges frm the encapsulatin, then there is n risk f cntaminatin and hence breakdwn due t that surce cannt ccur. (2) If any part f the circuit - such as a bare r insulated cnductr r cmpnent r the substrate f a printed wiring bard - exits the encapsulant, then cntaminatin can enter at that interface and cause breakdwn unless the encapsulant adheres at the interface. A3.2.1 (3.2) The abve facts indicate that what is required is t maintain a seal at the interfaces described and t d this it is necessary that the encapsulant adhere at thse pints. A3.2.2 (3.2) Temperature. All encapsulants have a maximum temperature abve which they may lse r change their specified prperties. Such changes may cause cracking r decmpsitin which culd result in surfaces htter than the utside surface f the encapsulant being expsed t a ptentially explsive atmsphere. A3.2.3 (3.2) Fr this reasn, it is necessary t cnfirm that the encapsulant des nt exceed its maximum rated perating temperature when the circuits enclsed are perated under fault cnditins. In achieving this it shuld be nted that cmpnents which are encapsulated may be htter r clder than they wuld be in free air depending n the thermal cnductivity f the encapsulant. A3.3 (3.4.3) Fr Class 2 circuits, Article 725 f NFPA , Natinal Electrical Cde, specifies nly that insulatin be suitable fr the particular applicatin. Fr Class 3 circuits, minimum requirements fr insulatin thickness are specified, primarily t ensure prtectin against electric shck. Shuld a fault ccur in a Class 2 r Class 3 circuit, heat might be generated in the wiring t damage the insulatin. Thugh this event is unlikely t result in a fire hazard in rdinary applicatins, it is necessary that it be given due cnsideratin in intrinsically safe systems. A3.4 (3.5) Requirements fr cmpnents given in this sectin are nt mandatry requirements fr the cnstructin f all intrinsically safe and assciated apparatus. Prtective cmpnents are nt required if the circuit is still incapable f causing ignitin after tw cmpnents are assumed t have failed.! 1

53 A6 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL 913 JULY 29, 1988 A3.4.1 ( ) The insulatin thickness specified fr Type 1 (a) transfrmers is less than presently interpreted as being required by Eurpean certifying authrities. In additin, althugh n thickness specificatin is given fr Type 2(a) transfrmers, interpretatin by certifying bdies in ther cuntries has required 1 mm f insulatin between the winding(s) supplying intrinsically safe circuits and ther windings. Type 3 cnstructin is permitted based n the assumptin that the transfrmer design is such that n thermal stress n the insulatin ccurs when windings are shrt-circuited due t, fr example, the rating f insulatin, winding impedances, and saturatin level. (See ) A ( ) The Type 2(a) and Type 3 transfrmer cnstructins d nt include a requirement fr fuses r circuit breakers in the primary wiring. This requirement differs frm the Canadian and Eurpean standards which require a fuse in each ungrunded line vltage input. In these tw excepted cases, the additin f a fuse r circuit breaker des nthing t enhance intrinsic breakdwn primary t secndary withut benefit f a fuse, and, in the Type 3 cnstructin, there is n significant heating f the transfrmer leading t a breakdwn. A3.5 Prtective cmpnents. A3.5.1 ( ) This differs frm sme Eurpean requirements that specify peratin at nt mre than tw thirds f rated current under fault cnditins. A3.5.2 (3.6.3) The limitatins in this standard n current, vltage, and vlt-amperes are in agreement with values accepted r prpsed in Eurpean standards. The limits were established because f a cncern that, in an enclsed vlume, as in relay enclsures, inizatin at arcing relay cntacts in the nnintrinsically safe circuit might cause breakdwn f the intrinsically safe circuit, even if creepage and clearance distance requirements in Table 1 are met. A (3.6.3) The 5 ampere, 250 vlt, 100 vlt-ampere figures represent, in the absence f a technical ratinale fr establishing limit values, levels at which adverse cnductin is presumed t be highly imprbable, but which wuld encmpass mst cmmn uses f relays. Fr high levels, additinal precautins, as given in , are required. A3.6 Cells and batteries. A3.6.1 (3.8.5) Optin (3) may be a mre stringent test than ptins (I) and (2), but may be used because it simplifies testing. Failure t pass this test des nt imply that the circuit is nt intrinsically safe. Intrinsic safety may be verified by use f (1) r (2). A3.6.2 (3.8.9) It may be determined by analysis r test that the battery r cells have such lw energy available that n further prtectin is required fr intrinsic safety. Such apparatus des nt require charging-cntact prtectin, utput current-limiting, r any ther energy-limiting cmpnents.

54 JULY 29,1988 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL 913 A7.~ \ ; ; A (3.S.9) The circular disc prbe described in item (2) is representative f a dime, the smallest U.S. cin. This prbe dimensin was selected n the assumptin that the apparatus might be carried in the user's pcket. A4. Additinal Requirements A4.1 (4.1) It is a fundamental requirement f intrinsically safe apparatus that it shall be incapable f causing ignitin either by arcing r thermal effects. If the temperature f any part f the apparatus expsed t the flammable r cmbustible material is belw the autignitin temperature (AIT) f the material, the apparatus is safe with regard t thermal ignitin. There is much data in literature, hwever, which shws that surfaces f limited extent and small cmpnents may exceed the AIT withut causing ignitin. SMRE (Safety in Mines Research Establishment) in England and Physikalisch-Technische Bundesanstalt in Germany have shwn that large resistrs may exceed the AIT by C (IS0-540 F), depending upn the gas and vapr invlved, withut causing ignitin. Smaller cmpnents and wires must reach even higher temperature. (See A4.1.3.) A4.I.l (4.1) Reliably designed electrnic equipment des nt nrmally have cmpnent r wire surface temperatures abve the AIT when perating nrmally. When ne cnsiders the effects f tw faults, it is frequently the case that resistrs r semicnductrs may be expsed t vltages and currents cnsiderably higher than they carry in nrmal peratins. It is under fault cnditins that cncern fr ht wire r ht s~r~ace ignitin, and the need fr careful analy SIS, IS greatest. A4.1.2 (4.1) Fr intrinsically safe equipment in Class II and III hazardus lcatins, the greatest danger is ignitin f a dust layer. Fr classified dusts, if the surface temperature f the apparatus under nrmal cnditins des nt exceed 120 C (24S0F), and under fault cnditins des nt exceed 165 C (329 F), it may be assumed that the device will nt cause ignitin as a result f high surface temperatures. A4.I.3 (4.1) There is cnsiderably less infrmatin in literature regarding the ability f small cmpnents t rise abve the 120 C (24S0F) r 165 C (329 F) value withut causing ignitin, but n theretical grunds, supprted by sme experimental evidence, it can be cncluded that even in Class II and III lcatins, the temperatures f small cmpnents may rise abve the temperature stated. Inability f the cmpnent t cause ignitin must, f curse, be demnstrated by test f the actual cmpnents under fault cnditins. A~.2 (4.1.2) If 1m is unknwn, it may be determmed by test. The current thrugh the wire shuld be increased in stages t allw thermal equilibrium befre incrementing the current t the next higher stage. A4.3 (4.1.3) The ignitin temperature f gases and vaprs which is listed in reference dcuments such as NFP A 497M is determined under cnditins where a significant vlume f gas is at the same temperature. When ignitin is attempted with a small cmpnent, cnvectin effects and partial xidatin at the surface f the cmpnent decrease the rate f heat transfer t the gas. Therefre the cmpnent must be at a temperature much higher than the quted ignitin temperature t ignite the flammable mixture. Typical transistrs, resistrs, and similar small cmpnents must have a surface temperature f C t ignite diethyl ether whse ignitin temperature is 160 C. Similar values have been measured in ignitin tests f carbn disulfide whse ignitin temperature is loo C. A4.3 (4.2.2) The markings may be abbreviated by using symbls as specified in Table AI. I '-

55 A8 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL 913 JULY 29, 1988 (TM-121) Electrical Parameter External Inductance-t- Resistance Rati Internal Inductance-t- Resistance Rati Maximum Input Vltage Maximum Input Current Maximum Internal Capacitance Maximum Internal Inductance Maximum Output Vltage TABLE A1 SYMBOLS FOR MARKINGS Maximum Output Current 10 Maximum Allwed Capacitance Maximum Allwed Inductance Abbreviatin Symbls SystemAa LlR Li/Ri U i Ii C i Li U C athis system is generally used utside the U.S.A. L bthis system is generally used inside the U.S.A. A5. Cmparisn Prcedure fr Determining Spark Ignitin Capacity SystemBb La/Ra Li/Ri V max Imax C i Li Vc A5.1 (5.1) The vltage and current levels specified fr judging the intrinsic safety f apparatus by analysis alne after tw faults are lwer than thse required when the apparatus is tested. A decrease in energy is impsed t allw fr errrs in determining circuit cnstants. Fr example, the measured inductance f many cmpnents depends n the methd used. The apprpriate inductance value t be used in ignitin calculatins may nt be self-evident. The safety f systems which are analyzed is als ensured by the nature f the cnditins under which the reference curves were determined. These curves were determined with the lee test apparatus in which the cntact gemetry is ptimized t encurage ignitin at lw currents. Isc C a La A5.1.1 (5.1 ) Additinally, the ignitin data represents the levels f current w?ic~ w~ll cause ignitin f the flammable matenal m Its m.st easily ignitible cncentratin mre than nce m a thusand attempts. I A6. Apparatus fr Class II arid Class III Lcatins A6.1 (6.2.4) If an enclsure is n~t dust tight the pssibility f reductin?f spacmgs by cnductive dusts must be cnsidered. Therefre, the mst hazardus cmbinatin f such reductin f spacings is specified. Th~s may necess~tate the device being evaluated WIth all capacitrs cnsidered t be paralleled, al.1 indu~t<:>rs cnnected in series, and the effective resistive lad n circuits supplying the device t be the lads which prduce the highest surface tempera.tur~s (maximum pwer transfer) and a shrt CIrCUIt (maximum igniting current). A6.1.1 (6.2.4) Althugh Grup G dusts are usually cnsidered nncnductive, the same requirement is applied. It was nt felt necessary t specify a different requirement and t srt ~t the pssibility f de~radati~::m ~ dust charactenstics ver a lng pend ~ time m the prese?ce f misture, ther cnductive agents, etc. I~ IS recgnized that this requirement is excessive f~r Grup G applicatins, espe.cially where there ~s n pssibility f the dust bemg wet and cntaminated with cnductive materials. A6.2 (6.3) The dust-tight enclsures defined by these requirements are intend~d t prevent ptentially hazardus accumul~tlon f dusts. These requirements are less stnng~nt ~ha? requirements fr enclsures f<:>r.?nmtrmsi~ally safe equipment in Class II, DIVISIn 1 lcatio?s. Thse latter enclsures must have mre stnngent requirements because the apparatus insi~e may be ignitin capable by arc r temperat.ure. m nrmal peratin. Such IS nt the case WIth m trinsically safe apparatus. I The curves fr Grup D are based n tests with prpane. The curves fr methane are based n tests with methane. The curves fr Grup C are based n tests with ethylene. The curves fr Grups A and B are based n tests with hydrgen.

56 JULY 29, 1988 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL 913 A9 A 7. Prtective Transfrmer Tests A7.l (7.6.4) The cmbined requirements f (7.6.3) and (7.6.4) are intended t ensure investigatin f nt nly the highest temperature (7.6.~) which may exist fr nly a shrt time, but als lwer temperatures which may exist fr a much lnger perid f time (7.6.4). AS. Spark Ignitin Tests AS.l (S.2) The apparatus is that described in lec Publicatin (See Figure 9) At currents greater than 3A, arc ignitin is aided by heating f the tungsten wires s that the igniting currents determined by test are t lw. Fr testing at higher current levels, heavier wires r a different type f apparatus may be needed. [Cpper wires 0.25 mm (0.0 1 in.) in diameter have been used.] AS.I.l (S.2) The apparatus is suitable fr testing circuits up t 300 vlts. Fr tests f capacitive circuits, a mdified apparatus (e.g., ne with tw r mre f the wires remved) may be needed t allw adequate charging time. AS.2 (S.2.2) Where field wiring is a part f the intrinsically safe circuit, it is nrmally assumed that cadmium r zinc is present, due t cmmn use f these metals fr crrsin prtectin. 1 IEC Publicatin 79 3 is the Internatinal Electrtechnical Cmmissin's "Electrical Apparatus fr Explsive Gas Atms pheres Part 3: Spark Test Apparatus fr Intrinsically Safe Circuits."

57

58 JULY 29,1988 INTRINSICALL Y SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL 913 Bl I/\. I \./ APPENDIX B Referenced Publicatins BI. General B 1.1 This prtin f the Appendix lists publicatins referenced within this dcument. B The fllwing publicatins are available frm the Natinal Fire Prtectin Assciatin, Batterymarch Park, Quincy, MA NFPA , Natinal Electrical Cde NFPA 497M 1986, Classificatin f Gases, Vaprs and Dusts fr Electrical Equipment in Hazardus (Classified) Lcatins. BI.2 Other Publicatins. ANSI C39.5, Safety Requirements fr Electrical and Electrnic Measuring and Cntrlling Instrumentatin, American Natinal Standards Institute, 1430 Bradway, New Yrk, NY ANSI C96.1, Temperature Measurement Thermcuples, American Natinal Standards Insti-' tute, 1430 Bradway, New Yrk, NY ASTM D , Test Methd fr Cmparative Tracking Index f Electrical Insulating Materials, ASTM, 1916 Race Street, Philadelphia, PA, ANSIjISA RPI2.6, Installatin f Intrinsically Safe Instrument Systems in Class I Hazardus Lcatins, Instrument Sciety f America, 67 Alexander Drive, Research Triangle Park, Nrth Carlina, USA IEC Publicatin 79-3, Electrical Apparatus fr Explsive Gas Atmspheres - Part 3: Spark Test Apparatus Jr Intrinsically Safe Circuits, Internatinal Electrtechnical Cmmissin, 1 Rue de Varembe, Geneva, Switzerland. NEMA Publicatin N , Enclsures fr Electrical Equipment (1000 Vlts Maximum), Natinal Electrical Manufacturers Assciatin., 2101 L St., N.W., Washingtn, DC SFA , British Apprvals Service fr Electrical Equipment in Flammable Atmspheres, British Standards Institutin, Linfrd Wd, Miltn Keynes, MK4 6LE. Sme Aspects f the Design f Intrinsically Safe Circuits, Research Reprt 256, 1968, D. W. Widgentn, Safety in Mines Research Establishment, Sheffield, England.

59

60 RECEIVED DEPT. OF L & I Underwriters Labratries Inc.@ An independent, nt-fr-prfit rganizatin testing fr public safety MAY CHiEt' clli...,, "...,,",L INSPECTOR'S OFFICE.& May 10, 1996 Revisin pages fr Standard fr Intrinsically Safe Apparatus and Assciated Apparatus Fr Use In Class I, IT, and ID, Divisin 1, Hazardus (Classified) Lcatins UL 913, Furth Editin Attached t this distributin ntice is a revisin f the Furth editin f UL 913. A CHANGE ON A PAGE DATED MAY 10, 1996 IS INDICATED BY A SMALL PRINT NOTE FOLLOWING THE AFFECTED ITEM, PRECEDED AND FOLLOWED BY AN ASTERISK. THESE NEW AND REVISED REQllREMENTS IN THIS STANDARD ARE NOW IN EFFECT EXCEPT FOR THOSE PARAGRAPHS, SECTIONS, TABLES, FIGURES, AND OTHER ELEMENTS OF THE STANDARD HAVING FUTURE EFFECTIVE DATES AS INDICATED IN THE NOTE FOLLOWING THE AFFECTED ITEM. TO RETAIN THE REQllREMENTS IN EFFECT UNTIL THESE FUTURE EFFECTIVE DATES, DO NOT DISCARD THE PAGES REPLACED BY THOSE HAVING FUTURE EFFECTIVE DATES UNTIL THOSE DATES. New prduct submittals made prir t a specified future effective date will be judged under all f the requirements in this standard unless the applicant specifically requests that the prduct be judged under the current requirements. Hwever, shuld the applicant elect this ptin, it shuld be nted that cmpliance with all the requirements in this standard will be required as a cnditin f cntinued Listing r Classificatin and Fllw-Up Services after the effective date and understanding f this shuld be signified in writing. The new and/r revised requirements are substantially in accrdance with UL's Bulletin n this subject dated June 30, The bulletin is nw bslete and may be discarded. As indicated n the title page (page 1), this UL Standard fr Safety is an American Natinal Standard. Attentin is directed t the nte n the title page f this Standard utlining the prcedures t be fllwed t retain the text f this ANSIIUL Standard. J Revised and/r additinal pages may be issued frm time t time. (Cntinued)

61 May 10, UL 913 With the inclusin f the accmpanying material, the standard cnsists f pages dated as shwn in the fllwing checklist: Page Date 1... July 29, 1988(Reprinted May 10, 1996) 2... May 10, , 4... July 29, May 10, July 29, , 8... May 10, July 29, , May 10, July 29, , 28..., December 12, July 29, 1988 Al - A9, B1... July 29, 1988

62 American Natinal Standard ~ c. JULY 29, 1988 ~SIflnL (Title Page Reprinted: May 10, 1996) 1 UL 913 Standard fr Intrinsically Safe Apparatus And Assciated Apparatus Fr Use In Class I, II, And ill, Divisin 1,.Hazardus (Classified) Lcatins The First editin was titled Standard fr Intrinsically Safe Electrial Equipment fr Use in Hazardus Lcatins. The Secnd editin was titled Standard fr Intrinsically Safe Electrical Circuits and Apparatus fr Use in Hazardus Lcatins and its assciated Apparatus. First Editin - Nvember, 1971 Secnd Editin - January, 1976 Third Editin - July, 1979 Furth Editin July 29, 1988 Apprval as an American Natinal Standard (ANSI) cvers the numbered paragraphs n pages dated July 29, These pages shuld nt be discarded when revised r additinal pages are issued if it is desired t retain the ANSI apprved text. An effective date included as a nte immediately fllwing certain requirements is ne established by Underwriters Labratries Inc. Apprved as ANSI/ULlNFPA , Nvember 5, 1979 Apprved as ANSIIUL , May 20, 1988 Figures 2-4 and 8 are frm British Apprvals Service fr Electrical Equipment in Flammable Atmspheres Certificatin Standard SF A 3012: Intrinsic Safety. Permissin t use this Crwn Cpyright Material is gratefully acknwledged. Figures 5 and 6 are frm "Sme Aspects f the Design f Intrinsically Safe Circuits," Research Reprt 256 by D. W. Widgentn, Safety in Mines Research Establishment, Sheffield, England, Revisins f this standard will be made by issuing revised r additinal pages bearing their date f issue. A UL Standard is current nly if it incrprates the mst recently adpted revisins, all f which are itemized n the transmittal ntice that accmpanies the latest published set f revisin pages. COPYRIGHT 1976, 1996 UNDERWRITERS LABORATORIES INC.

63 2 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL 913 MAY 10, 1996 CONTENTS SECTION 1. General Scpe Purpse Applicability f Other Standards Defmitins... 5 l.4a Class I, Zne, and Grup Equivalency Cntrl Drawing Evaluatin f Intrinsic Safety Fundamental Requirements Evaluatin Prcedure Entity Evaluatin Assciated Apparatus Evaluatin Intrinsically Safe Apparatus Inductance and Capacitance Determinatin Intrinsically Safe Apparatus Cntrl Drawing Evaluatin Intrinsically Safe Apparatus Evaluatin Cnstructin Requirements Creepage and Clearance Distances Encapsulatin Field Wiring Cnnectins Internal Wiring Cnductrs Prtective Cmpnents Miscellaneus Cmpnents Prtable Apparatus Enclsures Cells and Batteries Additinal Requirements Maximum Temperature Marking Cmparisn Prcedure fr Determining Spark Ignitin Capability General Maximum Vltage and Current Levels Apparatus fr Class II and Class III Lcatins Applicability f Other Requirements f this Standard Specific Requirements fr Intrinsic Safety Dust-Tight Enclsures... 31

64 ~ ~ ~~- MAY 10, 1996 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL CJ 1. General NOTICE: The asterisk fllwing the subsectin number signifies that explanatry material n that paragraph appears in Appendix A. 1.1 Scpe This standard applies t: (1) Apparatus r parts f a~paratus in Class I, II, r III, Divisin 1 lcatins ; (2) Thse parts f apparatus lcated utside f the Class I, II, r III, Divisin 1 lcatin having a design and cnstructin that may influence the intrinsic safety f an electrical circuit within the Class I, II, r III, Divisin 1 lcatin. (3) Apparatus r parts f apparatus in Class I, Zne 0 r 1, Grups IIA, lib, and IIC lcatins; (4) Thse parts f apparatus lcated utside f the Class I, Zne 0 and 1, Grups IIA, 1m, r IIC lcatin having a design and cnstructin that may influence the intrinsic safety f an electrical circuit within the Class I, Zne 0 and 1, Grup IIA, 1m, r IIC lcatin. *Paragraph revised May 10, 1996* 1.1.2* These requirements are based n cnsideratin f ignitin in lcatins made hazardus by the presence f flammable r cmbustible material under nrmal atmspheric cnditins Fr the purpses f this standard, nrmal atmspheric cnditins are cnsidered t be: (1) An ambient temperature f 40 C (104 F); (2) An xygen cncentratin nt greater than 21 percent; and (3) A pressure f ne atmsphere This standard des nt cver mechanisms f ignitin frm external surces, such as static electricity r lightning, which are nt related t the electrical characteristics f the apparatus: This standard des nt cver apparatus based n high vltage electrstatic principles, such as electrstatic paint spraying apparatus. 1 Sectin 500-3(a) f ANSIINFP A , Natinal Electrical Cde, states that equipment that has been apprved fr a Divisin 1 lcatin shall be permitted in a Divisin 2 lcatin f the same class and grup. 1.2 Purpse The purpse f this standard is t prvide requirements fr the cnstructin and testing f electrical apparatus, r parts f such apparatus, having circuits that are nt capable f causing ignitin in Divisin 1 hazardus lcatins as defmed in Article 500 f the Natinal Electrical Cde, ANSIINFPA This standard is nt t be cnsidered an instructin manual fr untrained persns. -It is intended t prmte unifrmity f practice amng thse skilled in the field f intrinsic safety. 1.3 Applicability f Other Standards Except where mdified by the requirements f this standard, intrinsically safe and assciated apparatus shall cmply with the applicable requirements fr rdinary lcatins Assciated apparatus and circuits shall cnfrm t the requirements f the lcatin in which the apparatus and circuits are installed Defmitins Assciated Apparatus. Apparatus in which the circuits are nt necessarily intrinsically safe themselves, but which affect the energy in the intrinsically safe circuits and are relied upn t maintain intrinsic safety. Assciated electrical apparatus may be either: (1) Electrical apparatus that has an alternative type f prtectin fr use in the apprpriate ptentially flammable atmsphere; r (2) Electrical apparatus nt s prtected that shall nt be used within a ptentially flammable atmsphere. 1 As an example f requirements fr rdinary lcatins, see ANSI C39.S, Safety Requirements fr Electrical and Electrnic Measuring and Cntrlling Instrumentatin, available frm the American Natinal Standards Institute, 1430 Bradway, New Yrk, NY Fr guidance n installatin, see ANSIIISA RP12.6, Installatin f Intrinsically Safe Systems fr Class I Hazardus (Classified) Lcatins, available frm the Instrument Sciety f America, 67 Alexander Drive, Research Triangle Park, Nrth Carlina,

65 6 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL 913 JULY 29, Cntrl Drawing. A drawing r ther dcument prvided by the manufacturer f the intrinsically safe r assciated apparatus that details the allwed intercnnectins between the intrinsically safe and assciated apparatus * Entity Evaluatin. A methd used t determine acceptable cmbinatins f intrinsically safe apparatus and cnnected assciated apparatus that have nt been investigated in such cmbinatins External Inductance-t-Resistance Rati. The rati f inductance t resistance f the intrinsically safe circuit cnnected t the assciated apparatus Fault. A defect r electrical breakdwn f any cmpnent, spacing, r insulatin that alne r in cmbinatin with ther faults may adversely affect the electrical r thermal characteristics f the intrinsically safe circuit. If a defect r breakdwn leads t defects r breakdwns in ther cmpnents, the primary and subsequent defects and breakdwns are cnsidered t be a single fault Internal Inductance-t-Resistance Rati. The rati f inductance t resistance f the intrinsically safe apparatus Internal Wiring. Wiring and electrical cnnectins that are made within the apparatus by the manufacturer. Within racks r panels, intercnnectins between separate pieces f apparatus made in accrdance with detailed instructins frm the apparatus' manufacturer are cnsidered t be internal wiring Intrinsically Safe Apparatus. Apparatus in which all the circuits are intrinsically safe Intrinsically Safe Circuit. A circuit in which any spark r thermal effect, prduced either nrmally r in specified fault cnditins, is incapabl~, under the test cnditins prescribed in this standard, f causing ignitin f a mixture f flammable r cmbustible material in air in the mixture's mst easily ignitable cncentratin Linear Output Assciated Apparatus. Assciated apparatus in which the utput current is limited by a resistr such that the utput vltage-current plt is a straight line drawn between pen circuit vltage and shrt-circuit current Maximum Allwed Capacitance. The maximum value f capacitance that may be cnnected t the intrinsically safe circuit f the assciated apparatus Maximum Allwed Inductance. The maximum value f inductance that may be cnnected t the intrinsically safe circuit f the assciated apparatus Maximum Input Current. The maximum dc r peak ac current that can be safely applied t the terminals f the intrinsically safe apparatus. The maximum input current may be different fr different terminals Maximum Input Vltage. The maximum dc r peak ac vltage that can be safely applied t the terminals f an intrinsically safe apparatus. The maximum input vltage may be different fr different terminals Maximum Internal Capacitance. The ttal equivalent internal capacitance f the intrinsically safe apparatus that must be cnsidered as appearing acrss the terminals f the intrinsically safe apparatus Maximum Internal Inductance. The ttal equivalent internal inductance f the intrinsically safe apparatus that must be cnsidered as appearing acrss the terminals f the intrinsically safe apparatus Maximum Nnhazardus Lcatin Vltage. The maximum vltage that may be applied t each f the nnintrinsically safe terminals f assciated apparatus withut affecting intrinsic safety Maximum Output Current. The maximum dc r peak ac current that may be extracted frm the intrinsically safe cnnectins f the assciated apparatus.

66 MAY 10,1996 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL (\,- ) () Maximum Output Vltage. The maximum dc r peak ac pen circuit vltage that can appear at the intrinsically safe cnnectins f the assciated apparatus Nrmal Operatin. Intrinsically safe apparatus r assciated apparatus cnfrming electrically and mechanically with its design specificatin Prtective Cmpnent r Assembly. A cmpnent r assembly that is s unlikely t becme defective in a manner that will lwer the intrinsic safety f the circuit that it may be cnsidered nt subject t fault when analysis r tests fr intrinsic safety are cnducted Shunt Dide Barrier. A fuse- r resistr-prtected dide barrier Fuse-Prtected Shunt Dide Barrier. A netwrk designed t limit current and vltage that cnsists f a series fuse, vltage-limiting shunt dides, and a current-limiting resistr r ther current-limiting cmpnents. The fuse is intended t prtect the dides frm pen-circuiting when high fault currents flw Resistr-Prtected Shunt Dide Barrier. A netwrk identical t a fuse-prtected shunt dide barrier, except that the fuse is replaced by a resistr. 1.4A Class I, Zne, and Grup Equivalency 1.4A.l Class I, Zne 0 and 1, Grup ITA 1.4A.1.1 Apparatus r parts f apparatus intended t be marked in accrdance with 4.2.1C shall cmply with all the requirements fr apparatus fr use in Class I, Grup D lcatins. *Paragraph 1.4A.l.l added May 10, 1996* 1.4A.2 Class I, Zne 0 and 1, Grup ITB I.4A.2.1 Apparatus r parts f apparatus intended t be marked in accrdance with 4.2.1B shall cmply with all the requirements fr apparatus fr use in Class I, Grup C lcatins. *Paragraph 1.4A.2.1 added May 10, 1996* 1.4A.3 Class I, Zne 0 and 1, Grup ITC 1.4A.3.1 Apparatus r parts f apparatus intended t be marked in accrdance with 4.2.1A shall cmply with all the requirements fr apparatus fr use in bth Class I, Grup A and Class I, Grup B lcatins. *Paragraph 1.4A.3.1 added May 10, 1996* 1.5 Cntrl Drawing A cntrl drawing shall be prvided fr all intrinsically safe apparatus r assciated apparatus that requires intercnnectin t ther circuits r apparatus. Paragraph effective September 13, An intrinsically safe system culd cnsist f apparatus investigated as a system r apparatus investigated under the entity cncept. If the intrinsically safe and assciated apparatus are investigated as a system, the cntrl drawing shall prvide infrmatin fr prper cnnectin and installatin. If the intrinsically safe r assciated apparatus is investigated under the entity cncept, the cntrl drawing shall include applicable electrical parameters t permit selectin f apparatus fr intercnnectin. Paragraph effective September 13, Evaluatin f Intrinsic Safety 2.1 Fundamental Requirements. Intrinsically safe apparatus and circuits shall cmply with the tw basic requirements specified in and The energy available in the hazardus. lcatin shall nt be capable f igniting the flammable mixture specified in thrugh due t arcing r ht surfaces during nrmal peratin Fr evaluatin purpses, nrmal peratin is t include all f the fllwing: (1) Supply vltage at maximum rated value; (2) Envirnmental cnditins within the ratings given fr the intrinsically safe apparatus r assciated apparatus;

67 8 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL 913 MAY 10, 1996 (3) Tlerances f all cmpnents in the cmbinatin that represents the mst unfavrable cnditin; (4) Adjustments at the mst unfavrable settings; (5) Opening f anyne f the field wires, shrting f any tw field wires, r grunding f anyne f the field wires f the intrinsically safe circuit being evaluated * Fr test purpses, nrmal peratin is t include an additinal test factr f 1.5 applied t energy. This factr is t be achieved accrding t the prcedures utlined in 8.6 thrugh The energy available in the hazardus lcatin shall nt be capable f igniting the flammable mixture specified in thrugh due t arcing r ht surfaces under fault cnditins. Befre faults are intrduced, the apparatus is t be in nrmal peratin as specified in Fault cnditins are t include the fllwing: (1) The mst unfavrable single fault and any subsequent related defects and breakdwns, with an additinal test factr f 1.5 applied t energy; (2) The mst unfavrable cmbinatin f tw faults and any subsequent related defects and breakdwns, with n additinal test factr. Such test factrs are t be achieved accrding t the prcedures utlined in 8.6 thrugh Apparatus in which n fault r nly ne fault can ccur shall be cnsidered acceptable if it cmplies with (1) the test requirements fr nrmal peratin as described in with an additinal test factr f 1.5 applied t energy, (2) the test requirements fr any fault that can ccur with an additinal test factr f 1.5 applied t energy, and (3) the requirements f this standard All intrinsically safe and assciated apparatus and circuits shall cmply with the requirements in Sectins 3 and * The circuits are t be analyzed t determine circuit parameters under the nrmal and fault cnditins specified in 2.1 thrugh Fr intrinsically safe apparatus, each pssible ignitin pint where circuit interruptin, shrt circuit, r grund fault may ccur is t be cnsidered Cnstructin details and temperatures are t be reviewed fr cmpliance with Sectins 3 and 4. The apparatus shall cmply with the applicable test prcedures f Sectin The pssibility f arc ignitin under nrmal and fault cnditins is t be determined by either f the fllwing tw prcedures: (1) Testing the circuit accrding t the test requirements f Sectin 8; r (2) Cmparing the calculated r measured values f current, vltage, and assciated inductances and capacitances t the apprpriate figures in Sectin 5 t establish that the current and vltage levels are belw the specified values in thrugh In evaluating circuits fr intrinsic safety, ignitin surces such as the fllwing are t be cnsidered: (1) Surces f spark ignitin: (a) Discharge f a capacitive circuit; (b) Interruptin f an inductive circuit; (c) Intermittent making and breaking f a resistive circuit; (d) Ht wire fusing. (2) Surces f thermal ignitin: (a) Heating f small gage wire strand; (b) Glwing f a filament; (c) High surface temperature f cmpnents. 2.2 Evaluatin Prcedure. Circuits are t be evaluated fr intrinsic safety as specified in thrugh

68 MAY 10,1996 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL A In additin t, r as an alternative t, the marking requirement in 4.2.1(2), apparatus r parts f apparatus that have been investigated and fund t cmply with the requirements fr Class I, Grup D lcatins may additinally r alternatively be marked as fllws: a) Class I, Zne 0, Grup lia; r b) Class I, Zne and 1, Grup lia. *Paragraph 4.2.1A adde" May 10, 1996* 4.2.1B In additin t, r as an alternative t, the marking requirement in 4.2.1(2), apparatus r parts f apparatus that have been investigated and fund t cmply with the requirements fr Class I, Grup C lcatins may additinally r alternatively be marked as fllws: a) Class I, Zne 0, Grup lib; r b) Class I, Zne and 1, Grup lib. *Paragraph 4.2.1B added May 10, 1996* 4.2.1C In additin t, r as an alternative t, the marking requirement in 4.2.1(2), apparatus r parts f apparatus that have been investigated and fund t cmply with the requirements fr bth Class I, Grup A, and Class I, Grup B lcatins may additinally r alternatively be marked as fllws: a) Class I, Zne 0, Grup lic; r b) Class I, Zne and 1, Grup IIC. *Paragraph 4.2.1C added May 10, 1996* 4.2.1D Apparatus r parts f apparatus marked Grup lib may als be marked Grup IIA. *Paragraph 4.2.1D added May 10, 1996* 4.2.1E Apparatus r parts f apparatus marked Grup lic may als be marked Grup lia, Grup lib, r bth Grup IIA and Grup IIB. *Paragraph 4.2.1E added May 10, 1996* 4.2.2* In additin t the minimum marking specified in 4.2.1, the marking shall include the fllwing. As much infrmatin as pssible shall be prvided n the apparatus label. It is recgnized, hwever, that it is impractical t mark small pieces f apparatus with all the required infrmatin. If this infrmatin is nt n the apparatus, it shall be included in the accmpanying literature. (1) Fr intrinsically safe apparatus: (a) An indicatin that the apparatus is intrinsically safe;. (b) If investigated using the entity evaluatin, the maximum input vltage, maximum input current, maximum internal capacitance and maximum internal inductance; ( c) If repair is pssible, a warning label wrded "Warning - Substitutin f Cmpnents May Impair Intrinsic Safety;" and (d) A reference t accmpanying literature, that prvides special installatin, maintenance, r perating instructins. If this infrmatin is nt n the apparatus, it shall be included r referenced n the cntrl drawing., (2) Fr assciated apparatus: (a) If investigated using the entity evaluatin, the maximum utput vltage, maximum utput current, maximum allwed capacitance, and maximum allwed inductance; (b) If repair is pssible, a warning wrded "Warning - Substitutin f Cmpnents May Impair Intrinsic Safety;" (c) Any ther necessary infrmatin, in particular, an indicatin f any ther type f prtectin and its characteristics; and (d) A reference t accmpanying literature, that prvides special installatin, maintenance, r perating instructins. If this infrmatin is nt n the apparatus, it shall be included r referenced n the cntrl drawing. Subitem (b) in item (1) and Subitem (a) in item (2) f paragraph effective September 13, 1991

69 22 INTRINSICALLY SAFE APPARATUS FOR USE IN HAZARDOUS LOCATIONS - UL 913 ~YI0, Terminals, terminal bxes, and plugs and receptacles fr cnnectin t intrinsically safe circuits shall be clearly identified and clearly distinguishable. If clr nly is used t cmply with this requirement, the clr shall be light blue Battery-pwered apparatus shall be marked with a cautin statement t (1) indicate the type, size, and vltage f batteries t be used r (2) indicate the specific battery by manufacturer and mdel number r equivalent t be used. If the batteries u~ed are nt intrinsically safe, the apparatus shall be marked with the fllwing warning r equivalent: "Warning - t reduce the risk f ignitin f a flammable atmsphere, batteries must nly be changed in an area knwn t be nnflammable. " 5. Cmparisn Prcedure fr Determining Spark Ignitin Capability 5.1 * General.! Apparatus may be cnsidered intrinsically safe withut spark ignitin testing if the circuits can be readily assessed. T be cnsidered intrinsically safe by the cmparisn prcedure, circuits and apparatus shall cmply with thrugh Circuits that cannt be readily assessed in terms f elementary circuits represented by the ignitin curves shwn in the figures in this chapter, circuits in which the current r vltage values exceed thse indicated n the curves, and circuits that d nt cmply with thrugh are t be evaluated by the test prcedures in Sectin Resistance Circuits. Figures 1 and 2 apply t resistance circuits nly and shw cmbinatins f vltage and current that will ignite gas and vaprs in air fr Grups A, B, C, D and fr methane. These figures apply nly t circuits having an utput vltage-current plt that is a straight liiie drawn between pen circuit vltage and shrt-circuit current Resistance-Inductance Circu~ts. Figures 3 and 4 apply t resistance-inductance circuits and shw the cmbinatins f inductance and current at 24 vlts which will ignite gases r vaprs in air fr Grups A, B, C, D and fr methane. Figures 5 and 6 apply t resistance-inductance circuits and shw cmbinatins f inductance and current at specific vltages which will ignite gases r vaprs in Grup B and methane, respectively Resistance-Capacitance Circuits. Figures 7 and 8 apply t resistance-capacitance circuits and shw cmbinatins f capacitance, vltage, and resistance which will ignite gases r vaprs in air fr Grups A and B and fr methane. These curves represent capacitr discharge nly. They d nt include the additinal current which may be available frm the assciated apparatus. 5.2 Maximum Vltage and Current Levels The circuit cnditins are t include all nrmal and fault cnditins described in this standard, excluding the 1.5 test factr Maximum vltage and current levels (de r peak ac) in circuits determined t be intrinsically safe by the cmparisn prcedure shall nt exceed the values in and , fr given circuit cnstants Fr nrmal r single-fault peratin, the current shall nt exceed 80 percent f the value determined frm Figures 1 thrugh 6. The vltage shall nt exceed 80 percent f the value determined frm Figures 7 and Fr tw-fault cnditin, the current shall nt exceed 90 percent f the value determined frm Figures 1 thrugh 6. The vltage shall nt exceed 90 percent f the value determined frm Figures 7 and 8. 1 All figures, except Figures 5 and 6, are reprinted frm Certificatin Standard SFA 3012, 1972 editin, with permissin f the Department f Trade and Industry, British Apprvals Service fr Electrical Equipment in Flammable Atmspheres. Figures 5 and 6 are frm "Sme Aspects f the Design fintrinsically Safe Circuits," Research Reprt 256, 1968, by D. W. Widgentn, Safety in Mines Research Establishment, Sheffield, England.