BS EN 60079-30-1:2017 BSI Standards Publication Explosive atmospheres Part 30-1: Electrical resistance trace heating — General and testing requirements BS EN 60079-30-1:2017 BRITISH STANDARD National foreword This British Standard is the UK implementation of EN 60079-30-1:2017 It is derived from IEC/IEEE 60079-30-1:2015 It supersedes BS EN 60079-30-1:2007, which is withdrawn The CENELEC common modifications have been implemented at the appropriate places in the text The start and finish o f each common modification is indicated in the text by The UK participation in its preparation was entrusted to Technical Committee EXL/31, Equipment for explosive atmospheres A list o f organizations represented on this committee can be obtained on request to its secretary This publication does not purport to include all the necessary provisions o f a contract Users are responsible for its correct application © The British Standards Institution 2017 Published by BSI Standards Limited 2017 ISBN 978 580 79820 ICS 29.260.20 Compliance with a British Standard cannot confer immunity from legal obligations This British Standard was published under the authority o f the Standards Policy and Strategy Committee on 31 July 2017 Amendments/corrigenda issued since publication Date Text affected BS EN 60079-30-1:2017 EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM EN 60079-30-1 April 201 ICS 29.260.20 Supersedes EN 60079-30-1 :2007 English Version Explosive atmospheres - Part 30-1 : Electrical resistance trace heating - General and testing requirements (IEC/IEEE 60079-30-1 :201 , modified) Atmosphères explosives - Partie 30-1 : Traỗage par rộsistance ộlectrique - Exigences gộnộrales et d'essai (IEC/IEEE 60079-30-1 :201 , modifiée) Explosionsgefährdeter Bereiche - Teil 30-1 : Elektrische Widerstands-Begleitheizungen - Allgemeine Anforderungen und Prüfanforderungen (IEC/IEEE 60079-30-1 :201 , modifiziert) This European Standard was approved by CENELEC on 201 7-03-06 CENELEC members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CENELEC member This European Standard exists in three official versions (English, French, German) A version in any other language made by translation under the responsibility of a CENELEC member into its own language and notified to the CEN-CENELEC Management Centre has the same status as the official versions CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom European Committee for Electrotechnical Standardization Comité Européen de Normalisation Electrotechnique Europäisches Komitee für Elektrotechnische Normung CEN-CENELEC Management Centre: Avenue Marnix 7, B-1 000 Brussels © 201 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members Ref No EN 60079-30-1 :201 E BS EN 60079-30-1:2017 EN 60079-30-1 :201 (E) European foreword This document (EN 60079-30-1 :201 7) consists of the text of IEC/IEEE 60079-30-1 :201 prepared by IEC/TC 31 "Equipment for explosive atmospheres" in collaboration with IEEE Standards Association (IEEE-SA), together with the common modifications prepared by CLC/TC 31 "Electrical apparatus for potentially explosive atmospheres" The following dates are fixed: • • (dop) latest date by which this document has to be implemented at national level by publication of an identical national standard or by endorsement latest date by which the national standards conflicting (dow) with this document have to be withdrawn 201 8-03-06 2020-03-06 This document supersedes EN 60079-30-1 :2007 The State of the Art is included in Annex ZY “Significant changes between this European Standard and EN 60079-30-1 :2007” For the significant changes with respect to EN 60079-30-1 :2007, see Annex ZY Annexes which are additional to those in IEC/IEEE 60079-30-1 :201 are prefixed “Z” This document has been prepared under a mandate given to CENELEC by the European Commission and the European Free Trade Association, and supports essential requirements of EU Directive For the relationship with EU Directive see informative Annex ZZ, which is an integral part of this document BS EN 60079-30-1:2017 EN 60079-30-1 :201 (E) Annex ZA (normative) Normative references to international publications with their corresponding European publications The following referenced documents are indispensable for the application of this document For dated references, only the edition cited applies For undated references, the latest edition of the referenced document (including any amendments) applies NOTE When an international publication has been modified by common modifications, indicated by (mod), the relevant EN/HD applies Publication Year Title EN/HD Year IEC 60050-1 51 2001 International Electrotechnical Vocabulary Part 51 : Electrical and magnetic devices - - IEC 60050-426 2008 International Electrotechnical Vocabulary Part 426: Equipment for explosive atmospheres - - IEC 60079-0 201 Explosive atmospheres - Part 0: Equipment – General requirements EN 60079-0 + A1 201 201 IEC 60695-1 -3 - Fire hazard testing - Part 1 -3: Test flames – 500 W flames - Apparatus and confirmational test methods EN 60695-1 -3 - ISO 4582 - Plastics - Determination of changes in colour and variations in properties after exposure to daylight under glass, natural weathering or laboratory light sources - - ISO 4892-1 - Plastics - Methods of exposure to laboratory light sources - Part : General guidance EN 4892-1 - ISO 4892-2 - Plastics - Methods of exposure to laboratory light sources - Part 2: Xenon-arc lamps EN 4892-2 - ASTM D5025 - Standard specification for laboratory burner used for small-scale burning tests on plastic materials - - ASTM G1 55 - Standard practice for operating xenon arc light apparatus for exposure of nonmetallic materials - - BS EN 60079-30-1:2017 EN 60079-30-1 :201 (E) Annex ZY (informative) Significant changes between this European Standard and EN 60079-30-1 :2007 The significant changes with respect to EN 60079-30-1 :2007 are as listed below Significant Changes Addition of clarification for the exclusion of EPLs Ga and Da Addition of table specifying the application or exclusion of specific clauses of IEC 60079-0 Edition For stabilized designs, a clarification for the need for verification by testing and the addition of a table for the specific requirements For controlled designs, a clarification for the need for verification by testing and the addition of a table for the specific requirements For controlled designs, clarifications and additions on the separate requirements for Gb/Db and Gc/Dc The requirements for calibration of the flammability test fixture are replaced with equivalent requirements for the energy levels of the test gases Addition of a minimum temperature impact test For thermal stability, the addition of a bending requirement on a mandrel The replacement of the thermal safety procedure with a thermal performance procedure The addition of a second procedure utilizing a plate fixture for the systems method for maximum sheath temperature determination Addition of outdoor exposure test Requirement changed for the marking of the minimum installation temperature Addition of new markings requirements for field assembled components Additions and changes to the documentation requirements Addition of Annex Addition of Annex Addition of Annex specifying trace heating design verification methodology, moved from IEC 60079-30-2 Clause Minor and editorial changes X X 4.5.2 X 4.5.3 X 4.5.3 5.1 Type Extension Major technic al change s X X 5.1 C1 5.1 1 C1 5.1 C2 5.1 3.2 C3 5.1 C4 6.1 C5 6.2 C5 Annex A Annex B Annex C X X C5 C6 NOTE The technical changes referred to include the significance of technical changes in the revised I EC Standard, but they not form an exhaustive list of all modifications from the previous version BS EN 60079-30-1:2017 EN 60079-30-1 :201 (E) Explanation of the Types of Significant Changes: A) Definitions Minor and editorial changes: • Clarification • Decrease of technical requirements • Minor technical change • Editorial corrections These are changes which modify requirements in an editorial or a minor technical way They include changes of the wording to clarify technical requirements without any technical change, or a reduction in level of existing requirement Extension: Addition of technical options These are changes which add new or modify existing technical requirements, in a way that new options are given, but without increasing requirements for equipment that was fully compliant with the previous standard Therefore, these will not have to be considered for products in conformity with the preceding edition • Major technical changes: • addition of technical requirements • increase of technical requirements These are changes to technical requirements (addition, increase of the level or removal) made in a way that a product in conformity with the preceding edition will not always be able to fulfil the requirements given in the later edition These changes have to be considered for products in conformity with the preceding edition For these changes additional information is provided in item B) below NOTE These changes represent current technological knowledge However, these changes should not normally have an influence on equipment already placed on the market B) Information about the background of ‘Major technical changes’ C1 – The requirements for additional mechanical testing have been included for harmonization and for added safety C2 – The requirements for thermal performance have been included to recognize the necessity for thermal stability of products in explosive atmospheres C3 – A second procedure utilizing a plate fixture has been included for sheath temperature determination, which may be used in lieu of the sheath temperature verification part of 5.1 3.4.2 C4 – An outdoor exposure test has been added to cover products that may be exposed to sunlight and moisture in the intended application C5 – Additional marking and documentation requirements have been added to provide additional information to the end user C6 – The trace heating design verification methodology has been added to align with the evaluation requirements for the stabilized design and the controlled design methods of maximum sheath temperature determination BS EN 60079-30-1:2017 EN 60079-30-1 :201 (E) Annex ZZ (informative) Relationship between this European standard and the essential requirements of Directive 201 4/34/EU aimed to be covered This European standard has been prepared under a Commission’s standardization request to provide one voluntary means of conforming to essential of Directive 201 4/34/EU of the European Parliament and of the Council of 26 February 201 on the approximation of the laws of the Member States concerning equipment and protective systems intended for use in potentially explosive atmospheres Once this standard is cited in the Official Journal of the European Union under that Directive, compliance with the normative clauses of this standard given in Table ZZ.1 confers, within the limits of the scope of this standard, a presumption of conformity with the corresponding essential requirements of that Directive, and associated EFTA regulations Table ZZ.1 – Correspondence between this European standard and Annex II of Directive 201 4/34/EU Essential Requirements of Directive 0.1 0.2 0.3 0.4 0.5 Clause(s) / sub-clause(s) of this EN All 4, 5, Annex C 4, 7.5, 7.6 4, 5, Annex C 0.6 1 2.6 2.7 4.1 , 4.2, 4.3, 5.1 2, 5.1 3, 5.1 4, 5.1 5, 5.1 6, 5.1 7, 5.1 8, 5.1 9, 5.1 1 , 5.1 4.5, 5.1 0, 5.1 2, 5.1 3, 5.1 4, 5.1 4.1 , 4.2, 4.3, 5.1 2, 5.1 3, 5.1 4, 5.1 5, 5.1 6, 5.1 7, 5.1 8, 5.1 9, 5.1 1 , 5.1 4, 5, Annex C 4.3, 5.1 9, Not covered 4.5, 5.1 8, 5.1 9, 5.1 3, 4.1 , 4.2, 4.3, 5.1 2, 5.1 3, 5.1 4, 5.1 5, 5.1 6, 5.1 7, 5.1 8, 5.1 9, 5.1 1 , 5.1 6, Not covered 4, 5, 7, Annex C 2.8 4.4 1 1 2.1 2.2 2.3 2.4 2.5 Remarks / Notes In conjunction with EN 60079-0 Not applicable Not applicable Covered except of avoidance of injury by touching hot surfaces of the trace heaters or work piece for this, refer to EN 60079-30-2 BS EN 60079-30-1:2017 EN 60079-30-1 :201 (E) Essential Requirements of Directive 2.9 3.1 Clause(s) / sub-clause(s) of this EN Not covered All 3.2 3.3 3.4 Not covered 4.1 , 5.1 5, Not covered 3.5 4.1 4.2 5.1 5.2 5.3 5.4 5.5 5.6 5.8 6.1 6.2 Not covered 4, 5, 7, Annex C 4, 4.5.3.2 4.5.3.2 4.5.3.2 4.5.3.2, 4.5.3.3 Not covered 5.1 3.4.2, 5.1 3.4.3, 5.1 3.4.4 5.1 3.4.2, 5.1 3.4.3, 5.1 3.4.4, 7.3.4 Not covered 4.4 a) Not covered 6.3 6.4 6.5 2.0.1 2.0.1 2.0.1 2.0.1 2.0.2.1 2.0.2.2 2.0.2.3 2.1 1 2.1 2.1 2.1 2.1 2.1 2.2 2.1 2.3 2.2.1 2.2.1 2.2.1 2.2.2.1 Not covered 4.3, 5.1 9, Not covered Not covered Not covered Not covered Not covered Not covered Not covered Not covered Not covered Not covered Not covered Not covered Not covered Not covered 4, 4, 5, Annex C 4.4, 7.4 c) 4, 5.7 Remarks / Notes Covered by the principle of the type of protection "60079-30-1 ": Non-arcing, non-sparking, temperature limited Electric trace heating is not moving, it is intended to be firmly installed on a workpiece, for which friction does not apply Covered except of vibration Not applicable, electric trace heating is generally ohmic and cools down when deenergized BS EN 60079-30-1:2017 EN 60079-30-1 :201 (E) Essential Requirements of Directive 2.2.2.2 2.2.2.3 2.2.2.4 2.3.1 2.3.1 2.3.2.1 2.3.2.2 2.3.2.3 3.0.1 3.0.2 3.0.3 3.0.4 3.1 3.1 3.1 3.1 3.1 3.1 3.1 3.1 Clause(s) / sub-clause(s) of this EN 4, 5, Annex C 4.3, 5.1 4.4, 7.4 c) 4, 4, 5, Annex C 4, 4, 5, Annex C 4.3, 5.1 Not covered Not covered Not covered Not covered Not covered Not covered Not covered Not covered Not covered Not covered Not covered Not covered Remarks / Notes Covered Covered Covered WARNING : Presumption of conformity stays valid only as long as a reference to this European standard is maintained in the list published in the Official Journal of the European Union Users of this standard should consult frequently the latest list published in the Official Journal of the European Union WARNING 2: Other Union legislation may be applicable to the product falling within the scope of this standard 10 BS EN 60079-30-1:2017 I EC/I EEE 60079-30-1 : 201 © I EC/I EEE 201 – 51 – b) th e statem ent “After m aintenance/repair/m od ificati on , test th e operati on of th e earth-fau lt device of each affected circui t” or eq u i val ent; c) th e statem en t “I n th e even t of an earth fau lt or over cu rrent i nterru pti on , the d evice sh al l not be reset u ntil th e cause of th e trip has been in vestigated by q u alified person nel ” or eq u ival ent; d) th e statem en t “U pon com pl etion of m ain ten ance/repair/m od ificati on, th e i nsu lation resistance of th e trace h eater shal l be m easured an d recorded after i nstall ation an d sh al l not be l ess th an 20 M Ω , except th at M I trace h eaters sh all n ot be less th an M Ω (or h igh er valu es if specifi ed by th e m an ufacturer)” or eq ui val en t BS EN 60079-30-1:2017 – 52 – I EC/I EEE 60079-30-1 : 201 © I EC/I EEE 201 Annex A (informative) Type test matrix for EPLs Gb/Gc/Db/Dc (Refer to IEC 60079-1 for the relationship of EPLs to Zones) Table A d em onstrates determ in ation of test sam ples Table A.1 – Determination of test samples Quanti ty/Len gth of Samples Temperature Termination s controll er / Trace Trace Heater Integral Separate limiter Heater Pad / Panel Clause Type test Di el ectri c test 3m f X El ectri cal i nsul ati on resi stan ce test 3m f X X X X Fl am m abi l i ty test 0, 45 m f 5 5 I m pact test Room tem peratu re i m pact test Mi n i m u m tem peratu re i m pact test 0, 45 m 0, 45 m f Deform ati on test 0, 45 m f 0, 45 m f f Col d bend test Water resi stance test 3m f I n tegral com pon ents resi stance to water test 3m f a) b) Veri fi cati on of rated ou tpu t Resi stance Therm al 1 Therm al stabi l i ty of el ectri cal i nsul ati ng m ateri al Therm al perform ance test 5.1 3.4.2 5.1 3.4.5 Product classification approach d Systems approach – pipe Sculpturea,d Systems approach – vessels a,d Systems approach – tubing Bundles a,d Systems approach – plate testa,d Veri fi cati on of start-u p cu rrent m f Veri fi cati on of th e el ectri cal resi stance of el ectri cal l y cond ucti ve coveri n g 3m f Ou td oor exposu re test 0, 45 m f 5.1 3.4.3 5.1 3.4.4 a 3m 3×3m × 0, m c f ,5 m me f f e × 0,7 m or × 3,5 m or × 0,9 m or × 2,5 m U se param eters of Tabl e 2, Tabl e D orD as appropri ate b From th ree separate sam pl es c Th e l owest rated vol tage l evel and th e m axi m u m The hi gh est rated vol tag e rated power ou tpu t; an d th e m i n i m um rated power ou tpu t e f g X X f f d X f b 3m -4,5 m X X X g X X g g X X X X X Al l sam pl es i n th e upper hal f of power outpu t tol eran ce Len gth of sam pl e d eterm i n ed by th e i n stal l ati on i n stru cti ons an d test apparatu s, am oun t of sam pl es m ay vary At l east on e representati ve sam pl e i s requ i red Th e exact si ze i s to be agreed between th e testi n g stati on an d m anu facturer I f appl i cabl e as req u i red by th e test BS EN 60079-30-1:2017 I EC/I EEE 60079-30-1 : 201 © I EC/I EEE 201 – 53 – Annex B (informative) Checklist for installation Table B g ives an exam ple of a trace heater install ati on record Table B.1 – Trace heater installation record – Example Locati on System Proj ect n u m ber Referen ce d rawi ng (s) Li ne nu m ber Trace h eater n u m ber Area cl assi fi cati on Tem peratu re cl ass or m axi m u m sheath/su rface tem peratu re Pan el n um ber Locati on Ci rcui t nu m ber Ci rcui t am p/vol tage Trace h eater m anu factu rer Trace h eater m od el Trace h eater wattag e u n i t l en gth/vol tag e rati ng Veri fy certi fi cati on m arki n g: M egohm m eter m anu facturer/m odel Vol tage setti ng Accuracy/ful l scal e M egohm m eter date of l ast cal i brati on M ul ti m eter m anu facturer/m odel Oh m setti n g Accuracy/fu l l scal e TRACE HE ATER TESTING Test val u e/rem arks Date I n i ti al s N OTES M i n i m um acceptabl e i nsul ati on resi stan ce sh al l be 20 M Ω except th at for #4 bel ow for MI trace heaters the m i n im um is M Ω when m easured at the trace heater j u ncti on box Mi n i m um acceptabl e test vol tage i s 500 V d c H owever, 000 V d c recom m en ded for MI , 500 V d c for pol ym eri c trace h eaters Recei pt of m ateri al on reel Con ti n u i ty test on reel I n su l ati on resi stance test on reel Pi pi ng com pl eted (approval to start trace h eater i n stal l ati on) Trace h eater i nstal l ed (approval to start therm al i n su l ati on i n stal l ati on ) Trace h eater correctl y i n stal l ed on pi pe, vessel or eq ui pm ent Trace h eater correctl y i n stal l ed at val ves, pi pe su pports, oth er h eat si n ks Com ponen ts correctl y i nstal l ed and term i nated (power, tee-en d seal ) I nstal l ati on ag rees wi th m anu factu rer's i nstructi on s an d ci rcu i t d esi gn Therm al i n sul ati on i nstal l ati on com pl ete Con ti nu i ty test I nsu l ati on resi stan ce test (5 M Ω for MI trace heaters) SYSTEM INSPECTED Marki n g, taggi n g an d i d enti fi cati on com pl ete (see I EC/I EEE 60079-30-1 : 201 4, Cl au se 6) Trace h eater effecti vel y earth ed Tem peratu re trol s properl y i nstal l ed an d set poi n ts veri fi ed J un cti on boxes al l certi fi ed an d cl osed Therm al i n sul ati on weath er ti gh t (al l penetrati on s seal ed) End seal s, covered spl i ces m arked on i n su l ati on outer cl ad di ng 11 Drawi ngs, d ocum en tati on m arked as-bu i l t Perform ed by: Com pan y Date Witnessed by: Com pan y Date Accepted by: Com pan y Date Approved by: Com pan y Date BS EN 60079-30-1:2017 – 54 – I EC/I EEE 60079-30-1 : 201 © I EC/I EEE 201 Annex C (normative) Trace heater product design verification methodology C.1 General The determ in ati on of system tem peratures, particu l arl y prod uct sh eath tem peratures i n specified ad verse cond itions, is critical for troll ed d esigns and stabil ized desi gns of circui ts The m anufactu rer sh al l m ain tain the capabi l ity to correctl y calcul ate system tem peratures over th e range of param eters covered by th e certificati on , and to d em onstrate th is capabil ity by test an d by com parison of th e resu lts to th e system desi gn calcu lations Calcu lation m ethod olog y is typical l y based on th e use of wi d el y known an d accepted h eat transfer form u lae, wh ich are adj usted as necessary to reflect the em piri cal d ata an d wh ich typi call y i ncorporate safety factors as needed This Ann ex i nd icates th e form ulae and consid erati ons that m an ufacturers typicall y rel y on to create th eir system desi gn capabi li ty C.2 Design methodology and selection of trace heaters I t is im portan t th at th e desi gn m ethod ol og y incl ud es trace heater selection criteria to optim i ze th e d eterm i nation of th e m axim um possi ble system tem perature u n der specifi ed ad verse d itions as specified i n th is stan dard Th e tem perature m ay be red u ced , for exam ple, through adj ustm ents to the system param eters, by th e use of m ultipl e tracers to red uce th e power prod uced per u n it len gth , or by the sel ecti on of th e tem perature trol system The m axim um withstan d tem perature of th e trace heaters sh al l be greater th an th e m axim um possible workpi ece tem perature (wh ich m ay be greater th an the norm al operati n g tem perature) As i nd icated i n , th e m axim um sheath tem peratures of trace h eaters are determ in ed by th e product classification m eth od , by stabil i zed desig n , or by troll ed d esi g n For the prod uct classificati on m ethod, furth er tem perature l im itin g trol m easures are n ot necessary, provided th at the tem perature cl ass of th e trace h eater is lower in tem perature th an th at specified for th e appl icati on N evertheless the control l im iti ng an d stabi l ized d esi gn m easures can be appli ed to operate the system in a narrower band of process tem peratures The consi d erations for stabi l i zed design an d for trol led d esig n are sim i lar, with a need i n both cases to accuratel y determ in e th e system heat loss an d th e m axim um system and sh eath tem peratures I n the case of stabi l i zed d esign, th e eval uation of en erg y balance of the system is add i tion all y n ecessary C.3 Stabilized design calculations Stabili zed d esi gn is based on th e princi ple of d eterm in i ng th e m axim um workpi ece an d trace heater sh eath tem peratu res un d er specified ad verse d iti ons Th is is a calcu lati on of the eq u i libri um d iti ons that occur wh en th e h eat i n pu t equ als the system h eat l oss The specified ad verse d iti ons inclu de: a) m axim um am bien t tem perature, typi call y assum ed to be 40 °C u n less otherwise specifi ed ; c) no win d (sti l l air); d) use of a conservative or m in im um valu e for the therm al ducti vity of th e th erm al i nsu l ati on ; BS EN 60079-30-1:2017 I EC/I EEE 60079-30-1 : 201 © I EC/I EEE 201 – 55 – e) no tem perature control by d esign or to sim u late a fai led tem perature control ler; f) th e trace h eater is operated at i ts stated operati ng vol tage plus % ; g) th e trace h eater is assum ed to be operati n g at the u pper l im it of th e m an ufacturing tol erance, or at th e m in i m um specific resistance for seri es trace h eaters h) th e m axim um runaway workpi ece tem perature, or th e m axim um eq ui libri um process tem perature if greater Testi n g for stabi li zed design is gi ven i n Typical l y th e m axim um sheath tem perature of th e trace h eater is calcu l ated from form ulae d eri ved from th e eval u ati on of em pirical d ata, or by the theoretical approach d escribed bel ow Al ternati vel y, d esi gn program s th at calcu l ate th e m axim um sheath tem perature on the basis of th ese specifi ed ad verse param eters m ay be used C.4 Trace heater performance and equilibrium conditions Depen d in g on the applicati on an d th e type of h eat tracin g, it m ay be n ecessary to evalu ate th e system at equ i l ibriu m condi tions Trace heati ng system s wi th n o trols and trace heati n g system s with am bient sensin g trols are typi cal exam pl es Fi gu re C sh ows exam ples of power ou tput curves for constant wattag e trace h eaters an d for PTC (positive tem perature coeffici en t) trace heaters wi th d ifferen t slope characteristics The h eat l oss l in e represents th e d ition s th at occur at th e lowest am bi ent tem peratu re This ill ustrates that th e constan t wattage trace heater m ain tai ns th e workpi ece at th e h ig h est tem perature (80 ° C), bu t si nce i t also h as th e h igh est outpu t (32 W/m) it also h as th e h i g h est operatin g tem perature Th e PTC trace heater wi th th e steepest slope m aintai ns th e workpi ece at th e l owest tem perature (50 ° C), but also h as the lowest ou tpu t (23 W/m ) an d therefore the lowest operati n g tem perature 50 45 40 Power output W/m 35 30 25 20 15 10 –20 –1 0 10 20 30 40 50 60 70 80 90 00 110 20 Pipe temperature °C Constant wattage PTC-2 PTC-1 Heat loss IEC Figu re C.1 – Equilibriu m conditions for workpiece maintenance Figu re C shows th e sam e exam pl e, but from th e perspecti ve of evaluating the u pper lim its I n th is case the h eat l oss l i ne is shifted to the h ig h est possible am bien t, and th e crossi n g poi nts i l lu strate th e m n tai n tem perature an d rel ative power ou tpu ts at th ese cond i ti ons Th e PTC-1 trace h eater n ow has a h ig h er m aintain tem perature th an before (91 ° C), but th e ou tpu t level h as decreased (1 W/m ) due to th e decreasin g slope of th e ou tpu t cu rve Th is sam e BS EN 60079-30-1:2017 – 56 – I EC/I EEE 60079-30-1 : 201 © I EC/I EEE 201 approach m ay be used when eval uatin g th e u pper lim it operati n g cond ition s for the stabi l ized desig n approach 50 45 40 Power output W/m 35 30 25 20 15 10 –20 –1 0 10 20 30 40 50 60 70 80 90 00 110 20 Pipe temperature °C Constant wattage PTC-2 PTC-1 Heat loss IEC Figu re C.2 – Equilibriu m conditions for upper limit evaluation The power ou tpu t levels of d ifferen t trace h eaters are typicall y provi ded by th e m anufacturer i n the product l iterature an d /or in a desi gn program I n m ost cases, th e output curves for th e PTC trace h eater types are d efi ned based on em pirical d ata from test fi xtures correl ated to th e test of The ou tpu t of seri es type trace heaters is typical l y defin ed from i ts electrical param eters b y usin g the followi n g form ul a: Q = V rs l (C ) wh ere Q is the power ou tpu t of th e trace heater (W/m ); V is the system voltage (V); r is the specific resistance of each cond uctor (ohm /m ); l is the len gth of each ductor (m ) s The specific resistance of th e cond uctor is a fu nction of th e cond uctor tem perature, as gi ven by th e form ul a: rs = r(1 + α ∆T ) wh ere r is the resistance of th e d uctor at 20 °C (ohm /m ); (C 2) BS EN 60079-30-1:2017 I EC/I EEE 60079-30-1 : 201 © I EC/I EEE 201 – 57 – α is the al pha coefficien t for the type of m aterial of the d uctor (1 /K); ∆T is th e difference between th e tem perature of th e d uctor in th e operati ng state an d 20 °C (K) I t is im portant to recogn i ze th at th e fol l owin g characteristics of a trace heati ng system sh ou ld exist for th e i nstal l ati on to be successful : a) The ou tput of th e trace h eater(s) shou l d be greater th an the system heat l oss incl ud i n g a su itable safety factor Th i s can be ach ieved by i nstalli n g a sin gle trace h eater wi th su itable ou tpu t, by usin g m ultiple passes, or by spirali n g i f need ed to keep th e outpu t level as low as possi bl e b) Poten tial voltage devi ati ons or other chan ges in system param eters over tim e sh oul d be determ in ed an d com pensated for by th e safety factor c) The u pper l im it of th e system shal l be eval uated for appl icati ons wh ere process tem perature accuracy is critical, or th at have a wi de rang e of am bien t temperatures, or for system s that h ave n o control or that h ave am bi en t sensi n g trol C.5 Heat loss calculations To d eterm in e actu al h eat l osses for a gi ven set of cond i ti ons, a com pl ete insu l ati on specification, includ i n g th e therm al d ucti vity of th e i nsu lati on at several m ean tem peratures, the type of weath er barri er specified, i nsu lati on si ze and th ickness, desired pipe m ain ten ance tem perature, an d th e am bient tem perature and win d d iti ons, is req u ired Gi ven th ese param eters, the h eat l oss for pipes and tu bes m ay be evaluated by Eq u ati on (C 3): q= ln ( D / D1 ) + + pD1 hi 2pk1 (Tp − Ta ) ln (D3 / D ) 1 + + pk pD3 h co pD3 h o (C 3) wh ere q is the h eat loss per u n it l en g th of pi pe (W/m ); Tp is the d esired m aintenan ce tem perature (° C); Ta is the specifi ed desi g n am bient tem perature (°C); D1 is the insi de di am eter of the in n er i nsul ati on l ayer (m ); D2 is the ou tsi d e d iam eter of the in n er i nsul ati on l ayer (m ), (i nsi de d i am eter of the ou ter i nsu l ation layer wh en presen t); D3 is the ou tsi d e d iam eter of the ou ter insu lati on layer (m ), (when presen t); k1 is th e th erm al cond ucti vity of th e in ner layer of insu lati on eval uated at i ts m ean tem perature (W/m K); ∙ k2 is th e th erm al cond ucti vity of the outer layer of insu lation, wh en present, evalu ated at its m ean tem perature (W/m K); ∙ hi is th e i nsid e air tact coeffici en t from the workpiece to the in ner insu l ati on surface wh en present (W/m K); ∙ h co is th e insi de air tact coefficient from th e ou ter insu lation surface to the weather barri er wh en present (W/m K); ∙ BS EN 60079-30-1:2017 – 58 – I EC/I EEE 60079-30-1 : 201 © I EC/I EEE 201 is th e ou tsid e air fi lm coeffici ent from the weath er barrier to am bient (W/m K) (typi cal valu es for th is term range from W/m K to 50 W/m K for l ow-tem perature applications below 50 ° C) ho ∙ ∙ ∙ The h eat loss for pi pes an d tu bes is described i n m ore d etai l, wi th an exam pl e, i n I EC/I EEE 60079-30-2 Fol lowi n g the sam e process, th e heat l oss for vessels m ay be eval uated by Eq uation (C 4): q= (Tp − Ta ) b1 b 1 + + + + k2 hco ho hi k1 (C 4) wh ere q is the h eat loss per u n it area of vessel (W/m ); b is the th ickness of th e i n ner insu l ation layer (m ); b is the th ickness of th e ou ter insu lati on layer (m ), (wh en present) Oth er term s are defin ed wi th form u la (3) The heat loss for vessels is descri bed in m ore d etail in I EC/I EEE 60079-30-2 For ease of prod uct sel ecti on, trace h eati ng su ppl iers often furn ish sim ple ch arts and graphs of h eat losses for vari ous m n tai n tem peratures and insu l ati ons, wh ich usual l y i nclud e a safety factor C.6 Heat loss desi gn safety factor Since h eat loss calcu lati ons based on th eoretical val u es n ot accoun t for im perfections associ ated wi th actu al work si te i nstallations, a safety factor sh ou ld be appl i ed to the calcu l ated valu es Th e safety factor sh ou ld be based u pon th e user’s req ui rem en ts th at typi call y ran ge from % to 25 % The ad d ition of a safety factor is used to com pensate for tolerances i n the trace heati ng system Safety factors sh ou l d be consi d ered for: a) th erm al insu lation d egrad ation ; b) suppl y voltage variations; c) branch wi rin g voltage drop; d) trace h eater voltage d rop; e) i ncreased rad i ati on an d vecti on on h ig h er tem perature appl ications; f) qu al ity of i nstal lation of therm al i nsu l ati on C.7 C.7 Maximum temperature determination Theoreti cal pi pe and sh eath temperatu re calculations – M etallic applications The m axim um possi ble pipe tem perature is calcul ated at m axim um am bient tem perature with th e trace h eater continu ousl y en ergi zed The form ula for calcu l ating th e m axim um poten ti al pipe tem perature is a rearrang em en t of th e term s of th e heat l oss form u la: Tpr = Qsf ln (D2 / D1 ) ln (D3 / D2 ) 1 + + + + + Ta p D1 hi k1 k2 D2 hco D2 ho (C 5) BS EN 60079-30-1:2017 I EC/I EEE 60079-30-1 : 201 © I EC/I EEE 201 – 59 – wh ere Tpr is the m axim um calcu lated ru naway pi pe tem perature (°C); Q sf is th e trace h eater ou tput For determ in ing tem perature cl asses for stabil i zed desi gn , Q sf is th e h i gh est d ecl ared power outpu t at the m axim um m anufactu rer’s output tolerance (W/m ), adj usted for 1 % of rated voltage; Ta is the m axim um specifi ed d esign am bient tem perature (°C) Oth er term s are d efi ned wi th form ula (3) I terati ve tech n iq u es m ay n eed to be appl i ed to the calcu l ation of form ula (5) in order to arrive at Tpr , since th e th erm al d ucti vity of the i nsu l ati on an d the trace h eater ou tpu t m ay be a fu ncti on of pi pe tem perature The sheath tem perature of th e trace h eater sh all be calcu lated as fol l ows, usi ng th e equ ati on for Tpm if Tpm is greater than Tpr: Tsh = Q sf + Tpr UC or Tsh = Q sf + Tpm UC (C 6) and (C 7) wh ere Tsh is the trace heater sheath tem perature (° C); U is th e overal l h eat tran sfer coefficient (W/m K) which is an em pirically d eterm in ed valu e; C is the trace heater circumference (m ); Tpr is the m axim um calcu lated ru naway pi pe tem perature (°C); ∙ Tpm is the m axim um declared process tem perature (° C) The overal l heat transfer coeffici en t is d ifferen t for each trace h eater type, i nstal lation m eth od an d system configurati on I t is a com bin ation of cond uctive, vective an d rad iation h eat transfer m od es Th e val u e of U can vary from for a cyli n drical trace heater i n air (prim ari l y vective), to 70 or m ore for a trace heater appli ed usin g h eat tran sfer ds (prim ari l y ducti ve) U pon req u est, the trace heati n g su ppli er sh ou ld provid e th e U-factor for gi ven applications, or furn ish calcu l ated or experim en tal l y d eterm in ed sheath tem peratures The power ou tpu t Q sf of th e trace h eater selected sh all provi de th e stabil ized d esi gn an d Tsh shall n ot exceed th e temperature cl ass C 7.2 Theoretical vessel and sheath tem peratu re cal cul ations – M etal li c appli cations Sim ilarl y, for vessels, th e m axim um possible vessel tem perature is calcu lated at m axim um am bi en t tem perature wi th th e trace h eater ti n uousl y en ergi zed The form ula for calcu l ati ng th e m axim um poten tial vessel tem perature is a rearran gem en t of th e term s of th e heat l oss form ula: b1 b2 1 + + + + Twr = Qsf + Ta h k k h h co o i (C 8) wh ere Twr is the m axim um calcu lated ru naway vessel tem perature (°C); Q sf is the trace h eater outpu t For d eterm in ing tem perature cl asses for stabi li zed desi gn, Q sf is th e hi ghest decl ared power ou tpu t at the m axim um m anufactu rer’s ou tpu t tol erance (W/m ), adj usted for 1 % of rated vol tage; BS EN 60079-30-1:2017 – 60 – Ta I EC/I EEE 60079-30-1 : 201 © I EC/I EEE 201 is the m axim um specifi ed d esig n am bient tem perature (°C) Other term s are defin ed above I terati ve tech n iq u es m ay n eed to be appl ied to the calcu l ati on of form ula (8) i n ord er to arrive at Twr, si nce th e th erm al d ucti vi ty of th e i nsu l ati on an d the trace h eater outpu t m ay be a fu ncti on of th e tem perature of the vessel The sh eath tem perature of th e trace heater pad or pan el sh all be calcu lated as foll ows, usi n g th e equ ati on for Twm if Twm is greater than Twr: Tsh = Qsf + T wr U or Tsh = Qsf + T wm U (C 9) and (C 0) wh ere Tsh U Twr Twm is the trace heater sheath tem perature (° C); is th e overal l h eat tran sfer coefficient (W/m K) which is an em piricall y d eterm in ed valu e; ∙ is the m axim um calcu lated ru naway vessel tem perature (°C); is the m axim um decl ared process tem perature (° C) The overall heat transfer coeffici en t is d ifferen t for each trace h eater type, instal lation m eth od an d system config urati on I t is a com bi n ati on of cond ucti ve, vecti ve an d rad iation h eat transfer m od es Th e val ue of U can vary from for a trace heater in air (prim ari l y vecti ve), to 70 or m ore for a trace heater appl i ed usin g h eat tran sfer ds (prim ari l y d ucti ve) U pon req u est, the trace heati n g su ppl i er sh ou l d provid e th e U-factor for g iven applications, or furn ish calcu l ated or experim en tal l y d eterm in ed sheath tem peratures The power outpu t Q sf of th e trace h eater selected over th e com bi nation of h eat loss q an d heat transfer from th e tracer, sh all provi de the stabil i zed d esi gn and ensure th at Tsh sh al l not exceed th e tem perature cl ass or an y oth er m aximum tem perature l im itati ons l isted above C.7.3 Sheath temperature – metallic applications utilizing a temperature limiter control sensing the trace heater sheath or an artificial hot spot When the l im iter control sensor is l ocated d irectl y on the trace h eater th e fol lowi n g shall be i nclu ded i n the eval u ati on of sheath tem peratures: Tsh = TL + ∆ Toffset (C 1 ) wh ere TL ∆ Toffset C.7.4 is the set poin t of th e tem perature l im iter is th e em piricall y d eterm ined tem perature d ifference between the sensor an d th e actu al m axim um tracer sheath tem perature ∆ Toffset is a function of variabl es such as g eom etry an d m ass of th e trace h eater an d sensor, power outpu t of th e trace heater, h eat transfer coeffici ent, an d control system hysteresis Theoretical sheath temperature calcu lations – Non-metallic applications For non-m etallic appl ications, th e workpiece wal l therm al resistance shou l d be consid ered, as th e n on-m etal lic m ateri al is a poor heat transfer med i um These m aterials m ay h ave a therm al d ucti vity (k-factor) /200 of th at of steel, an d a substan tial tem perature d ifference m ay devel op across the pipe or tank wall depen d in g on th e trace h eater power density Th is h i gh er th an n orm al tem perature (wh en com pared to tracin g m etallic pipes an d vessels) m ay h ave two ad verse effects: BS EN 60079-30-1:2017 I EC/I EEE 60079-30-1 : 201 © I EC/I EEE 201 – 61 – a) th e n on-m etall ic workpiece m axim um al lowabl e tem perature m ay be exceeded ; b) th e trace h eater m axim um al lowabl e tem peratu re m ay be exceeded The sh eath tem perature of th e trace h eater un d er norm al operatin g d i ti ons is i n pri nci pl e obtain ed from form ulae (6), (7), (9) or (1 0) H owever, i n obtain i n g th e effect of th e th erm al resistance of th e workpi ece wall sh oul d be i nclu d ed The overal l heat transfer coefficient for a plastic surface is: U, U p = U m + L (C 2) p k wh ere p is the overal l heat transfer coefficient for a non -m etal l ic pipe (W/m K); m is the overal l heat transfer coefficient for a m etall ic workpi ece (W/m ); U U ∙ is the workpiece wall th ickness, in m etres (m ); L p k is the th erm al cond ucti vi ty of workpi ece wal l m ateri al (W/m K) ∙ Because of th e ad dition al therm al resistance of th e n on-m etal lic m ateri al, a tem perature d ifference exists across th e workpiece wal l; th at is, the outsi de workpiece wal l an d flu i d tem perature are not th e sam e as i n th e case of a m etal l ic workpi ece Th erefore, flu id tem perature sh oul d be consi d ered For n on-m etall ic pipe, th en : sh = Q T U sf p C (C 3) + f T wh ere Q sf f T is th e trace heater output For d eterm i ni n g tem perature classes for stabil i zed d esig n , sf is th e h ig h est d eclared power ou tpu t at th e m axim um m anufacturer’s outpu t tol erance (W/m), adj usted for 1 % of rated voltage; Q is the flu id tem perature (° C) Sim ilarl y, for n on-m etal l ic vessels, th e eq u ati on is: sh = T Q sf + f p (C 4) T U wh ere Q sf is th e trace h eater ou tput For d eterm i n in g tem perature cl asses for stabili zed d esi gn , sf is the h igh est d eclared power ou tpu t at the m axim um m anufactu rer’s outpu t tol erance (W/m ), adj usted for 1 % of rated vol tage; Q f T is the fl u id tem perature (° C) Form ulae (1 3) an d (1 4) represent a conservati ve sim pl ification of a com plex probl em th at in vol ves cri teria beyon d th e scope of th is stan dard The trace h eati ng m anufacturer sh al l provi d e sh eath tem perature data for specific appli cati ons The power ou tpu t of th e trace h eater selected sh al l provi de the stabi li zed d esig n an d not exceed the tem perature class or an y oth er m axim um tem peratu re lim itations sh T shal l BS EN 60079-30-1:2017 – 62 – C.7.5 I EC/I EEE 60079-30-1 : 201 © I EC/I EEE 201 Sheath temperature – non-metallic applications utilizing a temperature limiter control sensing the trace heater sheath or an artificial hot spot When the lim iter control sensor is l ocated d irectly on the trace h eater th e fol l owin g shal l be incl u ded i n the evalu ati on of sheath tem peratures: Tsh = TL + ∆Toffset (C 9, repeated ) wh ere TL ∆ Toffset is the set poin t of th e tem perature lim iter is the em piricall y d eterm ined tem perature d ifference between th e sensor an d the actu al m axim um tracer sheath tem perature ∆ Toffset is a function of vari ables such as geom etry an d m ass of th e trace heater an d sensor, power ou tput of th e trace h eater, heat transfer coefficien t, an d control system h ysteresis Text deleted BS EN 60079-30-1:2017 I EC/I EEE 60079-30-1 : 201 © I EC/I EEE 201 63 – –– 69 Bibliograph y ASTM D5207, Sta n da rd pra ctice for co n firm a tio n of 20 m m (50 W) a n d 25 m m (500 W) te st fla mes for sm a ll-sca le b urn in g tests on p la stic m a teria ls CSA C22 , Ca n a dia n Ele ctrica l Co de, Pa rt CSA C22 N o 30-03, Re quire m en ts for e lectrica l re sista n ce h e a tin g ca b les a n d h e a tin g device se ts I EC 60079-7, I EC 62395-1 , Exp losive a tm osph eres – Pa rt 7: Electrica l resista n ce tra ce Equip m en t protection by in crea se d sa fe ty "e " he a tin g syste ms for in dustria l and com m ercia l for in dustria l and com m ercia l a p p lica tion s – Pa rt : G e n era l a n d testin g re quire me n ts I EC 62395-2, Electrica l resista n ce tra ce h e a tin g syste ms a p p lica tion s – Pa rt 2: A p p lica tion guide for syste m design , in sta lla tion a n d m a in te n a n ce I EEE Std 51 5™ , IEEE Sta n da rd for th e Testin g, Design , In sta lla tion , and Ma in te n a n ce of Electrica l Resista n ce Tra ce He a tin g for In dustria l A pp lica tion s I EEE Std 51 ™ , IEEE Sta n da rd for the Testin g, Design , In sta lla tion , a n d Ma in te n a n ce of Ele ctrica l Re sista n ce Tra ce He a tin g for Com mercia l A pp lica tion s N FPA 70, Na tion a l Ele ctrica l Code ® (NEC®) I EC/I EEE 60079-30-2, Exp losive a tmosp here s – Pa rt 30-2: Electrica l resista n ce tra ce h ea tin g – A pp lica tion guide for design , in sta lla tion a n d m a in te n a n ce _ _ National Electrical Code and NEC are b oth registered trademarks of the National Fire Protection Association, Inc This page deliberately left blank NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW British Standards Institution (BSI) BSI is the national body responsible for preparing British Standards 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