IEC/IEEE 60079 30 1 Edition 1 0 201 5 09 INTERNATIONAL STANDARD Explosive atmospheres – Part 30 1 Electrical resistance trace heating – General and testing requirements IE C /I E E E 6 0 0 7 9 3 0 1 2[.]
I E C /I E E E 60 -3 -1 ® Edition 201 5-09 I N TE RN ATI ON AL S TAN D ARD colour i n sid e E xpl os i ve atm os ph ere s – IEC/IEEE 60079-30-1 :201 5-09(en) P art -1 : E l ectri cal res i s tan ce trace h eati n g – G e n eral an d tes ti n g req u i rem en ts T H I S P U B L I C AT I O N I S C O P YRI G H T P RO T E C T E D C o p yri g h t © I E C , G e n e v a , S wi tz e rl a n d C o p yri g h t © I E E E All rights reserved Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing being secured Requests for permission to reproduce should be addressed to either IEC at the address below or IEC’s member National Committee in the country of the requester or from IEEE IEC Central Office 3, rue de Varembé CH-1 21 Geneva 20 Switzerland Tel.: +41 22 91 02 1 Fax: +41 22 91 03 00 info@iec.ch www.iec.ch I nstitute of Electrical and Electronics Engineers, I nc Park Avenue New York, NY 001 6-5997 United States of America stds.ipr@ieee.org www.ieee.org Ab ou t th e I E C The I nternational Electrotechnical Commission (I EC) is the leading global organization that prepares and publishes I nternational Standards for all electrical, electronic and related technologies Ab ou t th e I EE E IEEE is the world’s largest professional association dedicated to advancing technological innovation and excellence for the benefit of humanity IEEE and its members inspire a global community through its highly cited publications, conferences, technology standards, and professional and educational activities Ab ou t I E C/I EE E pu bl i cati on s The technical content of IEC/IEEE publications is kept under constant review by the IEC and IEEE Please make sure that you have the latest edition, a corrigendum or an amendment might have been published I E C Catal og u e - webstore i ec ch /catal og u e The stand-alone application for consulting the entire bibliographical information on IEC International Standards, Technical Specifications, Technical Reports and other documents Available for PC, Mac OS, Android Tablets and iPad I E C pu bl i cati on s s earch - www i ec ch /search pu b The advanced search enables to find IEC publications by a variety of criteria (reference number, text, technical committee,…) It also gives information on projects, replaced and withdrawn publications E l ectroped i a - www el ectroped i a org The world's leading online dictionary of electronic and electrical terms containing more than 30 000 terms and definitions in English and French, with equivalent terms in additional languages Also known as the International Electrotechnical Vocabulary (IEV) online I E C G l os sary - s td i ec ch /g l oss ary More than 60 000 electrotechnical terminology entries in English and French extracted from the Terms and Definitions clause of IEC publications issued since 2002 Some entries have been collected from earlier publications of IEC TC 37, 77, 86 and CISPR I E C J u st Pu bl i s h ed - webstore i ec ch /j u stpu bl i sh ed Stay up to date on all new IEC publications Just Published details all new publications released Available online and also once a month by email I E C C u stom er S ervi ce C en tre - webstore i ec ch /cs c If you wish to give us your feedback on this publication or need further assistance, please contact the Customer Service Centre: csc@iec.ch I E C /I E E E 60 -3 -1 ® Edition 201 5-09 I N TE RN ATI ON AL S TAN D ARD colour i n sid e E xpl os i ve atm os ph ere s – P art -1 : E l ectri cal res i s tan ce trace h eati n g – G e n eral an d tes ti n g req u i rem en ts INTERNATIONAL ELECTROTECHNICAL COMMISSION ICS 29.260.20 ISBN 978-2-8322-2758-9 Warn i n g ! M ake su re th a t you obtai n ed th i s pu bl i cati on from an au th ori zed d i s tri bu tor ® Registered trademark of the International Electrotechnical Commission –2– I EC/I EEE 60079-30-1 : 201 © I EC/I EEE 201 CONTENTS FOREWORD I NTRODUCTI ON 1 Scope 1 Norm ative references Terms and definitions General requirements 22 General 22 Mechanical strength 22 Terminations and connections 23 4 Circuit protection requirements for branch circuits 23 Temperature requirements 23 General 23 Stabilized design 24 Controlled design 24 Testing 26 Type tests 26 General 26 Dielectric test 26 Electrical insulation resistance test 27 Flamm ability test 27 I m pact tests 29 Deform ation test 32 Cold bend test 32 Water resistance test 33 I ntegral components resistance to water test 33 Verification of rated output 34 1 Thermal stability of electrical insulating m aterial 36 Thermal performance test 36 Determ ination of m axim um sheath temperature 38 Verification of start-up current 46 Verification of the electrical resistance of electricall y conductive covering 46 Outdoor exposure test 47 Routine tests 47 Dielectric test 47 2 Verification of rated output 47 Marking 47 Product markings for trace heaters 47 Markings for field assem bled com ponents 48 Documentation requirements 48 General 48 Circuit design docum entation 48 Trace heating system documentation 49 General 49 I EC/I EEE 60079-30-1 : 201 –3– © I EC/I EEE 201 For trace heating system s according to the product classification method 49 3 For trace heating system s according to stabilized design method 49 For trace heating system s according to controlled design m ethod 49 I nstructions for installation of trace heating system 50 I nstructions for com m issioning 50 I nstructions for maintenance / repair or modification 50 Annex A (informative) Type test m atrix for EPLs Gb/Gc/Db/Dc (Refer to I EC 60079-1 for the relationship of EPLs to Zones) 52 Annex B (informative) Checklist for installation 53 Annex C (norm ative) Trace heater product design verification m ethodology 54 C General 54 C Design m ethodology and selection of trace heaters 54 C Stabilized design calculations 54 C Trace heater perform ance and equilibrium conditions 55 C Heat loss calculations 57 C Heat loss design safety factor 58 C Maximum temperature determ ination 58 C Theoretical pipe and sheath tem perature calculations – Metallic applications 58 C Theoretical vessel and sheath temperature calculations – Metallic applications 59 C Sheath tem perature – m etallic applications utilizing a tem perature limiter control sensing the trace heater sheath or an artificial hot spot 60 C Theoretical sheath temperature calculations – N on-m etallic applications 60 C Sheath tem perature – non-metallic applications utilizing a tem perature limiter control sensing the trace heater sheath or an artificial hot spot 62 Annex D (norm ative) Requirements for Division and Division trace heating systems 63 D Application 63 D General 63 D Terminations and connections 63 D Control and tem perature requirem ents 63 D General 63 D Stabilized design 63 D Controlled design 64 D 4 Requirem ents for protective device in Divisions and 64 D Type tests 64 D Division trace heating equipm ent 64 D Division equipm ent 65 D Marking 65 D I nstructions – I nstallation requirements 65 Annex E (normative) Type test m atrix for Division and explosive atm ospheres 67 Bibliograph y 69 Figure Figure Figure Figure – Flamm ability test 28 – Exam ple of room tem perature im pact test 30 – Exam ple of minim um temperature impact test 31 – Cold bend test 33 –4– Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure I EC/I EEE 60079-30-1 : 201 © I EC/I EEE 201 5 – I ntegral components resistance to water test 34 – Verification of rated output 35 – Maxim um sheath temperature using product classification approach 39 – Verification of sheath tem peratures using pipe sculpture 41 – Verification of sheath tem perature, plate test 44 – Verification of sheath tem perature – plate test with serpentined sample 44 1 – Plate test with two samples crossed over 45 – Plate test with a single sample crossed over 46 C.1 – Equilibrium conditions for workpiece maintenance 55 C.2 – Equilibrium conditions for upper lim it evaluation 56 Table – Application or exclusion of specific clauses of I EC 60079-0 1 Table – Sheath tem perature design conditions based on equipment protection levels – Stabilized design approach 24 Table – Sheath tem perature design conditions based on equipm ent protection levels EPLs – Controlled design approach 25 Table – Test voltages for the dielectric test 26 Table A – Determination of test samples 52 Table B – Trace heater installation record – Example 53 Table D – Division trace heating system s 63 Table D – Sheath temperature design conditions – Stabilized design approach 64 Table D – Sheath temperature design conditions – With tem perature control device 64 Table E – Applicable trace heater and trace heater pads and panels tests by installation location 67 Table E – Applicable tests for integral components with trace heaters and trace heater pads and panels 68 I EC/I EEE 60079-30-1 : 201 © I EC/I EEE 201 –5– INTERNATI ONAL ELECTROTECHNI CAL COMMISSI ON E XP L O S I VE AT M O S P H E RE S – P a rt -1 : E l e c tri c a l re s i s ta n c e tra c e h e a ti n g – G e n e l a n d te s ti n g re q u i re m e n ts FOREWORD ) The I nternati on al Electrotechni cal Comm ission (I EC) is a worl d wid e organization for stan dardization com prisin g all n ation al el ectrotechnical comm ittees (I EC National Comm ittees) The object of I EC is to prom ote internati onal co-operation on all q uestions concerni ng stand ardi zati on in the el ectrical an d electronic fi elds To this en d and in additi on to other acti vities, I EC pu blish es I nternational Stan dards, Techn ical Specificati ons, Technical Reports, Publicl y Avail abl e Specificati ons (PAS) an d Gu ides (h ereafter referred to as “I EC Publication(s)”) Th ei r preparation is entrusted to tech nical comm ittees; any I EC N ational Comm ittee interested in the subj ect dealt with m ay partici pate in this preparatory work I nternational, governm ental an d n on governm ental org ani zati ons liai sing with the I EC also participate in this preparation I EEE Standards d ocum ents are devel oped within I EEE Societies and Standards Coordi nati n g Com m ittees of the I EEE Standards Association (I EEE-SA) Standards Board I EEE devel ops its standards throug h a consensus developm ent process, approved by the Am erican N ational Stand ards I nstitute, which bri ngs togeth er vol unteers representin g varied viewpoints and interests to ach ieve the fi nal prod uct Volu nteers are n ot n ecessaril y m em bers of I EEE and serve without com pensati on While I EEE adm inisters the process and establ ishes ru les to prom ote fairness in th e consensus d evelopm ent process, I EEE does not i ndependentl y eval uate, test, or verify the accuracy of any of the i nform ation contained in its standards Use of I EEE Stan dards d ocum ents is whol ly voluntary IEEE docume n ts a re m a de a va ila ble fo r use sub je ct to imp orta n t n otice s a n d le ga l discla im e rs (se e http: //stan dards ieee org/I PR/disclaim ers htm l for mo re in forma tion ) I EC collaborates closel y with I EEE in accord ance with cond itions d eterm ined by agreem ent between the two organi zati ons This Dual Logo I ntern ational Stand ard was j ointl y developed by the I EC and I EEE under the term s of that agreem ent 2) The form al decisions of I EC on technical m atters express, as nearl y as possibl e, an intern ation al consensus of opin ion on the rel evant subj ects since each technical com m ittee has representati on from all interested I EC National Com m ittees The form al d ecisions of I EEE on technical m atters, once consensus within I EEE Societies and Stand ards Coordi nating Comm ittees has been reached, is determ ined by a bal anced ball ot of m ateriall y interested parties who ind icate interest i n reviewing the proposed stan dard Fi nal approval of the I EEE standards docum ent is given by the I EEE Standards Associati on (I EEE-SA) Stan dards Board 3) I EC/I EEE Publications have the form of recom m endations for internati onal use an d are accepted by I EC National Com m ittees/I EEE Societies in that sense While al l reason abl e efforts are m ade to ensure that the technical content of I EC/I EEE Publications is accurate, I EC or I EEE cannot be h eld responsible for th e way i n which th ey are used or for an y m isinterpretation by an y en d u ser 4) I n order to prom ote intern ational u niform ity, I EC National Com m ittees und ertake to apply I EC Publications (inclu din g I EC/I EEE Publications) transparentl y to the m axi m um extent possibl e i n their n ation al and regi onal publ ications An y di verg ence between an y I EC/I EEE Publication and the correspondi ng national or reg ion al publ ication sh all be clearl y ind i cated in th e latter 5) I EC an d I EEE n ot provid e any attestati on of conform ity I ndepen dent certification bodi es provi de conform ity assessm ent services and, i n som e areas, access to I EC m arks of conform ity I EC and I EEE are not responsibl e for an y services carri ed out by independent certificati on bodi es 6) All users should ensure that th ey h ave the l atest editi on of thi s publicati on 7) No liability shall attach to I EC or I EEE or their di rectors, em ployees, servants or ag ents includin g indivi du al experts and m em bers of techn ical comm ittees and I EC N ational Com m ittees, or volunteers of I EEE Societies and th e Standards Coordi nati ng Com m ittees of the I EEE Stand ards Association (I EEE-SA) Standards Board, for an y personal inju ry, property d am age or other d am age of any n ature whatsoever, wh eth er direct or in direct, or for costs (inclu ding l egal fees) and expenses arising out of the publication, use of, or reli ance u pon, thi s I EC/I EEE Publication or an y other I EC or I EEE Publicati ons 8) Attention is d rawn to the norm ative references cited in this publicati on Use of the referenced publicati ons is indispensable for the correct applicati on of this publication 9) Attention is d rawn to the possibility that im plem entation of this I EC/I EEE Publication m ay requi re use of m aterial covered by patent ri ghts By publicati on of this stand ard, no position is taken with respect to th e existence or vali dity of any patent rights i n connection th erewith I EC or I EEE shall not be h el d responsibl e for identifyin g Essential Patent Cl aim s for wh ich a license m ay be requ ired, for cond ucting in qui ries into th e legal val i dity or scope of Patent Claim s or determ inin g wheth er any licensin g term s or conditions provided i n connection with su bm ission of a Letter of Assurance, if an y, or in any l icensing agreem ents are reason abl e or non -discrim inatory Users of th is standard are expressly advi sed that determ ination of the validity of an y patent rig hts, and th e risk of infri ng em ent of such ri ghts, is entirel y th eir own responsibil ity –6– I EC/I EEE 60079-30-1 : 201 © I EC/I EEE 201 International Standard I EC/I EEE 60079-30-1 has been prepared by I EC technical comm ittee 31 : Equipment for explosive atmospheres, in cooperation with the Petroleum & Chem ical Industry Committee of the I EEE I ndustrial Applications Society under the I EC/I EEE Dual Logo Agreement This publication is published as an I EC/I EEE Dual Logo standard NOTE A list of I EEE participants can be found at the foll owi ng U RL: http: //standards ieee org/downl oads/60079/60079-30-1 -201 5/60079-30-1 -201 5_wg-participants pdf This first edition of I EC/I EEE 60079-30-1 cancels and replaces the first edition of I EC 6007930-1 published in 2007 and constitutes a technical revision This edition includes the following significant changes, apart from the general revision and updating of the first edition of I EC 60079-30-1 and harm onization with I EEE Std 51 5, with respect to the previous edition: • • • • • • • • • • the inclusion of a minimum tem perature impact test; the addition of a mechanical procedure in the therm al stability test; the inclusion of a therm al perform ance test to replace the thermal safety requirements; the inclusion of a second procedure utilizing a plate fixture for sheath temperature determ ination; the inclusion of an ultraviolet and condensation test; the revision and significant expansion of documentation requirem ents; the addition of Annexes covering requirem ents for Divisions and 2; the addition of a table covering the applicability of requirements from I EC 60079-0; the addition of an Annex covering trace heater product design verification m ethodology (form erl y located in I EC 60079-30-2); the further harm onization of this edition with several national standards The significance of changes between I EC 60079-30-1 , Edition (2007) and I EC/I EEE 60079-30-1 , Edition (201 5) is as listed below: Type Changes Clause M inor and editorial changes Addition of clarification for th e exclusi on of EPLs Ga and Da Addition of requi rem ents for th e Di vision m ethod of area classification th at m ay be appl ied by som e users Addition of tabl e specifying the applicati on or exclusi on of specific clauses of I EC 60079-0 Edition X For stabi lized d esigns, a clarifi cation for the n eed for verification by testing and th e additi on of a tabl e for the specific requi rem ents X For controll ed desig ns, a clarifi cation for the n eed for verification by testing and th e additi on of a tabl e for the specific requi rem ents X For controll ed desig ns, clarifications and additi ons on the separate requi rem ents for Gb/Db and Gc/Dc The requirem ents for calibration of the flam m ability test fixture are repl aced with equi val ent req uirem ents for the energ y levels of the test gases Addition of a m inim um tem perature im pact test Exten sion M ajor techni cal changes X X X X C1 I EC/I EEE 60079-30-1 : 201 © I EC/I EEE 201 –7– Type Changes Clause M inor and editorial changes Exten sion M ajor techni cal changes For therm al stability, the additi on of a ben din g req uirem ent on a m and rel 1 C1 The repl acem ent of the therm al safety procedu re with a therm al perform ance proced ure C2 The additi on of a second procedure utili zi ng a plate fi xture for the system s m ethod for m axim um sheath tem peratu re d eterm ination C3 Addition of outdoor exposure test C4 Requirem ent chan ged for th e m arking of the m inim um installati on tem perature C5 Addition of new m arkings requ i rements for fiel d assem bled com ponents C5 Additions and ch an ges to the d ocum entation req uirem ents C5 Addition of Ann ex Annex A X Addition of Ann ex Annex B X Addition of Ann ex specifyi ng trace heating desig n verification m ethodol og y, m oved from I EC 60079-30-2 Annex C Addition of Ann ex for the Di visi on m ethod of area classification that m ay be appli ed by som e users Annex D X Addition of Ann ex for the Di visi on m ethod of area classification that m ay be appli ed by som e users Annex E X C6 NOTE The technical ch ang es referred to inclu de the sig nificance of technical chang es in the revised I EC Standard, but they d o not form an exh austive list of all m odifications from the previous version Explanations: A) Definitions M inor 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 requirem ents without any technical change, or a reduction in level of existing requirem ent Extension addition of technical options These are changes which add new or modify existing technical requirem ents, in a way that new options are given, but without increasing requirements for equipm ent that was full y com pliant with the previous standard Therefore, these will not have to be considered for products in conform ity with the preceding edition –8– M aj o r te ch n i ca l I EC/I EEE 60079-30-1 : 201 © I EC/I EEE 201 ch an g e s 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 clause B) below NOTE These ch an ges represent current techn ological kn owled ge However, these ch an ges shou ld not n orm ally have an influ ence on equi pm ent alread y pl aced on the m arket B) I n fo rm a t i o n a b o u t t h e b a c kg ro u n d o f ‘ M a j o r T e c h n i c a l Ch an g es ’ C1 – The requirem ents for additional mechanical testing have been included for harm onization and for added safety C2 – The requirements for thermal performance have been included to recognize the necessity for therm al 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 C4 – An outdoor exposure test has been added to cover products that m ay be exposed to sunlight and m oisture in the intended application C5 – Additional m arking and documentation requirements have been added to provide additional information to the end user C6 – The trace heating design verification m ethodolog y has been added to align with the evaluation requirem ents for the stabilized design and the controlled design m ethods of maxim um sheath tem perature determination The text of this standard is based on the following I EC docum ents: FDI S Report on votin g 31 /1 91 /FDI S 31 /1 201 /RVD Full information on the voting for the approval of this standard can be found in the report on voting indicated in the above table I nternational standards are drafted in accordance with the rules given in the I SO/I EC Directives, Part This standard is intended to be used in conjunction with I EC/I EEE 60079-30-2: 201 5, Explosive atmospheres – Part 30-2: Electrical resistance trace heating – Application guide for design, installation and maintenance A list of all parts of I EC 60079 series, under the general title Explosive atmospheres, can be found on the I EC website – 58 – I EC/I EEE 60079-30-1 : 201 © I EC/I EEE 201 is the outside air film coefficient from the weather barrier to am bient (W/m K) (typical values for this term range from W/m K to 50 W/m K for low-tem perature applications below 50 °C) ho ∙ ∙ ∙ The heat loss for pipes and tubes is described in more detail, with an example, in I EC/I EEE 60079-30-2 Following the same process, the heat loss for vessels may be evaluated by Equation (C.4): q= (Tp − Ta ) b1 b 1 + + + + hi k1 k2 hco ho (C 4) where q is the heat loss per unit area of vessel (W/m ); b is the thickness of the inner insulation layer (m ); b is the thickness of the outer insulation layer (m), (when present) Other terms are defined with formula (3) The heat loss for vessels is described in m ore detail in I EC/I EEE 60079-30-2 For ease of product selection, trace heating suppliers often furnish sim ple charts and graphs of heat losses for various maintain temperatures and insulations, which usuall y include a safety factor C.6 Heat loss design safety factor Since heat loss calculations based on theoretical values not account for im perfections associated with actual work site installations, a safety factor should be applied to the calculated values The safety factor should be based upon the user’s requirem ents that typicall y range from % to 25 % The addition of a safety factor is used to compensate for tolerances in the trace heating system Safety factors should be considered for: a) b) c) d) e) f) thermal insulation degradation; suppl y voltage variations; branch wiring voltage drop; trace heater voltage drop; increased radiation and convection on higher temperature applications; quality of installation of thermal insulation C.7 C.7.1 Maximum temperature determination Theoretical pipe and sheath temperature calculations – Metallic applications The m axim um possible pipe tem perature is calculated at m axim um ambient temperature with the trace heater continuously energized The formula for calculating the m axim um potential pipe temperature is a rearrangement of the terms of the heat loss formula: Tpr = ln (D2 / D1 ) ln (D3 / D2 ) 1 Qsf + + + + + Ta p D1 hi k1 k2 D2 hco D2 ho (C 5) I EC/I EEE 60079-30-1 : 201 © I EC/I EEE 201 where – 59 – Tpr is the maxim um calculated runaway pipe tem perature (°C); Q sf is the trace heater output For determining temperature classes for stabilized design , Q sf is the highest declared power output at the maximum manufacturer’s output tolerance (W/m), adj usted for 1 % of rated voltage; Ta is the m axim um specified design am bient temperature (°C) Other terms are defined with formula (3) I terative techniques m ay need to be applied to the calculation of form ula (5) in order to arrive at Tpr, since the therm al conductivity of the insulation and the trace heater output may be a function of pipe temperature The sheath tem perature of the trace heater shall be calculated as follows, using the equation for Tpm if Tpm is greater than Tpr: Tsh = Q sf + Tpr UC or Tsh = Q sf + Tpm UC (C 6) and (C 7) where Tsh is the trace heater sheath temperature (°C); U is the overall heat transfer coefficient (W/m K) which is an em pirically determined value; C is the trace heater circumference (m ); Tpr is the maximum calculated runaway pipe temperature (°C); ∙ Tpm is the maxim um declared process tem perature (°C) The overall heat transfer coefficient is different for each trace heater type, installation method and system configuration I t is a com bination of conductive, convective and radiation heat transfer modes The value of U can vary from for a cylindrical trace heater in air (primaril y convective), to 70 or more for a trace heater applied using heat transfer aids (primaril y conductive) U pon request, the trace heating supplier should provide the U-factor for given applications, or furnish calculated or experim entall y determ ined sheath temperatures The power output Q sf of the trace heater selected shall provide the stabilized design and Tsh shall not exceed the temperature class C.7.2 Theoretical vessel and sheath temperature calculations – Metallic applications Sim ilarly, for vessels, the m axim um possible vessel temperature is calculated at m axim um ambient tem perature with the trace heater continuousl y energized The form ula for calculating the maximum potential vessel temperature is a rearrangem ent of the term s of the heat loss formula: b1 b2 1 Twr = Qsf + + + + + Ta h k k h h co o i (C 8) where Twr Q sf is the maxim um calculated runaway vessel temperature (°C); is the trace heater output For determining temperature classes for stabilized design, Q sf is the highest declared power output at the maximum manufacturer’s output tolerance (W/m ), adj usted for 1 % of rated voltage; – 60 – Ta I EC/I EEE 60079-30-1 : 201 © I EC/I EEE 201 is the m axim um specified design am bient temperature (°C) Other terms are defined above I terative techniques may need to be applied to the calculation of formula (8) in order to arrive at Twr, since the therm al conductivity of the insulation and the trace heater output may be a function of the temperature of the vessel The sheath tem perature of the trace heater pad or panel shall be calculated as follows, using the equation for Twm if Twm is greater than Twr: Tsh = Qsf + T wr or Tsh U = Qsf + T wm U (C 9) and (C 0) where Tsh is the trace heater sheath temperature (°C); U is the overall heat transfer coefficient (W/m K) which is an empirically determ ined value; ∙ Twr is the m axim um calculated runaway vessel temperature (°C); Twm is the m aximum declared process tem perature (°C) The overall heat transfer coefficient is different for each trace heater type, installation m ethod and system configuration I t is a combination of conductive, convective and radiation heat transfer modes The value of U can vary from for a trace heater in air (primaril y convective), to 70 or m ore for a trace heater applied using heat transfer aids (prim aril y conductive) U pon request, the trace heating supplier should provide the U-factor for given applications, or furnish calculated or experim entally determined sheath temperatures The power output Q sf of the trace heater selected over the combination of heat loss q and heat transfer from the tracer, shall provide the stabilized design and ensure that Tsh shall not exceed the temperature class or an y other m aximum temperature limitati ons listed 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 limiter control sensor is located directly on the trace heater the following shall be included in the evaluation of sheath tem peratures: Tsh = TL + ∆ Toffset (C 1 ) where TL ∆ Toffset is the set point of the temperature limiter is the empiricall y determined temperature difference between the sensor and the actual maximum tracer sheath temperature ∆ Toffset is a function of variables such as geom etry and m ass of the trace heater and sensor, power output of the trace heater, heat transfer coefficient, and control system hysteresis C.7.4 Theoretical sheath temperature calculations – Non-metallic applications For non-m etallic applications, the workpiece wall thermal resistance should be considered, as the non-metallic material is a poor heat transfer medium These m aterials m ay have a therm al conductivity (k-factor) /200 of that of steel, and a substantial tem perature difference may develop across the pipe or tank wall depending on the trace heater power density This higher than norm al temperature (when com pared to tracing metallic pipes and vessels) m ay have two adverse effects: I EC/I EEE 60079-30-1 : 201 – 61 – © I EC/I EEE 201 a) the non-m etallic workpiece m aximum allowable temperature may be exceeded; b) the trace heater m aximum allowable tem perature may be exceeded The sheath tem perature of the trace heater under norm al operating conditions is in principle obtained from formulae (6), (7), (9) or (1 0) H owever, in obtaining the effect of the therm al resistance of the workpiece wall should be included The overall heat transfer coefficient for a plastic surface is: U, U p = U m + L (C 2) p k where U p U m is the overall heat transfer coefficient for a non-m etallic pipe (W/m K); ∙ is the overall heat transfer coefficient for a metallic workpiece (W/m ); is the workpiece wall thickness, in m etres (m); L p k is the therm al conductivity of workpiece wall m aterial (W/m K) ∙ Because of the additional therm al resistance of the non-metallic m aterial, a tem perature difference exists across the workpiece wall; that is, the outside workpiece wall and fluid temperature are not the same as in the case of a m etallic workpiece Therefore, fluid temperature should be considered For non-metallic pipe, then: sh = sf + f p (C 3) Q T T U C where Q sf f T is the trace heater output For determining temperature classes for stabilized design, sf is the highest declared power output at the m axim um manufacturer’s output tolerance (W/m), adjusted for 1 % of rated voltage; Q is the fluid tem perature (°C) Sim ilarl y, for non-m etallic vessels, the equation is: sh = T Q sf + f p (C 4) T U where Q sf is the trace heater output For determining tem perature classes for stabilized design, sf is the highest declared power output at the maximum manufacturer’s output tolerance (W/m ), adj usted for 1 % of rated voltage; is the fluid tem perature (°C) Q f T Formulae (1 3) and (1 4) represent a conservative simplification of a complex problem that involves criteria beyond the scope of this standard The trace heating manufacturer shall provide sheath tem perature data for specific applications The power output of the trace heater selected shall provide the stabilized design and sh shall not exceed the tem perature class or an y other maximum temperature limitations T – 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 located directly on the trace heater the following shall be included in the evaluation of sheath tem peratures: Tsh = TL + ∆Toffset (C 9, repeated) where is the set point of the temperature lim iter TL ∆ Toffset is the empiricall y determined tem perature difference between the sensor and the actual maximum tracer sheath tem perature ∆ Toffset is a function of variables such as geom etry and mass of the trace heater and sensor, power output of the trace heater, heat transfer coefficient, and control system h ysteresis I EC/I EEE 60079-30-1 : 201 © I EC/I EEE 201 – 63 – Annex D (normative) Requirements for Division and Division trace heating systems D.1 Application The Division method of area classification, including the indication of Classes I , I I , or I I I for explosive atm ospheres for gases, dusts, or fibres/fl yings respectivel y, m ay be applied by som e users of this standard Trace heating system s identified for Division are not intended for installation in applications where ignitable concentrations of flammable gases or vapors, or combustible dusts, or ignitable fibers or fl yings are present continuousl y or for long periods of time NOTE I nform ation on th e Di vi sion m ethod is gi ven i n NFPA 70 and CSA C22 D.2 General Trace heating system s identified for Divisions shall com pl y with the requirem ents for the EPL shown in Table D.1 , supplemented or modified by the requirem ents shown in D through D Table D.1 – Division trace heating systems Division D.3 Equipment protection level (EPL) Class I , Division ‘Gb’ Class I I , I I I Division ‘Db’ Class I , Division ‘Gc’ Class I I , I I I Division ‘Dc’ Terminations and connections Where possible, trace heater term inations and connections are intended to be located outside explosive atmospheres classified as Division I n case this is not possible, the terminations and connections in addition to the trace heater shall be identified for installation in Division areas D.4 D.4.1 Control and temperature requirements General The Class, Division, Group, and minimum gas, dust or fiber/fl ying autoignition tem perature for the location shall be specified As an alternative to autoignition tem perature, the tem perature class indicated in NFPA 70 and CSA C22.1 may be specified D.4.2 Stabilized design Table D defines the design conditions for the Division m ethod of area classification for the stabilized design approach – 64 – T ab l e D – S h e ath t e m p e t u re d e s i g n I EC/I EEE 60079-30-1 : 201 © I EC/I EEE 201 c o n d i ti o n s – S tab i l i z e d Cl as s I , I tem D i vi s i o n Percent of rated voltag e Maxim um workpiece tem peratu re for calculati on d es i g n II or I I I D i vi s i o n 110 110 a - a - Maxim um win d speed for calcu lation a p p ro a c h Sheath tem peratures for Divi sion shall be cal cul ated u sing m inim um heat transfer coefficient, U, without heat transfer ds The workpiece tem perature ( Tpr or Tp m , whichever is g reater) used to calcu late the m axim um sheath tem peratu re – see Ann ex C a D C o n t ro l l e d d esi gn The application of tem perature control to limit sheath tem peratures varies by area classification as indicated below and in Table D a) Class I , I I or I I I Division – temperature controller and high temperature limiter b) Class I , I I or I I I Division – tem perature controller T a b l e D – S h e ath t e m p e t u re d e s i g n c o n d i t i o n s – W i t h t e m p e t u re c o n t ro l Cl ass I , I tem D i vi s i o n Percent of rated voltag e II or I II D i vi s i o n 110 Maxim um workpiece tem peratu re for calculati on - Maxim um win d speed for calcul ation d evi ce 110 a - a or b 0 Sheath tem peratu res for Di visi on shall be calculated using m inim um heat transfer coefficient, U, without heat transfer ds a b D 4 Use the set point of the applicable protecti ve d evice (tem perature l im iter) Use the set point of the applicable tem peratu re controll er R e q u i re m e n t s fo r p ro t e c t i v e d e v i c e i n D i vi s i o n s an d The requirem ents of 4.4 appl y for trace heating to be used in areas classified using the Division method For Division equipment, the requirem ents of 4.5 also appl y except that the trace heating is to be suitable for the appropriate Class For Division trace heating, the requirements of 3 also appl y except that the trace heating is to be suitable for the appropriate Class D D D T yp e t e s t s D i vi s i on t c e h e a t i n g eq u i pm en t G e n e l Trace heaters shall be tested for increased im pact energ y and static m echanical load The requirements for system components other than integral components are covered in other applicable standards for equipm ent for use in Class I , I I or I I I , Division locations The following tests are intended to qualify trace heaters and integral com ponents (if appl icable) for application in these explosive atm ospheres and are required in addition to all the type tests described in The test samples needed for the type tests are sum marized in Annex E I EC/I EEE 60079-30-1 : 201 © I EC/I EEE 201 D V e ri fi c a t i o n – 65 – o f s h e a t h t e m p e t u re s The sheath tem perature test described in 5.1 shall be conducted at the conditions defined in Tables D and D 3, and the resultant sheath temperatures shall not exceed the declared temperature class or the maximum predicted sheath tem perature D M e ch a n i c a l t yp e t e s t s The deform ation test as described in 5.1 shall be conducted at 000 N The im pact test as described in 5.2 shall be conducted retaining the same impact area at an impact energ y of 27, J D D i vi s i o n D eq u i pm en t G e n e l The requirem ents for system components other than integral components are covered in other standards for equipm ent for use in the respective Class I , I I , or I I I Division locations The following test is intended to qualify trace heaters for use in these explosive atm ospheres and is required in addition to the type tests described in D V e ri fi c a t i o n o f s h e a t h t e m p e t u re s The sheath temperature test described in shall be conducted at design conditions defined in Tables D and D.3, and the resultant sheath temperature shall not exceed the declared temperature class or m aximum sheath temperature D M a rki n g This requirement supplem ents the requirements of Trace heaters shall be clearl y and perm anentl y surface marked to indicate Class, Division, Group(s), and Tem perature Class D I n s t ru c t i o n s – I n s t a l l a t i o n re q u i re m e n t s I n addition to the documentation requirem ents specified in Clause 7, the instructions and/or other documentation shall include the following information: a) The person(s) responsible for installation shall verify that the installation and inspection are perform ed by personnel who are trained, qualified, and knowledgeable in trace heating systems when using the Division m ethod of area classification The installation and inspection shall be in accordance with the system m anufacturer’s design docum ents, product recomm endations, and installation instructions; the installation checklist (see Annex B) shall be followed rigorousl y b) The proposed installation shall be verified for the proper selection of trace heaters and com ponent system s identified for the application; i e Division or Division The m anufacturer’s docum entation shall be reviewed for specific installation requirements and the proposed installation shall be verified that the heating system is com patible with the environment c) For Division installations onl y, each seal fitting shall be lim ited to one trace heater or power lead I n addition, it is required that a seal fitting be installed in the power supply circuit cable, or conduit imm ediately adj acent to the trace heater power connection box d) Earth-fault equipm ent protective devices intended for use with trace heating circuits in Division areas shall be appropriatel y identified for use in Division areas – 66 – I EC/I EEE 60079-30-1 : 201 © I EC/I EEE 201 e) For Division installations onl y, the person(s) responsible for the installation shall complete and retain a document similar in form at to the installation checklist in Annex B at the installation for future reference during maintenance and repair f) For Division installations, the minimum requirement for all insulation resistance tests according to item d) shall be at least 20 M Ω I EC/I EEE 60079-30-1 : 201 © I EC/I EEE 201 – 67 – Annex E (normative) Type test matrix for Division and explosive atmospheres Table E.1 – Applicable trace heater and trace heater pads and panels tests by installation location Clause Type test Division Division Diel ectric test X X Electrical insul ation resistance test X X Flamm ability test X X I m pact test Room tem peratu re im pact test X X Min im um tem perature im pact test X X Deform ation test X X Cold bend test X X Water resistance test X X I ntegral com pon ents resistance to water test X X Verification of rated output X X 1 Therm al stability of electrical i nsulatin g m aterial X X Therm al X X Prod uct classification approach X X System s approach – pi pe sculpture X X System s approach – vessels X X 4 System s approach – tubi ng bu ndles X X System s approach – pl ate test X X Verification of start-up cu rrent X X Verification of the electrical resistance of electrical ly conducti ve coverin g X X Outdoor exposu re test X X D Class I , I I and I I I Divisi on l ocations D Verification of sheath tem peratures X D Mech anical type tests X D Class I , I I and I I I Divisi on l ocations D 2 Verification of sheath tem peratures X – 68 – I EC/I EEE 60079-30-1 : 201 © I EC/I EEE 201 Table E.2 – Applicable tests for integral components with trace heaters and trace heater pads and panels Clause Type test Division Division Diel ectric test X X Electrical insul ation resistance test X X Flamm ability test X X I m pact test Room tem peratu re im pact test X X Min im um tem perature im pact test X Deform ation test X Water resistance test X X I ntegral com pon ents resistance to water test X X 1 Therm al stability of electrical i nsulatin g m aterial X X Verification of the electrical resistance of electrical ly conducti ve coverin g X X Outdoor exposu re test X X D Class I , I I and I I I Divisi on l ocations D Mech anical type tests X I EC/I EEE 60079-30-1 : 201 © I EC/I EEE 201 – 69 – Bibliography ASTM D5207, Sta n da rd pra ctice for firm a tion of 20 m m (50 W) a n d 25 m m (500 W) test fla mes for sm a ll-sca le b urn in g tests o n p la stic m a teria ls CSA C22 , Ca n a dia n Electrica l Code , Pa rt CSA C22 No 30-03, Re quire m en ts for e lectrica l resista n ce h ea tin g ca b les a n d h e a tin g device se ts I EC 60079-7, IEC 62395-1 , Exp losive a tm osph eres – Pa rt 7: Electrica l resista n ce tra ce Equip m e n t protectio n by in crea se d sa fe ty "e " he a tin g syste ms for in dustria l and co m m e rcia l for in dustria l and co m m ercia l ap p lica tio n s – Pa rt : G e n era l a n d te stin g re quire me n ts IEC 62395-2, Electrica l resista n ce tra ce he a tin g syste ms ap p lica tion s – Pa rt 2: A p p lica tio n guide for syste m de sign , in sta lla tio n a n d m a in te n a n ce IEEE Std 51 5™ , IEEE Sta n da rd for th e Te stin g, De sign , 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 IEEE Std 51 ™ , IEEE Sta n da rd for the Testin g, Design , In sta lla tio n , a n d Ma in te n a n ce of Electrica l Resista n ce Tra ce He a tin g for Com mercia l A pp lica tion s NFPA 70, Na tion a l Electrica l Co de® (NEC®) I EC/I EEE 60079-30-2, Exp losive a tmosp he res – Pa rt 30-2: Electrica l resista n ce tra ce h ea tin g – A pp lica tio n guide for design , in sta lla tio n a n d m a in te n a n ce _ _ National Electrical C ode and NEC are b oth registered trademarks of the National Fire Protection Association, Inc INTERNATIONAL ELECTROTECHNICAL COMMISSI ON 3, rue de Varembé PO Box 31 CH-1 21 Geneva 20 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