ISO INTERNATIONAL STANDARD 21013-3 Secondedition 2016-05-01 Cryogenic vessels Pressure-relief accessories for cryogenic service Part 3: Sizing and capacity determination Récipients cryogéniques - Dispositifs de sécurite pour le service cryogenique- Partie 3: Détermination de la taille et du volume Reference number ISO 21013-3:2016(E) ISO International Organization for Standardization @ IS0 2016 HEJIANG INST OF STANDARDIZATION C1 5956617 IS0 21013-3:2016(E) COPYRIGHTPROTECTEDDOCUMENT IS0 2016, Published in Switzerland All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below or ISO's member body in the country of the requester. ISO copyrightoffice Ch. de Blandonnet 8 . CP 401 CH-1214 Vernier, Geneva, Switzerland Tel. +41 22 749 01 11 Fax +41 22 749 09 47 [email protected] www.iso.org Intenationaibr PrganizationforStandardization ensee-ZHEJIANG INST.OF STANDARDIzARoISQ16- All rights reserved etworking permitted without license from IHS IS0 21013-3:2016(E) Contents Page Foreword ..V 1 Scope .1 2 Normative references ..1 3 Symbols 4 Calculation of the total quantity of heat transferred per unit time from the hot wall (outer jacket) to the cold wall (inner vessel) 6 4.1 General 4.2 Under conditions other than fire. .6 4.2.1 Vacuum-insulated vessels under normal vacuum 4.2.2 Pressure build-up device .7 4.2.3 Vacuum-insulated vessels in the case of loss of vacuum and non-vacuum insulated vessels .7 4.2.4 Supports and piping. .9 4.3 Under fire conditions. .9 4.3.1 Insulation system remains fully or partially in place during fire conditions .9 4.3.2 Insulation systemdoesnotremain inplaceduringfireconditions .10 4.4 Air or Nitrogen condensation.. .10 4.4.1 General. 10 4.4.2 Loss of vacuum with air and nitrogen ..10 4.4.3 Fire with loss of vacuum with air or nitrogen .11 4.5 Heat transfer per unit time (watts) .12 4.5.1 General ..12 4.5.2 Normal operation. .12 4.5.3 Pressure build up regulator fully open ..12 4.5.4 Lossofvacuumcondition. ..12 4.5.5 Fire condition with loss of vacuum, vacuum jacket, and insulation fully or partially in place.. ..13 4.5.6 Fire condition with loss of vacuum, insulation not in place. .13 4.5.7 Total heat transfer rate. ..13 5 Calculation of the mass flow to be relieved by pressure relief devices. .13 5.1 Relieving pressure, P, less than the critical pressure ..13 5.2 Relieving pressure, P, equal to or greater than the critical pressure. ..14 5.3 Example.... ..14 6 Piping for pressure relief devices. ..15 6.1 Pressure drop. .15 6.1.1 General ..15 6.1.2 Relief valves .15 6.1.3 Bursting discs .15 6.2 Back pressure consideration ..16 6.3 Heattransfer. .16 7 Sizing of pressure relief devices .17 7.1 General .17 7.2 Sizing of pressure relief valves ..17 7.2.1 Discharge capacity. ..17 7.2.2 Determination of critical vs. subcritical flow for gases ..18 7.2.3 Criticalflow .18 7.2.4 Subcritical flow .19 7.2.5 Recommended analysis method .20 7.2.6 Example 22 7.3 Sizing of bursting discs . .26 7.3.1 Discharge capacity. ..26 iii see=ZHEJIANG INST OF STANDARDIZATION C1 5956617 ed withoutlicense from IHS Not for Resale, 2016/7/20 08:14:23