Cryogenic vessels - Pressure-relief accessories for cryogenic service - Part 3: Sizing and capacity determination (ISO 21013-3:2016)

This standard provides a separate calculation method for determining the contributing mass flow to be relieved resulting from each of the following specified conditions: - vacuum insulated vessels with insulation system (outer jacket + insulating material) intact under normal vacuum. Outer jacket at ambient temperature. Inner vessel at temperature of the contents at the relieving pressure; - vacuum insulated vessels with insulation system remaining in place but with loss of vacuum, or non vacuum insulated vessels with insulation system intact. Outer jacket at ambient temperature. Inner vessel at temperature of the contents at the relieving pressure; - vacuum or non vacuum insulated vessels with insulation system remaining fully or partially in place, but with loss of vacuum in the case of vacuum insulated vessels, and fire engulfment. Inner vessel at temperature of the contents at the relieving pressure; - vessels with insulation system totally lost and fire engulfment. Good engineering practice based on well established theoretical physical science shall be adopted to determine the contributing mass flow where an appropriate calculation method is not provided for an applicable condition.

Kryo-Behälter - Druckentlastungseinrichtungen für den Kryo-Betrieb - Teil 3: Bestimmung von Größe und Durchfluss (ISO 21013-3:2016)

Récipients cryogéniques - Dispositifs de sécurité pour le service cryogénique - Partie 3: Détermination de la taille et du volume (ISO 21013-3:2016)

ISO 21013-3:2016 établit des méthodes de calcul distinctes permettant de déterminer le débit massique à décharger pour chacune des conditions spécifiées suivantes:
-      récipients isolés sous vide comportant un système d'isolation (enveloppe extérieure + matériau isolant) intact sous vide normal, enveloppe extérieure à température ambiante, récipient intérieur à la température du contenu à la pression de décharge spécifiée;
-      récipients isolés sous vide comportant un système d'isolation (enveloppe extérieure + matériau isolant) intact sous vide normal, enveloppe extérieure à température ambiante, récipient intérieur à la température du contenu à la pression de décharge spécifiée, régulateur de pression du système de mise en pression fonctionnant à pleine charge;
-      récipients isolés sous vide ou non, comportant un système d'isolation restant en place mais avec perte de vide en cas de récipients isolés sous vide, enveloppe extérieure à température ambiante, récipient intérieur à la température du contenu à la pression de décharge spécifiée, ou récipients isolés sous vide ou non, comportant un système d'isolation restant totalement ou partiellement en place, mais avec perte de vide dans le cas des récipients isolés sous vide, feu environnant, récipient intérieur à la température du contenu à la pression de décharge spécifiée;
-      récipients isolés sous vide contenant des fluides avec une température de saturation inférieure à 75 K à 1 bar avec un système d'isolation restant en place, mais avec perte de vide avec de l'air ou de l'azote dans l'espace sous vide;
-      récipients isolés sous vide contenant des fluides avec une température de saturation inférieure à 75 K à 1 bar avec un système d'isolation restant en place, mais avec perte de vide avec de l'air ou de l'azote dans l'espace sous vide avec feu environnant;
-      récipients avec perte totale du système d'isolation et feu environnant.
Il est nécessaire qu'une bonne pratique d'ingénierie reposant sur des données de physique théorique bien établies soit adoptée afin de déterminer le débit massique requis lorsqu'aucune méthode de calcul appropriée n'est fournie pour une condition donnée.
Des Recommandations concernant les dispositifs de décharge de pression pour cryostats sont données dans l'Annexe A.

Kriogene posode - Oprema za razbremenitev tlaka za kriogene namene - 3. del: Določanje velikosti in pretoka (ISO 21013-3:2016)

Ta standard določa ločeno računsko metodo za določanje prispevka masnega pretoka, ki se sprosti kot posledica vsakega od naslednjih določenih pogojev: – vakuumsko izolirane posode z izolacijskim sistemom (zunanja obloga + izolacijski material), ki je nepoškodovan pri normalnem tlaku. Zunanja obloga pri temperaturi v prostoru. Notranja posoda pri temperaturi vsebine pri tlaku za razbremenitev; – vakuumsko izolirane posode z izolacijskim sistemom, ki ostanejo na mestu, a izgubijo vakuum, ali nevakuumsko izolirane posode z nepoškodovanim izolacijskim sistemom. Zunanja obloga pri temperaturi v prostoru. Notranja posoda pri temperaturi vsebine pri tlaku za razbremenitev; – vakuumsko ali nevakuumsko izolirane posode z izolacijskim sistemom, ki delno ali v celoti ostanejo na mestu, a izgubijo vakuum v primeru vakuumsko izoliranih posod in v primeru izpostavljenosti ognju. Notranja posoda pri temperaturi vsebine pri tlaku za razbremenitev; – posode s povsem izgubljenim izolacijskim sistemom in v primeru izpostavljenosti ognju. Za določanje prispevka masnega pretoka, če ločena računska metoda ni na voljo za zadevno stanje, je treba uporabiti dobro inženirsko prakso.

General Information

Status
Published
Public Enquiry End Date
11-Jan-2015
Publication Date
11-Oct-2016
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
26-Sep-2016
Due Date
01-Dec-2016
Completion Date
12-Oct-2016

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Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN ISO 21013-3:2016
01-november-2016
1DGRPHãþD
SIST EN 13648-3:2003
.ULRJHQHSRVRGH2SUHPD]DUD]EUHPHQLWHYWODND]DNULRJHQHQDPHQHGHO
'RORþDQMHYHOLNRVWLLQSUHWRND ,62

Cryogenic vessels - Pressure-relief accessories for cryogenic service - Part 3: Sizing and

capacity determination (ISO 21013-3:2016)

Kryo-Behälter - Druckentlastungseinrichtungen für den Kryo-Betrieb - Teil 3: Bestimmung

von Größe und Durchfluss (ISO 21013-3:2016)

Récipients cryogéniques - Dispositifs de sécurité pour le service cryogénique - Partie 3:

Détermination de la taille et du volume (ISO 21013-3:2016)
Ta slovenski standard je istoveten z: EN ISO 21013-3:2016
ICS:
13.240 Varstvo pred previsokim Protection against excessive
tlakom pressure
23.020.40 Proti mrazu odporne posode Cryogenic vessels
(kriogenske posode)
SIST EN ISO 21013-3:2016 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 21013-3:2016
---------------------- Page: 2 ----------------------
SIST EN ISO 21013-3:2016
EN ISO 21013-3
EUROPEAN STANDARD
NORME EUROPÉENNE
June 2016
EUROPÄISCHE NORM
ICS 23.020.40 Supersedes EN 13648-3:2002
English Version
Cryogenic vessels - Pressure-relief accessories for
cryogenic service - Part 3: Sizing and capacity
determination (ISO 21013-3:2016)

Récipients cryogéniques - Dispositifs de sécurité pour Kryo-Behälter - Druckentlastungseinrichtungen für

le service cryogénique - Partie 3: Détermination de la den Kryo-Betrieb - Teil 3: Bestimmung von Größe und

taille et du volume (ISO 21013-3:2016) Durchfluss (ISO 21013-3:2016)
This European Standard was approved by CEN on 15 April 2016.

CEN 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 CEN

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 CEN member into its own language and notified to the CEN-CENELEC Management

Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,

Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,

Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and

United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels

© 2016 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 21013-3:2016 E

worldwide for CEN national Members.
---------------------- Page: 3 ----------------------
SIST EN ISO 21013-3:2016
EN ISO 21013-3:2016 (E)
Contents

European foreword ....................................................................................................................................................... 3

Annex ZA (informative) Relationship between this European Standard and the Essential

Requirements of EU Directive (2014/68/UE — Pressure Equipment Directive) .................................. 4

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SIST EN ISO 21013-3:2016
EN ISO 21013-3:2016 (E)
European foreword

This document (EN ISO 21013-3:2016) has been prepared by Technical Committee ISO/TC 220

“Cryogenic vessels” in collaboration with Technical Committee CEN/TC 268 “Cryogenic vessels and

specific hydrogen technologies applications” the secretariat of which is held by AFNOR.

This European Standard shall be given the status of a national standard, either by publication of an

identical text or by endorsement, at the latest by December 2016, and conflicting national standards

shall be withdrawn at the latest by December 2016.

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent

rights.
This document supersedes EN 13648-3:2002.

This document has been prepared under a mandate given to CEN by the European Commission and the

European Free Trade Association, and supports essential requirements of EU Directive.

For relationship with EU Directive, see informative Annex ZA, which is an integral part of this

document.

According to the CEN-CENELEC Internal Regulations, the national standards organizations of the

following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,

Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia,

France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta,

Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland,

Turkey and the United Kingdom.
Endorsement notice

The text of ISO 21013-3:2016 has been approved by CEN as EN ISO 21013-3:2016 without any

modification.
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SIST EN ISO 21013-3:2016
EN ISO 21013-3:2016 (E)
Annex ZA
(informative)
Relationship between this European Standard and the Essential
Requirements of EU Directive (2014/68/UE — Pressure Equipment
Directive)

This European Standard has been prepared under a mandate given to CEN by the European

Commission to provide a means of conforming to Essential Requirements of the New Approach

Directive (2014/68/UE – Pressure Equipment Directive)

Once this standard is cited in the Official Journal of the European Union under that Directive and has

been implemented as a national standard in at least one Member State, compliance with the clauses of

this standard given in Table ZA.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 ZA.1 — Correspondence between this European Standard and Directive (2014/68/UE –

Pressure Equipment Directive)

Clause(s)/subclause(s) of this EN Essential Requirements (ERs) of Qualifying remarks/Notes

Directive …
4, 5 Protection against exceeding the Annex I, 2.10
allowable limits of pressure
equipment
6, 7 Safety accessories Annex I, 2.11
4.3 External fire Annex I, 2.12

WARNING — Other requirements and other EU Directives may be applicable to the product(s) falling

within the scope of this standard.
---------------------- Page: 6 ----------------------
SIST EN ISO 21013-3:2016
INTERNATIONAL ISO
STANDARD 21013-3
Second edition
2016-05-01
Cryogenic vessels — Pressure-relief
accessories for cryogenic service —
Part 3:
Sizing and capacity determination
Récipients cryogéniques — Dispositifs de sécurité pour le service
cryogénique —
Partie 3: Détermination de la taille et du volume
Reference number
ISO 21013-3:2016(E)
ISO 2016
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SIST EN ISO 21013-3:2016
ISO 21013-3:2016(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 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 copyright office
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO 2016 – All rights reserved
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SIST EN ISO 21013-3:2016
ISO 21013-3:2016(E)
Contents Page

Foreword ..........................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Symbols .......................................................................................................................................................................................................................... 2

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 ........................................................................................................................................................................................................... 6

4.2 Under conditions other than fire ............................................................................................................................................. 6

4.2.1 Vacuum-insulated vessels under normal vacuum .............................................................................. 6

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 system does not remain in place during fire conditions .................................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 Loss of vacuum condition ......................................................................................................................................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 Heat transfer ..........................................................................................................................................................................................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 Critical flow .......................................................................................................................................................................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

© ISO 2016 – All rights reserved iii
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SIST EN ISO 21013-3:2016
ISO 21013-3:2016(E)

7.3.2 Determination of critical vs. subcritical flow for gases ...............................................................27

7.3.3 Critical flow .......................................................................................................................................................................27

7.3.4 Subcritical flow ...............................................................................................................................................................27

7.3.5 Recommended analysis method ......................................................................................................................28

7.3.6 Example ................................................................................................................................................................................31

Annex A (informative) Cryostats ............................................................................................................................................................................34

Bibliography .............................................................................................................................................................................................................................35

iv © ISO 2016 – All rights reserved
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SIST EN ISO 21013-3:2016
ISO 21013-3:2016(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www.iso.org/patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation on the meaning of ISO specific terms and expressions related to conformity

assessment, as well as information about ISO’s adherence to the WTO principles in the Technical

Barriers to Trade (TBT) see the following URL: Foreword - Supplementary information

The committee responsible for this document is ISO/TC 220, Cryogenic vessels.

This second edition cancels and replaces the first edition (ISO 21013-3:2006), which has been

technically revised.

ISO 21013 consists of the following parts, under the general title Cryogenic vessels — Pressure-relief

accessories for cryogenic service:
— Part 1: Reclosable pressure-relief valves
— Part 2: Non-reclosable pressure-relief devices
— Part 3: Sizing and capacity determination
— Part 4: Pressure-relief accessories for cryogenic service
© ISO 2016 – All rights reserved v
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SIST EN ISO 21013-3:2016
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SIST EN ISO 21013-3:2016
INTERNATIONAL STANDARD ISO 21013-3:2016(E)
Cryogenic vessels — Pressure-relief accessories for
cryogenic service —
Part 3:
Sizing and capacity determination
1 Scope

This part of ISO 21013 provides separate calculation methods for determining the required mass flow

to be relieved for each of the following specified conditions:

— vacuum-insulated vessels with insulation system (outer jacket + insulating material) intact under

normal vacuum, outer jacket at ambient temperature, inner vessel at temperature of the contents at

the specified relieving pressure;

— vacuum-insulated vessels with insulation system (outer jacket + insulating material) intact under

normal vacuum, outer jacket at ambient temperature, inner vessel at temperature of the contents at

the specified relieving pressure, pressure regulator of the pressure build-up system functioning at

full potential;

— vacuum or non-vacuum-insulated vessels with insulation system remaining in place, but with loss of

vacuum in the case of vacuum-insulated vessels, outer jacket at ambient temperature, inner vessel at

temperature of the contents at the specified relieving pressure or vacuum or non-vacuum-insulated

vessels with insulation system remaining fully or partially in place, but with loss of vacuum in the

case of vacuum-insulated vessels, fire engulfment, inner vessel at temperature of the contents at the

specified relieving pressure;

— vacuum-insulated vessels containing fluids with saturation temperature below 75 K at 1 bar

with insulation system remaining in place, but with loss of vacuum with air or nitrogen in the

vacuum space;

— vacuum insulated vessels containing fluids with saturation temperature below 75 K at 1 bar with

insulation system remaining in place, but with loss of vacuum with air or nitrogen in the vacuum

space with fire engulfment;
— vessels with insulation system totally lost and fire engulfment.

Good engineering practice based on well-established theoretical physical science needs to be adopted

to determine the required mass flow where an appropriate calculation method is not provided for an

applicable condition.
Recommendations for pressure relief devices for cryostats are given in Annex A.
2 Normative references
There are no normative references in this document.
© ISO 2016 – All rights reserved 1
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SIST EN ISO 21013-3:2016
ISO 21013-3:2016(E)
3 Symbols

A arithmetic mean of inner and outer surface areas of vessel insulating material m

A actual flow area of a pipe element m

A total outer surface area of pipe network between the outer jacket and location xm

A minimum flow area (reference area) in a pipe network m
A minimum flow area (reference area) in the pipe network, downstream of m
relief valve

A minimum flow area (reference area) in the pipe network, upstream of relief valvem

A total outside surface area of inner vessel m
A total outer surface area of pipe network between the inner and outer jackets m
(interspace)
A larger flow area of a pipe element containing two different flow area sizes m
A cross-sectional area, support, or pipe material m
A area ratio, A /A —
R S L
A smaller flow area of a pipe element containing two different flow area sizes m
A actual flow (orifice) area of a pressure relief valve mm

A actual flow (orifice) area of pressure relief valve selected for final analysis mm

A minimum required relief valve flow (orifice) area mm
A external heat transfer surface area of ambient air vaporizer m
c constant pressure specific heat capacity at the average of T and T kJ/(kg·K)
p n e

C experimentally determined flow rate through a pipe element or device gal/min/psi

e nominal insulating material thickness, normal vacuum, non-fire condition m
e minimum insulating material thickness, considering loss of vacuum, non-fire m
condition
e insulating material thickness remaining in place during fire conditions m
f pipe flow friction coefficient —
h enthalpy of fluid at conditions of ν kJ/kg
h specific enthalpy at relief valve inlet and outlet kJ/kg
K flow resistance coefficient of a pipe element in terms of A —
A F
K flow resistance coefficient of a pipe element in terms of A —
B B
K subcritical flow coefficient —
K derated coefficient of discharge —
2 © ISO 2016 – All rights reserved
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SIST EN ISO 21013-3:2016
ISO 21013-3:2016(E)

K derated coefficient of discharge of next largest available valve orifice area —

dr,a
greater than A
K derated coefficient of discharge of initially analyzed valve —
dr,1

k mean thermal conductivity of an individual support or pipe, between T and T W/(m·K)

n a
K flow resistance coefficient of complete pipe network in terms of reference —
area, A

K flow resistance coefficient at the transition between critical and subcritical flow—

K overall flow resistance coefficient of pipe network, downstream of pressure —
relief valve
K overall flow resistance coefficient of pipe network, upstream of pressure —
relief valve
K total flow resistance coefficient of a series or parallel pipe network —
SUM
K experimentally determined flow rate through a pipe element or device m /h/bar

k mean thermal conductivity of insulating material, normal vacuum, non-fire W/(m·K)

condition

k mean thermal conductivity of insulating material with air or gaseous lading, W/(m·K)

non-fire condition
L latent heat of vaporization of cryogenic liquid at relieving conditions kJ/kg
l length, pipe element m

L latent heat of vaporization of cryogenic liquid at a pressure of 1,013 bar kJ/kg

l length of support or pipe in vacuum interspace m

L’ enthalpy-to-volume expansion ratio for critical or all-gas fluid flow conditions kJ/kg

M molar mass kg/mol
m maximum mass capacity of vessel kg
max
N normal evaporation rate (NER) %/day
P relieving pressure, inner vessel bar
P pressure, safety relief valve outlet bar

P pressure at relief valve outlet for a downstream built-up backpressure of 10 % bar

b10
P pressure at pipe network exit bar
exit
P pressure, safety relief valve inlet bar
P pressure relief valve set pressure bar
Q mass flow rate kg/h
Q mass flow rate of a relief valve within a given pipe network kg/h
Q mass flow rate due to the normal evaporation rate kg/h
mNER
© ISO 2016 – All rights reserved 3
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SIST EN ISO 21013-3:2016
ISO 21013-3:2016(E)
R universal gas constant J/(mol·K)
r pipe elbow transition radius m
T relieving temperature, inner vessel K
T maximum external ambient temperature, non-fire condition K
T temperature at relief valve outlet K
b,Pb
T temperature at relief valve outlet for a downstream built-up backpressure K
b10
of 10 %
T external temperature for a given condition K
T temperature at pipe network exit K
exit,Pb
T external temperature, fire condition K
T temperature, safety relief valve inlet K
T temperature of fluid at a given flow start location along the pipe network K
T saturation temperature of fluid at a pressure of 1 bar K
sat
T temperature of fluid at a given location x along the pipe network K

U overall heat transfer coefficient of a pipe network for given temperature W/ (m ·K)

conditions

U heat transfer coefficient of insulating material, normal vacuum, non-fire W/ (m ·K)

condition

U overall convective heat transfer coefficient of ambient air vaporizer W/ (m ·K)

U heat transfer coefficient of insulating material with air or gaseous lading, non- W/ (m ·K)

fire condition

U heat transfer coefficient, air or nitrogen condensation, loss of vacuum, non-fire W/m

condition

U heat transfer coefficient of insulating material with air or gaseous lading, fire W/ (m ·K)

condition

U heat transfer coefficient, air or nitrogen condensation, loss of vacuum, fire W/m

condition
w heat leak from an individual support or pipe W/K
W total heat transfer rate for specified conditions Watt [W]
W total heat transfer rate under normal operation Watt [W]
W total NER heat transfer rate under normal operation Watt [W]
T1NER

W total heat transfer rate under normal operation, including pressure build-up Watt [W]

device

W total NER heat transfer rate under normal operation, including pressure build- Watt [W]

T2NER
up device
4 © ISO 2016 – All rights reserved
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SIST EN ISO 21013-3:2016
...

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