prEN ISO 21013-3

Cryogenic vessels - Pressure-relief accessories for cryogenic service - Part 3: Sizing and capacity determination (ISO/DIS 21013-3:2025)

ISO 21013-3:2016 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.

Kryo-Behälter - Druckentlastungseinrichtungen für den Kryo-Betrieb - Teil 3: Bestimmung von Größe und Durchfluss (ISO/DIS 21013-3:2025)

Récipients cryogéniques - Dispositifs de sécurité pour le service cryogénique - Partie 3: Détermination de la taille et du volume (ISO/DIS 21013-3:2025)

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 kriogeno območje - 3. del: Določanje velikosti in pretoka (ISO/DIS 21013-3:2025)

General Information

• Status: Not Published
• Publication Date: 13-Sep-2026
• ICS: 23.020.40 - Cryogenic vessels
• Technical Committee: CEN/TC 268 - Cryogenic vessels
• Drafting Committee: CEN/TC 268 - Cryogenic vessels
• Current Stage: 4020 - Submission to enquiry - Enquiry
• Start Date: 13-Feb-2025
• Due Date: 13-Feb-2025
• Completion Date: 13-Feb-2025
• Directive: 2008/68/EC - Directve 2008/68/EC of the European Parliament and of the council of 24 September 2008 on the inland transport of the dangerous goods
• Directive: 2014/68/EU - Directive 2014/68/EU of the European Parliament and of the Council of 15 May 2014 on the harmonisation of the laws of the Member States relating to the making available on the market of pressure equipment
• Mandate: M/071 - Mandate to CEN for standardization in the field of Pressure equipment
• Mandate: M/601 - COMMISSION IMPLEMENTING DECISION of 1.3.2024 on a standardisation request to the European Committee for Standardization and the European Committee for Electrotechnical Standardization as regards pressure equipment and assemblies in support of Directive 2014/68/EU of the European Parliament and of the Council
• Mandate: M/TDG - Standards for referencing in the RID-ADR
• Ref Project: oSIST prEN ISO 21013-3:2025 - Cryogenic vessels - Pressure-relief accessories for cryogenic service - Part 3: Sizing and capacity determination (ISO/DIS 21013-3:2025)

Relations

• Revises: EN ISO 21013-3:2016 - Cryogenic vessels - Pressure-relief accessories for cryogenic service - Part 3: Sizing and capacity determination (ISO 21013-3:2016)
• Effective Date: 18-Jan-2023

Standards Content (Sample)

SLOVENSKI STANDARD
01-april-2025
Kriogene posode - Oprema za razbremenitev tlaka za kriogeno območje - 3. del:
Določanje velikosti in pretoka (ISO/DIS 21013-3:2025)
Cryogenic vessels - Pressure-relief accessories for cryogenic service - Part 3: Sizing and
capacity determination (ISO/DIS 21013-3:2025)
Kryo-Behälter - Druckentlastungseinrichtungen für den Kryo-Betrieb - Teil 3:
Bestimmung von Größe und Durchfluss (ISO/DIS 21013-3:2025)
Récipients cryogéniques - Dispositifs de sécurité pour le service cryogénique - Partie 3:
Détermination de la taille et du volume (ISO/DIS 21013-3:2025)
Ta slovenski standard je istoveten z: prEN ISO 21013-3
ICS:
13.240 Varstvo pred previsokim Protection against excessive
tlakom pressure
23.020.40 Proti mrazu odporne posode Cryogenic vessels
(kriogenske posode)
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
International
Standard
ISO/DIS 21013-3
ISO/TC 220
Cryogenic vessels — Pressure-relief
Secretariat: AFNOR
accessories for cryogenic service —
Voting begins on:
Part 3: 2025-02-14
Sizing and capacity determination
Voting terminates on:
2025-05-09
Récipients cryogéniques — Dispositifs de sécurité pour le service
cryogénique —
Partie 3: Détermination de la taille et du volume
ICS: 23.020.40
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Reference number
ISO/DIS 21013-3:2025(en)
DRAFT
ISO/DIS 21013-3:2025(en)
International
Standard
ISO/DIS 21013-3
ISO/TC 220
Cryogenic vessels — Pressure-relief
Secretariat: AFNOR
accessories for cryogenic service —
Voting begins on:
Part 3:
Sizing and capacity determination
Voting terminates on:
Récipients cryogéniques — Dispositifs de sécurité pour le service
cryogénique —
Partie 3: Détermination de la taille et du volume
ICS: 23.020.40
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document is circulated as received from the committee secretariat.
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BEING ACCEPTABLE FOR INDUSTRIAL,
© ISO 2025
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Published in Switzerland Reference number
ISO/DIS 21013-3:2025(en)
ii
ISO/DIS 21013-3:2025(en)
Contents Page
Foreword .v
1 Scope . 1
2 Normative references . 2
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.8
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 .9
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 .10
4.5 Heat transfer per unit time (watts) .11
4.5.1 General .11
4.5.2 Normal operation.11
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 . 12
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 . . 15
6.3 Heat transfer . 15
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 .17
7.2.3 Critical flow .17
7.2.4 Subcritical flow .19
7.2.5 Recommended analysis method .19
7.2.6 Example .21
7.3 Sizing of bursting discs . 26
7.3.1 Discharge capacity . 26
7.3.2 Determination of critical vs. subcritical flow for gases . 26
7.3.3 Critical flow .27

iii
ISO/DIS 21013-3:2025(en)
7.3.4 Subcritical flow .27
7.3.5 Recommended analysis method .27
7.3.6 Example .
...