EN 17527:2021

SLOVENSKI STANDARD
01-februar-2022
Kriostati za helij - Zaščita pred prekoračitvijo tlaka
Helium cryostats - Protection against excessive pressure
Helium Kryostate - Schutz gegen Drucküberschreitung
Cryostats pour hélium - Protections contre les surpressions
Ta slovenski standard je istoveten z: EN 17527:2021
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.

EN 17527
EUROPEAN STANDARD
NORME EUROPÉENNE
December 2021
EUROPÄISCHE NORM
ICS 13.240; 23.020.40
English Version
Helium cryostats - Protection against excessive pressure
Cryostats pour hélium - Protection contre les Helium Kryostate - Schutz gegen Drucküberschreitung
surpressions
This European Standard was approved by CEN on 15 November 2021.

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, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, 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: Rue de la Science 23, B-1040 Brussels
© 2021 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 17527:2021 E
worldwide for CEN national Members.

Contents Page
European foreword . 6
Introduction . 7
1 Scope . 8
2 Normative references . 8
3 Terms and definitions . 8
4 Symbols . 14
5 Process flow-charts . 18
5.1 Process flow-chart concerning risk assessment and protection concepts . 18
5.2 Process flow-chart concerning scenario-specific dimensioning of helium circuit PRD
................................................................................................................................................................... 20
6 Risk assessment . 21
6.1 General information on risk assessment . 21
6.2 Sources of excessive pressure rise relevant for dimensioning . 21
6.2.1 Loss of insulating vacuum . 21
6.2.2 Loss of beamline vacuum . 21
6.2.3 Quench of superconducting device . 21
6.2.4 Leak of cryogenic fluid . 22
6.2.5 Dielectric breakdown . 22
6.2.6 Entrapment of cryogenic fluid. 22
6.3 Sources of excessive pressure rise to be mitigated . 22
6.3.1 Thermal acoustic oscillation . 22
6.3.2 Cryopumping . 23
6.3.3 Power failure . 23
6.3.4 Pressure surge . 23
6.3.5 Freezing . 23
6.3.6 Backflow . 23
6.3.7 Other sources of excessive pressure . 23
6.3.8 Earthquake . 24
6.3.9 Fire . 24
6.4 Combined scenarios . 24
6.5 Risk assessment before ordering . 24
6.6 Risk assessment in the design phase . 25
7 Protection concepts . 25
7.1 General. 25
7.2 Single-stage protection concept . 25
7.3 Multi-stage protection concepts . 26
7.3.1 General. 26
7.3.2 Pressure protection of high-pressure helium cryostats . 27
7.3.3 Pressure protection of low-pressure helium cryostats . 27
7.3.4 Pressure protection of sub-atmospheric helium cryostats . 28
7.3.5 Pressure protection of He-II cryostats . 28
7.3.6 Pressure protection of ultra-low temperature refrigerator systems . 28
8 Dimensioning of pressure relief devices . 28
8.1 Method for the dimensioning of pressure relief devices . 28
8.2 Calculation of the minimum discharge area . 29
8.3 Calculation of the fluid state properties at relieving conditions . 29
8.3.1 Calculation of the relieving pressure . 29
8.3.2 Calculation of the specific volume . 30
8.4 Calculation of the relieving mass flow rate . 32
8.4.1 General . 32
8.4.2 Loss of insulating vacuum . 33
8.4.3 Loss of beamline vacuum . 33
8.4.4 Quench of a superconducting device . 34
8.4.5 Leak of cryogenic fluid . 37
8.4.6 Dielectric breakdown . 38
8.4.7 Calculation of the specific enthalpy change . 38
8.5 Calculation of the mass flux . 39
8.5.1 General . 39
8.5.2 Influence of upstream pipework . 41
8.5.3 Influence of downstream pipework . 42
8.6 Calculation of the discharge coefficient . 42
8.6.1 General . 42
8.6.2 Adaption of the discharge coefficient of PRV . 43
8.7 Transfer line systems . 43
8.8 Dimensioning of vacuum vessel PRD. 43
9 Pressure relief devices . 44
9.1 General . 44
9.2 Pressure relief valves . 44
9.3 Bursting discs . 45
9.4 Combinations of pressure relief valves and bursting discs . 45
9.5 Magnetic pressure relief devices . 45
9.6 Pressure relief devices for insulating vacuum vessels . 45
9.7 Mechanical supports for pressure relief devices . 45
9.8 Materials for pressure relief devices . 46
10 Substance release . 46
10.1 General . 46
10.2 Discharge lines and discharge systems . 46
11 Operating, maintenance and inspection instructions . 46
11.1 General . 46
11.2 Specific instructions to be included in the operating, maintenance and inspection
instructions . 47
Annex A (informative) Thermodynamic characteristics of helium . 48
A.1 Basics . 48
A.2 Process path during relieving . 49
Annex B (informative) Additional information on risk assessment . 52
B.1 Loss of insulating vacuum .
...