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BS EN 17527:2021:2022 Edition

BS EN 17527:2021:2022 Edition

$215.11

Helium cryostats. Protection against excessive pressure

Published By Publication Date Number of Pages
BSI 2022 124
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This document specifies the minimum requirements for the protection of helium cryostats against excessive pressure, including superconducting magnet cryostats and cryostats for superconducting radio-frequency cavities, coldboxes of helium refrigerators and liquefiers as well as helium distribution systems including valve boxes. It covers the subjects of accidental scenarios and risk assessment, protection concepts, dimensioning of pressure relief devices, types of pressure relief devices, substance release, operation of helium cryostats and materials for pressure relief devices. In order to fulfil the aim of this Standard, the characteristics of pressure relief devices are taken into account.

PDF Catalog

PDF Pages PDF Title
2 undefined
10 1 Scope
2 Normative references
3 Terms and definitions
16 4 Symbols
20 5 Process flow-charts
5.1 Process flow-chart concerning risk assessment and protection concepts
22 5.2 Process flow-chart concerning scenario-specific dimensioning of helium circuit PRD
23 6 Risk assessment
6.1 General information on risk assessment
6.2 Sources of excessive pressure rise relevant for dimensioning
6.2.1 Loss of insulating vacuum
6.2.2 Loss of beamline vacuum
6.2.3 Quench of superconducting device
24 6.2.4 Leak of cryogenic fluid
6.2.5 Dielectric breakdown
6.2.6 Entrapment of cryogenic fluid
6.3 Sources of excessive pressure rise to be mitigated
6.3.1 Thermal acoustic oscillation
25 6.3.2 Cryopumping
6.3.3 Power failure
6.3.4 Pressure surge
6.3.5 Freezing
6.3.6 Backflow
6.3.7 Other sources of excessive pressure
26 6.3.8 Earthquake
6.3.9 Fire
6.4 Combined scenarios
6.5 Risk assessment before ordering
27 6.6 Risk assessment in the design phase
7 Protection concepts
7.1 General
7.2 Single-stage protection concept
28 7.3 Multi-stage protection concepts
7.3.1 General
29 7.3.2 Pressure protection of high-pressure helium cryostats
7.3.3 Pressure protection of low-pressure helium cryostats
30 7.3.4 Pressure protection of sub-atmospheric helium cryostats
7.3.5 Pressure protection of He-II cryostats
7.3.6 Pressure protection of ultra-low temperature refrigerator systems
8 Dimensioning of pressure relief devices
8.1 Method for the dimensioning of pressure relief devices
31 8.2 Calculation of the minimum discharge area
8.3 Calculation of the fluid state properties at relieving conditions
8.3.1 Calculation of the relieving pressure
32 8.3.2 Calculation of the specific volume
8.3.2.1 Initial specific volume
8.3.2.2 Specific volume at subcritical relieving pressure
33 8.3.2.3 Specific volume at critical and supercritical relieving pressure
34 8.4 Calculation of the relieving mass flow rate
8.4.1 General
35 8.4.2 Loss of insulating vacuum
8.4.3 Loss of beamline vacuum
36 8.4.4 Quench of a superconducting device
39 8.4.5 Leak of cryogenic fluid
40 8.4.6 Dielectric breakdown
8.4.7 Calculation of the specific enthalpy change
8.4.7.1 General
8.4.7.2 Specific enthalpy change at subcritical relieving pressure
41 8.4.7.3 Specific enthalpy change at critical and supercritical relieving pressure
8.5 Calculation of the mass flux
8.5.1 General
43 8.5.2 Influence of upstream pipework
44 8.5.3 Influence of downstream pipework
8.6 Calculation of the discharge coefficient
8.6.1 General
45 8.6.2 Adaption of the discharge coefficient of PRV
8.7 Transfer line systems
8.8 Dimensioning of vacuum vessel PRD
46 9 Pressure relief devices
9.1 General
9.2 Pressure relief valves
47 9.3 Bursting discs
9.4 Combinations of pressure relief valves and bursting discs
9.5 Magnetic pressure relief devices
9.6 Pressure relief devices for insulating vacuum vessels
9.7 Mechanical supports for pressure relief devices
48 9.8 Materials for pressure relief devices
10 Substance release
10.1 General
10.2 Discharge lines and discharge systems
11 Operating, maintenance and inspection instructions
11.1 General
49 11.2 Specific instructions to be included in the operating, maintenance and inspection instructions
11.2.1 Operating instructions for pressure relief devices
11.2.2 Periodic inspections of pressure relief devices
11.2.3 Pressure relief valves
11.2.4 Bursting discs
11.2.5 Maintenance
50 Annex A (informative)Thermodynamic characteristics of helium
A.1 Basics
51 A.2 Process path during relieving
54 Annex B (informative)Additional information on risk assessment
B.1 Loss of insulating vacuum
56 B.2 Loss of beamline vacuum
B.3 Quench of superconducting device
B.3.1 General
58 B.3.2 Main cooling scenarios
B.3.2.1 General
B.3.2.2 Direct cooling by forced flow of supercritical helium
B.3.2.3 Indirect cooling by solid conduction
B.3.2.4 Bath cooling of boiling or superfluid helium
59 B.3.2.5 Internal cooling by static helium
B.4 Leak of cryogenic fluid
B.4.1 General
B.4.2 Leak-before-break behaviour
B.4.3 Material characteristics
60 B.4.4 Thermo-mechanical stress
B.5 Dielectric breakdown
61 B.6 Thermal acoustic oscillation
63 B.7 Cryopumping
B.8 Qualitative risk assessment
B.8.1 General
66 B.8.2 Probability level
67 B.8.3 Severity level
B.8.4 Criticality matrix
69 B.8.5 HAZOP table
70 Annex C (informative)Protection concepts
C.1 Single-stage protection concept
71 C.2 Multi-stage protection concepts
C.2.1 General
C.2.2 Pressure protection of superconducting magnet systems
73 C.2.3 Pressure protection of superconducting radiofrequency cavities
74 C.2.4 Pressure protection of sub-atmospheric helium systems
75 C.2.5 Pressure protection of He-II systems
76 C.2.6 Pressure protection of ultra-low temperature refrigerator systems
78 Annex D (informative)Dimensioning of pressure relief devices
D.1 Equivalence between EN ISO 41267:2013/A1:2016/EN ISO 210133:2016 and D.2
82 D.2 Case-specific model for the dimensioning of pressure relief devices
D.2.1 General
D.2.2 Calculation of the minimum discharge area
D.2.3 Determination of the fluid velocity
83 D.2.4 Calculation of the discharge function
85 D.3 Influence of upstream pipework
87 D.4 Coefficient of discharge
D.5 Exemplary calculations of the minimum flow area
D.5.1 Example 1 ā€“ Vertical He-I magnet cryostat
D.5.1.1 Problem description
88 D.5.1.2 Solution for the primary PRD
92 D.5.1.3 Solution for the secondary PRD
93 D.5.2 Example 1 with the influence of downstream pipework
D.5.2.1 Problem description
D.5.2.2 Solution
94 D.5.3 Example 2 ā€“ Superfluid He-II cryostat protected by two PRD in series ā€“ Subcritical relief
D.5.3.1 Problem description
95 D.5.3.2 Solution for PRD 1
99 D.5.3.3 Solution for the helium guard PRD
101 D.5.4 Example 3 ā€“ Superfluid He-II cryostat protected by two PRD in series ā€“ Supercritical relief
D.5.4.1 Problem description
102 D.5.4.2 Solution for PRD 1
105 D.5.4.3 Solution for the helium guard PRD
108 Annex E (informative)Types of pressure relief devices
E.1 Application standards
109 E.2 Product standards
E.2.1 Purpose, prerequisites
111 E.2.2 Full-lift pressure relief valves
112 E.2.3 Standard pressure relief valves
E.2.4 Proportional pressure relief valves
E.2.5 Pilot-operated pressure relief valves
113 E.2.6 Controlled pressure relief valves with an additional pneumatic load
E.2.7 PRV with magnetic actuation
114 E.2.8 Specific cryogenic PRV features
E.2.8.1 Stainless steel bellows
E.2.8.2 Friction dampers
E.2.8.3 Lift increase and additional pneumatic load
E.2.8.4 Steel seal ā€” seat leak rate
E.2.8.5 Sealing gas system
115 E.3 Bursting discs
E.3.1 Functional characteristics
E.3.2 Metal bursting discs
116 E.3.3 Graphite bursting discs
E.3.4 Long-term behaviour
117 E.3.5 Leak rates
E.4 Pressure relief valve / bursting disc combinations
118 E.5 Pressure relief devices for vacuum vessels

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