1. ESS elliptical cryomodule
ESS CRYOMODULE FOR ELLIPTICAL CAVITIES
SAFETY REVIEW
LUND June 9th, 2016
Unité mixte de recherche CNRS-IN2P3
Université Paris-Sud 11
91406 Orsay cedex
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2. ESS elliptical cryomodule

3. ESS elliptical cryomodule

4. Circuits - characteristics
Temperature
(K)
Pressure
(bara)
Volume
(l)
Control valve
Safety device
Thermal shield ,5 3
CV60
(Kv 0.8m3/h)
SV60 (24barg)
Helium inlet
4.5 1
CV03
(Kv 2.8)
SV02 (3barg)
Couplers
1.3
Cooling down
1.5
CV02
(Kv 0.2)
Filling
CV01
(Kv 0.04)
Low pressure 2
0.030 – 1.43
219
(Diph. pipe half filled)
CV04
(Kv 71)
RD90 / RD91 (0.99barg)
CV91 (1.5bara)
SV90 (0.64barg)
Vacuum
300 K
SV70 (0.02 bar)

5. Helium distribution Jumper VLP circuit (8l) Rupture disk
& safety valves
Jumper VLP circuit (8l)
JT valve
CV01
Exchanger
Rupture disk
& purge valve + pressure gauges
Cooling down valve (CV02)
Diphasic pipe
(27l)
Helium tank (48l)
Coupler circuit (1,3l)
Filling line
(1l)
Thermal shield circuit (3l)
Cooling down circuit (1.5l)

6. cavities Medium beta High beta Ø neck 80mm Øext tank 418mm
Internal volume: 48l

7. Cryogenic interfaces Rupture disk CV01 & safety valves Jumper
connections
Vacuum safety valve
CV02
Rupture disk
& purge valve
& press. gauges
He coupler outlet (x4)

8. Vacuum vessel : safety device
Minimum flow section (mm²)
Set pressure
(barg)
11200
0.02
Considered worst scenario: Rupture of 2K phase separator
liquid helium fills the vacuum vessel
liquid helium mass : 30 kg
Volume of vessel : 6.3 m3
helium mass flow : 4.1 kg/s (1.04 bara, 4.76 K)
Diameter of relief valve SV70 : 200 mm

9. Thermal shield : Safety devices
Minimum flow section (mm²)
Set pressure
(barg) 34 24
Considered worst scenario: loss of insulation vacuum
air fully condensates onto the CM thermal shield surface covered with 30 MLI
considered heat power density : 1.5 kW/m²
thermal shield (~24 m²): 36 kW
helium mass flow : 0.1 kg/s (25 bara, 66K)
Diameter of relief valve SV60 : 10 mm

10. Cooling down and coupler circuits
A relief valve SV90 associated with a control valve CV90 (1.5 bara)
Minimum flow section (mm²)
Set pressure
(barg)
340
0.64
Considered worst scenario:
HP He supply: 3 bara, 5 K
Valves CV01, CV02, CV03 fully opened (at kv max)
Valve CV04 closed
helium mass flow : kg/s (1.74 bara, 4.85 K)
Diameter of relief valve SV90 : 25 mm
Kv of CV 90 : 11

11. Low pressure line

12. Safety strategy for the low pressure circuits
Operating constraints:
maximal allowable pressure of cavities is about 2 bar,
pressure required by the cryogenic plant is 1.43 bar,
1.43 bar is close of the opening pressure of the safety valves, the pressure margin between the operating pressure and safety device is low.
Safety strategy:
Two burst disks (RD90 – RD91) designed for accidental scenarios,
a safety valve (SV90) designed for abnormal operation and to avoid the bursting of RD90 or RD91,
a control valve (CV90) designed to limit the pressure at a level lower than the opening pressure of SV90.

13. 2 K vessel : safety devices
FAILURE SCENARIOS
(JP THERMEAU, Safety equipments for helium circuits)
scenarios
Circuit
Area
(m²)
heat flux
(kW/m²)
Heat load
(kW)
Mass flow
(kg/s)
Failure of the insulation vacuum
Helium vessel
4 x 1.53
 6.2
(10 MLI layers) 38 2
Failure of the beam vacuum
Cavity
4 x 1.81
(air on cavity wall)
275
14.5
Failure of insulation and beam vacuum
Vessel + cavity
312
16.4
7.25 Kg/s per bursting disk
Most credible & critical
Reference for the sizing of the safety devices
Unlikely
Minimum rupture disk diameter: 88mm
Maximum He volume to be evacuated: 200l
(about 30 Kg)

14. Dimensions updated by Witzenmann on 2016/04/07
Bursting disk
Ø97mm
Dimensions updated by Witzenmann on 2016/04/07
Ø90mm

15. Summary Pressure drop in the main line : > 3%PS,
Name
Minimum flow section (mm²)
Practical diameter (mm)
Set pressure
(barg)
SV60 34 10 24
SV02
Section of pipe 3
SV90
340 25
0.64
CV90
kv > 11
1.5 bara
RD90 - RD91
5300
100
0.99
SV70
11200
200
0.02
Pressure drop in the main line :
> 3%PS,
no risk to damage the cavities.
The pressure margins between the burst disks and the safety valves are very low (100 to 200 mbar).

16. Pressure equipment directive
Breakdown of each circuit in elementary sections to check the product Ps x V and the compliance to the Pressure Equipment Directive.
Each section is considered as a separate vessel.

17. Pressure equipment directive
1.04 48
Aim:
remain in 3.3 category
Volume of the largest circuit vessel: the cavity helium tank

18. Mechanical behaviour of the cavities under pressure
Pressure test scenario:
Cavity fully constrained
Pressure in the tank
Beam vacuum carried out
The maximum pressure allowable is
2.60 bar for 50 MPa VM (worst scenario)
3.64 bar for 70 MPa VM (best scenario)
Max. pressure (test at 1,25 Pmax):
2,6 barg
Maximum working gauge pressure:
2,6/1,25 = 2,08 barg
Maximum Ps:
2,08-1,013=1,067 barg
This value is very close to the limit of 1,04barg needed to stay in
PED chapter 3.3
(Andrea BIGNAMI, INFN LASA - PDR, LASA, 19 May 2016)

19. Safety devices operating range
ABSOLUTE PRESSURE
GAUGE PRESSURE
Pmax = 2.14 bar
Maximum pressure = 1.1 PS = 1.14 barg
2.04 bar
PS = MAWP = 1.04 barg
Rupture disk outlet
to the atmosphere
at 1 bara
Bursting area of the rupture disk
Bursting pressure = 0.99 barg ±0.05bar
1.94 bar
0.94 barg
Pressure margin ~ 0.2 bar
Max. pressure when the relief valve is open: 1.1 x 0.67 ~ 0.74 barg
1.74 bar
Opening area
of the
relief valve
1.05 Pset ~ 0.67 barg
Safety valve outlet
to SV relief line
at 1 bara
Set pressure = 0.64 barg ± 5%
0.95 Pset ~ 0.61 barg
1.55 bar
Min. pressure to allow the closing of the relief valve:
0.9 x 0.61 ~ 0.55 barg
1.5 bar
PLC Control valve ~ 0.5 barg
1.43 bar
Min./Max. operating pressure of the cryogenic plant:
~ 0.43 barg (cooling down phase)
Operating pressure area
30 mbar
Pressure operation at 2K

20. Safety devices operating range
ABSOLUTE PRESSURE
GAUGE PRESSURE
Pmax = 2.14 bar
Maximum pressure = 1.1 PS = 1.14 barg
2.04 bar
PS = MAWP = 1.04 barg
Rupture disk outlet
to the atmosphere
at 1 bara
Bursting area of the rupture disk
Bursting pressure = 0.99 barg ±0.05bar
1.94 bar
0.94 barg
Pressure margin ~ 0.1 bar
Max. pressure when the relief valve is open: 1.1 x 0.67 ~ 0.74 barg (% outlet circuit)
1.84 bar
Opening area
of the
relief valve
1.05 Pset ~ 0.67 barg (% outlet circuit)
Safety valve outlet
to SV relief line
at 1.1 bara
Set pressure = 0.64 barg ± 5% (% outlet circuit)
0.95 Pset ~ 0.61 barg (% outlet circuit)
1.65 bar
Min. pressure to allow the closing of the relief valve:
0.9 x 0.61 ~ 0.55 barg (% outlet circuit)
1.5 bar
PLC Control valve ~ 0.5 barg
1.43 bar
Min./Max. operating pressure of the cryogenic plant:
~ 0.43 barg
Operating pressure area
30 mbar
Pressure operation at 2K

21. Safety devices operating range
ABSOLUTE PRESSURE
GAUGE PRESSURE
Increase of the Ps value, if exhaust line > Patm
Pmax > 2.14 bar
Maximum pressure = 1.1 PS
PS = MAWP > 1.04 barg
>2.04 bar
1.04 barg (% outlet circuit)
Rupture disk outlet
to exhaust line
> 1 bara
Bursting area of the rupture disk
Bursting pressure = 0.99 barg ±0.05bar (% outlet circuit)
>1.94 bar
0.94 barg (% outlet circuit)
Pressure margin > 0.1 bar
Max. pressure when the relief valve is open: 1.1 x 0.67 ~ 0.74 barg (% outlet circuit)
1.84 bar
Opening area
of the
relief valve
1.05 Pset ~ 0.67 barg (% outlet circuit)
Safety valve outlet
to SV relief line
at 1.1 bara
Set pressure = 0.64 barg ± 5% (% outlet circuit)
0.95 Pset ~ 0.61 barg (% outlet circuit)
1.65 bar
Min. pressure to allow the closing of the relief valve:
0.9 x 0.61 ~ 0.55 barg (% outlet circuit)
1.5 bar
PLC Control valve ~ 0.5 barg
1.43 bar
Min./Max. operating pressure of the cryogenic plant:
~ 0.43 barg
Operating pressure area
30 mbar
Pressure operation at 2K

22. Remaining issues Value of Ps to remain in PED 3.3 category
Value of Ps to avoid any yielding of the cavities
Impact of the helium discharge of one cryomodule on the other disks: increase of the bursting pressure
Exhaust line at atmospheric pressure? (lost of the helium?)

23. ESS elliptical cryomodule
Thank you for your attention