1. Liquid Hydrogen Infrastructure Update
M Hills
M Courthold
T Bradshaw
I Mullacrane
P Warburton

2. Outline Cryostat Instrumentation Control System Safety Issues
Cartridge Heaters
Ventilation Fan Sizing
Cryostat Testing
Schedule

3. Cryostat Instrumentation 1
Level Sensors manufactured by AS using a chain of resistors and fitted
Cartridge heaters procured and fitted

4. Cryostat Instrumentation 2
Heater on cryocooler
Level sensor in absorber pot
Cartridge heaters in absorber pot base

5. Control System
Control Panel assembled with (almost) all components needed for He testing
Barriers provide intrinsic safety (<19µJ in the circuit) for all wiring except the heaters.
PLC programmed
Temperature logging
Valve control tested
Example control sequence tested
Heater control implemented
PLC
Barriers
GP & Cryostat Connectors

6. PLC Read Out

7. PLC Data Logging

8. Safety Issues 1 - Cartridge Heaters
“Where terminals of intrinsically safe and non-intrinsically safe circuits are adjacent, their points of connection shall be separated by a distance of 50 mm, or by an insulating barrier or earthed metal barrier which extends to at least the height of the terminals being protected” (IEC79-11 BS 5345 Part 4)
Copper tube used around feedthrough.
Heater feedthrough uses a 12-pin connector; all other connectors are 8-pin, so it is impossible to connect the non-IS circuitry to the thermometer and level sensor circuits.

9. Safety Issues 2 – Ventilation Fan Sizing
The Gas Panel Enclosure and ventilation system had previously been designated as Zone 2 for purposes of DSEAR regulations
But...is this justified by the level of ventilation available?
Guidance from Baseefa (DSEAR consultants) is that the ‘time of persistence’ of an explosive atmosphere in the event of a leak should be <30mins.
Time of persistence = f(air changes/hour, LEL)
~90s with fans at full speed
~7mins with fans on standby
The ‘hypothetical volume’ of the vapour cloud should also be less than the volume of the enclosure.
Hypothetical volume = f(release rate, air changes/hour)
<5m3 (volume of the enclosure) in both cases

10. Cryostat Testing

11. Cryostat Thermometry TS05 and TS06 PT1000 and Cernox TS04 – PT1000

12. (Early) Cooldown Results...
N2 pre-cool of absorber pot base

13. 2009/10 Schedule Controls development for switch to operation with H2
Acceptance Testing of complete system
He R&D Tests