1. Measures of solid hydrogen contamination problem in the liquid helium
6th International Workshop on Cryogenics Operations on November 2014
Measures of solid hydrogen contamination problem in the liquid helium
Hiroshi Ikedaa,*, Yutaka. Kondo
a Research Facility Center for Science and Technology Cryogenics Division,
University of Tsukuba, Tsukuba, Ibaraki , Japan

2. CONTENT Introduction History of L280 in University of Tsukuba
The trouble with solid hydrogen
Purity measurement and state understanding of internal purifier (New method !)
Improving method the purity of the regeneration gas
Gas chromatograph mass spectrometer impurity analysis of helium liquefaction machine
Consideration of decreased purity (Changes in Linde helium Liqufier）
Conclusions

3. Introduction
・In recent years, several universities that renewed their helium liquefier system have reported that solid hydrogen was mixed within the liquid helium produced by a helium liquefier. ・The University of Tsukuba has also installed a Linde L280 helium liquefier system in October Similar to other universities, cases where the helium flow of cryogenic equipment with flow impedance was blocked began to be reported around March ・In this work we focused on the internal purifier of the helium liquefier for the problem where solid hydrogen is mixed in the liquid helium produced by a helium liquefier.

4. History of L280 in University of Tsukuba

5. Decreased purity of helium recovery gas bag
About 1 year passed
Decreased purity of helium recovery gas bag

6. helium liquefier flow ( L280）

7. Internal purifier Flow
Gasbag
PV3415
CV3401
　V3410
CV3430
CV3420
Flow Meter
Cold Gas Line
Impurer Helium Gas
Atmospheric release
PV3435
TI3475
TI3465
Heater
PI3401
PI3445
HP Line
LP Line
Liqide Air
CV3410

8. Decreased purity of helium recovery gas bag
⇒　95％　（Nomalｙ＝99％）
Differential pressure occurs when introduced into the internal purifier gas was decreased purity

9. Trend graph of the differential pressure occurs
ΔP＝0.15MPa
Cool down Mode
Regeneration Mode
Purify Mode
Buffer tank

10. The trouble with solid hydrogen

11. The trouble with solid hydrogen
Flow impedance blocked by solid hydrogen
Quantum Design MPMS
PPMS
(equipment to control temperature while limiting the flow of helium by a filter and capillary)

12. Trouble Instrument Worldwide！ Japan Korea China India Spain France
Germany
Worldwide！

13. Purity measurement and state understanding of internal purifier
New method！

14. Gas bag purity is reduced to 95% by the regeneration gas, introduction into the internal purifier, differential pressure occurs.
‣ For gas purity measurement discharged from the internal purifier was installed simple helium purity monitor immediately after the flow meter.

15. Simple purity monitor installation flow diagram
Gas Bag
CV3415
CV3401
V3410
CV3430
CV3420
Flow
Meter
Cold Gas Flow
Impurer Helium Gas
CV3435
TI3475
TI3465
Heater
PI3401
PI3445
HP Line
LP Line
Liqid Air
１００％
Purity Monter
CV3410
Atmospheric release

16. Simple helium gas purity monitor
New Method！
Ulvac WP-01
Pirany type　SKD-20

17. A result of the purity measurement
The purity of the regeneration gas was reduced to 33% at maximum
Initial setting valu
・Purification operation state
Cold end temperature TI3475　　 　=　32.5 K
Internal pressure PI3445　　　 =　2.5 MPa
・ Regeneration during operation　
　　 Exit flow meter flow rate 　 =　120 L/min
　　 Regeneration completion temperature TI3465 =　140 K
　　 Heater control temperature TI3475 =　95 K
　　 Warming heater output R3470 = 18 ％

18. Improving method the purity
　of the regeneration gas

19. Comparison with the liquefier
Internal purifier Cold end temperature
Internal purifier Exit flow rate
TCF50
L280
２７．５ K
２００ L/min
３２．５ K
１２０ L/min
High temperature!　　　　　　　　 Low flow rate!

20. Setting changes 120L/min⇒190L/min CV3415 CV3401 V3410 CV3430 CV3420
Down fromD32.5K
Gas Bag
CV3415
CV3401
V3410
CV3430
CV3420
Flow
Meter
Cold Gas Flow
Impurer Helium Gas
CV3435
TI3475
TI3465
Heater
PI3401
PI3445
HP Line
LP Line
Liqid Air
１００％
Purity Monter
CV3410
Atmospheric release

21. Internal purifier regeneration gas purity measurement results
32.5K
120L/min

22. Internal purifier regeneration gas purity measurement results
29.0K
190L/min
26.0K
190L/min
32.5K
120L/min

23. Trend graph of the regeneration gas purity after improvement
26.0K
190L/min
ΔP＝0.039MPa

24. Befer　　　　　　　　　　　　　After
ΔP＝0.15MPa
ΔP＝0.039MPa
32.5K、120L/min
26.0K、190L/min

25. Gas chromatograph mass spectrometer impurity analysis　of helium liquefaction machine

26. Gas chromatograph mass spectrometer
SHIMADZU GC-2014 O

27. Gas chromatograph mass spectrometer impurity analysis　of helium liquefaction machine

28. Improvement result The purity of the regeneration gas, 33% ⇒ 99%
Cold end temperature change, the regeneration gas flow rate increase　　　　　　　　　　
　The purity of the regeneration gas, 33% ⇒ 99%
Pressure difference is reduced. Purification operation has stabilized

29. Consideration of decreased purity (Changes in Linde helium Liqufier）

30. 1996 TCF50 Flow diagrams Adosorber 3 point ! 80K 20K LHe GHe LN2
Gas Bag
InPur GHe
Adosorber
3 point !

31. 2010 L280 Flow diagrams Adsober Only One 20K LN2 LHe GHe Gas Bag
InPur GHe
Gas Bag

32. 2014 L140 New Flow diagrams Adosober Revival ! 20K LN2 LHe GHe Gas Bag
InPur GHe

33. Conclusions
Regeneration gas purity was improved from 33% to　99% by the setting change of internal purifier. Purification operation has stabilized generation of the differential pressure is reduced.
By monitoring established the purity helium simple monitor, it can insight into the operating state of the internal purifier at a low cost.
As the cause of differential pressure and decreased purity of the regeneration gas occurred, in addition to the incorrect setting, it is considered as the cause did not have the adsorber inside purifier.

34. Thank you for your attention