This paper deals with the considerations and an experiment concerning the reliability of the cryogenic refrigerator.
On the basis of extensive investigation it is pointed out that one of the most important factors which affect the reliability of a conventional cryogenic refrigerator is the expansion engine.
After making a fundamental study on expansion engines, on was designed for reliability testing, with NTBF (Mean Time Between Failures) aimed at 8, 000 hours aud the non-maintenance period at 4, 000 hours.
The trial expansion engine which incorporates an auto-valve was incorporated into a Compact-sized helium liquefying refrigerator for cooling a large-sized super-conducting magnet which generates a persistent magnetic field of 55kilo gauss. The refrigerator was operated for a total of 2, 500 hours including a 1, 000-hour continuous unattended operation, without trouble. Thus, the non-maintenance period was estimated at 5, 000 hours.
