Long term experience with cryoplant operation for superconducting magnets and RF cavities at CERN

Eighteen liquid-helium cryoplants are presently in use at CERN, four of them commissioned in 1992. Unit capacities (entropy equivalent) range from 0.1 to 6 kW/4.5 K. Four even larger cryoplants (12 kW/4.5 K, upgradable to 18 kW/4.5 K) are in the process of installation and commissioning. Apart from feeding laboratories for development and tests of cryogenic equipment, the cryoplants provide cooling for superconducting detector and accelerator magnets and superconducting RF cavities, where their uninterrupted availability is crucial for efficient accelerator operation. Integrated running time in 1992 was of the order of 100000 hours. This paper summarises experience from all phases of operation, normal running, emergencies, cool-down and warm-up. Some information is given on software controls, data acquisition, and fault analysis, and on conclusions concerning corrective or preventive maintenance and advisability of investments for increased availability of cryogenics.<<ETX>>