Cryocooler power failure due to stepping on the power cord

written by Eric Dufresne
June 1, 2004

A beamline failure occured on 5/24 following a cryocooler failure. One of our 
staff member stepped on the cryocooler power cord and the cord came loose. The 
crycooler stopped, the liquid N2 after some time boiled off and the closed loop
vented because the burst disk broke.  On Monday night, ED established that the 
cryocooler burst disk was broken, and planned the repair for Tuesday morning.
Dan Burke and Glen Moonier replaced the burst disk in the morning and several
upgrades were performed to the cryocooler set up to prevent this from happening

1) cable rerouting to prevent someone from stepping on the power cable. This 
was the root cause of the problem. This was the second time this happened. The
first time ED was able to catch the system before the LN2 boiled off. After 
the first incident, the power cord clamp was bent and one of the two forks did
not hold the cord properly anymore. It was thus probably easier to loosen it.

2) Proper anchoring and repair of the power cable connector forks. Cable ties 
now secure the forks from releasing the cord.

3)A new 50 PSI relief valve that should vent the closed loop if the pressure
goes too high. This will prevent the burst disk to break.

4) We would like the O2 monitor to be displaced so that no access to the 
back of the cryocooler is required by people other than S7 staff.

On Tuesday night, the system was returned to operation and Wednesday morning the
crystal was cooled to LN2 temperature. The beamline lost 4 shifts due to this 

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Récemment modifié le 06/25/2004
par Eric Dufresne,
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