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
The back of the cryocooler power supply. Note the black power cable.
This cable is held to the crycocooler by a clamp which freed itself up
when someone stepped on the cable. To prevent this from happening,
we have rerouted the cables behind the unit and strained reliefed them.
The clamp securing the power cord to the unit was also repaired to ensure
both forks were attached to the power receptacle.
Without power, the crycooler pump warmed up, the liquid nitrogen
boiled and the burst disk exploded to release the N2 gas. This picture
shows the busted burst disk.
To prevent this from happening again, a new 50 PSI relief valve
was added to the V6 HP vent valve before the ball valve. In this fashion,
whether V6 is opened or closed, the 50 PSI valve should open before the
burst disk explodes at 150 PSI.
Note that with the new O2 monitor next to 7ID-A, several people
may need access to the area behind the cryocooler. This is how the cable
clamp was broken in the first place: someone tripped on it.
I've asked Lisa Gades to request the O2 monitor to be moved away from the
corner to the area written on the wall.
The O2 monitor to be moved away from the
corner to the area written on the wall in June.
Back to the MHATT-CAT Operation page.
Récemment modifié le 06/25/2004
par Eric Dufresne,
Bldg 432 Rm D007 630-262-0274