Valves

V17 Valve Failure After Warm-up

We have found that almost every time we warmed up the cryopump the subsequent cool-down was accompanied with a failure of V17.1 (https://anl.box.com/s/lj0x4bf7uwf35s3keuxirxjehi2nzryj) to hold pressure. No direct cause of the failure was seen and looking at the surface of the valve seat did not show significant scarring (see photo here https://anl.box.com/s/8ririw2ozbtw6930jk5qdovqlau1qz2y). We never found a fix to this problem and were resolved to keep a stock of complete replacement valves to be ready for the next warm up/cool down cycle. We even tried replacing just the plunger but this did not work because in order to replace this you need to compromise the valve setup by dismantling the valve stem thereby creating another bad seating condition.

We did notice on the next generation of pumps, the feed going into V17.1 and V17.2 now has a fine gauze filter trap, so maybe some debris was getting into the valve and prevented a good seal.

The newer cryopumps have not reported this type of failure.