Frank and I finished ITW and TM2 leak check. TM2 internal water-cooling lines are leak free. They passed 70 psi helium pressure test. We found some small leaks on ITW primary and secondary vacuum vessel. I list them here:
- Exit module 2 service cap top plate to cap body O-ring at SW corner. Leak rate 2XE-8 atm.cc/sec. It is an old leak we found before. Solution: I sprayed high vacuum resin to leak area. It is improved to 3Xe-9atm/sec now. We can leave it there.
- Exit module 1 module to tank flange o-ring at target module side and north side. Leak rate 3XE-8atm.cc/sec. Solution: replace the o-ring. It involves in disconnect exit module 1 and remove it out. We may or may not change it. Let's check the schedule and discuss it later. We need Travis help on module moving out.
- Exit module 1 north side sqaure service panel o-ring. Leak rate 2XE-7 atm.cc/sec. Solution: replace the o-ring. It is a straight forward job. It will be done this shut down.
- Exit module 1 north side round roughing valve panel o-ring. Leak rate 8XE-9 atm.cc/sec. Solution: Replace the o-ring. It involves in disconnecting and removing ITW RV4. It could be done this shut down.
- Big T tank o-ring seal underneath the flange at exit 1 module north side . Leak rate 3XE-8 atm.cc/sec. Solution: None. All modules and module base flange have to been moved out to replace this big o-ring. It is a huge project to change this o-ring . I checked this big o-ring seal every year. It is first time a small leak is found. Maybe, we could try high vacuum resin spray first.
- Dump module flange o-ring at the side by Target module. Leak rate 8XE-9 atm.cc/sec. It cannot be confirmed since the TM o-ring is just beside it. Mostly, the leak is on dump module side. We changed TM flange o-ring every year. But we never changed dump module flange o-ring in history. Many copper cooling lines above the dump module has to be removed to remove the dump module out. I do not think we have time to do it this year. Also, the leak rate is pretty small. Maybe, we can schedule it next year.
Most these small leaks are close to turbopumps. This could be the reason the ITW vacuum on gauges are still pretty good. |