from meeting of 18/10/2021
Distribution pressure
- max pressure sustainable for gaps but also max pressure for pipes (main leaks developed there – pipe leaks way before the gap does)
- request from Salvatore: pressure to keep as low as possible
Endcap pressure safety
- main safety = output bubbler, few mbar BUT as of today, if output disconnected it remains normally closed -> only safety is input bubbler + software interlock
- today input bubblers set 8-10 mbar (most of them already very close to bubbling, cannot put higher flows) + software interlock 10-15mbar
- input pressure with higher flow > 8-10mbar? Only few rack tested (some ok for high flow some not, bubbler closed to complete test)
- to increase flow, input pressure also increases -> bubblers not ok, we need safety valves
- safety valves minimum pressure = 50mbar, way too high for pipes/gaps
- if output disconnected, only safety is software interlock (might fail for xyz reason) -> risk can be lowered if there are normally open quick connectors at output
- normally open quick connector problem : during flow tests (Aleksandar) lines are open and freon is lost and air gets in
- * on barrel safety valves (85/50 mbar) already there in place of bubblers -> to decide if also there we put quick output normally open or not
Flowcells reading
- Current situation: some readings are not correct (see slides attached, 10-30% depending on error accepted)
Aleksandar has xls file with all conversion factors, they will go on cms dcs but not on gas system winccoa
gas team would be blind for flow reading, cms rpc will tell what to do (i.e. what flow reading has to be reached) if flow change is needed
+ if in the future winccoa data will be looked at, there will be no indication that they are not correct
- Possibility: change all flowcells with big error
for gas team = calibration of 100-150 flowcells + install on manifold (can be done during stop)
for rpc team = change calibration curve on dcs wrt current one + again check with redflowmeter
no action needed on needle valves, they will stay the same and they are already regulated referring to real flow (Red-y by Aleksandar)
* gas team will prepare for end of November the flow-measure manifold to check 12 channels at the time
- Current flow rate in barrel is 0.5 vol/h, for Run3 operation will be necessary 0.65 vol/h: change will be done by pre-distribution rotameters (no touching flowcells)
Stop/Start of the system
- Stop of the system after pilot run: 1st November
- Restart of system?
CMS power cut 30th November, not worth to switch on gas system before
Possible system restart 6th December (Monday) but the tuning works for new regulation valves will take long time + fewer people available from mid-December
Not possible to leave system unstable during Xmas holidays but also leaving system off could be bad for leaks development
To consider restart of only Barrel (main leaks problem), focus on regulation valves of Barrel and leave Endcap for later
Demonstrator chambers
- No welding in USC for ZEC when system is ON, only with system OFF (de-classified atex area): they have to be done for sending mixture to demo chambers
Slides at link below:
https://docs.google.com/presentation/d/1g4JOb_HfqQSbfmG_6hcusMkcMhWkiePZnh1ecw-rSEA/edit?usp=sharing
