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Gas systems weekly project meeting
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32/1-A24 (CERN)
gas systems project meeting
Gas systems
Gas systems 2026 09 17
Key Outcomes
A pressure surge event on the CMS RPC gas system—triggered after restarting Purifier 3—caused over 200 alarms and required emergency intervention. Root cause is believed to be the purifier (more investigation needed), but remains unconfirmed. Underlying humidity control issues were identified, linked to a malfunctioning chiller (Lauda) and an oversized mass flow controller for water injection. Several maintenance actions are planned or in progress.
CMS-RPC Incident Summary
· Root cause of pressure event (Sep ~9:19 PM): Purifier 3 restarted in afternoon; ~40 min after Column B output valve opened, pressure began rising across the system.
· Cascade: Mixer reached 1.15 bar; 200+ alarms for rack pressure out of range, pump regulation, and buffer high-pressure — buffer alarms (only 2–3) were missed in the flood.
· Emergency response: Mixer stopped, bypass opened, purifier cut, humidifier injection forced off — pressure normalized. Rack 72 found with stuck rotameter ball the next morning.
· Hypothesis: Water accumulated inside Column B (regenerated 3 months prior, possibly pre-saturated); one-shot release may have blocked flow. Purifier confirmed as likely source; distribution rack pressure also increased, leaving some ambiguity.
CMS-RPC Humidity System Problems
· Condensation origin: From mid-June, pre-fire stopped → distribution input pressure rose. On Sep 3, Alexander found wet needle valves on manifolds — confirmed water condensation in system.
· Humidity stayed high: System left 10 days without wet gas injection; humidity did not decrease → Purifier 3 restarted to help dry the loop.
· Chiller (Lauda) malfunction: Set point reportedly 17°C but reading shows ~21°C (ambient); chiller likely lost refrigerant gas and cannot cool sufficiently — condensation trap ineffective.
· Mass flow controller oversized: When running without purifier, humidifier tried to inject ~7 g/hr; current controller scale (~100) is too large for that range — PLC may also not open below 10% request.
· Current status: Humidity at ~6,000 ppm return from chambers; set point lowered to 6,000; system stable for now. RPC minimum requirement is ~6,500 ppm per Alexander.
CMS-RPC Decisions Made
· Purifier: Remain off for now; no regeneration gas (argon/hydrogen) available until Christmas due to PGS works starting mid-October — no urgency to return purifier to loop.
· Run without purifier and humidifier (trial): Test equilibrium humidity level from chamber recirculation alone; decide humidifier set point based on result.
· Chiller replacement is first priority before adjusting other humidity parameters — change one variable at a time.
· Add overpressure alarm on purifier: No alarm currently exists for purifier overpressure; team to assess whether existing instrumentation can detect early warning or if new sensors are needed.
· Valve seat inspection (Rack 72): New Econex valve installed with spare seat; seat material must be examined carefully for aging — LS3 identified as right moment to replace all seats if degradation found.
Open Questions / Risks
· Purifier pressure event — exact mechanism unknown: Cannot isolate purifier vs. distribution issue from trend data; simultaneous bypass opening and purifier stop prevent definitive attribution.
· Alarm delay: Buffer high-pressure alarm received 6 minutes late when buffer was already at 1.1 bar; earlier alarm could have allowed controlled intervention.
· ATLAS-RPC Column B leak : Persistent slow leak; vacuum and pressure tests performed, safety valve replaced, pneumatic valves changed — source still not found. CO2 detector ("blue one") recommended for next test.
· ATLAS-RPC Pump inter-membrane pressure buildup: All three RPC pumps develop pressure between membranes over weeks (likely CO2 absorption); currently released manually ~weekly. Maintenance planned: replace flap gaskets with more appropriate materials; needle valves on all three pump lines also need replacement.
Action Items
· Andrea: Replace chiller (lauda) — confirm set point reading capability for PLC feedback integration. Replaced
· Gianluca: Check PLC logic for humidifier mass flow controller minimum opening threshold (with Gianluca, back next week).
· Andrea: Order correct-scale mass flow controller for water injection (~20 g/hr max scale based on observed demand).
· Gianluca/Maria Cristina/Roberto: Review purifier differential pressure trend to determine if early blockage detection is feasible; consider adding dedicated alarm.
· Andrea/Maria Cristina: Inspect Econex valve seat from Rack 70 for aging/deformation; assess all seats for LS3 replacement. Not yet dismounted
· Davide/Max: Continue CO2 pressure-drop tests on Column B (Atlas-RPC) — check if drop rate decreases over repeated tests (saturation indicator). -> stable rate
· Davide: Perform full pump maintenance on all three RPC pumps (gasket material upgrade, needle valve replacement). -> done maintenance p2, non return completely broken. replaced. pump 2 still not ok after. Plan to replace all non-return
· Roberto: Swap piquet Louis-Philippe<->Beatrice October 8-15 <-> 15-22 due to start of CLOUD data taking.
Gas systems 2026-09-03
Action Items
Maria Cristina: Generate pressure trend plots for Rack 70 from January (or earlier) to present; organize dedicated discussion before any manifold intervention.- Patrick/Gianluca: Investigate LHCb-UT
pressure regulator —confirm correct logic and pipe condition. - Andrea :
Complete panel for CSC 904;finalize TID and send link. Team: verify analysis chains (active/useful status).GIF: Monday Sept 7 — assist at GIF to remove an eco-RPC chamber (~2 hours).- Florian's mixer: Order required materials — planned for next week – who is ordering? Fabio ongoing
Mass Flow Controller: Confirm ticket exists in Jira confirming unit was sent.Rack storage: Create a kiosk storage area for the tent to list materials we have there -> Miguel.- Stefania: uCL electrical part to put in the workshop planning w42-45 empty but full. now in week 46.
piquet:
LHCb pump filters to be changed or something (for LS3)-> TICKET
O2+H2O analyser to be checked -> TICKET
ATLAS-RPC rack 66 and 69 pressure alarm during purif 2 change over -> TICKET
NA62
glitch of CEDAR 6105, is it the keller? -> TICKET to check
ATLAS-TGC putifier Col B leak. loosing 1 bar in 1 day -> TICKET Davide check with Argon or CO2
CMS-DT pressure sensor PT1303 went to 0 for 20 minutes -> TICKET to follow Andrea
ATLAS-RPC purif -> affecting chamber pressure -> R66 check
12/2 ATL-RPC purif 1 some software issue and sms not indicating the right reason for the alarm -> TICKET
IR status, spares, .... --> TICKET
test binary gas analyser... -> TICKET
outcome of binary gas analyser test --> TICKET & buy a 2nd one --> Maria Cristina
DP pressure for pump filter in ALICE and LHCb -> TICKET -> @LPh + @Patrick [GASSYSTEMS-903] DP pressure for pump filter increasing - CERN Central Jira -> Stefania
chiller fluids to uniform between CMS, LHCb and ATLAS -> TICKET Maria Cristina
check if NV in purif is really useful --> TICKET
Calibration bottles O2-H2O status
ALICE
70 report from Anité [GASSYSTEMS-70] TPC gas quality - filters to Benoit - CERN Central Jira (I don't see the report, can you please add it?)
several alarms blocked: [GASSYSTEMS-628] ALICE alarms blocked - CERN Central Jira
TOF gas mixture analysis -> [GASSYSTEMS-639] TOF gas mixture analysis - CERN Central Jira & ELOG
TRD membrane is connected ? -> [GASSYSTEMS-717] TRD membrane status - CERN Central Jira
P&ID drawing check who is doing -> [GASSYSTEMS-736] ALICE P&ID drawing check - CERN Central Jira
MID swap of pumps during MD because sometime the system stop -> TICKET
ATLAS
MDT frequency converter (need to be replaced TICKET) ELOG - ATLAS MDT Test convertisseur 4101 avec la pompe 4201
RPC distribution rack regulation valve (TICKET)
RPC secondary mixer (TICKET), info to be given to ATLAS
RPC purif 3 circuit breakers & meeting -> [GASSYSTEMS-718] RPC purif 3 electrical issue - CERN Central Jira --> meeting when?
ATLAS-TGC flow difference --> [GASSYSTEMS-612] ATLAS-TGC flow difference - CERN Central Jira
CMS
RPC purif test at workshop, PLC needed -> TICKET
R134a insulation - isol'tut to check and see what to do -> ticket IO [GASSYSTEMS-578] R134a insulation - isol'tut to check and see what to do - CERN Central Jira
How much gas flow we need for the RPC purifier? --> [GASSYSTEMS-579] CMS-RPC How much gas flow we need for the RPC purifiers? - CERN Central Jira @MariaCristina notes to be added
RPC bypass pump too much closed --> [GASSYSTEMS-604] RPC bypass pump too much closed - CERN Central Jira
RPC with CO2 like ATLAS and effect on R134a recuperation -> [GASSYSTEMS-606] RPC with CO2 like ATLAS and effect on R134a recuperation - CERN Central Jira
R134a Upgrade (hardware and software) to be tested -> [GASSYSTEMS-594] R134a Upgrade (hardware and software) to be tested - CERN Central Jira
DT vaisala reading difference between SG and US -> [GASSYSTEMS-677] CMS DT vaisala reading difference between SG and US - CERN Central Jira
CMS-FGR -> TICKET should we add a module. Do we need to buy something? follow-up
CMS-FGR -> TICKET Maria Cristina già fatto per bypass
CMS-FGR -> TICKET flowmeter for Huber
CMS-RPC IR not stable -> elog Maria Cristina -> TICKET
CMS-ID flushing. refurbishing of old racks material and manpower need to be estimated -> TICKET @Gianluca ticket number for project
R134a huber temperature can be controlled by PLC -> TICKET
LHCb
TS1-> RICH1 leak search (postponed), SciFi some work from others expected
RICH1 what we learn from 1st fill -> [GASSYSTEMS-608] RICH1 what we learn from 1st fill - CERN Central Jira
summary of the C4F10 bottles --> TICKET or ELOG -> [GASSYSTEMS-660] summary of the C4F10 bottles - CERN Central Jira
alarms blocked: [GASSYSTEMS-631] LHCb alarms blocked - CERN Central Jira
RICH2 filter blocking -> [GASSYSTEMS-731] RICH2 pump filter differential pressure sensor not working - CERN Central Jira
P&ID drawing check who is doing -> [GASSYSTEMS-739] LHCb P&ID drawing check - CERN Central Jira
RICH1 cleaning , when? not before mid-september? -> TICKET
RICH1 remove membrane rack before end of HL-LHC operation and/or change piping-> TICKET
RICH2 injection through recuperated CF4 -> TICKET
fire detection alarms reported by Pieter, more info? but not on us. Cleaning of SG room -> TICKET
CODEX-b interlock for flammable gas detection -> Patrick
RICH1 leak repair -> December 9th tbc -> TICKET
NA62
CEDAR maintenance needed -> [GASSYSTEMS-609] CEDAR maintenance needed - CERN Central Jira
change of pressure sensor used for leak warning? -> [GASSYSTEMS-741] NA62-CEDAR move to keller pressure sensor? - CERN Central Jira
GIF++ TGC gas system and return flow: [GASSYSTEMS-624] GIF++ TGC gas system return flow - CERN Central Jira
[GASSYSTEMS-674] MFCs to be checked - CERN Central Jira :
- Fondoscala del MFC di R134A e sensore umidità del gas RPC [GASSYSTEMS-645] Fondoscala del MFC di R134A e sensore umidità del gas RPC - CERN Central Jira
- Neutrino platform gas analysis: [GASSYSTEMS-622] RE: Analisi di outgassing di diversi materiali - CERN Central Jira
- ALICE T10 MFCs: [GASSYSTEMS-669] ALICE T10 TR: calibration MFC pour C4F10 - CERN Central Jira
- ND280 MFCs to check [GASSYSTEMS-679] ND280 MFCs to check - CERN Central Jira
non-LHC safety valve --> check lista di Fabio
[GASSYSTEMS-172] non-LHC safety valves to be verified - CERN Central Jira
ELOG - safety valves to be verified for non-LHC systems
Additional requests/projects/discussions
887 CEDAR new "mixers" --> [GASSYSTEMS-509] CEDAR for beam lines - CERN Central Jira
AMBER
EDMS leak test?
test certificate x-ray?
ATEX certificate?
who is technical coordinator
resource manager Oleg D?
no money? should we stop? and resume in 2026?
Commissioning when? -> TICKET
when they would like to start? Moritz? -> ask
LEAK DETECTORS LIST -> TICKET
MAINTENANCE INTERVENTIONS WORK ORDER FOR STATISTICS -> TICKET
PROJECT 2025
summary TICKET
examples of topics for the common discussions:
-cms id flushing -> Andrea
-cms r134a operation and spare -> Andrea
-cms cf4 operation and spare -> Andrea
-atl tgc nc5h12 -> Kacper
-Analysis boxes -> LPh
-C4F10 new recuperation installation -> Patrick
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