Gas systems 2026-09-24
The meeting addressed multiple active technical issues across gas systems, including a pump failure triggered by a power cut, humidity regulation problems, and purifier pressure anomalies. Several maintenance actions were completed or are in progress. Planning for upcoming power cuts, holiday coverage, and gas mixture changes for Atlas was also confirmed.
ATLAS-MDT :
· Power cut caused the primary pump to restart with abnormally high current draw; gas circulation was insufficient and did not trigger alarms due to oscillation.
· Switched to Pump 2 / second inverter; system stabilized after several hours of valve bypass adjustment.
· Not adequate protection of the pump during the power cut — possible mechanical or electronic fault; investigation ongoing.
· ATLAS-RPC Humidity reached ~12,000 ppm, above setpoint; likely linked to purifier pre-saturation and delayed regeneration during the stop.
· A second power cut is scheduled for Friday; operators confirmed they will restart everything promptly.
· During a prior incident at CMS, the first alarms received were for chamber pressure regulation, not the purifier — a gap in monitoring coverage.
· Proposal: add a dedicated high-pressure alarm on the purifier (e.g., trigger when purifier pressure exceeds loop pressure by >200 mbar).
· Challenge: determining a meaningful pressure threshold for the alarm, particularly for Purifier 2 (located after the buffer).
· High purifier pressure relative to buffer may indicate a clogged column or closed output valve.
· Buffer pressure alarm was received ~6 minutes late; suspected unit error in the delay setting (possibly "5 seconds" written as "5 minutes" in the recipe).
· Pump 2: clapper on top was completely broken and replaced; pump still not performing well after fix.
· Pump 3: also not producing good output despite appearing intact.
· Currently running on Pump 1 only as the sole reliable pump.
· Plan: replace clock/flap components on all pumps preventively, even if not visibly broken; both non-return valves after the pump replaced and in good condition.
· CO2 pressure drop on Column B : vacuum leak test proposed; results to be compiled and reviewed with Max.
· PLC logic issue: valve opening requests below ~10% of full scale are ignored by the software as "unreliable" — problematic when operating without a purifier and requiring very fine flow control.
· Action: check and correct this threshold logic with Gianluca.
· Atlas confirmed: switch back to isobutane from 5–16 October (2 weeks).
· After isobutane period, all flammable gases removed until approximately end of January (PGS panel work).
· Reminder issued: mixture change requires 3–5 days to stabilize; cannot switch directly to avoid destabilizing regulation valves and manual bypass paths.
· NA62 chamber disconnection: targeted for tomorrow (with Fabio) or early next week; Roberto to add Fabio to the access permit.
· PGS/Vago modules: cables to be disconnected now to prevent interference when PGS cuts cables; PLC node to be kept temporarily until final fate of Vago hardware is confirmed.
· Electrical part of microcirculation system: scheduled for week 46; mechanical and electrical parts to be ordered; Stefania to provide material arrival estimate at next meeting.
· Gianluca: Investigate PLC logic for minimum valve opening threshold below 10%. CMS-RPC humidifier
· Maria Cristina: Review purifier pressure trend; assess feasibility of dedicated purifier high-pressure alarm.
· Gianluca: Verify buffer pressure alarm delay unit (5 seconds vs. 5 minutes) in recipe.
· Davide/Roberto / Fabio: Proceed with NA62 Straw chamber disconnection; coordinate access permit with Roberto.
· Jonathan / Davide: ATLAS: Disconnect PGS/Wago cables from current system; defer PLC node removal until hardware fate confirmed.
· Stefania (microcirculation): Order mechanical and electrical material; report estimated arrival at next meeting.
· Davide/Max/GIanluca: Execute Atlas isobutane mixture change starting ~5 October, allowing 3–5 days for stabilization.
· Davide/Max/Gianluca: Check historical pump test record to identify which pump had the prior current absorption problem ATL-MDT.
· Christmas shutdown covers 20–25 December (inclusive).
· Several team members confirmed unavailable during this period; schedule definition still pending for a ~3-week window.
Gas systems 2026 09 17
· Gianluca: Check PLC logic for humidifier mass flow controller minimum opening threshold (with Gianluca, back next week) CMS-RPC.
· 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
Gas systems 2026-09-03
Action Items
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
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 :
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
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