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Reports until 19:22, Friday 18 August 2023
H1 PEM (DetChar)
robert.schofield@LIGO.ORG - posted 19:22, Friday 18 August 2023 - last comment - 11:13, Monday 11 September 2023(72331)
DARM 52 Hz peak from chilled water pump at EX: HVAC shutdown times

Genevieve, Lance, Robert

To further understand the roughly 10Mpc lost to the HVAC (https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=72308), we made several focussed shutdowns today. These manipulations were made during observing (with times recorded) because such HVAC changes happen automatically during observing and also, we were reducing noise rather than increasing it. The times of these manipulations are given below.

One early outcome is that the peak at 52 Hz in DARM is produced by the chilled water pump at EX (see figure). We went out and looked to see if the vibration isolation was shorted, it was not, though there are design flaws (the water pipes arent isolated). We switched from CHWP-2 to CHWP-1 to see if the particular pump was extra noisy. CHWP-1 produced a similar peak in DARM at its own frequency. The peak in accelerometers is also similar in amplitude to the one from the water pump at EY. One possibility is that the coupling at EX is greater because of the undamped cryobaffle at EX.

 

Friday HVAC shutdowns; all times Aug. 18 UTC

15:26 CS SF1, 2, 3, 4 off

15:30:30 CS SF5 and 6 off

15:36 CS SF5 and 6 on

15:40 CS SF1, 2, 3, 4 back on

 

16:02 EY AH2 (only fan on) shut down

16:10 EY AH2 on

16:20 EY AH2 off

16:28 EY AH2 on

16:45 EY AH2 and chiller off

16:56:30 EY AH2 and chiller on

 

17:19:30 EX chiller only off, pump stays on

17:27 EXwater pump CHWP-2 goes off

17:32: EX CHWP-2 back on chiller back on right after

 

19:34:38 EX chiller off, CHWP-2 pump stays on for a while

19:45 EX chiller back on

 

20:20 EX started switch from chiller 2 to chiller 1 - slow going

21:00 EX Finally switched

21:03 EX Switched back to original, chiller 1 to chiller 2

 

Non-image files attached to this report
Comments related to this report
jeffrey.kissel@LIGO.ORG - 10:29, Monday 21 August 2023 (72350)DetChar, FMP, ISC, OpsInfo
Turning Roberts reference to LHO:72308 into a hyperlink for ease of navigation.

Check out LHO:72297 for a bigger picture representation of how the 52 Hz peak in the broader DARM sensitivity, and from the Time Stamps in Elenna's plots, they were taken at 15:27 UTC, just after the corner station (CS) "SFs 1, 2, 3, 4" are off.

SF stands for "Supply Fans" i.e. those air handler unit (AHU) fans that push the cool air in to the LVEA. Recall, there are two fans per air handler unit, for the two air handler units (AHU1 and AHU2) that feed the LVEA in the corner station.

The channels that you can use to track the corner station's LVEA HVAC system are outlined more in LHO:70284, but in short, you can check the status of the supply fans via the channels
    H0:FMC-CS_LVA_AH_AIRFLOW_1   Supply Fan (SF) 1
    H0:FMC-CS_LVA_AH_AIRFLOW_2   Supply Fan (SF) 2
    H0:FMC-CS_LVA_AH_AIRFLOW_3   Supply Fan (SF) 3
    H0:FMC-CS_LVA_AH_AIRFLOW_4   Supply Fan (SF) 4
jeffrey.kissel@LIGO.ORG - 13:13, Monday 28 August 2023 (72486)DetChar, ISC, SYS
My Bad: -- Elenna's aLOG is showing the sensitivity on 2023-Aug-17, and the Robert logging of times listed above are for 2023-Aug-18. 

Elenna's demonstration is during Robert's site-wide HVAC shut down 2023-Aug-17 -- see LHO:72308 (i.e. not just the corner as I'd errantly claimed above.).
jeffrey.kissel@LIGO.ORG - 11:13, Monday 11 September 2023 (72805)FMP, ISC, OpsInfo
For these 2023-Aug-18 times mentioned in this LHO aLOG 72331, check out the subsequent analysis of impact in LHO:72778.
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