Commissioning and running of sPHENIX

["Hughes, Charles [PHYSA]" <chughes2 AT IASTATE.EDU>]

Hi everyone,

I thought I would send a notification. Since 5 PM yesterday, the power to the racks had been progressively turned off to prepare for the 8 AM test today - it turns out this is actually not a good thing for the ECW system.

When you turn off > 50 % off the racks, it causes the pressure to build in the ECW lines and at the pump because the cooling water is shut off to the rack. During the past few hours, the pressure at the pump had built up to a concerning level (90 psi - close to "dead head")

The system is fine, there were no bursts, and the pump is ok - this was confirmed by a tech (Peter) this morning upon discovering the high pressure and reducing it. However, there was a break-down in communication between the subsystem experts/shifters/tech crew at some point.

What the techs wanted us to do to prepare for the 8 AM test was for the subsystem experts to shut off LV/HV ONLY - not to shut off power at the racks. The techs were then going to progressively turn on the bypasses, THEN shut off the power at racks.

So essentially techs themselves were going to shut off rack power AT 7:30 AM, but the shift crews/subsystem experts thought they needed to power down racks BY 7:30 AM (AT got swapped for BY).

This particular issue (shutting down > 50 % of racks) is not expected to occur during runs except in case of an e-stop during the run. The techs inform me that during an e-stop, the pump will shut off. The pump didn't shut off this time because we manually powered off the racks - this won't happen again before the run. This was a special condition for today's test only.

In the future, should something like this happen (it should not but if it does) there will be an alarm for increased pressure at the ECW pump. In this case, the shifters would be directed to call one of the techs/ECW experts. The ECW expert might then direct the shifter to turn on the bypass valve in the rack room - which would relieve system pressure. It is in the back left corner by the door to the assembly hall (blue handle). Note that you should NEVER touch this unless directed to do so by a tech/ECW expert.