Kyle and I replaced a bad solenoid valve on the compressed air drying tower skid outside after getting alarms 'after hours'. Loss of compressed air caused the safety valves on the three turbo stations to close and thus spin down turbos. It also caused GV 6,8 to sag. After we regained compressed air we spun turbos back up, but YBM turbo is being difficult and keeps shutting itself down due to vibration (a known issue). We tried all the tricks with bypass valve and air admittance to load rotors. We'll let it spin 100% down tonight and try again tomorrow. I closed all three turbo isolation gate valves in a timely manner so the corner should not have been affected from back streaming. Pressure rose for a period while turbos were valved out. I didn't have time to check on in-vacuum high voltage equipment - don't think anything was turned on.

FYI: we did not replace the solenoid portion of the valve at the drying tower.