-Gas shed reset procedure http://www.jlab.org/~adaq/halog/html/0805_archive/080521112039.html
Looking in the EPICS archiver the gas system UPS seems to have gone down at 2:50AM this morning. The system was restarted at 9:50AM. The UPS supplies power to the pneumatic valve controllers, the system interlock box and the monitoring VME crate. The VME crate only reads the status of various things in the system. It is not used for any of the controls. So, if the VME crate itself goes down that does not necessarily affect the gas flow. If the Detectors Gas System Interlock Status unit loses power it cannot send an indication of trouble to the display unit in the Counting Room. The Counting Room will have no alarm from the display unit, nor will any LEDs be lit. If the Detectors Gas System Interlock loses power, the solenoids on the argon and ethane low pressure side of the manifolds will close. The gas will stop flowing to the VDC gas mixing subsystem. The VDC gas flow will not cease immediately. It looks like gas stopped flowing through the VDCs at 3:45AM. When the pneumatic valve controllers lose power the pneumatic valves close. These valves are on the high pressure side of the manifolds, one for each cylinder. This will close off each cylinder and no gas will flow out of them. If the pneumatic valves are closed for a long enough time the pressure in the nitrogen lines will bleed down low enough that even after power is restored there is not enough residual pressure in the nitrogen line to activate the pneumatic valves. In this case one needs to make sure the Right side nitrogen cylinder is "online" and then open the bypass valve by the Nitrogen manifold to charge the lines. Once the line is charged and the pneumatic valves are functioning the bypass valve must be closed.