1) The ethane bottle that is valved ON (as I found it at ~06:00) reads about ZERO on the weight scale and is tagged 'IN USE'. This is the bottle on the right-hand side. The bottle valved OFF (left side) indicates about 15-20 pounds and the tag reads 'EMPTY'.
2) All three GasMaster channels (which read the flammable gas sensors) have drifted up away from 0%. Channel 1 (gas shed) reads 7-8% LEL while Channels 2 and 3 (HMS hut and SOS hut) both read 5% LEL. This system was last calibrated on April 17, 2007. Historically, calibration every 12 months has been sufficient.
3) A 'HIGH' alarm on the GasMaster occurs when the reading exceeds 20% LEL. Only a 'HIGH' alarm interrupts the gas supply. If one of the channels momentarily read higher than 20%, this would have shut off the gas and caused a "Low PSI" condition on the gas interlock panel. Given the current baseline reading of 8% on channel 1, I'm surprised if the reading drifted above 20%.
Given the confusion about bottle weights and tags, which bottle
is/was actually valved ON, and the baseline drift in the GasMaster,
it is unclear what originally caused the gas system alarm. I'll
check with the technicians when they do their gas shed check around
0800.
A copy of this log entry has been emailed to: kenyon@jlab.org, vulcan@jlab.org, beaufait@jlab.org