1. VELO-cooling Pump pressure PT003P April  December C-side A-side Filters replacement  action successful VELO meeting

2. CO2 pump maintenance • Planned procedure for a pump maintenance while keeping the detector • cold. • cool the accumulator to -40 oC, such that all liquid gets sucked • into it. • The rest of the system will be much warmer and only contain gas • at 10 bar. • close the valve at the input of the accumulator • close the 2 valves at either side of the pump, in order to isolate • this pump section from the rest of the system • open the valve at the input of the accumulator • warm-up the contents of the accumulator, such that the system gets • filled with liquid CO2 • start the cooling system with the 2 remaining pumps • perform maintenance on the isolated pump VELO meeting

3. TL TR TLR = hand valve = electrical valve However, ……….. VELO meeting

4. In the startup-procedure of the cooling system the PLC opens all electrical valves at either side of a CO2 pump, making the planned procedure impossible for the TR and TLR pumps. So Krista and Martijn had to service the TL-pump. Trick for the other two pumps: either create a service mode in the PLC or make a special connector for the valve-cable to fool the PLC. VELO meeting