Note: Once the Dewar is empty (roughly it takes about overnight (~12hrs) ), we can attempt flushing the level sensor tubes without warming the Dewar all the way up to the room temperature. If you don't see gHe coming through the level sensor tubes, then warm the cold heads, Dewar up to room temperature.
Check whether the transfer line from the Dewar is installed.
1) Open GV02 (yellow hand valve on QT recovery manifold) a little bit
2) Open VPC and VJV(A/B: depending on which LQ)
3) Regulate GV02 to have no more than 160slm on the HMI-FMR
4) Wait until FMR goes down to lower values (~40-70slm) and check the Dewar pressure is very low (~1 psi).
5) Switch the Liquefier to "Run"+"Manual" mode to warm up
6) Wait for a few hours until the Dewar pressure gets more lower and stabilize.
If the flow is ~150slm-200slm, then it will roughly take about 12 hours to empty the Dewar.
To avoid going the LQ to "Alarm" mode, change the Dewar alarm pressure to 0.5 psi or below (box on the top right corner of the following screenshot).
7) Close GV02, then close VPC and close VJV(A/B: relevant LQ).
8) Turn ON cold-head heaters manually to bring the cold-head temperatures to room temperature
9) Pressurize the Dewar A/B to 8 psi by opening SV501(A/B) and then setting the flow to 20 slm on FC501BQMC (tap this box and enter 20 on the panel popping up on the lower right and press enter).
10) Open VPC, Open VJV(A/B), Open GV02 to regulate the flow from the Dewar to the tank with ~30 slm.
11) Repeat steps (9) and (10) several times until the cold-head temperatures are at room temp. and also the Dewar pressure holding at 8 psi once pressurized.
12) Close the two needle valves close to the Dewar level gauge.
12) Set the Dewar Alarm pressure to -30 psi on the Dewar settings page (this is to avoid the LQ(A/B) going to the alarm mode) on QT HMI (change top right box to -30 psi).
13) Connect a dry-pump with a KF flex hose to the relevant port shown on the following figure (LQ-B top section, LQ-A bottom section: check the labels on the manifold components.
14) Start the pump.
15) Open the relevant hand-valve (shown in the above image) to pump down the relevant Dewar.
16) Then purge/pressuzire using step (9)
17) Repeat steps (15) and (16) a few times by having 15 mins gap between each purge and pump-down.
18) Set the Dewar Alarm pressure back to 1 psi on the Dewar settings page.
19) Open the two needle valves close to the Dewar level gauge.
20) Consider one by one of each tube (at a time) connecting to the level meter (2 copper and 2 plastic) and disconnect each to relieve the gas for a few seconds while the Dewar pressure is at 8psi.
21) Make sure that all 4 tubes are reconnected properly, and also make sure that two needle valves close to the Dewar neck are fully opened.
22) Follow the steps on QT System Starting Procedure to get the Liqeufier back to Run+Auto+Liquefy mode.