SME's
- Adam White, adamwh@slac.stanford.edu
- Cynthia Melendrez, cymel123@slac.stanford.edu
- Chris Koerber, ckoerber@slac.stanford.edu
Hazards and Mitigations
- Asphyxiation
- Oxygen deficiency monitors (ODM) are required to be around dewar
- DO NOT ride with this on the elevators and use caution tapes inside the elevator
- Don't do work in small confined areas, areas must be approved to have a dewar in it
- Burns and fost bite
- Wear proper cryogenic PPE
- Keep heating gun around at all times.
- Do not touch frosted items without gloves!
- When inserting items into the dewar go slow! It needs to cool down or else it will boil.
- Heat valves with heat gun as needed to operate them.
- Crushing
- Wear steel toe shoes when moving the dewar.
- Do not tip dewar
- Pressure
- Vent the system in safe manner before doing work on the dewar
PPE
- closed toe shoes
- long pants
- cryo gloves
- face shield
- a cryo apron
Equipment
- He dewar bubbler (optional if there is a scale)
- It is a long ~8ft section of 3/8" SS pipe with a dropper squeezer on the end. On the bubblier are two zip ties or clamps to help tell volume
- Scale
- 9/16 open ended wrench
- 2x adjustable wrenches
- Balloon grade helium
- All PPE called out above
- Heater Gun
- Ladder
- Measuring tape
Procedure
You and one other person review the various valves on the stinger and helium dewar
- Bring a new dewar down to the hutch that needs the replacement. Do not ride on the elevator with it!
- On the stinger in the dewar, spin the needle valve counterclockwise to close the valve.
- Turn off the roughing pump that is hooked up to the cryohead.
- Close the cylinder that is hooked up to the dewar and isolate it.
- Close all valves on the dewar. You will not be able to close the vertical one because the stinger is in it.
- Vent the poly line that connects the dewar to the helium cylinder and undo the swage fitting on the the dewar side of the poly line.
- Wearing gloves and a face shield, open the low pressure relief vent valve to vent out the oolage of the dewar. Keep this open for the remainder of the procedure. Verify that the pressure is dropping on the dewar's gauge.
- Keep an eye out for the PRV to freeze over. Use the heat gun to warm up it up so the pressure relief device doesn't freezing open.
- Once the pressure is ~ 1 psi in the dewar, start to unscrew the seal that holds the singer into the dewar. You may have to wiggle it a bit.
- Take off the "Y" manifold on the horzontal vent valve off, break behind the 1/2" SS NPT female thread.
- Deploy a ladder right next to the dewar
- Both people need to wear all PPE called out above
- One person will climb the ladder and the other stands near the dewar
- The person on the ladder will grab the braided hose and near the valves and start to lift up while the person below keeps them lifting straight up and wiggling the stinger.
- Once it is fully out of the dewar close the vertical valve.
- You may have to pass it back an forth in order for them to climb down the ladder and rest it on a safe place.
- Start up the vacuum pump that is connected on the cryo head and make sure stinger is needle valve is fully closed.
- Start to heat up the whole stinger with the heating gun for about 10 mins then focus on the very end near the
- Undo the ratcheting straps that tie down the dewar
- With two of you remove it from the scale if it is on it, then roll up to the loading dock.
- Remove the ODM
