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SME's
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, helium dewar, below
![](/download/attachments/363439664/image2022-11-2_15-51-59.png?version=1&modificationDate=1667435784000&api=v2)
- Stinger Valves
![](/download/attachments/363439664/image2022-11-3_9-51-59.png?version=1&modificationDate=1667494319000&api=v2)
If there is already a dewar hooked up to the crysostat start here:
- Bring a new dewar down to the hutch that needs the replacement. Do not ride on the elevator with it!
- On the stinger, 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.
- 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 to air and undo the swage fitting on the the dewar side of the poly line.
- Open the low pressure vent valve to vent out the ooliage of the dewar, reading is on the gauge.
- Keep an eye out for the PRV to freeze over. Use the heat gun to warm up the valve or the pressure relief device to stop them from freezing over.
- Start to unscrew the seal that holds the singer into the dewar. You may have to wiggle it a bit.
- Once the pressure is gone, deploy a ladder nearby the dewar.