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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
    • 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
  • All PPE called out above
  • Heater Gun
  • Ladder
  • Measuring tape

Procedure

  1. You and one other person review the Helium Dewar Valves Picture below.
    1. Image Added
  2. Plug in heat gun and keep it ready.
  3. With both of you wearing all the appropriate PPE and in a safe place to test a dewar. Remove the plastic cap if it is still on but keep it nearby.
  4. Slowly open up the vertical valve on the very top of the dewar until the pressure is low.
    1. Be careful as to no stand over it, wait for frosty air to subside.
  5. Deploy ladder nearby so you can reach approximately 6 ft above the dewar.
  6. With one person standing on top of the ladder and the other helping guide, insert the bubbler all the way into into the bottom of the Dewar through the vertical valve.
    1. If you go too quick it will boil off too much helium and get everything very frosty.
  7. Once at the bottom move both zip ties to the neck of valve. These are your indicators.
  8. Now the person on the ladder takes off one glove, be sure to not touch any frosty parts of the cryo system, to better feel the measurement of the liquid.
  9. They will place their fingers gently squeezing the dropper knob and slowly lift the bubbler out of the dewar.
    1. They will feel the dropper



Further Reading