Page History

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• 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.
  • Image Added Image Added
• All PPE called out above
• Heater Gun
• Ladder
• Measuring tape

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1. You and one other person review the Helium Dewar Valves Picture below.
   1. 
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.
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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 start to vibrate, but it feel very subtle so you need a gentle touch.
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10. As they lift they will reach the liquid/gas interface. Once that is reached the dropper knob will vibrate even quicker.
11. Move the bubbler down just a little and try to pin point the interface again.
12. Once the interface is identified have the person not on the ladder pinch the bubbler against the neck of the vertical dewar valve as to hold it in place.
13. Then lower the bottom ziptie on the bubbler to the neck of the vertical valve.
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14. Slowly remove the bubbler from the dewar.
15. Measure the distance from the top ziptie to the bottom zip tie. This measurement is called out on the dewar and correlates how full the dewar is.
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16. Close the vertical valve and notify those who should know the amount in the dewar.
17. Heat up the bubbler before touching it with barehands.

Further Reading