Refill of LN2 in 190 liter Dewar

The big, heavy Dewar is mounted on a trolley with a scale integrated in the trolley.

The Dewar can be disconnected from the CryoRIE and moved to the liquid nitrogen generator room for refill. The scale is used to measure how much LN2 is filled.

Filling procedure details

One liter of LN2 weighs 0.81 kg
150 liters of LN2 weighs 121 kg
The dewar is mounted on special trolley with integrated scale.
The scale readout display is the blue-grey box with four buttons mounted on a black vertical bar.

The scale electronics is hooked up to a battery charger in this picture. This charger must of course be disconnected before moving the trolley.

The base of the scale is mounted on a special trolley.

 


There are three valves at the top of the Dewar:
  1. Blue valve, inlet/outlet valve, used for tapping off LN2 and refilling
  2. Green valve, used for pressurizing the Dewar
  3. Grey valve, outlet for boil-off, used for depressurize the Dewar

 


Principal sketch of the Dewar:
  1. Blue valve, inlet/outlet valve, tube going to bottom of Dewar.
  2. Green valve, used for pressurizing the Dewar, letting some LN2 out of the dewar towards the inner surface, increasing boil-off, thus increasing pressure.
  3. Grey valve, outlet for boil-off, used for depressurize the Dewar, tube ending above LN2 surface.
  4. Pressure regulator to control what pressure is reached, usually 4 Bars.
  5. Manometer, pressure gauge.
  6. Safety valve (over pressure valve).
  7. Safety valve, double for increased safety (if one gets stuck).
  8. Level indicator.

 


The level indicator.

 


The level indicator and the two safety valves.

 


The manometer showing 4 Bars (60 PSI).

Filling procedure details

Anders Liljeborg Nanostructure Physics, KTH.