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8.1
Setting Up the Autofill System
Your pressurised dewar must be equipped with a pressure regulator or pressure relief
valve which will ensure that the pressure does not exceed 1.5 bar. If the dewar has a
pressure build circuit, you may not need to use it, as adequate pressure will build up
naturally. A pressure in the range 0.3 to 1 bar (4 to 15 psi; 30 to 100 kPa) is recommended,
but up to 1.5 bar (22 psi, 150 kPa) is acceptable.
Insert the level probe into the straight stepped port on the dewar top fitting (Figure 3).
Push it down firmly until it goes no further. You may need to twist it to ensure the O-ring
seal slides over the top of the port.
Connect the level probe to the level meter using the cable supplied.
Check that the level meter is set for the correct supply voltage. This is indicated on the
back panel, just above the power supply socket. Switch on. Check that the label on the
solenoid valve indicates the correct voltage.
Remove fitting A from nut B on the autofill assembly (Figure 10).
Figure 10 Autofill nitrogen hose, detail of the end near the pressurised dewar
Screw fitting A into the liquid outlet of your pressurised dewar, using PTFE tape. (The
appearance of item A will depend on your dewar).
Engage the brass tube into fitting A, ensuring the ferrule is correctly positioned on the
tube and tighten nut B using two spanners. It is good practice for the solenoid valve to be
above the hose, so that water does not drip onto it.
Attach the other end of the nitrogen hose to the dewar top fitting, using the stainless
steel compression fitting that is normally already fitted to the end of the hose. If the nut
and ferrule (olive) are already on the dewar top fitting, just slide the end of the hose onto
the fill port, and tighten the nut securely using two spanners. If not, slide the nut and the
ferrule onto the fill port first, then slide the end of the hose on afterwards until it stops.
Ensure the hose is pushed down as far as it will go while you tighten the nut.
