44 400/54 Premium Shielded NMR Magnet System Product Overview
3 Maintenance
7
Precool the siphon.
8 Insert the transfer line into the transfer Dewar top seal
and then open the top valve.
9 Insert the transfer siphon into the liquid in the Dewar,
which causes the liquid to boil and the pressure to rise.
As the siphon cools, the vapor becomes denser and more
opaque, and eventually the transition is made from vapor
to liquid. This process usually takes a couple of minutes.
The liquid vaporizes immediately on contact with air.
If during this process, the transfer line develops frost or
is cold to touch, then the transfer siphon may have
insufficient vacuum or may be damaged. If insufficient
vacuum is suspected, then stop the helium fill until the
problem with the transfer siphon is resolved. If there is
insufficient vacuum in the transfer siphon, then pump it
down using a vacuum pump connected to the siphon,
using a siphon pump out tool (part number P222000008,
available from Agilent Technologies). If the siphon is
damaged and has a touch, then a replacement is probably
required.
Figure 10 Top seal of the Dewar
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