40 400/54 Premium Shielded NMR Magnet System Product Overview
3 Maintenance
5
After the fill, check that the o- rings are in good
condition and return the heat sinks/valves to the turrets.
6 Tighten the grub screw on the safety valve (if present).
7 Finally, check that the digital nitrogen monitor is reading
full. If not, follow the simple instructions for recalibrating
the nitrogen probe, outlined in the cryogen monitor
manuals section of this manual.
How to perform a standard helium fill (top-up)
The calibration charts and minimum levels for the helium
probes are given in Chapter 4, “Reference”. A separate
Helium Level Chart was also provided for your reference to
locate near the magnet.
This system has two helium turrets, one with 10- pin seals
fitted, the other with none. Fill from the side without the
10- pin seals (recommended). However, if logistically difficult,
you can perform top- ups from the other side, provided
sufficient care is taken not to damage the electrical wires in
the neck.
Figure 4 Recommended turret for helium fills
For the helium top- up, the helium siphon, phase separator,
and the helium fill adapter (all provided) are required, as
well as a nonmagnetic helium storage Dewar of appropriate
capacity.
Follow these instructions carefully to ensure that the magnet
is topped up quickly, cleanly and efficiently. Following these
instructions minimizes any exposure of the helium can to
air, avoids damage to connectors and baffles, helps maintain
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