38 400/54 Premium Shielded NMR Magnet System Product Overview
3 Maintenance
Cryogenic Fills
Safety during cryogen fills
How to perform a routine LN
2
fill
For safety reasons, only allow formally trained personnel to
perform cryogenic top-ups.
Wear safety goggles and loose fitting nonabsorbent gloves.
Ensure adequate ventilation and oxygen monitoring of the area
consistent with the volume of cryogens being used. If the oxygen
level in the room falls below 19.5%, do not let personnel enter the
area without self contained breathing apparatus or air line
respirators.
Do not smoke. Liquid oxygen can condense on cold surfaces and
cause a fire hazard.
Never measure the helium level in the magnet cryostat by
“dipping” or “thumping” the helium can.
Do not let the pressure in the nitrogen can exceed 5 psi. Ensure
that the transport vessel has suitable pressure control.
The procedure given in this section assumes that there is some
liquid nitrogen left in the nitrogen can. Cooling and filling an
empty nitrogen can requires additional precautions. Contact
Agilent Technologies if you suspect that the liquid nitrogen has
run out.
The initial precool of the magnet helium can and nitrogen can is a
skilled task. Allow only suitably qualified personnel to perform
this task.
It is important to stop the transfer once LN
2
is seen to issue from the
nitrogen can. If the system is left unattended, it is possible to freeze
the OVC o-rings and cause a catastrophic loss of vacuum.
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