Agilent Technologies Varian MERCURY Series, Installation Planning

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2.12 Ventilation
01-999021-00 A0100 Installation Planning Guide
21
2.12 Ventilation
Air ventilation must be adequate to displace
the liquid helium gas during a quench,
especially when using any type of volatile
liquid for variable temperature experiments.
Consult with a safety engineer on this
subject. Gaseous helium or nitrogen
exhausted from the magnet will displace
oxygen and cause asphyxiation if not
properly ventilated. During a magnet quench,
the evaporated helium is exhausted from the
manifold by the pressure relief valves. The
amount of gas depends on the amount of
liquid helium held by the magnet.
Table 9
lists the amount of liquid helium for each
magnet.
The expansion ratio of liquid helium at room
temperature is about 740:1, meaning that for
every liter of liquid helium you get about 740
liters of helium gas
2.13 Helium and Nitrogen Refill Volumes and Intervals
Table 10 lists typical refill volumes and intervals for helium and nitrogen. Locating a
reliable local source of liquid helium and nitrogen is particularly important. Use the values
listed in
Table 10 when making arrangements for an on-going supply of liquid helium and
liquid nitrogen.
Table 9. Liquid Helium Displacement
for Room Ventilation Considerations
Magnet/Bore
(MHz/mm) LHe Max. Volume
(liters)
200/54 30
200/54 LH235 87
200/54 LH365 136
300/54 30
300/54 LH235 87
300/54 LH365 136
400/54 74
400/54 LH365 123
Table 10. Helium and Nitrogen Refill Intervals and Volumes
Magnet
(MHz/mm) Helium Refill Interval
(Days) Helium Refill Volume
(Liters) Nitrogen Refill Interval
(Days) Nitrogen Refill Volume
(Liters)
200/54 80 26 14 32
200/54 LH235 235 79 14 61
200/54 LH365 365 122 14 67
300/54 80 26 14 32
300/54 LH234 234 78 14 61
300.54 LH365 365 122 14 67
400/54 183 61 14 61
400/54 LH365 365 106 14 67