4.1 Required Installation Supplies and Equipment
01-999021-00 A0100
Installation Planning Guide
33
Helium Gas Supply
lists the recommended
number of helium gas cylinders. A
regulator must be provided. Each
cylinder should hold at least 8000
liters (285 ft
3
). The helium gas must
be the highest purity available, not
less than 99.995% or U.S. Bureau
of Mines Grade A.
Helium gas can be supplied in a
magnetic container, provided the
unit remains outside the 5 gauss
limit of the magnet and the cylinder
is firmly secured to avoid
movement caused by magnetic field
attraction.
Nitrogen Gas Required for Magnet Installation
During installation, one cylinder of nitrogen gas is required for precooling the magnet and
for transfer of liquid nitrogen. Nitrogen gas can be supplied in a magnetic container
provided the unit remains outside the 5 gauss limit of the magnet and the cylinder is firmly
secured to prevent attraction to the magnet.
If the system is equipped with the variable temperature accessory, a nitrogen gas supply is
required. If a fixed source is not available, obtain a nitrogen gas cylinder with pressure
regulator. The gas must be dry and chemically pure with a flow rate through the pressure of
19 LPM (40 SCFH) at 207 kPa (30 psig). For low-temperature operation, use prepurified
grade gas (99.99%, –85
°
C dew point).
CAUTION:
To avoid movement caused by magnetic field attraction, helium gas
and nitrogen gas cylinders made of magnetic material must be kept
outside the 5-gauss limit of the magnet and firmly secured.
Face Mask and Thermal Gloves
If cryogenic helium or nitrogen contact living tissue, a serious injury (similar to a burn) can
occur. Order appropriate safety coverings for use during dewar servicing, including a mask
that protects the face completely and loose-fitting thermal gloves.
WARNING:
Avoid helium or liquid nitrogen contact with any part of the body. If
liquid helium or nitrogen contact living tissue, a serious injury (similar
to a burn) can occur. Never place your head over the helium and
nitrogen exit tubes on top of the magnet. If helium or nitrogen contacts
the body, seek medical attention, especially if the skin is blistered or
the eyes are affected.
Heat Gun
Order a 120 or 220 Vac, 20 A heat gun (Dayton Model 27046 or equivalent) for thawing ice
accumulation and drying out moisture on dewar servicing equipment.
Table 17. Helium Gas Supply
Magnet field
(MHz)
Helium gas
(cylinders)
200/54
1
200/54 LH235
2
200/54 LH365
2
300/54
1
300/54 LH235
2
300/54 LH365
2
400/54
1
400/54 LH235
2
