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The MR System (magnet) requires a cryogenic venting system to direct helium gas to an
unoccupied space if the magnet quenches. The cryogen venting system must direct all the
helium gas outside the facility, and it must keep all helium out of all facilities. The helium in the
magnet is a cold gas, which rapidly expands as it becomes warmer. The cryogen vent designer
must adhere to the following requirements for the material, construction and maintenance of the
vent. The customer is responsible for all of the cryogenic venting system.
Note the following:
1. All pipe or tube dimensions specified in this document are outside diameters unless
otherwise noted
2. See Magnet Cryogenic Venting Pressure Drop Reference Tables to calculate pressure drop
for a specific system
Table 3-4: Magnet Cryogen Specifications
Magnet Types
1.5T LCC RD Magnet
8.6 Vent Requirements Inside the Magnet Room
8.6.1 General
1. The customer is responsible for design, installation, and maintenance of all cryogenic
venting materials inside the Magnet room
a. The cryogenic vent must be connected to the magnet within 24 hours of magnet delivery
b. Appropriate ventilation must be provided to evacuate the helium gas in the case of a
quench before the magnet is connected to the cryogenic vent.
2. The cryogenic vent must not transfer load to the magnet adaptor
3. GE Healthcare provides a flanged vent adapter that is 8 in. (203 mm) OD and 24 in. (610
mm) long. GE installs it straight up from the magnet (inline with the waveguide in the RF
shield). The vent tube can be cut as short as 4 in. (102 mm). See
4. The customer must provide any additional vent tube (above the 1.0 ±0.25 in.gap) beyond
the 24 in. (610 mm) provided
5. Other cryogenic venting systems are allowable (e.g., sidewall, ceiling offset) as long as all
other cryogenic venting requirements are met
6. Do not remove or modify the vent adaptor bolted to the magnet
NOTE:
The GE Healthcare supplied flanged adapter must be bolted directly to the magnet
vent adaptor bolt flange
7. The vent must be located within 0.25 in (6.35 mm) of the location (in relation to isocenter)
shown in
Illustration 3-20
8. A 1.0 ±0.25 inch (25.4 ±6 mm) isolation gap must be included at the top of the GE
Healthcare supplied vent tube
86
Helium Volume gallons (liters)
520 (1970)
SIGNA Voyager Pre-Installation
Direction 5680008–1EN, Revision 2
Peak Helium Flow During
Quench ft³ per min (m³ per min)
2737 (77.5) [Gas]
See,Section 8.3
Illustration
8 Magnet Room Venting Requirements
Magnet Vent Pipe OD inches
(mm)
8 (203.2)
3-15.
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