MRI Quench Vent Requirements & Design Considerations
An MRI quench vent system is a critical part of an MRI installation, providing a dedicated path for helium gas to safely discharge from the magnet to the exterior of the building during a quench.
During a quench, liquid helium rapidly changes to gas and expands dramatically as it returns toward ambient conditions. This rapid expansion creates significant flow, temperature, and pressure considerations that must be accounted for when designing the vent system.
A properly designed quench vent system must be fabricated and installed according to the MRI manufacturer’s requirements, project specifications, applicable building codes, and the specific configuration of the installation.
Every MRI Installation Is Different
There is no one-size-fits-all quench vent system.
The required configuration depends on the MRI manufacturer and model, magnet location, building layout, vent route, termination location, required pipe diameter, material specifications, thermal movement, support requirements, and applicable project specifications.
That’s why accurate system dimensions and a centerline schematic are so important when ordering a custom quench vent system.
Need a Quench Vent System?
Ernie’s Welding & Fabricating has manufactured MRI quench vent systems and components for decades. Our Quench Vent Division works directly with the requirements of the major MRI manufacturers to provide complete systems, replacement components, bellows, terminations, RF shielding, waveguides, and custom-fabricated assemblies.
Have a drawing or system layout? Send it to us and we’ll help determine what you need.
Material Requirements
MRI quench vent systems are typically fabricated from non-magnetic stainless steel, with 304 stainless steel commonly used for vent piping and components.
Material selection is important because the vent system is located in the MRI environment and must be compatible with the magnetic field and the extreme conditions associated with a quench.
Depending on the system design, quench vent assemblies may include:
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Stainless steel pipe and tubing
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Elbows and formed sections
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Flanged connections
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Bellows and expansion joints
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Flexible sections
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Supports and guides
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RF shielding
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Waveguides
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Exterior terminations and weather caps
Ernie’s Welding & Fabricating manufactures these components to the dimensions and specifications required for the individual MRI installation.
Thermal Expansion & Flexible Sections
The temperature change during a quench can be extreme. The vent system must therefore be designed to accommodate thermal expansion and contraction without compromising the integrity or alignment of the piping.
Stainless steel bellows and flexible sections may be incorporated into the system where required to accommodate thermal movement.
Proper placement of expansion components, supports, and guides is important to allow the system to move as designed while maintaining the required alignment.
Vent Routing & Geometry
Quench vent routing should be designed to provide an efficient path from the MRI magnet to the exterior termination.
Where practical, the system should minimize unnecessary changes in direction and restrictions. The overall configuration, pipe diameter, length, fittings, elbows, and elevation changes all contribute to the system’s pressure drop and must be considered during design.
Quench vent systems should not contain unnecessary restrictions, valves, dampers, or other components that could interfere with the required flow path. Any components incorporated into the system must be approved for the specific MRI application and manufacturer requirements.
Avoiding Low Points
Vent routing should also be evaluated for areas where condensation or moisture could collect.
The system should be configured to minimize the possibility of accumulated moisture or ice restricting the vent path. Where the installation requires drainage provisions, those provisions should be incorporated into the system design.
Pressure Drop & System Performance
Pressure drop is an important consideration in MRI quench vent design.
The vent system must be sized and configured to meet the maximum allowable pressure and pressure-drop requirements specified for the particular MRI system.
Pressure drop can be affected by:
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Pipe diameter
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Overall pipe length
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Number and type of elbows
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Changes in direction
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Bellows and flexible sections
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Transitions and connections
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Exterior termination configuration
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Elevation changes
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Because these requirements vary between MRI systems and manufacturers, there is no single pressure-drop value that should be applied to every installation.
Ernie’s works from the applicable manufacturer and project specifications when fabricating custom quench vent systems.
Building Supports & Guides
A quench vent system must be properly supported by the building structure.
Supports and guides serve different purposes. Supports carry the weight of the piping and components, while guides help control movement and maintain alignment as the system experiences thermal expansion and contraction.
The support system must also account for the forces generated during a quench and the structural requirements of the particular installation.
Exterior Termination
The exterior termination provides the final discharge point for the quench vent system.
The termination must be positioned and configured according to the applicable MRI manufacturer requirements, project specifications, and building requirements. Roof and wall penetrations must also be properly coordinated with flashing and weatherproofing.
The discharge location should be selected to provide appropriate clearance from building openings, occupied areas, air intakes, and other locations where discharged helium could create a hazard.
RF Shielding & Waveguides
MRI installations can also require specialized RF shielding and waveguide components where the quench vent system passes through or interacts with the MRI room’s RF shield.
These components must maintain the integrity of the RF enclosure while allowing the required quench vent configuration to pass through the shield.
Ernie’s manufactures custom components and assemblies to accommodate the specific dimensions and requirements of the installation.