20 400/54 Premium Shielded NMR Magnet System Product Overview
2 Installation and Operation Safety
Siting Requirements
Vents or quench ducts
In order to reduce the risk of asphyxiation in the event of a
quench, vent the helium exhaust from the magnet to the
outside of the building. Make sure the ducting to the outside
of the building is of large enough diameter to avoid
excessive pressure build- up due to the flow impedance of
the duct. (This exhaust ducting is often referred to as a
“quench duct”.) Only allow service personnel to have access
to the exit end of the quench duct. In addition, protect the
exit opening from the ingress of rain, snow, or any debris
which can block the system. Inspect the quench duct exit
periodically to ensure that the presence of debris does not
restrict the gas flow.
It is also essential to ensure that any gas which vents from
the quench duct cannot be drawn into any air conditioning
or ventilation system intakes. Carefully locate the exit of the
duct to prevent this situation from happening in all
atmospheric conditions and winds.
Although “quenches” are short- lived and infrequent
phenomena. However, as quench gases are liberated, the
temperature of the quench duct can become low enough to
cause cold burns on unprotected skin. This cold can also
damage electrical wiring or other services routed close
enough to touch the quench duct. (Do not route water pipes
near quench ducts.) Make sure that quench ducts are
protected with suitable proprietary thermal insulation, such
as fiberglass cladding or the equivalent. Make sure that the
thermal insulation is:
• Fire resistant (due to the possibility of condensation of
liquid oxygen)
• At least 50 mm thick
• Resistant to deterioration upon contact with water (Frost
formed on the pipe within the thermal insulation
eventually thaws.)
If a quench duct fails during a quench, gas can release
rapidly into the magnet room, causing the pressure to rise
(and create an asphyxiation hazard there). This pressure rise
can prevent an exit through inward- opening doors along
escape routes. For safety, make sure that exit doors always
open outwards, away from the magnet.
Provide a secondary escape route for large volumes of
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