Air Products Gasguard 250, Installation Manual

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Gasguard
®
250 VMB System Installation Manual
Air Products and Chemicals, Inc. Page 3 - 6
3.4 Venturi Line
Air Products strongly recommends a separate venturi supply source rather
than a houseline source.
Most process cylinder pressures are significantly higher than houseline operating
pressures. In the event of multiple failures of certain process panel components,
there is a remote possibility of back contamination of the houseline source
connected to the vacuum venturi.
Contact your Air Products representative for design details.
The venturi line requires 75-95 psig of nitrogen to adequately produce the vacuum
needed during purge cycles. The supply is usually taken from a bulk liquid source,
but it can also originate from a cylinder manifold system. The vacuum generator
will demand a flow of 50-60 LPM of nitrogen during purge cycles.
3.5 Purge Line
A purge line is provided for connection to the designated inert purge source for the
valve manifold box. The pressure required during purging is 80-90 psig. The
external purge source must have sufficient over pressure protection. Do not
exceed the valve manifold box component maximum allowable working pressure
(MAWP) in the event of purge source regulator failure.
The purge gas source for the valve manifold
box should be used only to purge other
VMBs or gas cabinets handling the same
process gas. It must not be used to purge
systems handling other process gases. It is
recommended that the purge gas cylinders
be placed in an exhausted enclosure.