Air Products GASGUARD TE10, Installation, Operation And Maintenance Manual

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Section 3: Tubing Connections
Revision – February 2005 Page 3 - 7
The purge gas source for the GASGUARD
Distribution System should be used only to
purge other gas source systems or VMBs
handling the same process gas. It must not
be used to purge systems handling
incompatible process gases. It is
recommended that the purge gas cylinders
be placed in an exhausted enclosure. Purge
gas must not be supplied from a low
pressure bulk gas source.
3.6 Pneumatic Supply
A nitrogen (or compressed clean dry air) source is required for this system for
pneumatic valve operation. This nitrogen supply needs to be regulated to 85-95
psig (5.9-6.6 barg). The flow rate required for pneumatic valve operation is
negligible. If compressed air is used as the pneumatic source, the compressor shall
be located in a non-classified area. If the air intake line for the compressor passes
through a classified location, the line shall be made of a non-combustible material
designed to prevent leakage and protect against mechanical damage. If electrical
power for the purge air is required, this power shall be on a separate disconnect or
before the gas
source system
disconnect.
This supply is also used for Type Z purge of the electrical enclosure. In certain areas,
the Type Z purge is required to maintain a positive pressure at or above 0.1" H
2
O
(24.9 Pa). This is in accordance with Article 496 of the National Fire Protection
Agency (NFPA) regulations. In applications where Type Z purge is required, the
controller will be equipped with a pressure switch to monitor the pressure. The Type
Z purge will require a flow rate of approximately 2.5-2.8 LPM (5-6 CFH).
Typically this supply is taken from a houseline nitrogen source. A 1/4" Swagelok
®
connection at the back of the controller is provided for the pneumatic supply inlet
connection as shown in Figure 3.5. Piping for the pneumatic supply must be
protected from mechanical damage. Maximum allowable working pressure is 100
psig (6.9 barg). Over-pressurization protection, such as a safety relief valve, must
be provided for the internal solenoids.