6500 Series Purge and Pressurization System
I/O Manual
35
7 Installation and operation - the 6500 purge and pressurization system
The 6500 control unit, EPV6500 vent, and manifold can be universally mounted to the customer's
enclosure to produce a certifiable system.
7.1 The ‘pxb’ and ‘pyb’ systems
The 6500 allows the user to configure the system for a ‘pyb’ or ‘pxb’ system.
For ‘pyb’ systems, all electrical equipment within the pressurized enclosure must be rated Zone 2 or 22,
if applicable, and the enclosure contacts do not have to be de-energized when loss of pressure, but an
alarm has to be activated. In the ‘pyb’ mode, the AUX contacts will energize when the pressure drops
below the minimum overpressure set point. Because the AUX is automatically mapped to this alarm, one
output function can be assigned to the AUX contacts.
Note!
The AUX contacts will energize on either function. For applications where the enclosure contacts have to
be de-energized when loss of pressure in a ‘pyb’ classification, choose the ‘pxb’ mode.
7.2 For gas atmospheres
In order to make sure an enclosure does not have hazardous gas trapped inside, purging is required. This
is done any time the enclosure is below the minimum overpressure in the hazardous area. For purging, a
protective gas is introduced into the enclosure so that the pressure builds up and the flow is exhausted
through the enclosure. The measurement of this flow is achieved through the vent which feeds back to
the control unit pressure and flow. The enclosure must be purged at least 5 times its volume (10 times for
motors) before it is purged of hazardous gas. The enclosure then must maintain a minimum pressure to
prevent the hazardous atmosphere from entering into the enclosure which power to the enclosure then
can be energized. After purging, the flow into the enclosure can be reduced to hold the pressure due
to leakages. The vent will feed back the pressure to the control unit to alarm, de-energize the enclosure
contacts, and control the pressure, if possible.
7.3 For dust atmospheres
Purging is not required for dust atmospheres. If the enclosure is located in a dust atmosphere and is below
the minimum overpressure set point, the enclosure must be checked and cleaned of all combustible dust,
sealed (door and any other access points closed), and then pressurized to prevent combustible dust from
getting inside. As long as the minimum overpressure is above the set point, the power to the enclosure can
be energized. The vent will feed back the pressure to the control unit to alarm, de-energize the enclosure
contacts, and control the pressure, if possible.
7.4 For dust and gas atmospheres
Danger!
proper certification body or AHJ will have to be consulted.
7.5 Dilution applications
Dilution applications usually deal with gas analyzers that are located inside the pressurized enclosure and
are bringing in a stream of the hazardous gas for analysis. Any equipment including piping, that contains
this hazardous gas within the pressurized enclosure is called the containment system. The containment
system will have the potential to leak under normal and abnormal conditions, with either a known or
unknown leakage rate of this hazardous gas. If the leakage rate is known, the 6500 system may be used to
dilute the area or specific area within the enclosure to make other equipment safe to operate in the dilution
area.
Warning!
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