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7500 S
M
P
erieS
anual
2. Product Description
2.1. Introduction
Purge and pressurization is one of the most versatile ignition protection classes.
Purge and pressurization systems are based on the principle that in Zone 2/Class I
Division 2 (gas), the gas mixture in the ambient atmosphere, which may ignite under
certain circumstances, is removed from the housing by an initial purge process.
After the purge phase, sufficiently compressed inert gas, usually air, is supplied to
compensate for leaks in the housing and any installed equipment. This permanent
overpressure prevents any potentially explosive atmosphere in the ambient air from
entering the housing. During the purge phase, an internal pressure is achieved.
Any hot spots that may occur on individual components in the control cabinet are
monitored by temperature sensors (optional).
For applications in Zone 22/Class II Division 2 (dust), the purge process is omitted
because purging would raise explosive dust into a cloud, creating a possible hazard.
Instead of pre-purging, the interior of the housing is inspected for dust and cleaned
manually if dust is present.
Purge and pressurization systems are particularly suitable for installed equipment that
is not approved for use in hazardous areas. The equipment can then be used directly
in the hazardous area.
2.2. 7500 System Overview
The 7500 series system consists of a control unit, an enclosure protection vent, and
manual or automatic manifold. The control unit has a touch screen display that is
menu driven and will easily guide the user in selecting pre-programmed and user-
selected variables. The 7500 can be used with a digital valve/manifold system like the
7500-MAN-... or 5500-MAN-... unit to make a fully automatic system. The enclosure
pressure and leakage can be monitored and, in the event of a loss in enclosure
pressure, the solenoid valve can engage to restore the defined pressure settings and/
or alarm for the pressure drop. An easy-to-see display also has 4 LEDs for system
condition indication from a distance.
2.3. Control Unit
The 7500 control unit is a control device for Type Z & Ex pz purge systems and is
suitable for purge time and pressure monitoring in Class I or II, Division 2, Zone 2 or
22. It controls the volume of purge gas flowing into the explosion-protected control
cabinet, and it maintains and monitors an overpressure relative to the ambient air
when purging is complete.
The 7500 control unit can be ordered as a stand-alone unit for panel mounting to your
enclosure or mounted to a panel with the 7500-MAN-MV-01 valve in a configuration.
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