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5500 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) and switched off safely if necessary. This
ensures that no unacceptably high surface temperatures can reach the exterior.
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. 5500 System Overview
The 5500 series system consists of a control unit with a user interface mounted in a
316 stainless steel enclosure. The control unit works in conjunction with enclosure
protection vents (EPVs) and pneumatic solenoid valves or manual valves.
The 5500 is a purge/pressurization controller and is not protected by pressurization.
2.3. Control Unit
The 5500 control unit is a control device for Type Z and Ex pzc purge systems. The
unit 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 protected control cabinet,
and it maintains and monitors an overpressure relative to the ambient air when
purging is complete.
The 5500 control unit can be ordered for internal or external mounting with different
optional cable glands and conduit fittings for easy and approved wiring methods.
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