6500 Series Purge and Pressurization System I/O Manual
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of unit, purge supply requirement)
The operator and/or installer undertake to ensure that only specialist, trained personnel work on the 6500
purge/pressurization system and that they:
Are familiar with the occupational safety and accident prevention regulations and have been briefed
regarding handling of the unit
Have additional knowledge of explosion protection that is required for the work on explosion
protected components.
Are familiar with the relevant rules and regulations for the installation, operation and maintenance of
explosion-protected systems.
The operator and/or installer must also ensure that:
The 2-wire RTD for temperature measurement is suitable for the area classification, Zone 1 or
Zone 21, and maximum length of 3 meters
The bypass switch, if used, is suitable for the area classification, Zone 1 or 21
Cable glands must be suitable for the area classification, Zone 1, or 21, and IP ratings required.
1.1.8 General information on the ignition protection class – purging/pressurization system
Purging and pressuring systems are one of the most versatile ignition protection classes. They are based
on the principle that in Zone 1 (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,
sufficient compressed air is supplied to compensate for leaks in the housing and any installed equipment.
This permanent overpressure, achieved using compressed air, prevents any potentially explosive
atmosphere in the ambient air from entering the housing.
During the purge phase an internal pressure is achieved.
Any hotspots that may occur on individual components within the control cabinet should be monitored by
temperature sensors and switched off safely if necessary. This ensures that no unacceptably high surface
temperatures can reach the exterior.
For applications in Zone 21 (dust) the purge process is omitted because purging would raise explosive
dust. Instead of pre-purging, the interior of the housing is inspected for dust and cleaned manually if dust
is present.
When dealing with containment systems and dilution applications, refer to the applicable standards for the
requirements. In some cases, dilution with compressed air is not possible and Nitrogen or some other type
inert gas is required.
Note!
When using an inert gas like nitrogen, an asphyxiation hazard can exist.
The purge and pressurizing system is particular suitable for installed equipment that is not approved for
the use in hazardous areas. It can then be used in the hazardous area when properly installed.
Note!
provides a solution for both at the same time but would have to be evaluated by the certification bodies for
approval.