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3. Installation and Operation
The 5500 series control unit, vent, and manifold can be universally mounted to the
customer enclosure. The control unit can be mounted within the enclosure or outside
the enclosure. A rotating display allows mounting at the left, right, top, or bottom of the
enclosure. The EPV-5500 vent can be externally or internally mounted with just the
cap showing for exhaust or pressure.
The 5500 system is designed to allow an enclosure that is located in Zone 2 or 22,
Class I or II, Division 2 hazardous locations to operate safely by first making it safe
internally. This is done either by purging out the hazardous gas or manually cleaning
out the dust hazard and then pressurizing the enclosure so that the internal pressure
prevents the hazardous atmosphere from entering. The 5500 control unit has a
differential pressure sensor within the unit that is pneumatically connected to the
protective enclosure to provide pressure for evaluation of the enclosure pressure
and the flow through the enclosure during purging. If pressure is lost, then power
might remain on. An indication by an alarm or display has to notify the operator of the
condition. If the pressurized enclosure has been opened or a positive pressure has
not been maintained, then purging for hazardous gas or cleaning the enclosure out
for dust atmospheres is required. The flow measurement is evaluated by using the
pressure in the enclosure and the known measured flow in the graphs through one of
the vents selected.
3.1. Installation
3.1.1
For Gas Atmospheres
If the protective enclosure has been opened or has been subjected to the hazardous
atmosphere, purging is required to flush out the hazardous gas that may be inside
the protective enclosure. A protective gas is introduced into the enclosure so that the
pressure builds up and is exhausted through the enclosure. The measurement of flow
is achieved by the 5500 control unit pressure sensor measuring enclosure pressure
and using that pressure for the flow tables of the vent selected and enclosure size.
Each vent has an enclosure pressure vs. flow table for enclosure size that can be
used to determine flow rate. This flow rate is used to determine the purge time
required to make the protective enclosure safe.
Note
The flow rate curves generated for each vent are measured on a completely sealed
enclosure with no leakage from the enclosure. In real applications, there will be some
leakage from the enclosure, which will depend on the integrity of the seals and door
windows, etc. As the enclosure pressure increases, the leakage may also increase.
Always plan on more flow from the protective gas to achieve enclosure pressure
because of the leakage.
After purging, the flow into the enclosure can be reduced so that just a small flow is
used for leakage compensation for pressurization of the enclosure.
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