OPERATIONS
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CAUTION
Avoid mixing combustible dust with dust from spark generating
operations, such as ferrous or non-ferrous material grinding
operations. Under no circumstances should lighted cigarettes, etc.
be permitted to enter the air inlet or dust collection drawers of the
AirWall unit. Failure to follow this instruction may result in severe
damage to the equipment and personnel injury.
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Filter Cleaning Operation
The filter cleaning system uses compressed air to back flush or pulse accumulated
particulate from the cartridge pleats. A timer control board starts the cleaning
sequence. The system begins cleaning the filters anytime the pressure differential
between the entrance (dirty) side of the filter cartridges and the exit (clean) side
reaches a pre-determined level. This differential is constantly monitored by a
Photohelic gage and switch or digital pressure sensing module. As the filter cartridges
become more restricted by dust accumulation, the exhaust fan creates a greater
vacuum or pressure drop in the clean air plenum on the clean side of the filter
cartridges. The Photohelic gage or digital sensing module monitors this vacuum and, as
the pre-determined high set point is reached, reverse pulse cleaning cycle is started
automatically.
At the start of the cleaning cycle, a time delay of approximately 8 seconds will elapse.
This is referred to as the "off time" and is the time necessary between pulses for the
pressure accumulator to recharge for the next pulse.
At the end of the "off time," a pilot solenoid will release the pressure on a diaphragm
valve and a short burst of air will be transmitted through an orifice in a blow-pipe located
above each of the rows of filter cartridges. The AirWall LD models have 3 blow-pipes,
while the AirWall MD and HD models have 5 blow-pipes. The air pulse will cause a
shock wave to blow backward through the filter cartridge. This dislodges the
accumulated dust, which falls into dust collection drawers at the bottom of the AirWall
unit. The pulse time is adjustable from .05 to .5 seconds in duration and is referred to
as the "on time". Normal pulse time is 0.3 second.
The cleaning cycle will continue with an "off time" and "on time", producing a full pulse
each time, until the Photohelic gage or digital sensor module registers a pressure drop
sufficient to stop the cleaning process. This is pre-determined and is referred to as the
low set point. The high and low set points can be adjusted using the two adjustment
