AAF International PRU - Manual (Page 17)

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5.4 Gas-phase Filter Monitoring: A discussion of sophisticated
gas-phase filter monitoring is beyond the scope of this manual. At its
most simple, when the filter is used to remove nuisance odors, the time
to change out the gas-phase chemical media cassette is when the odor
begins to be regularly detected on the clean side of the filter system. In
more stringent applications where the system is supplied to protect
health and/or high value plant and product, active real time electronic
and passive coupon corrosion monitoring systems are available to
determine the performance of the system. The remaining life of the
media in the SAAF Cassette can be determined by taking a sample of
media and returning it to AAF for analysis. Consult with your AAF
representative regarding active and passive monitoring systems and
media sampling for remaining life analysis.
5.5 Removal and Replacement of Particulate and Gas-phase
Chemical Filters: Removal of filters will be the reverse of the
installation process described earlier in this manual. Filter replacement
will be carried out exactly the same as at initial installation.
5.6 Disposal of Used Filters: Used chemical filters and particulate
filters shall be packaged and disposed of in full accordance with all
required and applicable laws and regulations. Consult with local
environmental control authorities such as local, state, and federal EPA
& OSHA authorities for direction. Material Safety Data Sheets (MSDS)
are available on all products supplied by AAF. Contact your AAF
representative for further information.
5.7 Gas-phase Chemical Filter Cassette Face Sealing Gaskets:
The proper maintenance of the hollow core gaskets located in the
track on the entering air, or sealing, face of each cassette is critical to
the performance of the system. Check the gaskets carefully whenever
the gas-phase chemical filters are replaced. If gaskets are worn,
frayed, or damaged in any way, they should be replaced. Check the
seal between the gas-phase chemical filter cassette and the hollow
core gasket on the air entering face of the gas-phase cassettes
whenever new SAAF Cassettes are installed.
5.8 After-filter and High Efficiency Particulate Filter Sealing
Gaskets: The proper maintenance of the hollow core gaskets located
in the after-filter and high-efficiency particulate filter tracks is critical to
the performance of the system. Check the gaskets carefully whenever
the after-filters and high-efficiency particulate filters are replaced. If
gaskets are worn, frayed, or damaged in any way, they should be
replaced. Check the seal between the filters and the hollow core
gaskets whenever new particulate filters are installed.
5.9 Access Door Sealing Gaskets: There are two types of door
sealing gasket that must be considered, the access door perimeter
sealing gasket and the access door side sealing gasket. The proper
maintenance of the access door sealing gaskets is critical to the
When the fan system is started up, the airflow volume can be controlled
by varying the fan speed using a variable speed control or by increasing
the static pressure using dampers, if these have been supplied. The HD
cassettes are nominally rated to operate at a face velocity of 250 feet
per minute. Note that some systems may be supplied with single speed
fans. Review the product drawing and wiring diagram for details.
Immediately on start-up, examine the filter system for any apparent air
leaks or other anomalies. Air leaks may be detected by noise or by use
of a synthetic smoke puffing device at the external joints and seams of
the filter system installation. Correct or repair any discrepancies, as
necessary. Repeat this examination after 24 hours of operation and
again after one week of operation.
Monitor the pressure drop across the filter system to ensure that the
filters are operating within the pressure range expected and to ensure
that the pressure drop is not too high. Consult the AAF drawing for the
expected clean filter pressure differentials.
5.0 Maintenance
5.1 Prefilter: Record the pressure drop weekly to obtain the status of
the particulate filter. A normal particulate filter can be expected to last for
between two and three months before reaching its final recommended
pressure drop (see the AAF drawings for details). However, under
heavier or lighter dust loading conditions, this may vary. At an airflow
velocity of 250 feet per minute, the 2" deep AAF PerfectPleat filter can
be expected to have an initial pressure drop in the range of 0.11" water
gauge. The recommended final pressure drop is 1.0" water gauge. This
means that when a pressure drop increase of 0.89" water gauge has
been recorded, it is time to change the prefilter.
5.2 After-filter: Install an after-filter in the system to collect any initial
plume of dust that might be blown from the gas-phase chemical filters.
This filter can eventually be removed from the system to reduce the
energy required to operate the system. Monitor the pressure drop across
this filter. When the pressure ceases to increase, it is safe to remove this
filter from the system. This should typically be no longer than after 40
hours of operation. If after-filters still have significant life remaining at the
time of removal (based on the pressure drop reading), they should be
retained for re-use as after-filters following the change-out of the
chemical filters or be used as replacements for the prefilters.
5.3 High Efficiency Final Filters: Record the pressure drop weekly to
obtain the status of the filter. A normal high efficiency filter can be
expected to last for one year or more before reaching its final
recommended pressure drop (see the AAF drawings for details).
However, under heavier or lighter dust loading conditions, this may vary.
At an airflow velocity of 250 feet per minute, the 6" deep AAF VariCel
M-Pak filter can be expected to have an initial pressure drop in the range
of 0.23" water gauge. The recommended final pressure drop is 1.5" water
gauge. This means that when a pressure drop increase of 1.27" water
gauge has been recorded, it is time to change the high efficiency filter.