AAF International SAH - Manual (Page 17)

5.2 After-filter: If an after-filter has been installed in the system to
collect an initial plume of dust that might be blown from the gas-phase
chemical filters, it can eventually be removed from the system to
reduce the energy required to operate the system. Monitor the
pressure drop across this filter and 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 reuse 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: If a high efficiency final filter has
been included as part of the system, 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 500 feet per minute the 6" deep AAF
M-Pak filter can be expected to have an initial pressure drop in the
range of 0.55" w.g. The recommended final pressure drop is 1.5" w.g.
This means that when a pressure drop increase of 0.95" w.g. has
been recorded it is time to change the high efficiency filter.
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.
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3.12.2 Provision, installation and wiring of a properly sized motor
starter and disconnect with fuses / circuit breakers as required.
These components will normally be supplied by the owner or installer.
CAUTION: An electrical disconnect shall be incorporated into the
power wiring and mounted adjacent to the equipment so that power
can be cut when required during start-up and maintenance. The
disconnect will typically be supplied by others.
3.12.3 Wiring of the Motor Starter to the Fan:
3.12.4 Provision, installation and wiring of any special controls, and
interconnecting wiring to associated equipment such as dampers,
air flow monitors, chemical sensors, etc.
For guidelines on fan selection see paragraph 9.1
4.0 Start-up Instructions
When the fan system is started up ensure that the airflow volume is
controlled so that the actual airflow velocity across the filter system
does not exceed the rated face velocity shown on the AAF submittal
drawing. If there is any doubt about the required face velocity the
default maximum velocities shall be as follows:
– MD and CG cassettes: 500 feet per minute
– HD cassettes: 250 feet per minute
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: If a prefilter has been included as part of the system,
record the pressure drop weekly to obtain the status of the particulate
filter. A normal particulate filter can be expected to last between 2 and
3 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 500 feet
per minute, the 2" deep AAF PerfectPleat filter can be expected to
have an initial pressure drop in the range of 0.35" w.g. The
recommended final pressure drop is 1.0" w.g. This means that when
a pressure drop increase of 0.65" w.g. has been recorded it is time to
change the prefilter.