ETL 1110-3-490
13 May 98
field conditions and will be field adjusted to maintain a maximum airflow rate of 1,120 m3/hr (660
cfm). Adjusting the FFA-580 unit for this airflow rate allows the unit to maintain the minimum
1,020 m3/hr (600 cfm) airflow rate when the HEPA filter becomes slightly loaded with dirt and
atmospheric dust. Airflow rates above 1,120 m3/hr (660 cfm) should be avoided because higher
airflow rates reduce filter adsorption capacity and residence time. The FFA-580 unit does not have
a prefilter, and therefore the HEPA filter will load more quickly than a filtration system with a
prefilter. The FFA-580 unit requires periodic airflow testing to ensure it is maintaining an airflow
rate in the range of 1,020 m3/hr (600 cfm) to 1,120 m3/hr (660 cfm). An airflow rate of 1,020
m3/hr (600 cfm) will be used for design of the overpressure filtered air system and an airflow rate
(b) The M49 Adsorption Filter. The M49 adsorber is a military developed and produced gas
adsorber. Quality control and testing is also provided and managed by the military. The M49 filter
comes in two sizes: 1,120 m3/hr (600 cfm) and 2,040 m3/hr (1,200 cfm). The M49 adsorber is of
modular design and can be stacked in multiples to achieve a higher airflow rate. When compared
to commercially available adsorber filters, the M49 requires only one stage of filtration for an
airflow rate of 2,040 m3/hr (1,200 cfm). Therefore, using the M49 will require somewhat less
floor space than a commercial filter system. The M49 pressure drop is approximately 1,750
pascals (7 inches wg) lower than a comparable commercially available filter. The lower static
pressure drop results in less initial blower cost due to the lower static head requirement. For CP
filtration systems that operate continuously, the lower static pressure drop of the M49 results in
lower operating costs. However, for CP systems that operate only when needed, the energy cost
savings will be minor. The M49 carbon trays are refillable by the Government. The disadvantage
of the M49 filter is its relatively high initial cost compared to commercially available filters. The
M49 adsorption filter requires prefilters, HEPA filters, and test sections or test points similar to
commercial filter systems. To procure the M49 filter, contact the Technical Director, U.S. Army
Edgewood Research, Development and Engineering Center, ATTN: SCBRD-ENP-A/ Fixed
Installation Engineer, 5183 Blackhawk Road, Aberdeen Proving Ground, MD 21010-5423.
(2) Commercial Filtration Systems. Commercial filtration systems are of modular sectional
design and each section can filter 850 m3/hr (500 cfm) to 2,125 m3/hr (1,250 cfm) with two stages
of adsorption. The CP overpressure filter system will require, in series, the following filter
sections: roughing filter, prefilter, HEPA filter, and typically two stages of adsorber. Test sections
can be provided with the filtration system to ease in-place leak testing of the filtration system,
isolate which filter section fails the leak test, and for future leak testing of the filter system. If test
sections are not used, test ports approximately 10 duct diameters before and after the filter system
must be provided. The filter system will be quality assurance tested in accordance with ASME
N510 and MIL-PRF-32016(EA).
(a) Filter Housing. The filter housing will be a bag-in and bag-out design conforming to the
applicable sections of ASME N509, and will be constructed of type 304 stainless steel.
B-6
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