MIL --- DTL --- 51222E(EA)
(c) After being filled, the filter frame should be placed on a table and the carbon packed
beneath the aluminum channel flanges with the fingers or a suitable tool. The carbon should be
carefully brushed off the frame onto the sorbent bed and the bed leveled with a leveling device
which directs the carbon away from the frame and levels the bed evenly 1/4 --- inch above the
frame.
(d) The upper perforated sheet with attached fines filter should be placed onto the draw-
bolts, aligned properly with the edge of the frame and secured with several self --- tapping screws.
The four composition gaskets, steel washers and nuts should be assembled and the nuts hand
tightened.
(e) The frame should be placed on a suitable vibrating press and the perforated sorbent
retainer pressed firmly down on the frame, applying a compressed air pressure of 40 pounds per
square inch (psi) which acting through a 6 inch diameter air cylinder exerts a force of about 1100
pounds on the frame. The self --- tapping screws should then be assembled all around the periph-
ery of the perforated retainer. The nuts on the drawbolts should be tightened to approximately
40 inch pounds. The filter should be vibrated for 30 seconds at a frequency of 200 strokes per
minute and amplitude of one --- half inch using an air pressure of 5 psi on the compressed air cylin-
der (this corresponds to a pressure on the frame of about 140 pounds.) After 30 seconds, the
vibrator should be stopped and the drawbolt nuts retightened to 40 inch pounds. The vibration
procedure should be repeated for an additional 30 seconds, and at the end of that time, the draw-
bolt nuts should be retightened to 40 inch pounds. After retightening the four bolts, the thick-
ness of the filter should be calipered in the area immediately adjacent to each bolt. The thickness
of the filter should not be less than 2.03 inches at these four points. The filter should be removed
from the press, the drawbolts should be cut off flush with the nuts, and the nuts and washers
coated with nonhardening Pernatex 2.
(f) The perforated sheet in the areas immediately adjacent to each end of the bolts (four)
should be examined. If the perforated sheet is torn or separated, the filter should be rejected and
reworked. The difficulty may be insufficient carbon or overtorquing.
6.4 Moisture control. One method to control moisture content in carbon to 3 percent or less
is to control the humidity in the air during the carbon filling and filter assembly process. Any
daily production runs of filters whose average moisture content exceeds 3 percent may be dried
by passing dry air at less than 3% relative humidity through the filters for 20 hours at room tem-
perature.
6.5 DMMP and CK life tests. Samples for DMMP and CK tests should be forwarded by the
contractor, together with DD Form 1222, to U.S. Army Edgewood Chemical Biological Center,
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