MIL --- PR F --- 51193E (E A)
4.3.6 Tests.
4.3.6.1 Air flow resistance. The pre ssure drop a cross the filte r sha ll be in a ccorda nce with
3.5.1 a nd sha ll be de te rmine d a t the ra te d a ir flow. The up --- stre a m a nd down --- stre a m sta tic
pre ssure me a suring tube s sha ll be a s close a s possible to the filte r a nd sha ll not be on a se ction
of duct tha t ha s a cha nging cross se ctiona l a re a . Te st for a ir flow re sista nce a s follows:
(a ) Conne ct the filte r to a source of force d a ir.
(b) Se t the flow of a ir through the filte r to 283 sta nda rd lite rs pe r minute
.
(c) Re cord the ba rome tric pre ssure .
(d) Me a sure a nd re cord the a ir stre a m te mpe ra ture .
(e ) D e te rmine a nd re cord the diffe re nce in sta tic pre ssure he a d up --- stre a m of the filte r
to tha t down --- stre a m of the filte r. NO TE : If using te st pa ra me te rs diffe re nt tha n those sta te d
in 3.5.1, ca lcula te a nd re cord the a ir flow re sista nce DP(ca l) using the e qua tion be low to corre ct
te st me a sure me nts to sta nda rd conditions.
DP(ca l) = P(te st) x DP(me a sure d) x 86.2
1.768
(492 + 1.8T)
DP(ca l) --- Air flow re sista nce corre cte d to sta nda rd conditions in millime te rs of wa te r
ga ge
P(te st) --- Ba rome tric pre ssure a t time of te st in millime te rs of me rcury
DP(me a sure d) --- Va lue re corde d from te st me a sure me nt in millime te rs of wa te r
T
--- Te mpe ra ture of a ir stre a m flowing through filte r in de gre e s C
If DP(ca l) is more tha n the a ir flow re sista nce sta te d in 3.5.1, the filte r sha ll be re je cte d.
4.3.6.2 Leakage. Position the filte r to be te ste d rigidly with the long a xis in the ve rtica l posi-
tion. Conne ct the filte r to a source of force d a ir a nd pla ce a mixing cha mbe r a t the influe nt side
of the filte r. Re gula te the a ir flow from the blowe r to 57 sta nda rd lite rs pe r minute . Introduce
R --- 134a into the inta ke of the blowe r; monitor a nd ma inta in a conce ntra tion of 1000 ppm by
volume of R --- 134a in a ir a t a n a ir flow of 57 sta nda rd lite rs pe r minute on the influe nt side of
the filte r a t the prope r te mpe ra ture a nd re la tive humidity for the spe cifie d pe riod of time (se e
3.5.2). Le a ka ge sha ll be in a ccorda nce with 3.5.2 a nd sha ll be de te rmine d using a suita ble le a k
de te ctor (se e 6.5) for sa mpling a nd de te cting R --- 134a a t the e fflue nt side of the filte r. Purge the
filte r by pa ssing fre sh a ir in the re ve rse dire ction of tha t indica te d a bove through the filte r a t 283
sta nda rd lite rs pe r minute for 1 minute . Ke e p the e xposure of the filte r to a ir to a minimum.
The a ir flow time for le a ka ge should not e xce e d 3 minute s.
4.3.6.3 Moisture content of gas filter. The filte rs sha ll me e t the moisture conte nt spe cifie d
in 3.5.3 whe n the moisture conte nt of the ca rbon is de te rmine d in a ccorda nce with ASTM D
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