MIL-PRF-14512L(EA)
4.3.6 Tests.
4.3.6.1 Air flow resistance. The pressure drop across the filter shall be in accordance with
3.5.1 and shall be determined at the rated airflow. The up-stream and down-stream static
pressure measuring tubes shall be as close as possible to the filter and shall not be on a section
of duct that has a changing cross sectional area. Test for air flow resistance as follows:
(a) Connect the filter to a source of forced air.
(b) Set the flow of air through the filter to 340 standard liters per minute.
.
(c) Record the barometric pressure.
(d) Measure and record the air stream temperature.
(e) Determine and record the difference in static pressure head up-stream of the filter
to that down-stream of the filter. If using test parameters different than those stated in 3.5.1,
calculate and record the air flow resistance, DP(cal), using the equation below to correct test
measurements to standard conditions.
ĆP(cal) = P(test) x ĆP(measured) x 86.2
(492 + 1.8T)1.768
ĆP(cal) Air flow resistance corrected to standard conditions in millimeters of
water
P(test) Barometric pressure at time of test in mm Hg
ĆP(measured) Value recorded from test measurement in millimeters of water
T Temperature of air stream flowing through filter in degrees C
If ĆP(cal) is more than the air flow resistance stated in 3.5.1, the filter shall be rejected.
4.3.6.2 Leakage. Rigidly position the sample gas filter in the test fixture with the inlet and outlet
faces in a vertical plane. Use R134a refrigerant that conforms to the characteristics of ARI STAN-
DARD 700. Connect the filter to a source of forced air and place a mixing chamber at the influent
side. Regulate the flow of air from the blower to 68 l/m (1/5 of the 340 l/m rated airflow). Introduce
R134a into the intake of the blower; monitor and maintain a concentration of 1000 ppm by volume
of R134a in airflow of 68 l/m on the influent side of the filter at 24±5°C (75±9°F) and relative
humidity of no higher than 50 percent. Leakage shall be determined using a suitable leak detector
(see 6.4) for sampling and detecting R134a at the effluent side of the filter. Monitor the effluent
airstream for at least 2 minutes. Determine whether the effluent concentration exceeds 1 ppm within
2 minutes after the introduction of the refrigerant at the inlet of the filter. Purge the filter by passing
clean air in the reverse direction through the filter at rated flow for 3 minutes. Keep the exposure of
the filter to air to a minimum.
4.3.6.3 Moisture content of filter. The filters shall meet the moisture content specified in 3.5.3
when the moisture content of the adsorbent is determined in accordance with ASTM D 2867, Oven
Drying Test Method, except that the oven temperature shall be 103107°C and the drying time shall
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