MIL-PRF-83861D
4.6.8.1 Blank value (C). A dummy element shall be installed in a test filter housing and
placed in a test system (see figure 5) and flushed with pre-cleaned test fluid (see 4.4.1.1) for 10
minutes at rated flow (see table I). Close the test system, pressurize 2,000 mL of test fluid to
obtain rated flow, pass the test fluid through the dummy element, and then through a previously
cleaned and weighed filter membrane (0.8 micron absolute) (see 6.5). The test fluid shall be
collected and the filter membrane weighed. The difference in weight between the filter
membrane before and after this test is the blank value and must be less than 0.0007 gram. If this
value is exceeded, flush the dummy element and test system with pre-cleaned test fluid (see
4.4.1.1) for 10 minutes at rated flow (see table I) and repeat this test.
4.6.8.2 Analysis value (A). The filter element shall be installed in a test filter housing
filled with pre-cleaned test fluid (see 4.4.1.1), capped at both inlet and outlet ports, soaked at
275° ± 10°F for 72 hours, and then cooled to 70° to 90°F. The filter element and test filter
housing shall be mounted in the normal position (bowl at bottom) and subjected to a sinusoidal
vibration test in three mutually perpendicular axes. The rate of change of frequency shall be
logarithmic. The vibration tolerances are: amplitude ±10%, frequency ±2%, and acceleration
±10%.
4.6.8.2.1 Resonance search. Determine filter element resonant frequencies by varying
the level and frequency of applied vibration as specified in part 1 of table IV. Repeat the
resonance search for each of the three axes.
TABLE IV. Vibration data.
Part
Vibration level
Frequency band (Hz)
(double amplitude inch or gravity)
1
0.1 inch
5 to 14
1.0g
14 to 23
0.036 inch
23 to 74
10.0g
74 to 2,000
2
0.2 inch
5 to 10
1.0g
10 to 18
0.06 inch
18 to 81
20.0g
81 to 2,000
4.6.8.2.2 Resonance dwell. The filter assembly shall be vibrated along each axis at the
four most severe resonant frequencies for 30 minutes at each resonance. Vibration levels are
given in part 1 of table IV and vibration times are given in part 1 of table V.
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