MIL-F-18327F
e.
Test condition letter.
f.
Depth of immersion in the molten solder (if applicable to the specified test condition).
g.
Cooling time prior to final examinations and measurements.
h.
Examinations and measurements before and after test, as applicable.
i.
Method of internal inspection, when specified (see 3.1).
4.7.5 Seal (see 3.8). Filters shall be tested in accordance with 4.7.5.1, and 4.7.5.2, when applicable. When
specified (see 3.1), the alternate test specified in 4.7.5.1.1 shall be used in lieu of the test specified in 4.7.5.1.
4.7.5.1 All filters. Filters shall be immersed for 2 to 3 minutes in a bath of water or any other suitable liquid of no
greater density, and maintained at a temperature of at least 85°C. The temperature of the filter shall not exceed 40°C
at the time of immersion.
4.7.5.1.1 Alternate test. When specified (see 3.1), the filters shall be immersed in a container of water containing
approximately 1 percent aerosol which shall then be placed in a vacuum chamber. A vacuum resulting in an absolute
pressure not greater than 3.4 inches of mercury shall be drawn over the bath and held for a minimum of 3 minutes.
4.7.5.2 Liquid-filled filters. Grade 4 liquid-filled filters shall be heated in an oven for not less than 3 hours for filters
weighing 20 pounds or less, and for not less than 6 hours for filters weighing over 20 pounds.
4.7.5.2.1 Oven temperature. The oven shall be maintained at a temperature equal to or greater than the sum of
the specified maximum ambient temperature and the allowable temperature rise for the class (see 3.1).
4.7.6 Dielectric withstanding voltage (see 3.9). Filters shall be tested in accordance with method 301, MIL-STD-
202. The following details shall apply:
a.
Magnitude of test voltage.
Initial test: As specified (see 3.1).
(1)
(2)
Tests subsequent to initial test: 90 percent of initial test voltage.
b.
Nature of potential: Alternating current (ac).
c.
Duration of application of test voltage.
(1)
Initial test: 60 seconds.
(2)
Tests subsequent to initial test: 5 seconds.
Points of application of test voltage: As specified (see 3.1).
d.
e.
Examinations after dielectric withstanding voltage test: Filters shall be examined for evidence of arcing,
flashover, breakdown of insulation, and damage.
4.7.7 Insulation resistance (see 3.10). Filters shall be tested in accordance with method 302, MIL-STD-202. The
following details shall apply:
a.
Test condition letter: A, unless otherwise specified (see 3.1).
b.
Points of measurement: Between the terminals and mountings or terminals and case.
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