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|  MIL-F- 14252 (AR )
100 percent of the sand and dust shall pass through
(a)
a 100-mesh screen, U S Standard Sieve Seriesa
(b) 98/2 percent of the sand and dust shall pass Series.
through a l4O-mesh screen U S Standard Sieve
(d 90 / 2 percent of the sand and dust shall pass
through a 200-mesh screen, U S Standard Sieve Series.
(d) 75 / 2 percent of the sand and dust shall pass
through a 325-mesh screen, U S Standard Sieve Series.
(e) Chemical analysis of the dust shall be as follows:
The Internal temperature of the test chamber shall be maintained
a
at 25C (77 F) for a period of 6 hours with sand and dust velo-
city through the test chamber between 200 / 100 feet per minute,
(2, 300 / 500 feet per minute if so specified by the detail speci-
fication). After 6 hours at the above conditions, ( during all
Or part of which time the equipment shall be Operating$ if so
specified by the detail specification)0 the temperature shall be
0
raised to and maintained at 71 C (160 F). These conditions
shall be maintained for 6 hours At the end of this period,
the equipment shall be removed and allowed to cool to room
temperature and shall be operated and the results shall conform
to those obtained in 4.2.2 and examined in accordance with
4.2.3. Thes test shall be repeated at O0F If so specified In
the detail specification
4.3.10 Vibration.- Filters used in vibration tests shall have
Cut-off frequenci es selected to eliminate all harmonics above
the fundamental from the measured values. The procedures for
the vibration tests shall, at the 0option of the detail specifi-
cation, be operated at high /160 F) or low (-40F or -65F)
and standard ambient temperatures. The equipment shall or
shall not be 0perated during the test, In accordance with di-
rection as specified in the detail specificatiOn.. If the
eqUipment is not operated during the test period3 then at the
conclusion of the period the equipment shall be operated and
the results shall conform to those of 4.2.2..
4.3.10.1 Procedure I.- This procedure Is intended for equip-
The equipment shall be
ment weighing
less than 150 pounds.
57
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