MIL-DTL-197L
4.4.2 Fingerprint corrosion and cleanliness test. Sample specimens shall be selected in
unpacked samples in the air over the water in a static humidity chamber at 75 ±5 °F (24 ±3 °C)
for 24 hours. If no corrosion (such as pitting, cracking, or material discoloration) is seen without
visual aid at the conclusion of the test, satisfactory cleanliness has been achieved.
4.4.3 Corrosion test. Packaged bearings selected in accordance with 4.2.1.1.3 shall be
exposed for 1 week (168 hours) to 90 ±5 percent R.H. at 120 ±5 °F (50 ±3 °C). If no corrosion
(such as pitting, cracking, or material discoloration) is seen without visual aid at the conclusion
of the test, satisfactory preservation and packaging has been achieved.
4.5 Atmosphere in workrooms.
4.5.1 Temperature, humidity, and airborne particle count. Relative humidity and
continuous basis. Testing for airborne particle count shall be performed on a quarterly basis in
accordance with class 5, class 7, and class 8 of ISO 14644-1 and ISO 14644-2. Applicable
workrooms shall be tested in accordance with 4.5.3.1 quarterly to determine conformance to
these requirements.
4.5.2 Equipment calibration. Equipment used to control and monitor clean room and
workstation conditions shall be calibrated annually.
4.5.3 Environment and process cleanliness tests.
4.5.3.1 Clean room environment test (airborne particle counting methods). This test
shall be conducted in accordance with ISO 14644-1 and ISO 14644-2.
4.5.4 Cleanliness of general purpose and precision bearings manufactured to ABEC or
RBEC 3 or better, excluding 5T for torque and extra-thin bearings (see 6.5.1). Contamination on
cleaned or preserved bearings visible to the unaided eye is unacceptable. Verification of
abrasive or metal (except silver) particles may be accomplished by the following or equivalent
method. Flush the bearing with solvent capable of dissolving the preservative or lubricant. The
solvent used to flush the bearing shall be filtered through a 1-inch diameter 0.5-µm absolute
filter, or finer, marked in 3.10 by 3.10 mm grids in accordance with ASTM F311. The filter
shall be inspected in accordance with ASTM F312, method B, for particle abrasive or metal
(except silver) contamination to the acceptability limits below. Cause and corrective action is
required for any failure of this test.
Maximum allowable number of particles
Particle size range (mm)
0.051 to 0.127
15 max allowable per 4 random grid squares
> 0.127 to 0.254
10 entire filter
> 0.254
0 entire filter
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