FED-STD-791D
6.1.2 Test-oil pressure and scavenge pumps. The test-oil pressure and scavenge pumps
are completely disassembled and then cleaned to remove all deposits from the previous test.
6.1.3 Test-oil accumulator. The test-oil accumulator located directly below the bearing
head is disassembled and then cleaned with a stainless steel brush in dry cleaning solvent, or
equivalent.
6.1.4 Test-oil lines. All of the straight run test-oil lines and fittings (elbows, tees) are
removed from the test-oil system and hand reamed with stainless steel wire brushes in a bath of
dry cleaning solvent, or equivalent.
6.1.5 Oil filter assemblies. All oil filter housings in the test-oil system are removed and
cleaned with a stainless steel brush in dry cleaning solvent, or equivalent. A soft fiber brush is
usually adequate in scrubbing the filter elements after a short soaking in a solvent bath.
6.1.6 Pressure gage line. The test-oil lines leading to the pressure gage and safety switch
units are flushed with approximately 25 mL of test oil prior to each test. Prior to starting the
drive motor and to insure correct pressure transmission, the drain valve at the end of the line is
opened momentarily while the system is under pressure.
6.1.7 Bearing head. The bearing head should be disassembled as far back as the seal and
all of the removable parts, except the test bearing, are cleaned with a suitable carbon remover
followed by scouring with No. 400 emery paper and solvent to remove all traces of deposits from
the previous test. The entire seal assembly should be removed and cleaned when the level of
deposits on the rear seal plate exceeds a light varnish condition.
6.1.8 Test bearing. A new 100-mm bearing is used for each 48-hour test. The new
bearing is cleaned in solvent to remove preservative oil. In order to facilitate deposit rating, the
bearing cage is thoroughly cleaned at three points using a stainless steel wire brush. This
procedure removes the brown coating applied to the cage and allows for a more accurate
evaluation of cage deposits by initially exposing the bright base metal. The three positions on
the cage are arbitrarily selected for brushing but are approximately equally spaced. All exposed
sides of the cage are cleaned at each position, covering a circumferential distance equal to that
between identical points on two successive rollers. The bearing is recleaned in solvent taking
care to remove all adhering wire bristles. The bearing is dipped in test oil prior to installation in
the machine.
6.1.9 Metal specimens. Clean and pre polish the specimens by appropriate means of
choice. If the specimens are being reused from a previous test, no pits, etchings, or signs of
corrosion should be visible at this point. Finish with No. 400 grit silicon carbide paper,
removing all marks that may have been left by previous polishing. The specimens should not
be handled with bare fingers from this point; handle them only with a clean cloth or paper, or
with tongs or forceps. Cotton swab wash the specimens with solvents, first with n-heptane
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