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|  MIL-F-27656C(USAF)
i.
The membrane disk shall then be removed and dried to a constant weight at 125F and
weighed to an accuracy of 0.1 mg The contaminant weight shall be less than 0.0004 gram/2,000 ml.
4.6.6.2.2 Filter element tests. The degree of filtration for filter elements shall be determined as follows
a.
The system shall be checked for oil cleanliness in accordance with paragraph 4.6.6.2.1
b . Prefiltered hydraulic fluid shall be added through plug valve A to bring the level in the
mixing chamber to 2,000 ml. The element shall be installed in the filter housing.
Valve B shall be closed.
c.
d.
A 10-ml slurry containing 3 grams of contaminant shall be added to the fluid through a
small funnel inserted in plug valve A. The contaminant shall be 1.5 grams of APM F-9 beads ( see figure
8) and 1.5 grams of standardized fine air cleaner (AC) test dust (see paragraph 4.6.6.4d).
e.
The contaminant shall be uniformly distributed by churning the fluid for 5 minutes with an
agitator.
f.
Plug valve A shall be closed, and the glass chamber containing hydraulic fluid and con-
taminant shall be pressured by the air regulator. The air regulator shall be used to maintain flow.
Sufficient air pressure shall be employed to maintain rated flow.
g. Gate valve B shall be opened and air pressure shall torte fluid containing contaminant
through the sample filter unit at rated flow. This 2,000 ml of filtrate shall be collected m a 5,000-ml
beaker from sampling valve C. Seven hundred and fifty milliliters of petroleum ether (boding point 95
to 130 F) shall then be washed through the contaminant mixing chamber and test falter unit using
wash bottle. The wash fluid shall be collected in the same 5,000-ml beaker.
h. A Type AA4-047 Millipore membrane falter paper disk shall be washed with 200 ml of
petroleum ether and dried to constant weight at 125 F. The weight shall be accurate to 0.1 mg.
i.
The weight filter membrane shall be assembled into the filter holder assembly (see figure
6) and fitted to a 5,000-ml vacuum flask connected to a vacuum pump (minimum 25 inches Hg vacuum).
All fluid passed through the test filter shall be filtered through the membrane disk. The
j.
5,000-ml beaker shall then be washed with 500 ml of petroleum ether (boding point 95 to 130 F). and
this fluid from the washed beaker shall pass through the membrane. The falter funnel shall be washed
with 100 ml of petroleum ether and this wash passed through the membrane.
k. Maintaining vacuum. the top half of filter funnel assembly shall be removed, exposing
the filter paper for further washing.
With a wash bottle of faltered petroleum ether (boiling point 95 to 130 F), the rim of
l.
the filter paper shall be gently washed to remove the traces of oil, being careful not to disturb the
contaminant cake. Vacuum shall be maintained during the above operation.
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