Repeat this operation three or more times to remove
Preparation
residual hydraulic fluid. When the bottle is considered
The components of the contamination analysis kit
clean, flush down the external threads of the sample
are shown in figure 8-4. Look at this figure as you read
bottle and the internal threads of the bottle cap with
about the procedure you should follow to prepare
filtered solvent. Replace the cap on the bottle.
hydraulic fluid for contamination analysis.
Sample Taking
The Millex point-of-use filter unit consists of two
threaded half-sections and an internal support screen.
Samples taken from aircraft hydraulic systems and
Use forceps to place one 25-mm solvent filter on the
SE should be representative of the fluid in the system
gridded plastic surface of the filter holder.
under test. Aircraft samples should be taken
immediately after flight. If postflight samples cannot be
NOTE: Packaged filter membranes are separated
obtained, the system is cycled according to directions in
by blue separator discs. Remove separators before
the applicable aircraft MIM or MRC before drawing a
installing solvent filter in the filter holder.
sample. Before sampling SE hydraulic systems,
Position the perforated support screen on top of the
recirculate the fluid for a minimum of 5 minutes at full
solvent filter to provide support for both sides of the
flow rate or for a proportionately longer time at a lower
solvent filter. Reassemble the two halves of the filter
flow rate. Remove external contaminants from the
holder finger tight. Fill the wash bottle (with short
sampling point by flushing it with solvent and wiping
spout) with an approved solvent. Dry-cleaning solvent,
the sampling point with clean, disposable wiping
MIL-PRF-680, is the preferred solvent. However, when
cloths.
using this solvent, sufficient drying time must be
When the sampling point is visibly free of external
allowed.
contaminants, subject it to a final solvent flush.
Sampling points not adequately cleaned before use may
produce test results that needlessly cause the rejection
WARNING
of the system under test. Begin the flow of fluid to be
MIL-PRF-680 must be used only in
sampled, by appropriate means, allowing an initial
well-ventilated areas, and you should avoid
quantity to flow into a waste receptacle. This procedure
inhalation of vapors. MIL-PRF-680 is combustible,
serves to flush away any contaminant in the sampling
and should be kept away from open flames. You
line and any contaminants generated by mechanical
should wear rubber gloves and chemical or
operation. Without interrupting the flow of fluid, take
splashproof goggles. You should also avoid skin
the required sample by placing a clean sample bottle
contact with MIL-PRF-680. Failure to observe
under the fluid stream. You should take two samples at
proper safety precautions could result in personal
this time. In the event the first sample is rejected, you
injury or death to personnel. Consult the local safety
will have another sample readily available. End the
office regarding respiratory protection.
flow of sample fluid after the sample bottles are full,
and it is removed from the stream. Install the caps on
the bottle, and put a tag or label on the bottles that
Fill the wash bottle (with long spout) with
identifies the aircraft or equipment sampled and the
dry-cleaning solvent MIL-PRF-680 to flush sampling
specific sampling point that was used.
points. Replace their screw caps. Attach the filter
holder to the wash bottle with the short spout. Make
Sample aircraft filter assemblies by removing the
sure the tip of the wash bottle is not damaged by forcing
filter bowl and transferring the fluid contents of both
the filter holder on too tightly. If damaged, the other
the bowl and the element to a clean sample bottle. The
wash bottle may be modified by carefully cutting off
amount of fluid obtained varies, depending on the type
the tip so that the filter holder will fit. The damaged
of filter assembly.
wash bottle may then be used for flushing fittings and
sampling points.
Sample Processing
Clean the required number of sample bottles before
Before the sample is processed, the fluid to be
use by rinsing and flushing them with filtered solvent.
tested is examined visually for evidence of possible free
Fill the bottle to be cleaned approximately half full.
water. Water can be found in hydraulic fluid samples as
Replace the cap on the opening, shake the sample bottle
droplets that usually settle to the bottom of the sample
several times, remove the cap, and dump the contents.
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