dome-shaped head that provides an even, unrestricted
flow of fuel from the separator elements.
A test connection for obtaining a sample of the fuel
being discharged is located at the bottom of the outlet
chamber. When it is necessary to drain the filter com-
pletely, the outlet chamber is drained into containers
through this line.
Two pressure gages (one for each chamber) and a
differential pressure gage are installed on a gage board
conveniently located in the filter room. These gages are
provided for determining the pressure drop across the
filter elements. A shutoff valve is installed in each gage
line to permit removal of the gages for maintenance.
OPERATION OF THE MAIN FUEL FIL-
TER. It is imperative that the filter be properly
vented so full use of all filtering elements will occur.
JP-5 enters the inlet chamber of the filter. The JP-5
then passes to the inside of the coalescing elements,
where solids 5 microns and larger are retained on the
inner walls of the elements. As the JP-5 passes
through the elements into the fallout chamber, any
water is coalesced into large droplets on the outside of
the elements. These water droplets fall out of the JP-5
by gravity and into the sump as the JP-5 passes across
the fallout chamber to the separator elements. JP-5
enters the separator elements from the outside and, as
it passes through the elements to the outlet chamber,
any final traces of coalesced water that did not fall are
repelled. The JP-5 then leaves the outlet chamber of
the filter from the top and flows through the automatic
shutoff valve into the forward and aft legs of the
quadrant. Rated capacity is 2,000 gpm.
Exercise care at all times when opening and
closing valves that govern flow through the
filter to prevent a hydraulic hammer shock to
the filter. This may overstress the housing or
rupture the filter elements.
Immediately after a filter with new elements is
placed in operation, the pressure gages must be read and
the pressures logged. A pressure differential between
the inlet and fallout chambers should be noted. This
pressure drop will increase in time due to the buildup of
solid contaminants on the inner walls of coalescing
Pressure Checks. The inlet, outlet, and differen-
tial pressure gages should be read and recorded as
indicated in the filter operating log. As solids build up
on the elements, the pressure drop across the filter
increases. The differential gage determines the actual
differential pressure across the entire filter assembly.
The pressure drop across the coalescer elements is the
As the maximum allowable pressure drop across
the coalescing elements is reached, they fail to perform
their designed function and must be replaced. The maxi-
mum allowable pressure drop limits for coalescer ele-
ments are found on the instruction sheet in the
manufacturers packing crate. Although pressure drop
limits may vary, 15 psi is the typical pressure drop limit.
Sample Checks. Daily checks are taken from the
filter sump and outlet chamber at the beginning of initial
flow and every 15 minutes thereafter. The contents of
each sample should be recorded in the operating log.
These samples can be used to determine the condition
of the coalescer and separator elements.
If the sample taken from the filter sump contains
solids, it is a probable indication that the coalescer
elements have failed. If the sample taken from the outlet
chamber is contaminated, it is a probable indication that
the coalescer and/or separator elements have failed. In
either case, the elements should be inspected and re-
placed as necessary.
Also, coalescer elements should be replaced at each
overhaul and before deployment. If no overhaul or
deployment occurs, they should be replaced in accord-
ance with PMS. When coalescer elements are replaced,
separator elements should be cleaned and inspected.
Only defective separator elements need be replaced.
Coalescer elements of one manufacturer may be used
with the separator elements of another manufacturer.
FILTER HYDRAULIC CONTROL SYS-
TEM. The filter hydraulic control system is a safety
device installed on all fuel filters. It functions to drain
automatically the accumulated water from the filter
sump, and to shut off the filter flow if more water
accumulates than can be drained off automatically.
This system consists of three hydraulic control
valves and afloat operated control valve. Two hydraulic
control valves (the automatic shutoff valve and pilot
valve) are located in the filter discharge line. The other
hydraulic control valve (the automatic water drain
valve) is located in the filter sump drain line. The float
operated control valve (rotary valve) is located on the
side or bottom of the filter sump.
Automatic Shutoff Valve. The automatic shut-
off valve is of a modified globe valve design, using a
well supported and reinforced diaphragm as a working
means. A tension spring located in the upper valve
chamber (above the diaphragm) assists in seating the
valve when closing, and provides a cushioning when
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