(b) As water accumulates in the filter sump
happens, whatever fuel is passed through is still within the
of the M970 and M970A1, a float rises. When the float
specified standards for purity.
rises a certain level, a valve will open in the automatic
Filter/Separator Gage. The filter elements have a
drain valve, allowing pump pressure to be applied to a
limited capacity for retaining solids. As the solids content
diaphragm valve in the automatic drain valve and to the
increases, a pressure drop across the elements increases.
pilot control on the 3-inch flow control valve. The pump
The pressure drop can be measured by a pressure gage
pressure opens the diaphragm valve and closes the 3-inch
flow control valve. Fuel flow is then shut off, preventing
pressure readings should be taken and recorded at the first
dispensing of water-contaminated fuel, and the water in
day of operation and each day of operation thereafter. At
the filter sump is passed through the automatic drain
initial operation or with replacement elements, the
valve. When the fuel flow is stopped by the closing of the
pressure gage reading should not exceed 3 psi. When the
3-inch flow control valve, no coalescing occurs, and the
pressure gage reading reaches 25 psi, the elements are
automatic water drain valve will continue passing water
dirty and should be replaced. Notify unit maintenance
until the float lowers. With the float in the lowered
personnel when pressure reaches 25 psi.
control valve opens. When this happens, pressure is
2-16. Filtered Fuel Servicing Operations (M969
trapped in the line to the automatic drain valve diaphragm
and pilot control of the 3-inch control valve, preventing
resumption of fuel flow. To release the pressure, a bleed
Filtered Bulk Delivery. This operation is to be used
line from the automatic drain valve diaphragm and pilot
when filtered fuel is required in the storage facility
control will relieve the pressure at the discharge side of
the water drain valve. Fuel flow will automatically start
through the filter/separator to the storage facility.
Filtered bulk delivery operation is as follows:
(3) Cold Weather Draining. During cold weather
operations, the accumulated water in the sump may
(2) Ensure that all valves are closed.
freeze. It is important that the manual drain N (fig. 2-30)
on the sump be opened after each operation to drain the
(3) Connect grounding wire to storage facility
water accumulation. Be sure to close the drain valve after
and semitrailer (fig. 2-7). Remove 4-inch bulk fuel hose
receiving facility. Remove dust cap from outlet B and
(4) Go-No-Go Fuses. Each of the 5 second-stage
connect bulk fuel hose to outlet.
coalescing elements is equipped with three Go-No-Go
fuses. These fuses are fuel contaminant monitoring
(4) Remove fire extinguishers and bring them to
devices located "down-stream" of the second-stage. The
the point of operation.
fuses restrict the fuel flow when small amounts of water
adjust engine speed to 1000-1200 rpm.
(a) Each fuse consists of a perforated metal
(6) Put selector valve E in UNLOAD position.
tube filled with thin cellulose washers, except for a space
about l-inch long at one end. This space is for a plastic
piston forced against the washers by a spring. A plastic
nipple at the other end of the metal tube fits into an outlet
(8) Adjust engine throttle for desired flow rate
socket in the housing. Fuel flow is through the spirally
arranged perforations in the metal tube. The fuel must
flow through the very small passages (about 5 microns)
(9) At end of operation, adjust engine to idle
between the cellulose washers to reach the outlet.
speed (1000-1200 rpm).
(10) Close all valves.
(b) As solid contaminants accumulate on
the outer surface of the stack of washers, resistance to fuel
(11) Remove all hoses and store in hose troughs.
flow increases. The resulting increased pressure further
Secure hose trough latches. Reinstall dust cover on outlet
compresses the washer stack. When the contaminant is
water, it is also absorbed by the cellulose washers, and the
action of the filter is similar.
(13) Remove grounding wire.
present, the compression of the washer stack continues
(14) Cover and store fire extinguishers.
until fuel flow is stopped completely. But until this