Pumping units and filter/separators are widely used throughout the theater. Pumping units serve as a
primary means for the receipt, storage, and issue of petroleum fuels during bulk and retail Class III
operations. Filter/separators provide an effective means for insuring that fuels are free from contamination.
As a senior NCO there are several assignments that would require knowledge of maintaining this equipment.
PART A SUPERVISING THE USE OF FILTER/SEPARATORS
Filter/separators (Figures. 1-1) remove solid contaminants and entrained water from liquid fuels.
Filter/separators range in size from 15 GPM to 600 GPM capacity. Organizational maintenance personnel
are responsible (with the help of the equipment operators) for replacing the filter elements in all
filter/separators. The use of standard interchangeable elements and canisters make it simple to replace
elements in filter/separators. They may be used when ground products, such as automotive gasoline and
diesel fuel, are pumped to the user's vehicles. They must be used on all lines pumping fuel directly to
aircraft and to vehicles that refuel aircraft. In addition, all fuel loaded into aircraft refueling vehicles should
be filtered again before it is pumped to aircraft.
The standard filter element fits inside the canister. It is a perforated tube surrounded by a fiberglass
filtering material which, in turn, is wrapped with several layers of different material. The fiberglass material
filters solid particles from fuel. The outside of the element consists of layers of fiberglass, acetate, cotton
knit, and fiberglass screen. This part coalesces (combines) fine particles of water in the fuel to form water
droplets, which settle because they are heavier than fuel. The service life of a standard filter element is 24
The canister is a cylinder approximately 5 inches in diameter and 23 inches long. It consists of an outer
and inner tube. The inner tube is made of perforated metal and metal screen. The outer tube is made of
perforated metal lined with a Teflon coated screen.
Raw fuel enters the center tube of the filter element through a fitting at the bottom of the canister. Solid
contaminants are removed as the fuel flows outward from the perforated center tube and through the
fiberglass filtering material. As the fuel passes through the outer layers of the element, fine particles of water
in the fuel are coalesced into droplets. The fuel containing the coalesced water passes through the inner
tube of the canister to the space between the inner and outer tubes. The Teflon coated screen of the outer
tube throws off water droplets, and they fall to the bottom chamber of the filter/separator. Only clean fuel
passes through the outer canister tube into the filter/separator tank. Tank vehicles such as the M131A5C,
M969, and M970 tank semitrailers have filter/separators that work in three stages. The first stage has 15
filter elements that remove solid contaminants. The second stage has five canisters to separate water from
fuel and let water drain into the sump. The third stage has 15 go/no go fuses. They shut off the flow of fuel
if the other two stages allow water or contaminants to exceed a safe level. M49A2C filter/separators have
three filter elements, three separator canisters, and three go/no go fuses. The go/no go fuses automatically
shut off the flow of fuel if the water and/or contaminants reach a high level.
Different Sizes of Filter/separators.
15-GPM liquid fuel filter/separator is a vertical, portable unit consisting of an aluminum tank mounted on
an aluminum skid. This tank has fuel inlet and outlet valves, a water drain valve, and a water level sight
gage. The pressure vent valve's working pressure is 25 psi. The 15-GPM filter/separator is used with
the 15-GPM hand operated dispensing pump.
50-GPM filter/separator consists of an aluminum tank with removable cover, inlet pipe with dust plug,
outlet pipe with dust cap, water drain valve, an air vent valve, a pressure differential indicator, sight
glass, four elements, and a canister. A reading in the green (0-20 psi) means the elements are clean. A
reading in the yellow (20-35 psi) means the elements must be changed at the end of the day's
operations. A reading in the red (35 psi and up) means the elements must be changed at once.
Maximum working pressure is 75 psi. It is used in refueling systems and for servicing ground vehicles.
100-GPM filter/separator, aluminum pressure tank with removable head. The tank is welded in a tubular
aluminum frame. Maximum working pressure is 75 psi.
The 350-GPM filter/separator is used in 150 psi airfield refueling systems, motor fuel servicing
equipment, military hoseline systems, and as a component of the FSSP.