TM 5-6115-593-34NAVFAC P-8-631-34TO-35C2-3-463-2Air trapped in the fuel causes erratic performance andhard starting. For this reason, piping must becompletely sealed against entrance of air and fine dustor dirt.17-62. Auxiliary tank fuel filters and sediment drains arelocated in the set and are easily accessible to promoteregular and frequent service. Cleanliness of the fuel isespecially important on diesel engines which have easilyclogged, precision fuel injectors, and pumps.17-63. Black iron pipe or copper tubing must be usedfor diesel fuel systems galvanized tanks and piping mustnot be used since the diesel fuel and the galvanizedcoating react chemically to produce flaking whichquickly clogs filters or causes failure of the fuel pump orinjectors. Flexible lines must be of the type approvedfor diesel fuels.17-64. The auxiliary fuel tank should be vented so thatair and other gases can escape to atmosphere (seefigure 17-16 through 17-18). The vent must, however,prevent dust, dirt, and moisture from entering the tank.Where return lines are required, keep the return spacedat least 12 inches (30.5 cm) away from the pickup orfuel dip tube if this is not done, air bubbles could beentrained in the fuel and cause erratic operation. Atleast 5 percent of capability should be allowed in adiesel main tank for expansion of the fuel. Auxiliary fueltank capacity can be computed by using table 17-6.Table 17-6. Fuel Consumption for 500 KW DOD Generator Set17-65. SET FUEL TANK. The capacity of the fuel tankis determined by the fuel consumption of the unit andthe continuous operating time necessary. Fuel supplycapacity for generator service is 2 hours under full loadwithout refueling. All auxiliary tanks must have:a. A vent line terminating above grade level in ascreened or hooded type vent cap with unrestricted opening to atmosphere.b. A fuel fill line terminating above grade level and fitted with an appropriate cap or terminating in a fuel filler box with an appropriate cap and plainly marked for the fuel utilized.c.A fuel supply line connected from the tank to the electric fuel transfer pump.d. The tank should be fitted with a foot valve (permits flow in one direction only) to prevent loss of transfer pump prime when thetransfer pump is not in operation.17-66. The auxiliary fuel oil transfer pump is an internalpart of the generator set and has the capacity to fill thefuel tank in one hour when pumping fuel at atemperature of 25°F (-31.7°C). Additionally, the pump iscapable of lifting fuel 10 feet (3 m) and providessufficient pressure to supply fuel through the filtrationsystem under all possible viscosities of the fuel.17-20
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