Figure 5-16.—Gravity fueling nozzle.smaller valve, and the nozzle is then completelyclosed.Never block the gravity fueling nozzle in an openposition. Ratcheted handles that allow the operator tolock the handle in the open position are prohibited.The nozzle must always be controlled by hand, sothat the flow of fuel may be instantly stopped whennecessary. A strainer or screen installed in the nozzleprovides a last means of stopping any dirt or foreignmatter from entering the aircraft fuel tanks. Thisstrainer should never be left out of the nozzle if it isto be used for fueling aircraft.DEFUEL PUMPThe defuel pump used in Cla-Val fueling stationsis the Blackmer rotary vane, positive displacementpump. It is described in detail in chapter 4 of thismanual.Flight and hangar deck station defuel pumps arenormally set to pump 100 gpm at 15 psi.PORTABLE DEFUEL PUMPSThe portable defueling pumps are either an air-motor-driven internal gear pump or an air twin-dia-phragm pump mounted on a mobile cart. Both pumpsare operated off the ship’s low-pressure air system.Three hoses are used with the defueling unit: anair hose, which has a 1/2- or 3/4-inch inside diameter,and two defueling hoses, which have 1 1/2 or 2 1/2-inch inside diameter. One defueling hose is used as asuction hose. It should be as long as necessary toreach from the aircraft to the defueling unit. Thelonger the hose, the less effective the defueling unitis. The other defueling hose is used for the defuelingunit discharge hose. The length of this hose has littleeffect on the defueling unit operation as long as itdoes not become kinked.The defueling suction hose is connected to theaircraft in several different ways. For jet aircraft hav-ing single-point fueling/defueling capability, the hoseis connected to the aircraft through a pressurefueling nozzle. For aircraft drop tanks, the hosewithout a fitting is inserted into the tank fill openingor pushed up over a drain fitting on the bottom of thetank. When defueling drop tanks only, the methodnormally used5-15
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