PORTABLE DEFUEL PUMPS

Figure 5-16.—Gravity fueling nozzle. smaller valve, and the nozzle is then completely closed. Never block the gravity fueling nozzle in an open position. Ratcheted handles that allow the operator to lock the handle in the open position are prohibited. The nozzle must always be controlled by hand, so that the flow of fuel may be instantly stopped when necessary. A strainer or screen installed in the nozzle provides a last means of stopping any dirt or foreign matter from entering the aircraft fuel tanks. This strainer should never be left out of the nozzle if it is to be used for fueling aircraft. DEFUEL PUMP The defuel pump used in Cla-Val fueling stations is the Blackmer rotary vane, positive displacement pump. It is described in detail in chapter 4 of this manual. Flight and hangar deck station defuel pumps are normally set to pump 100 gpm at 15 psi. PORTABLE DEFUEL PUMPS The 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 pumps are operated off the ship’s low-pressure air system. Three hoses are used with the defueling unit: an air 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 a suction hose. It should be as long as necessary to reach from the aircraft to the defueling unit. The longer the hose, the less effective the defueling unit is. The other defueling hose is used for the defueling unit discharge hose. The length of this hose has little effect on the defueling unit operation as long as it does not become kinked. The defueling suction hose is connected to the aircraft in several different ways. For jet aircraft hav- ing single-point fueling/defueling capability, the hose is connected to the aircraft through a pressure fueling nozzle. For aircraft drop tanks, the hose without a fitting is inserted into the tank fill opening or pushed up over a drain fitting on the bottom of the tank. When defueling drop tanks only, the method normally used 5-15