Transfer mainside valve (cutaway)

Aviation Boatswains Mate F - Aviation theories and other practices
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The transfer mainside valves are specially de- signed globe valves that are welded to the top of the manifold header (fig. 4-20). They are cylindrical in shape (about 10 inches in diameter) and consist of a body and bonnet. The body houses the seat ring and a guide for the valve disk. Perfect seating of the valve disk with the seat ring is assured by the disk guide centered in the base of the valve body. The lower section of the valve body is welded to the manifold Figure 4-20.—Transfer mainside valve (cutaway). header. A hole is machined in the back of the valve body (above the valve seat) for attaching the nozzle. On the front of the valve body, a hole is drilled and tapped (also above the valve seat) for installing the telltale valve. The bonnet, which provides a working area for the stem, is bolted to the top of the valve body. Leakage of JP-5 is prevented by a gasket between the valve body and bonnet, and packing in the bonnet packing gland around the stem. The tankside valve is identical to the transfer mainside valve, except there is no telltale valve con- nection and the bottom of the valve body is fitted with a standard pipe flange. The storage tank fill and suc- tion tail pipe that the valve serves is bolted to this flange. The nozzle is a short section of pipe connecting one transfer mainside valve to one tankside valve in parallel so the two valves serve only one tank. The telltale valves are small, angle type globe valves installed on the front side of the transfer main- side valves. NOTE Most ships are replacing the telltale valve with a GAMMON sample connection. The GAMMON sample connections are less likely to break or leak, and require no maintenance. There is one telltale valve for each set of manifold valves. These valves are installed on the front side of the transfer mainside valves, above the valve seat. They are used to determine the condition of the valve seats. The telltale valves should be opened periodically. If fuel leaks from the valve, it is an indication either the transfer mainside or the tankside valve is leaking. Both should be inspected as soon as possible and the leaking valve repaired. The manifold header drain valve is installed at the bottom near one end of the header. It is used to drain the header before maintenance. A locking device is installed for each of the tank- side valves. It is typically a bar with a rotating hook to fit around and locked to the tankside valve handle. It is arranged so the valve can only be locked in the closed position. Tankside valves MUST be locked in the closed position when the tanks are ballasted. 4-24

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