indicates its findings on a dial that is calibrated in gallons. This gage consists of three basic units: the bellows, torque tube, and dial mechanism. The flow indicator (fig. 6-10) provides visual iden- tification of the flow of seawater through a pipeline. The indicator has a hinged flapper suspended from the body so it rests against the inlet passage at no flow. As liquid begins to flow, the flapper swings outward to a position generally proportional to the flow rate. The in-tank reservoir connecting lines are gasoline- tight, cylindrical tanks with a nontight flanged cover. They are open to liquid pressure near the top by two holes directly opposite each other. The in-tank reser- voirs are brazed to the ends of connecting lines. One is located near the top of the tank and the other located near the bottom of the same tank. Connecting lines terminate 1/2 inch off the bottom of the reservoir. The in-tank reservoirs are filled with seawater because of purging. The connecting lines are purged with seawater to prevent gasoline from entering the pump room through the lines. The flow-limiter valve is a globe-type needle valve used to reduce seawater pressure to the desired pressure. It is located between the firemain supply and the purge valve. The seawater pressure gage indicates the pressure of the seawater supply and is located between the flow- limiter valve and the purge valve. With one exception, the TLI used in MOGAS tanks is just like the TLI used in JP-5 tanks. The float for the TLI used in MOGAS systems is constructed of Hycel. This material is designed to float on water and sink in fuel. That means the float will be at the cleavage line (interface) of the water and MOGAS. Refer to chapter 4 for information on TLI components and operations. SEAWATER PIPING AND VALVE ARRANGEMENT The seawater system supplies seawater (under pres- sure) to the outer tank to force gasoline up to the transfer (gasoline booster) pump. It also provides a means for flushing and draining the storage tank, and limits the Figure 6-10.—Flow indicator. amount of pressure that can be applied to the tanks at maximum pump capacity. Seawater is supplied directly from the sea, through a sea chest located in the cofferdam around the storage tanks. A steel grating installed in the opening of the ship’s bottom prevents large objects from being drawn into the system. Steam is used for cleaning out the sea chest in the event of clogging. Steam has a two-fold effect for cleaning purposes. It can be supplied at an adequate pressure for blowing out any debris, and it also provides a “cooking effect” to remove remaining gaso- line vapors as well. A shutoff valve is located between the sea chest and the sea chest supply riser. This valve is LOCKED OPEN. The sea chest supply riser connects directly to the suction header of the seawater pump. An additional shutoff valve is installed in this line at the pump room level. The motor-driven, centrifugal seawater pump is located in the MOGAS pump room, and the motor is in the adjacent pump motor room. The shaft connecting the pump to its motor passes through a watertight stuff- ing box in the bulkhead. The pump takes suction from the suction header and discharges into a discharge header. The pump suction line is fitted with a basket strainer, a one-way check valve, and a compound gage. The discharge line contains a pressure gage and a shut- off valve. On centrifugal pumps, the pump inlet is always larger than the discharge line. NOTE LPDs have a separate seawater pump room, located in the starboard shaft alley. The discharge header is connected to the outer tank seawater supply riser and the seawater expansion tank fill line. Shut off valves installed in this line can be used to direct pump discharge pressure into the outer tank for pressurizing the system during normal operations or filling the expansion tank. The expansion tank is a 500-gallon tank kept full of seawater. Its purpose is to keep the MOGAS tanks full at all times by compensating for contraction of the MOGAS. The outer tank seawater supply riser terminates in a diffuser at the bottom of the outer tank. This line contains a spectacle flange (or pipe blind) and a steam- out connection. The spectacle flange is rotated to the closed position when steam is injected either here or at the outer tank manhole cover for steaming tanks. The overboard discharge line is led upward in a loop from the expansion tank and then overboard just above 6-10