Chapter 6 TPD1317e Fuel tanks should have the following features: The filler neck should be raised so that water will not enter when filling. The filler cap should seal effectively to prevent water entering when under way. A vent pipe should be fitted, again in such a way as to avoid the entry of water. The tank should have a sump or angled bottom with a drain tap so that water and sediment can be removed. (This is not always possible). Internal baffles may be required to prevent fuel surge. The tank should have a removable panel to simplify cleaning.
The fuel pipework should be as simple as possible with the minimum of valves and cross connections, so that obscure fuel feed problems are minimised. A fuel sedimenter (i.e. water trap) is required in the fuel system between the fuel tank and the engine mounted lift pump. To avoid problems when venting air after draining the sedimenter, it should preferably be installed below the normal minimum level of fuel in the fuel tank. (This is not always possible!). The tank should have at least two connections; a fuel feed connection, and a fuel return connection. Whenever possible a tank should only supply one engine, but in any case each engine should have its own fuel pipes, from tank to engine.
6.2 Typical Fuel Systems The more simple the fuel system, the better it will perform in service. Figure 1 shows an ideal system. Fuel return pipe Stop cock Fuel tank Main fuel feed Water separator Figure 1 - A Simple Fuel System. Page 34