Fire Safety Engineering

Each Diesel Fuel tank shall have the following connections : -

.
Fill pipes shall enter the top of the tank and shall terminate within 6 in. of the bottom of the tank.

.
Shall be located in the lowest point of the tank and size of 1 in. NPT.

.
- Normal vents shall be 2 in. NPT or sized according to ANSI/UL 142.
- As an alternative, the normal vent can be at least as large as the largest filling or withdrawal connection, but in no case shall it be less than 11∕4 in. nominal inside diameter.

.
The fuel supply pipe connection shall be located on a side of the tank so that 5 percent of the tank volume provides a sump volume not usable by the engine.
The tank connection shall be no smaller than the fuel supply piping to the engine.

.
The tank connection shall be no smaller than the fuel return piping from the engine.
FUEL LEVEL SWITCH CONNECTION.
The fuel tank shall have one 2 in. NPT threaded port in the top, near the center, of the tank to accommodate the low fuel level switch.
.
The fuel tank shall have one minimum 1 in. NPT threaded port in the top of the tank to accommodate the connection of a line for the return fuel from an active fuel maintenance system.
Where there is not an active fuel system installed, a plug shall be installed in this connection.

Reference :- NFPA 20