Multiquip MQP30DZ, MQP20IZ Mechanical Installation — Fuel System Diesel, Subbase Tank, Day Tank

MECHANICAL INSTALLATION — FUEL SYSTEM (DIESEL)

Subbase Tank

Base mounted or subbase fuel tanks are used to store fuel directly underneath the engine-generator set, eliminating the need for a remote main fuel supply tank and/or auxiliary fuel transfer pumps. This mounting arrangement offers the convenience of having a fuel supply tank mounted at the generator.

These tanks are designed to be contained in a rectangular base on which the engine-generator set is mounted. Generally, these tanks only increase the height of the generator set since the tank base is usually matched to the generator skid dimension. For many installations, this type of tank offers advantages over above ground and below ground tanks due to stringent environmental laws making it difficult or impossible to gain necessary approvals.

Subbase fuel tanks are available with the UL142 listing under the special purpose tank category of NFPA. These tanks are available in various capacities and designs.When a subbase fuel tank is used, the tank should be designed with a stub-up area on the generator-end of the tank.

This feature allows for an open area on the tank assembly whereby electrical terminations can be brought up underneath the engine-generator for final termination (refer to Electrical Connections section).

Using oversized subbase fuel tanks, where the tank is larger than the skid of the generator, can cause difficulty in completing final electrical connections. The tank should be designed with a stub-up area on the generator-end of the tank. However, depending on the placement of the engine- generator on the tank, feeder terminations may not rise in a close proximity to the circuit breaker. This could require the feeder conductors to enter the circuit breaker enclosure from the side or top, necessitating special fittings and/or hardware. Be sure to check with the local inspection authority before proceeding

Failure to provide an overflow line to the supply tank from the day tank can cause spilled fuel, safety hazards, and damage to equipment. Wipe up any spilled fuel immediately. Spilled fuel if ignited can cause a fire or explosion, causing damage to the equipment and severe bodily harm — even death!

Day Tank

Fuel day tanks are used when the engine fuel pump does not have the capacity to draw the fuel from the supply tank; or the supply tank is overhead and presents problems of high fuel head pressure for the system.

In high ambient conditions, the day tank temperature might need to be considered. Warm fuel returning from the engine fuel injection pump should not be returned to the day tank if possible. As fuel temperature increases, fuel density and lubricity decrease, reducing maximum power output and lubrication of fuel handling parts such as pumps and injectors. This may be avoided by returning the fuel back to the supply tank rather than the day tank.

Supply Tank Lower than Engine Installation

If a supply tank is lower than the engine, the day tank is installed near the generator set and within the engine fuel pump lift capability, but below the fuel injection system. Install an auxiliary fuel pump as close as possible to the supply tank to pump fuel from the supply tank to the day tank. A float switch in the day tank controls operation of the auxiliary fuel pump.

The supply tank top must be below the day tank top to prevent siphoning from the fuel supply to the day tank.

Provide a return line from the engine injection system return connection to the day tank (near the top). Provide a day tank overflow line to supply tank in case the float switch fails to shut off the fuel transfer pump.

Supply Tank Higher than Engine Installation

If a supply tank is higher than the engine, the day tank is installed near the generator set, but below the fuel injection system. Fuel lines should at least be as large as the fuel pump inlet. The engine fuel return line must enter the day tank.

Include a shut-off valve in the fuel line between the fuel supply tank and the day tank to stop fuel flow when the generator set is not in use and the battery is disconnected (Off Mode).

Engine Fuel Connections

Identification tags are attached to the fuel supply line and fuel return line connections by the factory. Flexible lines for connecting between the engine and stationary fuel line are supplied as standard equipment.

PAGE 38 — INDUSTRIAL GENERATOR SETS — APPLICATION & INSTALLATION MANUAL — REV. #4 (09/07/07)