Operation of diesel fuel system and lube oil systems

Basic operations of a diesel fuel and lube oil systems is presented in the following paragraphs.

1. Diesel fuel system operation. The diesel fuel storage tank shown in figure 5- 1, Schematic of a typical diesel fuel system, must be a double wall tank or, when located above ground, a single wall tank surrounded by a dike for containment of a leak, can be used. For underground installations, the tank must be double wall with a leak detection system monitoring the annulus between walls. The tank is provided with level indication, either local, remote, and/or is interlocked to shut off fill flow. The tank is provided with a fill line, man access port, return line and two suction lines. The tank may be provided with suction line heaters or a tank heater (not shown) depending on the engine’s fuel requirement and type of diesel fuel selected. The fill line and the return lines are provided with traps to minimize the formation of vapors in the tank. One suction line is located higher than the other. Normally the pump will draw from the low suction line. As water separates from the fuel it will approach the lower suction line. If water is picked up in this line, the pump can be switched to the upper suction line until the water is removed through the man access port. A strainer provides a coarse means of particulate removal upstream of the pump. A coalescing filter provides for water and fine particulate removal downstream of the pump. An expansion tank may be installed to prevent expanding fuel oil from leaking from joints and shaft seals. An oil heater may be installed depending on the type of oil and climate, to reduce oil viscosity to the atomizing range. The fuel oil then enters the day tank and is discharged through a trap. The day tank holds a four- to eight- hour supply of fuel and is mounted above, or in close proximity to, the generator’s diesel engine. It is provided with a vent, overflow, return line, gravity feed line to the duplex engine filters, a pump and a level indication, either local, remote and/or interlocked to shut off supply flow. The engines positive displacement pump raises the diesel fuel to the correct pressure for engine operation and distributes it to the fuel injectors. An oil cooler is provided, when needed, in the return line to minimize flashing and formation of vapors. Oil lines may be electrically, or steam heat traced for winter service depending on the type of fuel, climate and installed pipe location.
2. Lube oil system operation. As shown in the lube oil system in figure 5-2, Schematic of a typical lube oil system, new lube oil passes through a strainer before entering the clean lube tank. The tank is provided with level indication, either local, remote and/or is interlocked to shut off fill flow. The tank is also equipped with a vent and a heater if required. The dirty lube tank incorporates a drain, level indication, vent, return line and suction line.
   1. A pump draws lube oil through a strainer and foot valve in either tank. The foot valve prevents the line from emptying when not in use. From this pump, lube oil can flow to the engine lube oil sump, to a tanker truck for hauling to an oil recycle center, or it can be heated and cleaned through a centrifuge. From the centrifuge, water/oil discharge is sent to a separator, sludge is sent to treatment for disposal and the treated lube is sampled. The treated lube if clean is pumped to the engine lube oil sum, or if dirty it is pumped to the dirty lube oil tank.
   2. From the engine lube oil sump, lube oil is pumped through a duplex strainer by a motor driven pump or an engine driven pump. As with duplex filters, duplex strainers provide for continuous operation. Switching from one strainer to the other can take place without impeding oil flow by switching the inlet and outlet three-way valves simultaneously. This permits cleaning of one strainer while the other is in service. When the standby power engine requires warm engine lube and a warm engine block for startup, the electric motor driven pump continuously circulates engine lube through a heater. Once the engine is started the engine driven lube oil pump will take over and lube will flow through a thermostatic valve to a cooler and by-pass line to maintain correct engine lube temperature for operation. The lube oil flows through a duplex filter before entering the engine. The electric motor driven pump can also be used as a pre-lube pump to circulate lube prior to starting the engine and after the engine shuts down for controlled cooling. The pump also transfers dirty lube from the engine lube oil sump to the dirty lube oil tank.
   3. The lube oil system may be integral with the engine or may be provided as a separate skid mounted unit. Lube oil tanks, pipes, and lines may be heated, or heat traced. Controls, alarms and engine shutdown interlocks are provided as needed and include alarms for low oil flow, low oil level, low oil pressure, low oil temperature, high oil temperature or high filter differential pressure.