RING 1708774 - Caterpillar

Illustration 1 g00996503
Flow of air and engine oil during operation of the prelube pump (typical example)
(1) Oil pressure switch
(2) Box for the relay
(3) Lubricator
(4) Prelube pump motor
(5) Prelube pump The prelube pump is an option which provides lubrication for the engine prior to start-up. The service life of the engine is extended because of reduction in the opportunity of wear from the contact of dry moving parts.Illustration 1 is a typical example. Several options are available for the prelubrication according to the needs of the customer. Usually, operation of the prelubrication system is associated with operation of the starting system. However, the starting and the stopping of the prelube pump is determined by the customer's equipment.The customer provides the wiring and an electrical power source for the normally closed oil pressure switch (1). Customer supplied wiring connects the switch to a relay coil in box (2). Electrical power to the relay coil closes the relay contacts. The customer determines the function of the relay contacts.During operation, pressurized air is routed through lubricator (3). The lubrication is entrained in the pressurized air in order to lubricate internal parts of prelube pump motor (4). The motor operates prelube pump (5). The pump draws engine oil from the oil pan. The oil is pumped upward into the oil cooler's inlet elbow. The oil circulates normally through the engine.The pressurized air is exhausted through the prelube pump motor's outlet. The air is routed through a hose to the air starting motor's silencer. The prelube pump operates until the supply of pressurized air is stopped.A hose is connected from the main oil gallery in the cylinder block to oil pressure switch (1). When the engine oil pressure rises to the pressure rating of the oil pressure switch, the switch opens. This interrupts the electrical power supply to the coil of relay (2) and the relay contacts open.
Illustration 2 g01020482
Electrical schematic for the oil pressure switch and the relay
Illustration 2 is a typical schematic for the described oil pressure switch and for the relay. Notice that the relay has two sets of contacts. The customer could use those contacts to activate an indicator and the starting motor solenoid. The schematic is only a reference. The customer determines the function of the relay and the routing of the wiring.