BOX A.-BATTERY 4H9051 - Caterpillar

Illustration 1 g00644620
The steering pressure reducing valve is located under the rear of the cab on the left side.The steering pressure reducing valve is located in the oil supply line between the steering control valve and the steering metering pump. The steering pressure reducing valve performs the following functions:
Reduce the pressure of the pilot oil supply to the steering metering pump. This is independent of the pump speed.
Maintain the pilot oil pressure at a preset level.
Provide shock relief against pressure surges.The oil supply to the steering pressure reducing valve passes through a cartridge type filter that is equipped with a bypass indicator. The filter is located on the back of the cab on the left side.
Illustration 2 g00644623
Pressure reducing valve (1) Jam nut (2) Adjusting bolt (3) Spring (4) Tank port (5) Chamber (6) Regulated pressure port (steering metering pump supply line) (7) Passage (8) Passage (9) Hole (10) Chamber (11) Inlet port from the steering control valve (12) Passage (13) Passage (14) Passage (15) Passage (16) SpoolOil from the steering control valve enters the steering pressure reducing valve through port (11). The oil then flows through passages. (12), (13), (8), (7) and port (6). Port (6) is the regulated pressure port that is connected to the inlet to the steering metering pump.When the steering wheel is stationary, oil from port (6) is blocked at the spool of the steering metering pump and the oil flows through hole (9) to chamber (10). This causes the pressure to rise. When the pressure in chamber (10) overcomes the force of spring (3), spool (16) is offset and the flow of oil between passage (12) and passage (13) is gradually restricted. When a certain pressure is reached, the spool will have moved far enough in order to block the flow of oil from passage (12) to passage (13). The pressure in regulated pressure port (6) is then at the preset value for the valve.When the steering wheel is turned, oil starts to flow through the steering metering pump. This decreases the pressure in regulated pressure port (6). This pressure decrease also occurs in chamber (10) and spring (3) starts to move the spool to the right until passage (12) is connected to passage (13). This allows inlet oil to flow to the steering metering pump.When the flow through the steering pressure reducing valve is sufficient to match the demand from the steering metering pump, the pressure in chamber (10) rises. This offsets the spool against the force of spring (3). The spool assumes a balanced position. The restriction between passage (12) and passage (13) allows only enough oil to pass in order to maintain the oil supply to the steering metering pump at the preset pressure level.If a pressure surge occurs in the supply line to the steering metering pump, the surge is transmitted to chamber (10). This moves the spool against spring (3), which closes the inlet to the valve at passage (12). If the pressure surge is high enough, the spool