797B Off-Highway Truck Fan Drive Hydraulic System: Pressure Reducing Valve (Fan Drive)

(1) Pressure reducing valve (2) Return hose to the hydraulic tank (3) Supply hose from the steering system (4) Pressure sensor for the steering pump(5) Signal hose to the piston pump for the fan drive and the brake cooling drive pump

Pressure reducing valve (1) is mounted on the frame assembly above pressure sensor (4) for the steering pump.
Steering oil flows through oil supply hose (3) to pressure reducing valve (1). The pressure reducing valve reduces the steering pressure to a lower signal pressure. Excess steering oil flows to the hydraulic tank through oil return hose (2). The reduced oil pressure signal flows through hose (5) to the piston pump for the fan drive and to the brake cooling drive pump. The piston pump for the fan drive and the brake cooling drive pump use the oil pressure signal to destroke to minimum flow at start-up and during cold temperatures.

Oil Filter (Steering/Fan Drive)

Steering/fan drive filter (1) Inlet line(2) Hydraulic filter for the steering system and for the fan drive system

(3) Outlet passage(4) Bypass valve

The hydraulic filter for the steering system and for the fan drive system is fastened to the right side of the main frame. The hydraulic filter for the steering system and for the fan drive system is located beside the steering accumulators. Oil from the makeup valve in the fan drive system flows to hydraulic filter (2) through inlet line (1). Oil from the solenoid and relief valve in the steering system also flows to hydraulic filter (2) through inlet line (1). Oil from hydraulic filter (2) for the steering system and for the fan drive system flows to the oil cooler for the steering system and for the fan drive system.
Oil goes through inlet passage (1). The oil fills the space between the inside of both filter housings and both filter elements. During normal operation, the oil goes through the filter elements to outlet passage (3). The oil then flows to the steering oil cooler. The elements stop any debris that is in the oil.
If the elements become full of debris and the restriction to the flow of oil causes the pressure increase inside the filter to exceed 138 kPa (20 psi) the bypass switch is activated. The bypass switch will be activated and an alarm will be registered in the cab. If the pressure inside the filter exceeds 345 kPa (50 psi) then the bypass valve (4) will open. The bypass valve allows the unfiltered oil to enter the system.
The oil then flows past the open bypass valve to the remainder of the hydraulic system. When the oil does not go through the filter elements, the debris that is in the oil will cause damage to other components in the hydraulic system.
Correct maintenance must be used in order to be certain that the element does not become full of debris. If the element is full of debris, the flow of clean oil to the hydraulic system will be stopped.

Hydraulic Tank

(1) The hydraulic tank for the brake actuation and rear axle lube drive (2) The return for the brake cooling oil (3) Hoist return screens (4) The return for the brake cooling oil (5) The steering and the brake cool drive and the fan motor drive tank. (6) Brake cooling relief valves (7) The screen for the rear brake cooling pump (8) The drive motor for the brake cooling pump(9) The screen for the front brake cooling pump

The hydraulic tank is actually three separate hydraulic tanks in one. The large section of the hydraulic tank contains oil for the hoist system and for brake cooling. The piston motor drives three brake cooling pump sections that are located inside the large section of the hydraulic tank. The front brake cooling pump section sends oil through screen (9) for front brake cooling to the front brake oil cooler. The rear brake cooling pump sections send oil through screen (7) for the rear brake cooling to the rear brake oil cooler. The oil coolers are protected from high pressure by relief valves (6). Brake cooling oil is returned back to the large section of the hydraulic tank through return ports (2) and return port (4). Oil for the hoist system is returned back to the large section of the hydraulic tank through hoist return screens (3) .
Small internal tank (1) is located near the top of the large section of the hydraulic tank. Internal tank (1) contains oil for brake actuation and oil for the rear axle motor drive. The internal tank is used to keep the brake actuation oil free of contaminants that return with the brake cooling oil. A passageway is located in the side of internal tank (1) that connects the internal tank to the large section of the hydraulic tank. The large section of the hydraulic tank is filled with oil that flows through the passageway.
Hydraulic tank (5) is located at the bottom of the hydraulic tank. The hydraulic tank contains oil for the steering system, the piston pump that drives the brake cooling pump sections, and the piston pump that drives the fan drive motor. The oil level in lower rear tank (5) is monitored by an oil level sensor.

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797B Off-Highway Truck Fan Drive Hydraulic System: Pressure Reducing Valve (Fan Drive) 2013-01-25T20:03:00-08:00 Rating: 4.5 Diposkan Oleh: Unknown