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| Illustration 1 | g00288984 |
Solenoid and Relief Valve (1) Solenoid (2) Passage (3) Port for right accumulator (4) Orifice (5) Port for Auxiliary Power Unit (6) Port for inlet oil (7) Port for left accumulator (8) Passage (9) Port to steering metering pump (10) Cavity (11) Port for return oil from the steering metering pump (12) Cavity (13) Valve (14) Spring (15) Setscrew (16) Backup relief valve (17) Return port to steering hydraulic tank (18) Oil outlets (19) Plunger | |
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| Illustration 2 | g00301297 |
(1) Solenoid (3) Port for right accumulator (5) Port for Auxiliary Power Unit (6) Port for inlet oil (7) Port for left accumulator (9) Port to steering metering pump (11) Port for return oil from the steering metering pump (16) Backup relief valve (17) Return port to steering hydraulic tank (20) Oil sampling valve | |
The steering solenoid and relief valve is located on the front frame rail under the engine.
The pressure oil from the steering pump is routed through port (6) in order to fill cavity (10) . Cavity (10) connects the following components: port (6) from the steering pump, ports (3) and (7) for the accumulators, port (9) for the steering metering pump, passage (2) for accumulator purge solenoid (1) and backup relief valve (16) .
Return port (17) drains oil to the steering tank. Cavity (12) connects the following components: return port (17), port (11) for return oil from the steering system, passage (2) for accumulator purge solenoid (1) and backup relief valve (16) .
Accumulator Purge Solenoid
The accumulator purge solenoid (1) is used to drain pressure oil from the accumulators when the machine is not active.
Pressure of the accumulators is in cavity (10) . This oil flows through orifice (4) into passage (2) . When solenoid (1) is deactivated, this oil is blocked by plunger (19) . When the engine start switch is moved to the OFF position, solenoid (1) is activated. When solenoid (1) is activated, plunger (19) moves up. Pressure oil goes through orifice (4) in passage (2) , past plunger (19) and out return port (17) to the steering hydraulic tank. Orifice (4) limits the return oil pressure from the accumulators to a rate lower than the pressure setting of the filter bypass valve in the steering hydraulic tank. When solenoid (1) is deactivated, the plunger (19) moves down. Plunger (19) blocks oil in passage (2) .
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| Illustration 3 | g00441843 |
Location of electronic control for the steering accumulators | |
The accumulator purge solenoid is activated for 70 seconds. The accumulator purge solenoid is activated by the electronic control for the steering accumulators when the engine start switch key is moved to the OFF position. The electronic control for the steering accumulators is located inside the console that is between the operator seat and the buddy seat. The accumulator purge solenoid is not activated when the battery disconnect switch or the engine shutdown control is used.
Backup Relief Valve
The backup relief valve protects the steering system if the steering pump fails to destroke. The oil in cavity (10) enters passage (8) in backup relief valve (16) . If the pressure of the oil is within limits, valve (13) will block the oil. If oil pressure reaches approximately 20700 kPa (3002 psi), valve (13) compresses spring (14) . The oil from cavity (10) flows past valve (13) through oil outlets (18) . This oil is now open to return port (17) and the oil drains to the steering hydraulic tank.
When the oil in the steering circuit can go through passage (8) and oil outlets (18) , the pressure of the oil cannot increase to a pressure higher than the setting of backup relief valve (16) . The pressure setting of backup relief valve (16) can be changed by a change in the force of spring (14) that keeps valve (13) closed.
Use the following procedure to change the pressure setting of the backup relief valve:
- Place the backup relief valve on the test stand.
- Remove the protective cap.
- Turn setscrew (15) clockwise in order to increase the pressure setting of backup relief valve (16) .
Note: Turn setscrew (15) counterclockwise in order to decrease the pressure setting of backup relief valve (16) .
The pressure setting of the backup relief valve (16) is 20700 ± 400 kPa (3002 ± 58 psi) .
Secondary Steering
The machine does not have a secondary steering pump. If the steering pump fails, an Auxiliary Power Unit can be used in order to operate the steering circuit on a disabled machine. The Auxiliary Power Unit connects to port (5) on the steering solenoid and relief valve and to a suction port on the hydraulic tank. This arrangement will provide pressure oil in order to charge the accumulators. Steering capability is then available to tow the machine.
See Special Instruction, "Using 1U-5000 Auxiliary Power Unit (APU)" and Special Instruction, "Using the 1U-5525 Attachment Group" for instructions.