TM 5-3810-306-20The selector valve, is located at the center of the carrier frame just forward of the rear axle. At crane start-up in travelmode, with boom-overfront, the valve solenoids are energized, allowing rear axle oscillation, by an electrical circuitcontrolled by a cam actuated roller switch mounted on the swivel. As the superstructure is rotated more than five degreeseither direction from boom-over-front-position, the switch roller rides off a cam, opening the circuit, de-energizing thesolenoids, and allowing cartridge springs to close the valve, blocking through flow and locking out rear axle oscillation.The system is designed so that with the loss of power rear axle oscillation lockout is automatic.Steering Relief ValveA pressure relief valve is provided on the discharge of the steering pump to relief the pressure in the power steeringsystem when the pressure reaches 2500 psi (17,238/172.3). The relief valve is mounted on the front face of the framecross-member to rear of centerline of rotation. When the pressure in the power steering system exceeds the setpoint, therelief valve opens to relieve hydraulic oil to the hydraulic return system.The relief valve protects the system if pressure exceeds the designated setting. The relief valve can be pressure adjusted.The poppet assembly is constructed with the spool area being larger than the poppet area. When pressure against thespool reaches the pre-determined setting, the poppet assembly shifts against the springs. This opens the relief port to thereservoir, and oil flows to the reservoir. When pressure decreases, the spring forces the poppet assembly to the neutralposition. This closes the relief port to the reservoir. A passage in the relief valve prevents a vacuum buildup within therelief valve.Bypass Valve AssemblyThe bypass valve assembly consists of a single selector valve, air cylinder, and a three way air solenoid valve. Thisassembly, controlled by a temperature switch mounted in the return manifold, allows hydraulic oil to bypass thesuperstructure oil cooler fan motor when the hydraulic oil temperature is less than 111 degrees F (44 degrees C).When the oil temperature is 120 degrees F (49 degrees C) the bypass valve is closed and the oil flows through the oilcooler fan motor. When the temperature drops to 111 degrees F (44 degrees C), sensed by the temperature switch, the3-way air solenoid valve is energized to move the valve spool to allow air pressure on the cylinder moves it’s piston rodagainst the single selector valve to open the valve, bypassing the oil cooler fan motor.1-40
Integrated Publishing, Inc. - A (SDVOSB) Service Disabled Veteran Owned Small Business
