HYDRAULICS 1.21 Pressure Reducing Valve (PRV) - for the parking brake (8) NOTE: (Fitted to Machines up to S/No.51200551 only The Pressure Reducing Valve (PRV) (8) for the parking brake is electrically controlled from a switch in the cab (refer to electrical section). The PRV is located in the engine pod for Machines up to S/ No.51200317 and adjacent to the front axle for Machine S/No's.51200318 to 51200551. The switch operates a solenoid on the valve to give proportional operation. The pressure can be tested using test point 2 (66 - Refer to Page 1.30), which is in the output from connection A. NOTE:
The voltage to the solenoid is supplied through a voltage transformer, to achieve the proportionality required. Under no circumstances should battery voltage be applied to this solenoid. Specifications: T. Return to hydraulic tank (1) P. Supply from Auxiliary pump (6) A. Supply to Parking Brake actuators (14) Operating pressure 16 bar (230 psi) Maximum pressure 20 bar (290 psi) Solenoid 3mm/12vdc/100% prop Pressure filter (9) NOTE: (Fitted to Machines up to S/No.51200471 only) The oil pressure filter (9) is installed in the return line, between the fan motor (7) and the hydraulic tank (1). NOTE:
(Fitted to Machines from S/No.51200472 only) The oil pressure filter (9) is installed in the return line, between the reverse fan valve (72) and the hydraulic tank (1). If the filter becomes blocked, a filter blockage warning light in the cab illuminates and a bypass will open at 3.5 bar (50 psi). When the warning light is illuminated NO filtration is taking place. Always change the filter IMMEDIATELY. Specifications Filtration 10 µ m 1. Pressure switch 2. Bypass valve 3. Filter bowl 4. Filter media