BLOCK 8V2979 - Caterpillar

General Information
The hydraulic system consists of two identical winches. One winch is independent of the other winch. The winches are hydraulically driven and hydraulically controlled. Each winch is capable of variable speeds in the HIGH range, LOW range, or BRAKE OFF mode. The mode of operation of one winch does not affect operation of the other winch.Winches (5) control the boom functions and the hook functions.Two hydraulic circuits control the winch operation. One circuit supplies oil to control valve (1) for the winch drive motors. The other circuit supplies oil to winch control valves (7). The winch control valves control the following functions:
Winch brakes
Winch speed
Selection of HIGH or LOW range
Brake release during lowering operationsA third circuit is for controlling the counterweight.The winch drive circuit consists of the following components:
(1) Control valve
(12) Hook control lever
(10) Boom control lever
(6) Winch drive motors for the hook and for the boomWinch motor control valve (1) is supplied with oil by the two large sections of hydraulic pump (13) .Control valve (1) contains two spools. One spool controls oil flow to hydraulic motor (5) (bottom motor) for the hook winch.The other spool controls the oil flow to the hydraulic motor (5) (top motor) for the boom winch.Control valve (1) also contains the main relief valve for the drive circuits for the hydraulic motors and the power down relief valves for each winch motor.The winch control circuit consists of the following components:
(12) Hook control lever
(10) Boom control lever
(8) Brake metering pump (bottom) for the hook
(8) Brake metering pump (top) for the boom
(7) Winch brake and speed control valve (bottom) for the hook
(7) Winch brake and speed control valve (top) for the boom
(2) Brake accumulatorThe winch brake and speed control valves (7) for the hook and for the boom are supplied with 2750 kPa (400 psi) pressure oil from the transmission hydraulic system.Brake metering pumps (8) control the brake pressure in order to maintain an even lowering speed for the winches.The counterweight control circuit consists of the following components:
(9) Counterweight control lever
(11) Counterweight control valve
(4) Two counterweight hydraulic cylinders
(3) An orifice check valve is fastened to the head end port of each hydraulic cylinder.The orifice check valves are installed in order to prevent the hydraulic cylinders from falling freely if hydraulic pressure is lost.The counterweight circuit is supplied with oil by the small section of hydraulic pump (5) .The return oil from the counterweight circuit is directed through oil cooler (16) .Counterweight control valve (11) contains a relief valve for the counterweight circuit.The hydraulic system is designed as a continuous flow (loop) that permits minimum pressure in the system when the