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| Illustration 1 | g00476129 |
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| Illustration 2 | g00476750 |
Pipelayer hydraulic system (1) Lubrication outlet port (2) Lubrication inlet port (3) Winch for the boom (4) Winch motor for the boom (5) Lubrication outlet port (6) Lubrication inlet port (7) BOOM RAISE port (8) BOOM LOWER port (9) Brake release port (10) Return manifold (11) Lubrication inlet port (12) QUICK-DROP port (13) Lubrication outlet port (14) Hook winch (15) Lubrication outlet port (16) Hook winch motor (17) Combination valve (18) Brake release port (19) Lubrication inlet port (20) Port for winch speed (21) Drain port (22) Brake release port (23) HOOK LOWER port (24) HOOK RAISE port (25) LOWER motor port (26) RAISE motor port (27) Speed control valve (hook winch motor) (28) Hook pilot control valve (29) Boom pilot control valve (30) Counterweight cylinder (31) Counterweight control valve (32) Boom kickout valve (33) Auxiliary hydraulic pump (34) Main hydraulic pump (35) Oil cooler (36) Accumulator (37) Distribution manifold (38) Load sensing manifold (39) LOWER motor port (40) RAISE motor port (41) Brake release port (42) Hook control valve (43) Boom control valve (44) Manifold (45) Shutoff valve (AA) Pump pressure (PP) Pilot pressure (LL) Return oil | |
The hydraulic system consists of the following major components: winch (3) for the boom, winch motor (4), hook winch (14), hook winch motor (16), combination valve (17), counterweight cylinder (30), counterweight control valve (31), boom kickout valve (32), auxiliary hydraulic pump (33), main hydraulic pump (34), oil cooler (35), accumulator (36), load sensing manifold (38), hook control valve (42), boom control valve (43) and manifold (44)
Operating Principles
The hydraulic system is a continuous flow system that permits a minimum flow in the system when hook control valve (42) , boom control valve (43) and counterweight control valve (31) are not activated. Main hydraulic pump (34) and auxiliary hydraulic pump (33) work together to supply oil pressure to the hydraulic components.
Counterweight Circuit
Auxiliary hydraulic pump (33) supplies oil for the counterweight hydraulic circuit and lubrication for the winches. When counterweight control valve (31) is operated, the oil goes to counterweight cylinder (30) . The return oil from the cylinder exits valve (31) and the oil goes to oil cooler (35) in order to lower the oil temperature. When counterweight control valve (31) is in the HOLD position, the oil supply to valve (31) passes through the valve and the oil goes directly to oil cooler (35) . The oil passes through oil cooler (34) to distribution manifold (37) for lubrication of the winches.
Note: If oil cooler (35) ever becomes frozen or plugged, a bypass in counterweight control valve (31) reroutes the oil directly to distribution manifold (37) .
Pilot Circuit
Main hydraulic pump (34) supplies oil for the boom and hook control valves and the pilot circuit. The oil from pump (34) travels to manifold (44) . A portion of the oil travels through manifold (44) to the pilot circuit. Accumulator (36) is charged with this oil to the pilot pressure. After the accumulator is charged, the oil exits manifold (44) and pressure is sent to the pilot control valves. Speed control valve (27) controls the speed of hook winch motor (16) . Hook pilot control valve (28) controls the operation of hook winch (14) . Boom pilot control valve (29) controls the operation of winch (14) for the boom.
Note: Shutoff valve (45) controls the flow of pilot oil to the controls. When valve (42) is in the OFF position, all of the controls are disabled and all of the implements are locked in the HOLD position.
Speed Control Circuit
Speed control valve (27) receives oil from manifold (44) through shutoff valve (45) . When valve (27) is in the UP position, a signal is sent to port (20) on hook winch motor (16) . A spool in hook winch motor (16) shifts and the motor decreases speed. When speed control valve (27) is in the DOWN position, the oil pressure to valve (27) is blocked and the signal oil from port (20) in the winch motor is allowed to drain to the tank. The spool in hook winch motor (16) is allowed to return to the original position and the motor increases speed.
Hook Winch Control Circuit
Hook pilot control valve (28) receives oil from manifold (44) through shutoff valve (45) .
When valve (28) is in the HOOK RAISE position, a signal is sent to manifold (44) . This signal shifts hook control valve (42) and oil pressure from main hydraulic pump (34) is sent to port (24) on combination valve (17) . The oil exits combination valve (17) through port (26) and the pressure is felt in hook winch motor (16) . Hook winch (14) raises the load. Return oil from the winch motor enters port (25) in combination valve (17) . The oil exits the combination valve through port (23) and the oil returns to hook control valve (42) . This oil is then supplied to boom control valve (43) if oil pressure is needed. If oil pressure is not needed, the oil returns to the hydraulic tank.
When hook pilot control valve (28) is in the HOOK LOWER position, a signal is sent to manifold (44) . This signal shifts hook control valve (42) and oil pressure from main hydraulic pump (34) is sent to port (23) on combination valve (17) . A signal is sent from port (21) to port (18) on hook winch (14) in order to release the brake. The pressure oil exits combination valve (17) through port (25) and the pressure is felt in hook winch motor (16) . Hook winch (14) lowers the load. Return oil from the winch motor enters port (26) in combination valve (17) . The return oil passes through a counterbalance valve which controls the rate of return oil from the winch motor. The counterbalance valve will not allow the winch motor to overrun due to an excessive load. The oil exits the combination valve through port (24) and the oil returns to hook control valve (42) . This oil is then supplied to boom control valve (43) if oil pressure is needed. If oil pressure is not needed, the oil returns to the hydraulic tank.
When hook control valve (28) is moved to the QUICK-DROP position, a pilot signal is sent to port (12) on hook winch (14) . This signal releases the clutch in hook winch (14) and the hook is allowed to drop. When hook control valve (28) is returned to the HOLD position, the signal oil is allowed to drain and the clutch is engaged.
Note: When the engine is not running, the QUICK-DROP function can be performed by using the oil pressure from the accumulator. This is done by the process that is explained above.
Boom Winch Control Circuit
Boom pilot control valve (29) receives oil from manifold (44) through shutoff valve (45) .
When valve (29) is in the BOOM RAISE position, a signal is sent to manifold (44) . This signal shifts boom control valve (43) and oil pressure from main hydraulic pump (34) is sent to port (7) on the combination valve for the boom. The oil exits the combination valve through port (40) and the pressure is felt in winch motor (4) . Winch (3) raises the boom. Return oil from the winch motor enters port (39) on the combination valve. The oil exits the combination valve through port (8) and the oil returns to boom control valve (43) . This oil returns to the hydraulic tank.
When valve (29) is in the BOOM LOWER position, a signal is sent to manifold (44) . This signal shifts boom control valve (43) and oil pressure from main hydraulic pump (34) is sent to port (7) on the combination valve for the boom. A pilot signal from this pressure is sent to port (41) on the combination valve to port (9) on the winch in order to release the brake. The pressure oil exits the combination valve through port (40) and the pressure is felt in winch motor (4) . Winch (3) lowers the boom. Return oil from the winch motor enters port (39) on the combination valve. The return oil passes through a counterbalance valve which controls the rate of return oil from the winch motor. The counterbalance valve will not allow the winch motor to overrun due to an excessive load. The oil exits the combination valve through port (8) and the oil returns to boom control valve (43) . This oil returns to the hydraulic tank.
Load Sensing Circuit
Load sensing manifold (38) is used to determine the maximum pressure that is needed in the hydraulic system. Manifold (38) receives pressure signals from hook control valve (42) and boom control valve (43) . Manifold (38) resolves the highest pressure that is required by the hook or the boom in order to perform the current task. The highest pressure signal is then sent to main hydraulic valve (34) and the pump adjusts the output in order to fit the required pressure.
The following sections give detailed explanations of the major components of the pipelayer hydraulic system.