Section 7
Hydraulic System
20412971
8-2012/Rev 08
7-3
The hydraulic system operates at high or low pressure settings up to the maximum flow capacity
of the hydraulic pump. The high and low limit compensators mounted on the pump regulate the
flow of hydraulic fluid to maintain constant operating pressures. Operating pressures are set and
adjusted at the high and low pressure control valves on the manifold.
If the machine is equipped with proportional pressure control, low pressure is adjusted at the
manifold, and the high pressure setting is made from the control panel or a remote console.
The high and low limit compensators regulate the flow of hydraulic fluid to the
system by controlling the angle of the swashplate. If the oil is not properly
maintained, the compensators can become blocked with debris. As a result, pump
control will be lost and you will not be able to create hydraulic oil pressure.
The normally closed, two pressure solenoid valve is controlled by the operator’s selection of high
or low pressure. The valve is closed while operating in high pressure and is open during low
pressure operation. A light on the solenoid connector indicates low pressure operation.
At startup, hydraulic pressure is automatically switched to low, limiting torque demand. After 5-
60 seconds, depending on the interval selected by the operator, hydraulic pressure automatically
returns to the previously selected pressure setting.
A reference gauge on the top of the manifold displays hydraulic pressure to the intensifiers.
When the intensifier shifts, it is normal for the pressure to quickly fall and then rise again.
The 4-way directional control valve directs pressurized oil to one end the hydraulic cylinder and
returns fluid to the reservoir from the opposite end, causing the intensifier to stroke. The
movement is controlled hydraulically by a pilot valve that is electronically operated by two
solenoids, energized by the PLC. Indicators light up as each solenoid is energized.
The directional control valve sends flow to the hydraulic cylinder in one direction until the
hydraulic piston activates the proximity switch at the end of the stroke. The activated switch
sends a signal to the PLC to reverse the direction of flow. The piston then moves in the opposite
direction until it activates the proximity switch at the opposite end of the stroke.
If the machine is equipped with redundant intensifiers, manual hydraulic valves are opened or
closed to direct the hydraulic flow to either intensifier. If the machine is equipped with dual
intensifiers, the directional control valve supplies hydraulic pressure to both intensifiers.
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