SECTION 9
HYDRAULIC SYSTEM
Dec 2002
p. 9-3
05130471
9.2 Operation
The hydraulic system operates at its adjusted pressure setting up to the
maximum flow capacity of the variable displacement piston pump.
During motor start the piston pump flow is ported to reservoir to reduce
load on the motor.
The electric motor (1) drives the piston pump (2) and gear pump (3). See
Section 10 Recirculation for discussion of the gear pump circuit. The
hydraulic manifold (25) is mounted to the underside of the intensifier
assembly (30). The flow from the piston pump (2) passes through check
valve (8) to the directional control valve (11), and the directional control
valve sends the flow to one end of the hydraulic cylinder (14) until the
piston activates the proximity switch (23) at the end of the stroke. The
activated proximity switch sends an electrical signal to the pneumatic
directional control valve (26) that in turn shifts the hydraulic directional
control valve (11). The hydraulic valve shifts to reverse direction of
movement of the piston (29) until activating the opposite end-of-stroke
proximity switch.
9.2.1 Hydraulic Pressure Compensation
A pressure compensation (22) feature on the variable- displacement,
piston pump (2) maintains constant hydraulic operating pressure even
under variable flow demands. When the HP water flow is blocked or
restricted, the piston pump delivers only enough hydraulic oil to
maintain compensator (22) set pressure. If HP water flow is high, for
example, the nozzle orifice is too big, then the pressure compensator
commands full flow capacity from the piston pump.
9.2.2 Hydraulic System Pressure Protection
Besides the pump compensator (22), the hydraulic system pressure is
limited by the main relief valve (24). The operating hydraulic pressure is
indicated by hydraulic gage (28).
Pressure Adjustment Hyd. Pressure Bar (psi)
Control Valve
Increase Decrease Maximum Minimum
Compen-
sator
Pressure
22 Clockwise Counterclockwise 207 (3,000) 1.7 (25)
Main
Relief
24 Fixed Fixed 234 (3,400)
(Not
applicable)
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