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Frame
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Hydraulic system
Introduction
The hydraulic system includes any component that controls or routes hydraulic fluid (oil) through the
testing system. For specifications of the hydraulic oil, refer to maintenance information provided in the
System Operating Instructions (supplied separately).
Hydraulic power supply
The function of the HPS is to act as the power supply for the frame. This includes powering the hydraulic
cylinder, crosshead motor, and hydraulic grip actuators (for frames with G7-style crossheads). The HPS is
a variable pressure unit; it creates hydraulic pressure as required depending on system demand.
The HPS is enclosed in the rear of the frame base. The components of the HPS can vary depending on
the configuration of the system. In general however, major components of the HPS are: a reservoir; a
pump; an electric motor; a heat exchanger; one or more manifold assemblies; and the hydraulic fluid (oil).
Figure 17 identifies typical HPS components. An electrical panel mounted inside the base houses the
motor starters, with overloads, for the electric motor.
When the HPS is on, the hydraulic cylinder should be positioned so that the piston is neither fully
retracted nor fully extended. When the hydraulic cylinder is in either of these conditions, it is difficult for
the 59 Series controls to maintain the position and the servo loop control could build up enough error to
shut down the HPS.
Reservoir
DO NOT start the HPS without the screen trapper or air breather assembly installed on the
reservoir. Starting the HPS with the solid cap (that is used for shipping) on the reservoir
instead of the air breather assembly could cause pump cavitation.
The reservoir holds the oil that is needed to operate the various hydraulic components. For approximate
reservoir capacity, and information on adding oil to or changing the oil in the reservoir, refer to
maintenance information provided in the System Operating Instructions (supplied separately). The
reservoir is equipped with a sight gauge, air breather assembly and screen trapper.
Sight gauge
The reservoir is equipped with an oil level and temperature sight gauge. The sight gauge (4, Figure 17) is
visible through the opening provided on the right side of the frame base. The reservoir should be filled so
Shut down the HPS and discharge hydraulic pressure before disconnecting any hydraulic
fluid coupling.
Do not disconnect any hydraulic coupling without first shutting down the HPS and
discharging stored pressure to zero. Tie down or otherwise secure all pressurized hoses to
prevent movement during system operation and to prevent the hose from whipping about
in the event of a rupture.
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