MTS Series 505G2 SilentFlo Hydraulic Power Unit Model 505G2-180 - Manual (Page 21)

HPU Functional Description
Pump assemblies
Pump assemblies draw hydraulic fluid from the reservoir and pressurize it to a maximum preset pressure.
Each pump assembly contains a variable volume pump, a motor, and an electrical enclosure. Each pump
assembly has a flow capacity that contributes to the total hydraulic flow capacity of the HPU.
Manifold
The manifold combines the pressurized hydraulic output of the discrete pump assemblies, and provides the
hydraulic connection to your hydraulic system. The manifold contains the high/low pressure solenoid valve
and a nonadjustable relief valve. Check valves are located within the manifold to prevent pressurized hydraulic
fluid from being forced back through the pumps.
The hydraulic power unit uses solenoid-operated valves to control when high-pressure is available to the
hydraulic circuit. Start/low/high control settings are selected at the operator interface on the electrical enclosure’s
front panel.
The HPU is designed to start in low pressure to reduce the amperage needed for starting, which will extend
the life of the pump and motor. When operating at this setting, low-pressure hydraulic fluid circulates back to
the reservoir through the manifold. The direct fluid path back to the reservoir limits pressure and flow available
out to the external hydraulic circuit. When high pressure is selected, the unit forces pressurized hydraulic
fluid out to the hydraulic circuit.
Filtering
As hydraulic fluid returns to the reservoir, it is filtered by a full flow element. This ensures that all hydraulic
fluid is filtered, whether it travels out through the circuit or returns by way of the unit’s manifold under low
pressure. Filter cleanliness is automatically monitored. A warning registered on the unit’s operator interface
signals when the filter needs to be changed.
Heat exchanger
Hydraulic fluid temperature is maintained with a high–efficiency stainless steel heat exchanger that cools the
fluid. A regulating valve monitors the temperature of the hydraulic fluid and adjusts the flow of water through
the plates. The flow of cooling water regulates the temperature of the hydraulic fluid. If the hydraulic fluid
temperature exceeds the maximum preset temperature, a switch opens and shuts down the HPU. When the
HPU is shut off, the flow of water is automatically stopped by a shutoff solenoid valve.
Options Available for the HPU
Accumulator option
Accumulators can be added to the hydraulic output lines to damp pressure line fluctuations. This option
accommodates one pressure line accumulator.
Series 505G2 SilentFlo™ Hydraulic Power Unit Product Information 21
Introduction