MTS Series 505 SilentFlo Hydraulic Power Unit Model 505-180 - Manual (Page 18)

Model 505.60 - 505.180 SilentFlo™ HPU 18
HPU Functional Description
Introduction
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.
Run-on-demand option
The run-on-demand (ROD) option will turn individual pumps on and off as
needed to accommodate the system’s demand for hydraulic fluid. The PLC
monitors the fluid flow; when flow changes beyond preset limits for a preset
time, a pump will be turned on or off as needed.