MTS Series 505 SilentFlo Hydraulic Power Unit Model 505-11 - Manual (Page 16)

Model 505.07/.11 SilentFlo™ HPU 16
Functional Description
Introduction
The unit automatically starts in low pressure to reduce the amperage needed for
starting, which will extend pump and motor life. When operating at this setting,
low-pressure fluid is available to the hydraulic circuit. Low pressure is achieved
by diverting a portion of the hydraulic fluid through the high pressure solenoid
and returning it to the reservoir. Selecting high pressure blocks the low pressure
return path and makes all of the pressurized hydraulic fluid available to the
hydraulic circuit.
The output pressure can be adjusted from about 1 MPa (145 psi) to 21 MPa (3000
psi). The HPU is designed to provide 21 MPa (3000 psi). A nonadjustable relief
valve is set at 22.4 MPa (3250 psi) to protect the hydraulic system from excessive
pressure.
Filtering
As hydraulic fluid returns to the reservoir, it is filtered by a 3-micron element.
This ensures that all hydraulic fluid is filtered whether it travels out through the
circuit or returns by way of the unit’s control manifold under low pressure. Filter
cleanliness is automatically monitored. An indicator lights on the front panel
signaling when the filter needs an element change.
Heat exchanger
Hydraulic fluid temperature is maintained with a heat exchanger that cools the
fluid. The water-cooled heat exchanger cools the hydraulic fluid as it passes over
water-filled plates. 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.
• The typical operating temperature range of the hydraulic fluid is
43–49°C (110–120°F).
• If the hydraulic fluid temperature exceeds 55ºC (131ºF), a switch opens and
shuts down the HPU.
• When the HPU is shut off, the flow of water is also stopped by a shutoff
solenoid valve.
Note For additional information see the Heat Exchanger Care and Water
Quality Guide (part number 015-164-000).