MTS Series 505 SilentFlo Hydraulic Power Unit Model 505-180 - Manual (Page 84)

Model 505.60 - 505.180 SilentFlo™ HPU 84
Low/High Pressure Functionality
Operation
Once the HPU has cleaned the reservoir hydraulic fluid, sections of the system
should be isolated and sequentially cleaned. Flushing of hard line sections takes
place in high pressure mode. If the HPU is run in low pressure, flow losses in the
system will minimize the external flow and reduce the effectiveness of the
system flushing and fluid conditioning.
System cooling
A Series 505 HPU running in low pressure maximizes the cooling efficiency of
the unit:
• Because the motor is not working to pressurize the fluid, it runs at a low
power level, producing less waste heat.
• Flow rates are high in low pressure mode, providing an ample volume of
coolant (hydraulic fluid) with a lower BTU per gallon heat content to the
heat exchanger. The heat exchanger operates with greater efficiency when
flows are near the designed flow rate as boundary layers are minimized.
Energy consumption
All Series 505 HPUs have variable volume pumps. Switching from high to low
pressure operation when external demands are absent will conserve energy and
water:
• Leaving an HPU idling in high pressure mode uses roughly 40% more
electrical power than idling in low pressure mode.
• When the hydraulic fluid is pressurized, cooling water usage is higher.
When operating in low pressure, the motor consumes less energy and less
heat needs to be removed by the heat exchanger.
High pressure
When the Series 505 HPUs are running in high pressure, a considerable amount
of heat is generated. During normal testing this heat is dissipated by running the
hydraulic fluid through the system to the return line to the heat exchanger. During
periods of low system demand, this heat is dissipated by running the hydraulic
fluid through the circulation pump to the heat exchanger.