MTS Series 505G2 SilentFlo Hydraulic Power Unit Model 505G2-180 - Manual (Page 69)

• With the HPU running in low pressure, acceptable particle counts are obtained in a relatively short time.
• Keeping the HPU in low pressure effectively isolates the external or system flow because the relative back
pressure is normally much higher in the external system circuit.
• Running the HPU in low pressure maximizes fluid flow, allowing the HPU to circulate the reservoir contents
across the filter more times per hour.
• Starting the commissioning process with an isolated HPU reduces the possible number of problems
encountered during start-up.
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.
Series 505G2 SilentFlo™ Hydraulic Power Unit Product Information 69
Operation