TSM 363 Fluid Power Systems

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TSM 363 Fluid Power Systems

• Control of Hydraulic Pumps

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Goals of this Lecture

• Basic Principles of Hydraulic Pump Controls
• Pressure limiting
• Load sensing
• Torque limiting
• Basic Concept of Pump Efficiency
• Pump efficiency definitions
• Key parameters

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Energy Flow in a Fluid Power System
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Power Wasted in a Fixed-Displacement Pump
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Solution to Reduce Wasted Power
By controlling the displacement of the pump, we
can adjust the amount of fluid discharged from
the pump. It will significantly reduce the power
loss due to the excess flow.
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Pressure Limiting for Displacement Control
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Operation of Pressure Limiting
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Power Saved through Pressure Limiting
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Load Compensation Displacement Control
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Operation of Load Compensation
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Power Saved through Load Compensation
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Torque Compensation Displacement Control
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Operation of Torque Compensation
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Power Saved via Torque Compensation
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Theoretical Pump Power Output
In theory, pump power output can be
determined based on its output flow rate and
outlet pressure. Power can be measured
by horsepower (hp) Kilowatt (kW)
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Theoretical Pump Power Consumption
As any other machinery, the hydraulic pump needs
an input power to drive the pump to produce an
output flow and to overcome the load (outlet
pressure). Input power is also measured
by horsepower (hp) Kilowatt (kW)
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Pump Efficiency
Although modern hydraulic pumps are well designed
and efficient, they are not 100 efficient in
converting all of the mechanical input power
into hydraulic output power. Some of the power
is consumed by the pump. We can use pump
efficiency to measured the power loss.
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Example Determination of Pump Efficiency
One pump takes 20 input horsepower to delivery 8
gpm fluid at 3000 psi. The pump capacity is 10
gpm. Try to determine pump efficiencies.
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Exercise Estimating Pump Efficiency
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Lecture Summary

• Discussed the basic principles of three commonly
  used pump control methods, as well as
  efficiencies
• Pressure limit
• Load sensing
• Torque limit
• Pump efficiency