The source of Hydraulic Power: Pumps

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The source of Hydraulic Power Pumps
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Contents

• Introduction
• Pumping theory
• Pump classification
• Gear pumps
• Vane pumps
• Piston pumps

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Introduction
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Pumping theory
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Pump Classification

• Hydrodynamic or non-positive pumps
• They are used for low-pressure, high-volume flow
  applications.
• Normally their maximum pressure capacity is
  limited to 250-300 psi.
• Hydrostatic or positive pumps (Gear, vane, piston
  pumps)
• High pressure capability (up to 10,000 psi or
  higher)
• Small compact size
• High volumetric efficiency
• Small changes in efficiency
• Great flexibility of performance

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Gear Pumps

• External gear pumps
• Internal gear pumps
• Lobe pumps
• Screw pumps

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External gear pumps
For simple systems with a relatively low level of
pressure (about 140 to 180 bar or 14 to 18 MPa)
the gear pump is the most used type of pump.
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Internal gear pump
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Vane Pumps

• Unbalanced vane pumps
• Balanced vane pumps
• On many industrial installations with a maximum
  pressure of about 200 bar, vane pumps are
  applied.

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Piston pumps

• Axial design
• Radial design

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Axial piston pumps animation
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Pump performance
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Pump selection

• Select the actuator (hydraulic cylinder or motor)
  that is appropriate based on the loads
  encountered.
• Determine the flow-rate requirements. This
  involves the calculation of the flow rate
  necessary to drive the actuator to move the load
  through a specified distance within a given time
  limit.
• Determine the pump speed and select the prime
  mover.
• pump type based on the application
• Select the system pressure. This ties in with the
  actuator size and the magnitude of the resistive
  force produced by the external load on the
  system.
• Select the reservoir and associated plumbing,
  including piping, valving, hydraulic cylinders,
  and motors and other miscellaneous components
• Calculate the overall cost of the system.

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Hydraulic actuator

• Linear Hydraulic actuators
• Single-acting cylinders
• Double-acting cylinders

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Cylinder cushions
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Example 7.2