This document discusses different types of hydraulic pumps. It begins by classifying pumps as either positive displacement pumps, which include gear pumps, vane pumps, piston pumps and screw pumps, or non-positive displacement pumps. Gear pumps are then explained in more detail, including how external and internal gear pumps work. Advantages and disadvantages are provided for different pump types like gear pumps, lobe pumps and screw pumps. Key aspects like pumping theory, pump efficiency calculations and example problems are also covered.

1. Unit II
Pumps and Actuators
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2. • Pumps - types, classification,
• Principle of working and constructional
details of vane pumps, gear pumps, radial
and axial plunger pumps, screw pumps
• Power and efficiency calculations, and
characteristics curves.
Syllabus
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3. • Purpose of hydraulic pump is to
generate flow so that energy
conversion from mechanical to fluid
energy is possible.
• Mechanical energy is provided to
pump by electric motor.
Hydraulic Pumps
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5. Pumps classifications
1. Classification based on displacement
I. Non positive displacement pumps (hydrodynamic
pumps)
II. Positive displacement pumps (hydrostatic pumps)
2. Classification based on delivery
I. Constant delivery pumps
II. Variable delivery pumps
3. Classification based on motion
I. Rotary pump
II. Reciprocating pump
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6. Non-Positive Displacement Pumps
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7. Non-Positive Displacement Pumps
The advantages are as follows:
 Non-displacement pumps have fewer moving parts.
 Initial and maintenance cost is low.
 They give smooth continuous flow.
 They are suitable for handling almost all types of fluids
including slurries and sledges.
 Their operation is simple and reliable.
The disadvantages are as follows:
 Non-displacement pumps are not self-priming and hence
they must be positioned below the fluid level.
 Discharge is a function of output resistance.
 Low volumetric efficiency.
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8. Classification of Positive Displacement Pumps
1. Based on the construction,
I. Gear Pumps ( fixed displacement pumps)
a. External gear pump
b. Internal gear pump
c. Gerotor pump
d. Lobe pump
II. Screw pump
2. Vane Pumps ( fixed or variable displacement pumps)
I. Balanced Vane pump
II. Unbalanced Vane pump
I. Piston Pumps ( fixed or variable displacement pumps)
I. Axial piston pump
II. Radial piston pum
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10. Pumping Theory
1. First, it creates a partial vacuum at the pump
inlet port. This vacuum enables atmospheric
pressure to force the fluid from the reservoir
into the pump
2. Second , the mechanical action of the pump
traps this fluid within the pumping cavities,
transports it through the pump and forces it into
the hydraulic system.
3. It is important to note that pumps create flow
not pressure. Pressure is created by the
resistance to flow.

11. Pumping Theory

12. Pump Efficiency (η)

13. Gear Pumps
Working External Gear Pumps

14. Q. A gear pump has an outside diameter of 80mm, inside
diameter of 55mm and a width of 25mm. If the actual pump flow
is 1600 RPM and the rated pressure is 95 LPM what is the
volumetric displacement and theoretical discharge.

15. Advantages and disadvantages of gear pumps
The advantages are as follows:
1.They are self-priming.
2.They give constant delivery for a given speed.
3. They are compact and light in weight.
4. Volumetric efficiency is high.
The disadvantages are as follows:
1. The liquid to be pumped must be clean, otherwise it
will damage pump.
2. Variable speed drives are required to change the
delivery.
3. If they run dry, parts can be damaged because the
fluid to be pumped is used as lubricant.

16. Internal Gear Pumps :
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17. Working Internal Gear Pumps :

18. Lobe Pumps

19. Advantages & Disadvantages of Lobe Pump
The advantages :
1. Lobe pumps can handle solids, slurries, pastes and
many liquid.
2. No metal-to-metal contact.
3. Superior CIP(Cleaning in Place) /SIP(Sterilization in
Place) capabilities.
4. Long-term dry run (with lubrication to seals).
5. Non-pulsating discharge.
The disadvantages :
1. Require timing gears.
2. Reduced lift with thin liquids
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20. Screw Pumps
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21. Working Screw Pumps
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22. Significant Characteristic of Screw Pump
• They are quiet pumps
• Screws are continuous , most reliable
• No pressure pulsation will occur
• High speed operation is possible
• No pump turbulence and oil
churning
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23. Advantages and disadvantages of screw pump
The advantages are as follows:
1.They are self-priming and more reliable.
2. They are quiet due to rolling action of screw spindles.
3.They can handle liquids containing gases and vapor.
4. They have long service life.
The disadvantages are as follows:
1.They are bulky and heavy.
2.They are sensitive to viscosity changes of the fluid.
3. They have low volumetric and mechanical efficiencies.
4. Manufacturing cost of precision screw is high.
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