Pumps can be classified as positive displacement pumps or nonpositive displacement pumps. Positive displacement pumps include gear pumps, vane pumps, piston pumps, and lobe pumps. Gear pumps are further classified as external gear pumps and internal gear pumps. External gear pumps have straight or helical gears that transport fluid through the expanding and contracting space between gears. Internal gear pumps have gears that remain constantly meshed to pump fluid. Vane pumps use a rotor with sliding vanes to pump fluid, and can be balanced or unbalanced. Piston pumps use reciprocating pistons to draw in and expel fluid and include axial, radial, and bent-axis configurations. Each pump type has different operating characteristics, advantages, and limitations for various industrial

1. PUMPS:
Hydraulic pumps are broadly classified as positive
displacement pumps or nonpositive displacement pumps.
Nonpositive displacement pumps are used in hydrodynamic
systems to transport fluids from one location to another.
Positive displacement pumps are used in hydrostatic systems
to overcome the pressure resulting from the mechanical loads
on the system as well as the resistance to flow due to friction.
Positive displacement pumps are further classified as gear
pumps, vane pumps and piston pumps according to the
construction

2. A pump is a device that moves fluids (liquids or gases), or
sometimes slurries, bymechanical action. Pumps can be
classified into three major groups according to the method
they use to move the fluid: direct lift, displacement, and
gravity pumps.
A positive displacement pump has an expanding cavity
on the suction side and a decreasing cavity on discharge
side.Liquid flows into the expanding cavity and then the
same amount of liquid is discharged as the cavity
reduces.Thus a constant flow is maintained by the pump.

3. GEAR PUMP:
Classified as External Gear Pump and Internal Gear Pump
EXTERNAL GEAR PUMP:
Gear pumps come with a straight spur, helical, or herringbone
gears. Straight spur gears are easiest to cut and are the most
widely used. Helical and herringbone gears run more quietly, but
cost more.
Large capacity gear pumps typically use helical or herringbone
gears.
Works well up to 1500 PSI.

4. WORKING:
In external gear pump one gear is driven by a motor and
it in turn drives the other gear. Each gear is supported by a
shaft with bearings on both sides of the gear.
Gear pump works in following stages:
1.
As the gears come out of mesh, they
create expanding volume (vacuum) on
the inlet side of the pump.
And oil is pushed into the cavity by the
atmospheric pressure and it is trapped
by the gear teeth as they rotate.

5. 2.
Liquid travels around the interior of
the casing in the pockets between
the teeth and the casing .
It does not pass between the gears.
3.
Finally, the unmeshing of the gears
decreases the volume and oil is
forced out of the chamber under
pressure.

6. Advantages:
1.Simple in structure
2.Compact
3.No overhung bearing loads
4.High pressure
5.High speed
Limitations:
1.Fixed end clearances
2.Unable to vary displacement
3.Large pulsations of flow & pressure
ANIMATION:
http://www.pumpschool.com/principles/eg_ani.htm

7. INTERNAL GEAR PUMP:
Exceptionally versatile
Can handle viscous as well as high temperature fluids

11. Gears In Constant Mesh – No Fluid
Travel At This Point
3. Fluid Fills Void & Moves
Towards Discharge Port
2. Diverging Gears
Create Suction 4.Converging Gears Expel
Fluid
1. Fluid Enters
Through Intake Port
5. Fluid Exits Through
Discharge Port

12. ADVANTAGES:
1.Non-pulsating discharge
2.Excellent for high-viscosity liquids
3.Constant and even discharge regardless of pressure conditions
4.Operates well in either direction
5.Can be made to operate with one direction of flow with either
rotation
6.Low NPSH required (Net Positive suction Head)
7.Single adjustable end clearance
8.Easy to maintain
9. Flexible design offers application customization
DISAVANTAGES:
1.Usually requires moderate speeds
2.Medium pressure limitations
3.One bearing runs in the product pumped
4.Overhung load on shaft bearing

13. VANE PUMP:
Two types : unbalanced and balanced vane pumps
Can handle low viscosity liquids
Can handle fluid temperatures -25 F to -35 F
Suitable for pressure upto 200 bar ( above for hydraulic pumps)

14. UNBALANCED VANE PUMP

16. Two rotors offset within the housing and vanes constrained by
cam ring as they cross inlet and outlet ports.
As vane tips are held against the housing, there is little leakage
and vanes compensate for wear at vane tips
However there is small leakage between rotor faces and body
sides.
Difference in pressure at inlet and outlet ports creates a severe
load on vanes and large side load on rotor shaft which leads to
failure hence called unbalanced vane pump.

17. BALANCED VANE PUMP

18. Balanced vane pump features an elliptical cam ring with two
inlet and two outlet ports.
Pressure loading occurs in pump but two identical pump
halves create equal and opposite forces on the rotor leading
to zero net force in the shaft and bearings. Hence ths pump
is called as balanced vane pump.
This pump offers improved service life than unbalanced
pump.
(hydraulics and pneumatics by andre parr—page no 45, 46)

19. ADVANTAGES:
1.Handles thin liquids at relatively higher pressures
2.Compensates for wear through vane extension
3.Sometimes preferred for solvents, LPG
4.Can run dry for short periods
5.Can have one seal
6.Develops good vacuum
DISADVANTAGES:
1.Complex housing and many parts
2.Not suitable for high pressures
3.Not suitable for high viscosity
4.Not good with abrasives
ANIMATION:
http://www.pumpschool.com/principles/vane_ani.htm

20. PISTON PUMPS:
Pumping effected by reciprocating piston in finely machined and
polished bore in cylindrical block
Piston allows oil to be drawn in while retracting
Oil is expelled from the cylinder during forward stroke of the piston.
Classification:
1.fixed displacement pump
2.variable displacement pump
As per geometry and physical arrangement classification is:
1.in line crank shaft driven pump
2.axial piston pump
3.radial piston pump

22. INLINE AXIAL PISTON PUMP
Pistons are arranged parallel to each other around the
periphery of cylinder block.
Pistons are driven inside the number of bores in the cylinder.
Either the swash plate or the cylinder barrel is rotated which
makes the pistons to have to and fro motion in the cylinder.
Controlled by the ball valves, oil is sucked in or pumped out of
through the cylinder.
If the speed of rotation of prime mover changes flow will be
variable otherwise flow remains constant.

25. BENT AXIS PUMP
Pistons are at an angle to the drive shaft and thrust plate. The
piston block shaft is connected to the drive shaft by a universal
joint.
The drive shaft, thrust plate, piston block shaft, and piston block all
revolve. The connecting rods are attached to the thrust plate and
revolve with it, unlike the swash plate pump where the piston rods
slide past a stationary swash plate.
The outlet ports are semi-circular holes in the Valve Plate.
As the pump revolves, half the pistons suck in fluid as they pass
over the intake port. The other pistons discharge their fluid through
the outlet port.
USED FOR HIGH PRESSURE AND HEAVY DUTY APPLICATIONS.

27. RADIAL PISTON PUMP
It consists of:
pintle to direct fluid in & out
cylindrical barrel with pistons
rotor containing reaction ring (ring mounted eccentrically
with respect to cylinder axis)
piston remain in constant contact with reaction ring due to
centrifugal force & back pressure
SUCTION: As the cylinder barrel rotates, piston on one side
travel on outward. This draws in fluid as each cylinder passes
the suction ports of pintle.
Delivery: When the piston passes point of maximum
eccentricity, it is forced inward by the reaction ring. This
forces fluid to enter discharge port of pintle.

29. Pressure range: 3000 to 12000PSI
Efficiency: 85 to 95 %
Flow capacity: 1 to 200 GPM

30. Pump Type
Pressure
Rating (bar)
Speed
(RPM)
Overall
efficiency
Flow (lpm)
External Gear
Pump
130-200 1200-2500 80-90 5-550
Internal Gear
Pump
30-135 1200-2500 70-85 5-750
Vane Pump 70-135 1200-1800 80-95 5-300
Axial Pump 135-800 1200-3000 90-98 5-750
Radial Piston
Pump
200-800 1200-1800 85-95 5-750

31. Lobe pump

33. Screw Pump