Introduction, classification, principle of working and constructional details of vane pumps, gear pumps, radial and axial plunger pumps, screw pumps, power and efficiency calculations, characteristics curves, selection of pumps for hydraulic Power transmission.

1. Unit 3: Hydraulic pumps
Contents:
Introduction, classification, principle of working and
constructional details of vane pumps, gear pumps,
radial and axial plunger pumps, screw pumps, power
and efficiency calculations, characteristics curves,
selection of pumps for hydraulic Power transmission.
by
Abhishek D. Patange
Assistant Professor
College of Engineering Pune

2. 2
 Converts mechanical energy into hydraulic energy
that can be used to perform desired operation.
 Mechanical energy is used to drive the pump.
Pump

3. Classification of pumps

4. Pumps which delivers fixed amount of liquid per cycle of
rotation of shaft is called as positive displacement
pumps. (High pressure and low volume)
The fluid flow enters and leaves with same velocity
hence there is no change in kinetic energy. The pressure
is generated because the load which is acting on system.
Positive displacement pumps

5. 1. High pressure range up to 800 bar
2. High volumetric efficiency from 90% to 98%
3. Highly efficient and provide almost constant discharge
for designed pressure range
4. Compact and have a high power-to-weight ratio
5. A smooth and precisely controlled motion
6. Produces the amount of flow required to move the load
at the desired velocity
Characteristics

6. • Pumps which delivers discharge using
inertia of fluid in motion.
• Do not develop a high pressure but
move a large volume of fluid at low
pressures.
• Used for transporting fluids such as
water, petroleum etc., from one
location to another considerable apart
location.
Non Positive displacement pumps

7. • The displacement between the inlet and the outlet is
not positive.
• It depends on the speed at which the pump is operated
and the resistance at the discharge side.
• As the resistance builds up at the discharge side, the
fluid slips back into the clearance spaces, or in other
words, follows the path of least resistance.
• When the resistance gets to a certain value, no fluid
gets delivered to the system and the volumetric
efficiency of the pump drops to zero for a given speed.
Non Positive displacement pumps

8. 1. Non-displacement pumps have fewer moving parts.
2. Initial and maintenance cost is low.
3. They give smooth continuous flow.
4. They are suitable for handling almost all types of fluids
including slurries and sledges.
5. Their operation is simple and reliable.
6. Non-displacement pumps are not self-priming and hence
they must be positioned below the fluid level.
7. Discharge is a function of output resistance.
8. Low volumetric efficiency.
Characteristics

9. Comparison

10. 10
 Two spur or helical gears are in mesh with each other externally. One
is driver (driven by prime mover) and other is driven.
 Oil is trapped in the pockets between teeth and the casing, and carried
towards the outlet port.
External Gear Pump

11. 11
External Gear Pump Animation

12. 12
External Gear Pump Animation

13. • Gear pumps are less expensive, long operating life with high
efficiency. It is limited to pressures below 140 bar.
• When the outlet flow is resisted, pressure in the pump
outlet chamber builds up rapidly and forces the gear
diagonally outward against the pump inlet.
• When the system pressure increases, imbalance occurs.
This imbalance increases mechanical friction and the
bearing load of the two gears.
• It is noisy in operation than either vane or piston pumps.
Characteristics

14. 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.
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.
Advantages and disadvantages of gear pumps:

15. 15
The crescent seals the low-pressure pump inlet from the high-pressure
pump outlet.
The major use for this type of pump occurs when a through shaft is
necessary, as in an automatic transmission.
Internal gear pump

16. Internal gear pump

17. 17
Internal gear pump

18. 18
Gerotor pump
• The gerotor has one tooth less than the outer internal idler gear.

19. 19
Gerotor pump

20. 20
Lobe pump

21. 21
Lobe pump

22. 22
Screw Pump
 As the screws rotate, inlet side of the pump is flooded with
hydraulic fluid because of partial vacuum.
 When the screws turn in normal rotation, the fluid contained in
compartments is pushed uniformly along axis toward center of
pump, where compartments discharge fluid.

23. Unbalanced vane pump

24. Unbalanced vane pump

25. • Consists of a cylindrical rotor, which is mounted with an offset inside a
circular casing.
• Vanes are seated in the radial slots of the rotor and held against the
casing by spring or hydraulic force.
• No leakage of oil between the vane tips and the casing.
• As the rotor rotates, the vanes carry the liquid from inlet port to
outlet port.
• The difference is pressure between inlet and outlet ports create a side
thrust on the rotor shaft, which consequently load bearings.
• During half of rotation of rotor, the volume of chambers goes on
increasing while pressure of liquid decreases. For further half rotation
volume of chamber decreases and pressure increases.
Characteristics: Unbalanced vane pump

26. Unbalanced vane pump

27. Unbalanced vane pump

28. 28
Balanced type Vane Pump
 Two inlets and two outlets are
employed.
 The center axis of the rotor
and that of the elliptical casing
are the same.
 Two identical halves of the
pump created equal but
opposite loads on the pump
shafts and bearing.
 Hence, pump gives better
service and larger life
compared to unbalanced type
vane pump.
 Capacity and pressure ratings
of vane pumps are less than
that of gear pumps.

29. Balanced type Vane Pump

30. 30
Advantages of Vane Pump
 Self-priming, robust and supply constant delivery at a given
speed.
 Provide uniform discharge with negligible pulsations.
 Self-compensating for wear and vanes can be replaced
easily.
 Do not require check valves.
 Light in weight and compact.
 Can handle liquids containing vapors and gases.
 Volumetric and overall efficiencies are high.
 Discharge is less sensitive to changes in viscosity and
pressure variations.

31. 31
Disadvantages of Vane Pump
 Relief valves are required to protect pump in case of sudden
closure of delivery.
 Not suitable for abrasive liquids.
 Require good seals.
 Require good filtration systems and foreign particle can
severely damage pump.

32. Classification of piston pumps

33. Single action plunger pump

34. The Swash Plate block is a model of a swash plate mechanism used in
axial-piston hydraulic pumps and motors to convert translational motion
of a piston into rotational motion of a drive shaft. The mechanism is a
combination of a cylinder block or rotor, with the piston fitted inside,
and an angled swash plate.

35. A swashplate (also known as slant disk), invented by Anthony George Maldon
Michell in 1917,[1] is a device used in mechanical engineering to translate the
motion of a rotating shaft into reciprocating motion, or vice versa. The
working principles is similar to crankshaft, Scotch yoke, or
wobble/nutator/Z-crank drives, in engine designs. It was firstly invented to
replace crankshaft, and is one of the most popular concepts used in
crankless engines.

36. A piston pump is a type of
positive displacement pump where the
high-pressure seal reciprocates with
the piston. Piston pumps can be used
to move liquids or compress gases.
Swash plate piston pumps

37. Swash plate piston pumps

38. Swash plate piston pumps

39. Swash plate pumps have a rotating cylinder containing pistons. A spring
pushes the pistons against a stationary swash plate, which sits at an angle
to the cylinder. The pistons suck in fluid during half a revolution and push
fluid out during the other half.

40. •Swash plate pumps have a rotating cylinder containing pistons.
•A spring pushes the pistons against a stationary swash plate, which sits at
an angle to the cylinder.
•The pistons suck in fluid during half a revolution and push fluid out during
the other half.
•Shown on edge on the far right in the animation is a dark stationary disk.
•It contains two semi-circular ports. It is shown again in a head-on view
below, right.
•These ports allow the pistons to draw in fluid as they move toward the
swash plate (on the backside and not shown here) and discharge it as they
move away.
•For a given speed swash plate pumps can be of fixed displacement like this
one, or variable by having a variable swash plate angle.
•The greater the slant the further the pistons move and the more fluid
they transfer.
•Note similarities to, and differences from, the wobble pump, radial piston
pump, and bent axis pump.

41. Piston pumps are meant for the high-pressure applications. These pumps
have high-efficiency and simple design and needs lower maintenance. These
pumps convert the rotary motion of the input shaft to the reciprocating
motion of the piston.

43. Bent Axial Piston Pump

44. 44
Bent Axial Piston Pump

46. Piston shoe 9
Cylinder block 1
Valve plate R 1
Valve plate L 1
Retainer plate 1
Ball guide 1
Drive shaft 1
Swash Plate 1
Saddle Bearing 2
Bearing Seat 2
Disk Spring 4
internal Rotor 1
External Rotor 1
Slide Plate 1
Socket Blot 2
Coupler 1
O Ring 1
Composite Bearing 1
Locating Pin 1
Shaft Seal 1
Big Bearing 1
Small Bearing 1
Charge Pump 1

47. Advantages:
Typical displacements to 500 cm3/r
Typical pressures to 350 bar
Multiple assemblies possible
High overall efficiency
Compact package.

48. This kind of pump consists of piston mounted radically in a housing and
spring loaded which permit the piston to goes out to be filled with oil.
Radial piston pump:

49. Advantages:
•Displacements to 250 cm3/r
•Pressure capabilities to 350 bar
•Suitable for open & closed loop
•High overall efficiency
•Good life expectancy
•Short, wide shape
•Simple multiple pump assemblies
•High cost

50. Pump Comparison

51. 51
Characteristic Curve
Curve 1: relationship between input power and pump output flow
as a function of pump speed
NOTE: Selection of
appropriate pump is
done based on
characteristics
curve.

52. 52
Curve 2: overall and volumetric efficiencies as a function of speed
Characteristic Curve

53. 53
Curve 3: Discharge flow over a broad pressure range
Characteristic Curve

54. 54
Curve 4: relationship between pump noise and operating speed,
pressure and displacement
Characteristic Curve

55. 55
Selection of Pump
Need to consider:
 Maximum operating & delivery pressure
 Pump drive speed, size and weight
 Pump efficiency
 Cost
 Type of fluid
 Availability and interchangeability
 Maintenance and spares
 Pump contamination tolerance
 Pump noise

56. •In general the applications of Hydraulic Pumps can be summarized as,
•Hydraulic pumps are used to transfer power via hydraulic liquid. These
pumps have a number of applications in automobiles, material handling
systems, automatic transmissions, controllers, compressors and household
items.
•The hand operated hydraulic pump is used in a hydraulic jack where many
strokes of the pump apply hydraulic pressure to lift the ram.
•A backhoe uses an engine driven hydraulic pump to drive the articulating
parts of the mechanical hoe.
•The hydraulic pumps are commonly used in the automotive vehicles
especially in power steering systems.
•The lift system of tractor is operated by the hydraulic pumps. These are
used in automatic transmissions and material handling systems in
industries.
•Many precise controllers are developed by using hydraulic pumps. The
commonly used compressor is operated by reciprocating pumps.
•The hydraulic pumps are also used in routine household systems like power
lift and air-conditions. Therefore, it can be said that the hydraulic pumps
have significant applications in industries as well as ones routine life.