Pumps and actuators are the main components of any hydraulic systems. Pump is also called as heart of hydraulic system..

1. Aldel Education Trust’s
ST. JOHN COLLEGE OF ENGINEERING AND MANAGEMENT, PALGHAR
(ST. JOHN POLYTECHNIC)
DEPARTMENT OF MECHANICAL ENGINEERING
SUB: INDUSTRIAL HYDRAULICS AND PNEUMATICS
TOPIC: PUMPS & ACTUATORS
PREPARED BY:-
Prof. Pranit Mehata
Lecturer, SJCEM
7972064172

2. PUMPS

3. INTRODUCTION
 The pump plays a specific and unique position in the system. It is heart of the hydraulic systems.
 The main function of pump is to take oil from reservoir and deliver it to the rest of the hydraulic circuit.

4. CLASSIFICATION OF PUMPS

5. GEAR PUMP
 When a pair of meshing gears are used to increase the
pressure of oil, it is known as gear pump.
 Gear pumps are of three types: a) External gear pump, b)
Internal gear pump and c) Gerotor Pump.

6. EXTERNAL GEAR PUMP
 External gear pump consists of two spur or helical gears, which are in
mesh with each other, and mounted inside the casing.
 One is driver and other is driven.
 When the driver is rotated by means of any prime mover (i.e. electrical
motor), driven will also rotate.
 Oil is trapped in the pockets between teeth and the casing, and carried
towards the outlet port.
 Gear pumps can produce pressure up to 200 bars. Volumetric
efficiency of gear pumps is about 80%.

7. INTERNAL GEAR PUMP
It has two gears, one is having external teeth and the
other is having internal teeth. The external gear is
inside the internal gear.
 The two gears are in mesh witheach other.
 A crescent seal is provided between these two gears,
which fills the gap between the two gears.
 Oil fills in the pockets between the teeth, crescent seal
and the casing, and carried along with the gear towards
outlet and finally delivered at outlet port.

8. GEROTER PUMP
This pump has two generated rotors as
shown in the figure.
One is having external teeth and other is
having internal teeth.
 The rotor with external teeth rotates
inside the rotor having internal teeth.
 The inner rotor is having one tooth less
than that of outer rotor.
 The inner rotor is driver to which, the
shaft of any prime mover is coupled.

9. VANE PUMP
 When sliding vanes are used to increase pressure of oil, it is
known as vane pump.
 Vane pumps are of three types: a) Unbalanced vane pump, b)
Balanced vane pump, c) Variable displacement vane pump.

10. UNBALANCED VANE PUMP
 It consists of a cylindrical rotor, which is mounted with an offset
inside a circular casing.
 The vanes are seated in the radial slots of the rotor and held
against the casing by spring or hydraulic force.
 Hence there will not be any leakage of oil between the vane tips
and the casing.
 But still, there is some leakage of oil between the rotor faces and
the body sides.
 Hence its volumetric efficiency will be wound 95%.
 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.

11. BALANCED VANE PUMP
In this type of pump two inlets and two outlets
areemployed.
The center axis of the rotor and that of the
ellipticalcasing are the same.
Pressure loading still occurs,but the two
identical halves of the pump created equal but
opposite loads on the pump shafts and bearing.
Hence, balanced vane pump givesbetter
service and larger life compared to unbalanced
type vanepump.
Capacity and pressure ratings of vane pumps
are less than that of gear pumps.

12. VARIABLE DISPLACEMENT VANE
PUMP
Three extreme different positions of the
eccentricity (e)
1. When e is positive i.e., for 𝑒 =+𝑒, Q is
maximum.
2. When e is zero, then Q becomes zero as both
rotor and cam ring become concentric.
3. When e is negative, i.e., for 𝑒=−𝑒, the direction
of flow gets reversed.

13. SCREW PUMP
 The screw pump is a positive displacement pump, which
comes with two or three screws.
 Each shaft has a left-hand screw and a right-hand screw, for
hydraulic pressure balance.
 The inlet is at each end and the outlet is in the middle.
 While running, liquid fills in the gap between the screws and
the casing and moves it along with the screws from inlet to
outlet.
 Screw pumps are used in lubricating systems.
 They have no valves or small parts to wear out or break.
Hence maintenance cost is less and has more life.

14. PISTON PUMP
When reciprocating movement of piston is utilized for obtaining
rotary motion by pressurised oil, it is known as piston pump.
Piston pumps are of two types: a) Swash plate axial piston pump, b)
Radial Piston pump.

15. SWASH PLATE AXIAL PUMP
1. θ = 0 then no flow of oil, because pistons are at same level.
When θ = 0 swash plate is vertical. No reciprocation of piston,
hence no flow. As shown in fig. a
2. θ = max or +ve, then x will be stroke length which is
maximum and there will be maximum forward flow. As
shown in fig. b
3. θ = -ve, then ‘x’ i.e., stroke length will be maximum in reverse
direction and hence there will be reverse flow. By changing the
swash plate angle, we can vary the stroke length of the piston.
and also output flow can be changed. As shown in fig .c

16. BENT AXIS PISTON PUMP
 In swash plate axial pump, the axis of cylinder block is
horizontal and angle is given to swash plate.
 Opposite to it is bent axis piston pump, the cylinder block is at
an angle and driving flange is horizontal.
 As the shaft rotates the flange, the flange imparts rotary motion
to cylinder block, which is turn rotates the pistons.
 Due to the inclination of block, the pistons in addition to rotating
with cylindrical block start reciprocating.
 The reciprocating motion of piston causes suction and delivery
of fluid as the respective pistons uncover the suction and
delivery ports.

17. CRITERIA FOR SELECTION OF
PUMP
 Maximum operating pressure: When pressures up to 150 bars are required then gear pumps can be
selected. For pressure of 150 to 250 vane pump is suitable and for above 500 bar pressure piston pumps are
useful.
 Maximum delivery: The pump system selected must be capable of delivering the maximum flow rate
demanded by the circuit.
Pump Flow rate (litres/min)
Gear Pump 400-450
Vane Pump 200
Screw Pump 7500
Axial Piston Pump 800-1000
Radial Piston Pump 2000

18. CRITERIA FOR SELECTION OF
PUMP
 Pump drive speed: The fluid delivery rate is proportional to the speed of rotation . The speed of pump is decided by
rated capacity of the manufacturer. If wrong speed is selected for pump then efficiency and working of hydraulic
system may get hamper.
 Efficiency of the pump: The selected pump must have good efficiency. We can consider following efficiencies: 1)
Volumetric 2) Mechanical 3) Overall. In general piston pumps have higher overall efficiency than gear and vane
pumps. Gear pumps have volumetric efficiency about 65-85% while overall efficiency about 60-70%, vane and screw
pumps has overall efficiency of 75-85%.
 Oil compatibility: The oils used in pump should be compatible with the material of the pump. If wrong oil gets
selected then pump will not work to its rated performance.
 Cost: The initial cost of a pump is usually of secondary importance to running and maintenance costs. Gear pumps are
cheaper, vane and piston pumps are expensive.

19. Performance characteristics of Pumps
 Characteristic curve is a graphical representation of behaviour of pump under certain conditions on which pump
operates.
 The graphs are obtained by testing the pumps in ideal condition as well as under actual condition.
It is clear from fig that
1. Power increases at higher pressure
2. Efficiency increases at medium pressure but drops
to some extent if pressure further increases.
It is clear from the graph that when pressure is
higher the discharge volume reduces to some
extent.
FOR
VANE
PUMP
AT
CONST
ANT
SPEED
FOR GEAR
PUMP AT
CONSTANT
SPEED

20. ACTUATOR

21. INTRODUCTION
 Hydraulics or pneumatics in its applications is generally concerned with, moving gripping, lifting and
rotating motions with force.
 Devices that actually achieve this objective are called actuators.
 Actuators are the elements of hydraulic system, which transform the hydraulic energy into useful work.
 Depending upon the motion they transmit, the actuators are classified as,
ACTUATORS
LINEAR (For linear
actuation)
ROTARY (For rotary
actuation)

22. HYDRAULIC CYLINDERS
Hydraulic cylinders are of the following types:
1. Single-acting cylinders.
2. Double-acting cylinders.
3. Telescopic cylinders.
4. Tandem cylinders.

23. SINGLE ACTING CYLINDER
When pressurised oil/compressed air acts only from face side of the piston and return stroke is completed
by spring/external load, it is called as Single Acting Cylinder (SAC)
Single-acting cylinders produce
force in one direction by
hydraulic pressure acting on the
piston.
Single-acting cylinders can exert a
force in the extending
directiononly
The return of the piston is not
done hydraulically.
In single-acting cylinders,
retraction is done either by gravity
or by a spring.

24. DOUBLE ACTING CYLINDER
When pressurised oil/compressed air acts on both side of the piston i.e., on face side and piston side it is known as
Double Acting Cylinder (DAC)
 To extend the cylinder, the pump flow is sent to the blank-end port the
fluid from the rod-end port returns to the reservoir.
 To retract the cylinder, the pump flow is sent to the rod-end port and
the fluid from the blank-end port returns to the tank

25. TELESCOPIC CYLINDER
 A telescopic cylinder is used when a long
stroke length and a shortretracted length are
required.
 The telescopic cylinder extends in stages.
 One application for this type of cylinder is
raising a dump truck bed.
 Telescopic cylinders are available in both
single-acting and double-acting models.
 They are more expensive than standard
cylinders due to their more complex
construction.

26. TANDEM CYLINDER
 A Tandem cylinder is the combination of two or
more cylinders working in tandem i.e., coupled
mechanically to each other. Each cylinder has its
own inlet outlet ports
 Tandem cylinder, shown in Fig, is used in
applications where a large amount of force is
required from a small diameter cylinder.
 Pressure is applied to both pistons, resulting
increased force because of the larger area.
 The drawback is that these cylinders must be longer
than a standard cylinder to achieve an equal speed
because flow must go to both pistons.

27. ROTARY ACTUATORS-HYDRAULIC
MOTORS
 A hydraulic motor is a device
which converts fluid power into
rotary motion.
 Types of hydraulic motors:
1. Gear motor
2. Vane motor
3. Piston motor
 The construction and working of
hydraulic motor is same as that of
the hydraulic pumps.