hydraulics pneumatics

1. Prof. Charlton S. Inao
Defence University
College of Engineering
Ch .3 Input and Output Devices
PE -3231 Week
4

2. Objective: The students shall thoroughly
understand the following:

4. Symbol for Pumps

5. Pumps
 Hydraulic pumps convert mechanical energy from
a prime mover (engine or electric motor) into
hydraulic (pressure) energy.
 The pressure energy is used then to operate an
actuator.
 Pumps push on a hydraulic fluid and create flow.

6.  PUMP
Hydraulic pump is heart of a hydraulic system. It
pumps oil in hydraulic system and converts the
mechanical energy of prime-mover into hydraulic
energy. (Hydraulic horsepower). Only positive
displacement types of pumps are used in high-
pressure hydraulic system.

7. Description of a Pump
1) Type
2) Displacement
3) Delivery
4) Pressure Rating
5) Volumetric Efficiency

8. Terms related to pumps: -
A pump is described in following terms.
a) Type of Pump: -
There are three types of pumps namely, vane pump,
gear pump and piston pump. These each type of
pumps has many verities, which will be discussed
later in this chapter.
b) Displacement: -
This is oil discharge of pump per revolution of its shaft.
This is generally indicated as Cubic Centimeter per
revolution.

9. c) Delivery: -
This is total discharge of pump at particular RPM of
prime mover, and at particular pressure. It is
indicated as liters per minute. Delivery of pump
changes with RPM of primemover and operating
pressure, hence it is generally indicated as graph.
For example a vane pump of 28 CC per
revolution displacement will have 40 LPM
discharge at 1440 RPM at 10 kg/cm2 working
pressure, and same pump will have 35 LPM
discharge at 1440 RPM and 175 kg/cm2 working
pressure.

10. d) Pressure Rating: -
Vane pump can operate up to maximum pressure 210
kg/cm2, Gear pump 250 kg/cm2, and Piston pump
550kg/cm2. This is the maximum limit; many
manufacturers have much less working pressure.
Hence it is indicated with pump, so that it is always
operated within safe limit, to avoid any damage to
pump.
e) Volumetric Efficiency: - All pump give higher or
theoretical discharge at low-pressure. And discharge
decrease as pressure increase due to internal
leakage between various parts of pump.
Efficiency = Actual Output / Theoretical Output.
Higher the efficiency, better the performance and low
Vane Gear Piston
210 bars 250 bars 550 bars

11. Gear Pumps
Applications:
Forklift, Hydraulic mobile crane, tractor
etc. uses gear pump.
Maximum Pressure : 250 bars

12. External Gear Pump

13. Internal Gear Pump

14. Vane Pumps
. Vane pumps are economical and simple in maintenance and
repair. Their discharge capacity can be changed by simply
changing cam ring, vanes, pressure-plate etc. all are made from
harden alloy steel, hence they are comparatively less susceptible
to heat and oil contamination as compare to other pump. Hence
for most moderate pressure and heavy duty operation vane
pumps are most suited. Most of the injection mounding machines
uses vane pump.
Application: Injection moulding Machine hydraulic
pump

15. Vane Pumps
Balanced Unbalanced Double Vane
Maximum pressure : 210 bars

16. Fluid flow from vane-type double pumps

17. Piston Pumps
Radial Axial
Maximum pressure : 550 bars
bars

18. Non-positive-Displacement
Pumps
 With this pump, the volume of liquid delivered for
each cycle depends on the resistance offered to flow.
 A pump produces a force on the liquid that is constant
for each particular speed of the pump.
 Resistance in a discharge line produces a force in the
opposite direction. When these forces are equal, a
liquid is in a state of equilibrium and does not flow.
General Types of Pump

19. Non positive displacement Valve

20. Positive displacement pump
 With this pump, a definite volume of liquid is
delivered for each cycle of pump operation,
regardless of resistance, as long as the
capacity of the power unit driving a pump is not
exceeded.
 If an outlet is completely closed, either the unit
driving a pump will stall or something will break.
 Therefore, a positive-displacement-type pump
requires a pressure regulator or pressure-relief
valve in the system

21. Positive displacement pumps

22. Positive displacement pumps

23. Performance
 Pumps are usually rated according to their
volumetric output and pressure.
 Volumetric output (delivery rate or capacity) is the
amount of liquid that a pump can deliver at its
outlet port per unit of time at a given drive speed,
usually expressed in GPM or cubic inches per
minute.

24. Contn’d
 Pressure is the force per unit area of a liquid,
usually expressed in psi. (Most of the pressure in
the hydraulic systems covered in this manual is
created by resistance to flow.
 Resistance is usually caused by a restriction or
obstruction in a path or flow
 Pressure is the force per unit area of a liquid,
usually expressed in psi. (Most of the pressure in
the hydraulic systems covered in this manual is
created by resistance to flow.
 Resistance is usually caused by a restriction or
obstruction in a path or flow

25. Cont’d
 As pressure increases, volumetric output
decreases.
 This drop in output is caused by an increase in
internal leakage (slippage) from a pump's outlet
side to its inlet side
 Slippage is a measure of a pump’s efficiency and
usually is expressed in percent. Displacement is the amount of liquid transferred
from a pump’s inlet to its outlet in one revolution
or cycle.
 In a rotary pump, displacement is expressed in
cubic inches per revolution and in a reciprocating
pump in cubic inches per cycle.

26. Fluid flow from vane-type double pumps

27. Cylinders

28. Cylinders

29. Cylinders and Actuators
 Single Acting

30. Double Acting Cylinder
Double Acting Cylinder

31. Rodless Cylinder

32. Used in Robotics, hi speed
manufacturing, semi conductor
assembly and manufacturing and
proportional pneumatics

33. Ram Cylinder

34. Hydraulic Cylinder
Linkages/Mountings

36. Mountings

37. Electric Motors

38. Motor

39.  PRIME-MOVER (MOTOR)
 Two types of prime movers are used in hydraulic
system.
1. Electric Motor
2. I. C. Engine
 The hydraulic system used in mobile vehicles
drives their power from main I. C. Engine of
automobile. As well as those hydraulic
equipments, which are going to be used at those
areas where there is no electricity supply, then in
such case also I.C. engine are used to drive the
hydraulic pump of hydraulic equipment.
 Electric motors are convenient and most
commonly used prime-mover in hydraulic system.

40.  Electric Motors :-
1. Standard motors are available in four speeds 750, 1000, 1440, 3000
RPM. In hydraulic
generally 1440 RPM is used.
2. Standard motors are available in many classes of insulation. In hydraulic
power pack we
use ‘F’ class of insulation. Common motor have ‘B’ class insulation, good
quality motor
‘E’ grade insulation but ‘F’ grade is best, most reputed manufacturer using
‘F’ grade
insulation.
3. In refinery and chemical plant, a small spark in junction box, connection
box of motor
may cause an explosion or fire. Due to the combustible fumes around.
Hence in such
atmosphere “Flame and Explosion Proof” electrical items are used. Such
items have
two metallic casing or enclosure. In one casing main equipment is
enclosed and in other
enclosure it’s electrical connection is fitted. All incoming and outgoing wires
are through
special cables and gland. All these arrangement is done so the heated

41. combustible gases even if an explosion take place within enclosure of
electrical component
then it remain confined in enclosure and do not come-out in open
atmosphere.
Electric motor, solenoid valves, limit switch etc. are available in flame and
explosion
proof grade. Hence whenever such requirement of safety arises, only such
safe electrical item should be used.
4. Motors are made in many grade of protection against entry of water and
dust etc. generally
commercial grade of motor are with protection grade of IP44. But better
grade protection
is IP65 in which case water can not enter in motor from rear (Fan side)?
5. Nowadays most of the pumps are flange mounted type. If such pumps are
coupled to
flange of motor through a accurately machined bracket and coupling, then

42. At full load and working pressure electric motor
should draw only 90% of it full rated current.
7. When a hydraulic system starts and motor is
switch on, motor may start with no load on it, or
full load on it. In case of no load start equipment,
use slip ring type of electric
motor, and in full load start type of requirement
use squire cage type of electric motor.
8. Up to 15HP and no load start type of requirement
DOL starter could be used while above 15HP use
star-delta type of motor-starter.

43. Hydraulic Motors

44. Hydraulic Motors
Objectives
 After reading this chapter, the student will be able to:
 Differentiate between hydraulic pumps and motors
 Understand and describe the design and construction
of various motors used in
hydraulics
 Explain the operation of the various hydraulic motors
of the likes of gear, vane and piston motors and also
evaluate their performance by determining their
mechanical, volumetric and overall efficiencies
 Select and size motors for hydraulic applications
 Understand the performance parameters of hydraulics
motors.

45. Hydraulic Motors
 Hydraulic motors are classified as rotary
actuators
They resemble pumps very closely in
construction. However, as
already understood, pumps perform the
function of adding energy to a hydraulic
system for transmission to some remote
point, while motors do precisely the opposite.
They extract energy from a fluid and convert it
to a mechanical output to perform useful
work. To put it more simply, instead of
pushing on the fluid as the pump does, the
fluid pushes on the internal surface area of
the motor, developing torque. Since both the
inlet and outlet ports in a motor may be

46. Types of Hydraulic Motor
Hydraulic motors can be classified
into two types:
 1. Limited rotation hydraulic motors
 2. Continuous rotation hydraulic
motors.

47. Limited Rotation
Pressure = 350 bars(4978
psi)
Rotation up to 100
degrees

48. Applications of Hydraulic Motors

49. Continuous rotation hydraulic
motors
 Continuous rotation hydraulic motors are actuators,
which can rotate continuously.
 Instead of acting on (or pushing) the fluid as pumps
do, motors are acted upon by fluids.
 In this way, hydraulic motors develop torque and
produce continuous rotary motion.
 Since the casing of a hydraulic motor is pressurized
from an outside source, most hydraulic motors have
casing drains to protect their shaft seals.
These are further classified as:
1) • Gear motors
2) • Vane motors and
3) • Piston motors.

50. Gear Motors

51. Gear Motor
Gear motors are simple in construction. A
gear motor develops torque due to the
hydraulic pressure acting on the surfaces
of the gear teeth.
By changing the direction of the flow of
fluid through the motor, the direction of
rotation of the motor can be reversed. As in
the case of a gear pump, the volumetric
displacement of the motor is fixed. The
gear motor is not balanced with respect to
pressure loads. The high pressure at the
inlet, coupled with the low pressure at the
outlet, produces a large side load on the
shaft and bearings, thereby limiting the
bearing life of the motor.

52.  The main advantages associated
with gear motors are its simple
design and cost effectiveness.
 They also possess good tolerance
to dirt. The main disadvantages with
gear motors are their lower
efficiency levels and comparatively
higher leakages.

53. Vane type motors

54. Vane Motors
 The internal construction of the vane motors is
similar to that of a vane pump; however the
principle of operation differs.
 Vane motors develop torque by virtue of the
hydraulic pressure acting on the exposed
surfaces of the vanes, which slide in and out of
the rotor connected to the drive shaft.
 As the rotor revolves, the vanes follow the
surface of the cam ring because springs are used
to force the vanes radially outward.

55. Basic working principle of a
motor
No centrifugal force exists until the rotor starts to revolve. Therefore, the
vanes must
have some means other than the centrifugal force to hold them against the
cam ring.
Some designs use springs, while other types use pressure-loaded vanes. The
sliding action
of the vanes forms sealed chambers, which carry fluid from the inlet to the
outlet.

56. Piston Type
Axial with tilting
cam plate
Axial
w/tilting
block

57. Piston type Motors
Radial

58. Piston Motors
Piston motors are also similar in construction
to that of piston pumps.
Piston motors can be either fixed or variable
displacement units.
They generate torque through pressure acting
at the ends of pistons, reciprocating inside a
cylinder block.
Piston-type hydraulic motors use single-acting
pistons that extend by virtue of fluid pressure
acting on them and discharge the fluid as they
retract.
The piston motion is translated into circular
shaft motion by different means such as an

59.  Piston motors are the
most efficient of all
motors.
 They are capable of
operating at very high
speeds of 12 000 rpm and
also pressures up to 350
kg/cm^2 (4980 psi
approx.).

60. Axial Piston
Axial piston motors
In an axial piston motor, the rotor rotates on
the same axis as the pistons. There are
basically two types of axial piston motor
design. They are:
1. In-line piston motor (swash plate type)
and
2. Bent-axis type.

61. In line Piston

62. Bent Axis Piston

63. Hydraulic Power Pack/Tank

64. Tank/Power Pack Unit

74. Tank
 The reservoir system
 The 'reservoir' as the name suggests, is a tank which
provides uninterrupted supply of fluid to the system, by
storing the required quantity of fluid. The hydraulic fluid is
considered the most important component in a hydraulic
system or in other words its very heart. Since the reservoir
holds the hydraulic fluid, its design is considered quite
critical.
 The reservoir functions such as dissipating heat through
its walls, conditioning of the fluid by helping settle the
contaminants, aiding in the escape of air and providing
mounting support for the pump and various other
components.. Some of the essential features of any good
reservoir include components such as:
 • Baffle plate for preventing the return fluid from entering
the pump inlet
 • Inspection cover for maintenance access

75.  Filter breather for air exchange
 • Protected filler opening
 • Level indicator for monitoring the fluid level
 • Connections for suction, discharge and drain
lines.
The monitoring of the temperature of the fluid
in the reservoir is also important. At the very
least, a simple visual thermometer whose
ideal temperature range is around 45 °C (113
^^F) to 50 °C (122 °F), needs to be provided
on the reservoir.
.

76. Types of Reservoir
There are basically two types of
reservoirs:
1. Non-pressurized reservoir
2. Pressurized reservoir

77. Non Pressurized Reservoir

79. Function of a Baffle
 Essentially the baffle plate performs the following
functions:
• It permits foreign substances to settle at the
bottom
• It allows entrained air to escape from the fluid
• It prevents localized turbulence in the reservoir
• It promotes heat dissipation from the reservoir
walls.

80. Sizing of Tank
 The sizing of the reservoir is based on the following
criteria:
 • It should have sufficient volume and space to allow
the dirt and metal chips to settle and the air to escape
freely.
 • It should be capable of holding all the fluid that might
be drained from the system.
 • It should be able to maintain the fluid level high
enough to prevent air escaping into the pump suction
line.
 • The surface area of the reservoir should be large
enough to dissipate the heat generated by the
system.
 • It should have sufficient free board over the fluid

81. Pressurized reservoirs
Although it has been observed that non-
pressurized reservoirs are the most
suitable ones in a hydraulic system,
certain hydraulic systems need to have
pressurized reservoirs due to the nature
of their application.
For example, the Navy's aircraft and
missile hydraulic systems essentially
need pressurized reservoirs in order to
provide a positive flow of fluid at higher
altitudes where lower temperatures and
pressure conditions are encountered.

82. Accumulators

83. Accumulators
Accumulators
Accumulators are devices, which simply store energy in the form of fluid
under pressure. This energy is in the form of potential energy of an
incompressible fluid, held under pressure by an external source against
some dynamic force. This dynamic force can come from three different
sources: gravity, mechanical springs or compressed gases. The stored
potential energy in the accumulator is the quick secondary source of fluid
power capable of doing work as required by the system. This ability of the
accumulators to store excess energy and release it when required, makes
them useful tools for improving hydraulic efficiency, whenever needed.

84. A system operates intermittently at a pressure
ranging between 150 bar (2175 psi) and 200 bar
(2900 psi), and needing a flow rate of 100 1pm
for 10 s at a frequency of one every minute. With
a simple system consisting of a pump, pressure
regulator and loading valves, this requires a 200
bar (2900 psi), 100-lpm pump driven by a 50 hp
(37 kW) motor, which spends around 85% of its
time, unloading to the tank. When an accumulator
is installed in the system as shown in Figure it
can store and release a quantity of fluid at the
required system pressure.

86. 3 Types of Accumulators
 There are three basic types of accumulators used
extensively in hydraulic systems. They are:
1. Weight-loaded or gravity-type
accumulator
2. Spring-loaded-type accumulator
3. Gas-loaded-type accumulator.

87. 3 Types of Accumulators

88. Gas Loaded Accumulators

89. 3 Types of Separator Type Gas
Loaded Accumulator
Piston Diaphragm Bladder

90. Shock Absorber
 Shock absorbers
 A shock absorber is a device, which brings a
moving load to a gentle rest through the use of
metered hydraulic fluid.

91. Hydraulic shock absorber
One of the most important industrial
applications of accumulators is in the
elimination or reduction of high-pressure
pulsations or hydraulic shocks. Hydraulic
shock (or water hammer, as it is frequently
called) is caused by the sudden stoppage or
deceleration of a hydraulic fluid flowing at a
relatively higher velocity in the pipelines. This
hydraulic shock creates a compression wave
at the location of the rapidly closing valve.
This wave travels along the length of the
entire pipe, until its energy is fully dissipated
by friction. The resulting high-pressure
pulsations or high-pressure surges may
end up damaging the hydraulic
components. An accumulator installed

92. Accumulator

93. A system operates intermittently at a pressure ranging
between 150 bar (2175 psi) and 200 bar (2900 psi),
and needing a flow rate of 100 1pm for 10 s at a
frequency of one every minute. With a simple system
consisting of a pump, pressure regulator and loading
valves, this requires a 200 bar (2900 psi), 100-lpm
pump driven by a 50 hp (37 kW) motor, which
spends around 85% of its time, unloading to the
tank. When an accumulator
is installed in the system as shown in Figure.

96. Compressors

97. Compressors

98. Compressor
• Compressor is a machine used to transport gas
from one point to another point with higher
energy level.
• Air compressor is a machine that compresses air
from low from a low inlet pressure to a higher
desired pressure level. This is accomplished by
reducing the volume of the gas.

99. Types of Compressors
Gasses can be compressed in the following ways:
• Reciprocating piston compressors
• Low flow rates
• High compression ratios
• Rotating centrifugal compressors
• High flow rates
• Low compression ratios
• Several centrifugal stages may be used to obtain higher
compression ratios

100. Uses of Compressed Air
1) Operation of small engines and
pneumatic tools
2) Operation of air hoists
3) Cleaning air blasts
4) Tire inflation
5) Paint spraying
6) Air lifting of liquids
7) Other specialized industrial
applications

101. Types of Compressors
Centrifugal Compressors

102. Types of Compressors
Radial Flow Compressors (multi-stage)

103. Types of Compressors
Axial Compressor

104. Types of Compressors
Reciprocating Compressor

105. Typical Compressor Installation

106. The End