Download Design of Hydraulic System - A Review

International Journal of Trend in Research and Development, Volume 2(5), ISSN 2394-9333
www.ijtrd.com
Design of Hydraulic System - A Review
1
Mr.S.R.Jadhav, 2Mr.Y.P.Ballal and 3Mr. A.R. Mane
1
UG student, 2Asst.Professor, 3Asst.Professor,
Department of Mechanical Engineering,
Annasaheb Dange College of Engineering & Technology, Ashta, Maharashtra, India.
Abstract - Hydraulic components are manufactured to
provide the control function required for the operation of a
wide range of system and application. This review on
hydraulic system design gives an understanding of basic
types of hydraulic components, their operational principle
and estimation of their performance in various
applications. The analytical methods that are used helps to
designing the hydraulic components like reservoir, pump,
motor, cylinder (actuator), control valves.
Keywords- Fluid, Reservoir, Filters, Pumps, Motor,
Cylinder, Control Valve.
I. INTRODUCTION
In the industry we use three methods for
transmitting power from one point to another. Mechanical
transmission is through shafts, gears, chains, belts, etc.
Electrical transmission is through wires, transformers, etc.
Hydraulic transmission is through liquids or gas in a
confined space.
Hydraulics is a type of science and engineering
that deals with mechanical properties of liquids and gases.
Hydraulics is part of the more general discipline of fluid
power. Fluid mechanics provides the foundation for
hydraulics, which focuses on engineering uses of fluid and
gas properties.
Hydraulics means study of water or other fluids at
rest or in motion, especially with respect to engineering
application. Hydraulics and hydraulic systems can be
found almost everywhere. Hydraulics can be found at any
construction site. Some machines that use hydraulics are
bulldozers, fork lift, and cranes. Hydraulics are used to lift
cars so mechanics can work underneath them. Many
elevators use the same operating technique.
Hydraulics is the science of transmitting force
and/or motion through the medium of a confined liquid. In
a hydraulic device, power is transmitted by pushing on a
confined liquid. The transfer of energy takes place
because a quantity of liquid is subject to pressure. To
operate liquid-powered systems, the operator should
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have a knowledge of the basic nature of liquids. This
chapter covers the properties of liquids and how they act
under different conditions.
II. HYDRAULIC PRINCIPLE
The basic idea behind any hydraulic system is
very simple: force applied at one point is transmitted to
another point using and incompressible fluid, which is
almost always going to be a type of oil. In some systems,
such as brake systems in a car, multiply the process. A
major part of hydraulics is Pascal’s principle: Pascal’s
principle - the change in pressure on one part of a
confined fluid is equal to the change in pressure on any
other part of the confined fluid. Following fig. shows the
principle of hydraulic.
Fig 1: Pascal’s Principle
III. COMPONENTS IN HYDRAULIC SYSTEM
A hydraulic system consists of a many
components for operating the system. Hydraulic systems
are power-transmitting assemblies employing pressurized
liquid as a fluid for transmitting energy from an energygenerating source to an energy-using point to accomplish
useful work. Figure 2 shows a simple circuit of a
hydraulic system with basic components.
A hydraulic system consist of fluid for system
reservoir, filter, pump, motor, pressure regulator, direction
control valve, cylinder (actuator), gripper these main
parameters. [1]
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International Journal of Trend in Research and Development, Volume 2(5), ISSN 2394-9333
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reservoirs. Compare the two reservoirs item by item and,
except for the filters and bypass valve, notice the
similarities.
Fig 2 Components in Hydraulic System
A .FluidHydraulic fluid is the medium of power transfer in
hydraulic equipment, it is important to know the
properties of hydraulic fluids and its influence on system
performance. There are different types of fluids based on
their availability, working purpose etc.
A hydraulic the fluid is transmitting medium of a
hydraulic system. It is, therefore, an essential part of the
system and we must know enough about it to ensure that
the hydraulic system works efficiently. The most common
liquid that is used as a medium in fluid power systems is
petroleum-based mineral oil. [7]
In order to the suitable for the demand of heat
dissipation and air separation, the oil reservoir must be
designed be as large as possible. Primarily size of
reservoir is decided by the pump delivery flow. By an
imperial rule these are taken as

Where V=Reservoir size in liter.
Factors Influencing the Selection of a Fluid
The selection of a hydraulic fluid for a given
system is governed by the following factors:
1. Operating pressure of the system.
2. Operating temperature of the system and its
variation.
3. Material of the system and its compatibility with oil
used
4. Speed of operation.
5. Availability of replacement fluid.
6. Cost of transmission lines.
7. Contamination possibilities.
8. Environmental condition (fire proneness, extreme
atmosphere like in mining, etc.).
9. Lubricity.
10. Safety to operator.
11. Expected service life.
[7]
B. RESERVIORThe hydraulic reservoir is a container for holding
the fluid required to supply the system, including areserve
to cover any losses from minor leakage and evaporation.
The reservoir can be designed to provide space for fluid
expansion, permit air entrained in the fluid to escape, and
to help cool the fluid. Fig. No. 3 shows two typical
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Fig 3. Cut Section of Reservoir
V=3.5 for stationery installation
V=1*Q………….For mobile installation
Q=Pump delivery flow in liter per minute.
C. FILTERSContamination of hydraulic fluid is one of the
common causes of hydraulic system troubles. Installing
filter units in the pressure and return lines of a hydraulic
system allows contamination to be removed from the fluid
before it reaches the various operating components. Filters
of this type are referred to as line filters.

Filtering Material and Elements:
The general classes of filter materials are
mechanical absorbent, inactive and absorbent active.
1. Mechanical filters contain closely woven metal
screens or discs. They generally remove only fairly coarse
particles.
2. Absorbent inactive filters, such as cotton, wood
pulp, yarn, cloth, or resin, remove much smaller particles;
some remove water and water-soluble contaminants. The
elements often are treated to make them sticky to attract
the contaminants found
in hydraulic oil.
3. Absorbent active materials, such as charcoal
and Fuller's Earth (a claylike material of very fine
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International Journal of Trend in Research and Development, Volume 2(5), ISSN 2394-9333
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particles used in the purification of mineral or vegetablebase oils), are not recommended for hydraulic systems. [1]
Let,
D= Outside diameter of gear teeth in mm.
d= Inside diameter of gear teeth in mm.
D. PUMPA hydraulic pump is a heart of hydraulic system.
Its function is to convert mechanical energy into hydraulic
energy by pushing the hydraulic fluid into the system.
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.
L= Width of gear teeth in mm.
N= Speed of pump in rpm.
V= Displacement of pump in m/rev
M= Module of gear.
z= Number of teeth.
Volume Displacement,

Gear pumpA fixed positive displacement external gear pump
has been selected in this system with maximum flow rate
of 36 lit./min and volume displacement of24 cm3/rev.
Technical data of this pump is summarized in Table No. 1
Table No.1Technical Data of Hydraulic Pump
Sr. No.
1
2
3
4
Name of
Component
Maximum flow
rate at speed 1500
rpm
Displacement
Continuous
maximum
pressure
Maximum Speed
Specification
V=π/4(𝐷 2 − 𝑑2 )L
Theoretical discharge,
Q= V*N
If the gear is specified by it’s module and number of teeth,
then the theoretical discharge can be found by
Q= 2 πL𝑚2 N[z+(1+(π2 𝑐𝑜𝑠 2 α/12 ) )]
36 lit/min

24 cm3/rev
220 bar
3000 rpm
Selection of pump can be based on following points:
a) Safe and maximum system working
pressure
b) Allowable pump speeds
c) System flow requirement
d) Leakage loss
e) Drive type and mounting
f) Hydraulic oil characteristics
g) Heat, noise and vibration generation
h) Power-to-weight ratio
i) Initial and running cost
Following steps can be adopted while selecting hydraulic
pump:
Fig. No. 4 External Gear Pump

a)
b)
c)
d)
Select the actuator and its size
Select the system operating pressure
Determine the pump speed
Select the pump type
[4]
Design of External Gear Pump:
The flow rate of an external gear pump is depends
on the volume displacement and theoretical discharge.
The flow rate of an external gear pump can be
calculated as follows:
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E. MOTORHydraulic motors are installed in hydraulic
systems to use hydraulic pressure in obtaining powered
rotation. A hydraulic motor does just the opposite of what
a power-driven pump does. A pump receives relative
force from an engine or other driving unit and converts it
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International Journal of Trend in Research and Development, Volume 2(5), ISSN 2394-9333
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into hydraulic pressure. A hydraulic motor receives
hydraulic fluid pressure and converts it into relative force.
Fig No. 6 Hydraulic Cylinder

Fig. No.5 Hydraulic Motor

Selection of motor depends on following factorTheoretical Torque, Power, and Flow rate
DESIGN OF CYLINDER-
For designing the hydraulic cylinder following
parameters are to be consider
1. Force
2. Piston rod velocity
3. Power developed during extension and
retraction stroke

Theoretical TorqueThe torque generated by a frictional
hydraulic motor is known as theoretical torque.
Theoretical Torque (T)
T= (p*V)/2π
P = Pressure in N/m^2
V = Volumetric displacement in m^3/rev

PowerThe power generated by a frictional
hydraulic motor is known as theoretical power.
Power P =T*ω
ω = Seed of motor in rad/sec

Flow RateThe flow rate hydraulic motor would
consume if there were no leakage is known as
theoretical flow rate.
Flow Rate Q= V * n
n = speed of motor in rev/s
[7]
F. CYLINDER (ACTUATOR)A basic actuating cylinder consists of cylinder
housing, one or more pistons and piston rods, and one or
more seals. The cylinder housing contains a polished bore
in which the piston operates and one or more ports
through which fluid enters and leaves the bore.
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Force and velocity during extension
Velocity v = Q/A
Q= Flow rate of fluid
A= Circular piston area
Force F = p * A
p = Pressure in N/m^2
Force and velocity during extension
Velocity
v = Q/(A-a)
Q= Flow rate of fluid
A= Circular piston area
a = Area of piston rod
Force F = p * (A - a)
Power developed during extension and retraction
P=p*Q
p = pressure in N/m^2
Q= Flow rate in [7]
G. CONTROL VALVESValves are used in hydraulic systems to control
the operation of the actuators. Valves regulate pressure by
creating special pressure conditions and by controlling
how much oil will flow in portions of a circuit and where
it will go. The three categories of hydraulic valves are
pressure-control, flow- (volume-) control, and directionalcontrol valves have multiple functions, placing them into
more than one category. Valves are rated by their size,
pressure capabilities, and pressure drop per flow.

Pressure Control ValveA pressure-control valve may limit or regulate
pressure, create a particular pressure condition required
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International Journal of Trend in Research and Development, Volume 2(5), ISSN 2394-9333
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for control, or cause actuators to operate in a specific
order. All pure pressure-control valves operate in a
condition approaching hydraulic balance. Usually the
balance is very simple: pressure is effective on one side or
end of a ball, poppet, or spool and is opposed by a spring.
In operation, a valve takes a position where hydraulic
pressure balances a spring force.

Directional Control ValveA DCV is mainly required for the following
purposes:
1.To start, stop, accelerate, decelerate and change the
direction of motion of a hydraulic actuator.
2, To permit the free flow from the pump to the reservoir
at low pressure when the pump’s delivery is not needed
into the system.
3. To vent the relief valve by either electrical or
mechanical control.
4. To isolate certain branch of a circuit. [7]
[3] En Li, Zize Liang; “Design of hydraulic cylinder
pressure
based”; March 2011
[4] X. S. Li; “Research on variable pump based system” ;
June 2012
[5]. N. Harris, McClaroch; “A end effector of an electro
hydraulically controlled robot; Oct 1984
[6]. S. A. Ahmed, A. J. Ishak; “Design of Gripper” ; Dec
2012.
[7]. “Fluid Power Generation Transmission and Control”;
Jagadeesha T., Thammaiah Gowda; 2013; page no. 42 to
287.

Flow Control ValveFlow control valve achieve their primary
function
of regulating the fluid flow by varying the
area of an orifice. Flow through control orifice is usually
considered to be turbulent and the quantity of the fluid
flowing given by,
q =KA ∆𝑝
Where q =Flow rate through the valve
A=Orifice area
∆𝑝 =Pressure drop across the orifice
CONCLUSION
Studying the various components used in
hydraulic system it helps to know the selection of proper
component used for any hydraulic system. In this study a
co-relation and co-ordination of different types of
hydraulic fluid, filter, reservoir, pump, motor, cylinders,
valves, power pack, end effectors is help to design of
hydraulic system.
References
[1] D. J. Dunn; “Basic hydraulic system and component”;
September 1994
[2] Chen Huanming; “Research on features of hydraulic
oil for hydraulic pump”: June 2012
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