basic hydraulic system

1

Assembly & Maintenance of

Pneumatic & Hydraulic System

(SED 23103)

Basic Automation System

(SRD 23403)

Malaysian Spanish Institute

MSI Pneumatic System

v5

Assembly & Maintenance of Pneumatic & Hydraulic System

(SED 23103) - (Assessment)

1. Basic Pneumatic System Technical Report 10%

Mini Project 10%

Test 10%

Exam Practical 20%

2. Basic Hydraulic System Technical Report 10%

Mini Project 10%

Test 10%

Exam Practical 20%

Total Marks (SED 23103) Technical Report 20%

Mini Project 20%

Test 20%

Exam Practical 40%

100%

2

MSI Electrical System


(SED 23103) - (Assessment)

1. Basic Pneumatic System Pneumatic Power

Pneumatic Control

Pneumatic Actuator

2. Basic Hydraulic System Hydraulic Power

Hydraulic Control

Hydraulic Actuator

End of Course Comparison of Power System

Selection of Power System

3



(SED 23103) (Study Planning)

1. Basic Pneumatic System Week 1 6 (Study week)

Week 7 (Practical Test)

2. Basic Hydraulic System Week 8 13 (Study Week)


4


Extra Assessment

Attitude marks

1. Attendant (per/minute = 0.019%)

2. Cheating (per/cheat = 1%)

3. Attire (per/day = 5%)

4. Behavior (per/hour = 5%)


(SRD 23403) - (Assessment)

1. Basic Pneumatic System Technical Report 7%

Mini Project 7%

Test 7%

Exam Practical 14%

2. Basic Hydraulic System Technical Report 7%

Mini Project 7%

Test 7%

Exam Practical 14%

3. Basic Electrical System Technical Report 6%

Mini Project 6%

Test 6%

Exam Practical 12%

Total Marks (SRD 23403) Technical Report 7+7+6%

Mini Project 7+7+6%

Test 7+7+6%

Exam Practical 14+14+12%

100%

5



(SRD 23403) - (Content Summary)

1. Basic Electrical System Electrical Power

Electrical Control

Electrical Actuator

2. Basic Pneumatic System Pneumatic Power

Pneumatic Control

Pneumatic Actuator

3. Basic Hydraulic System Hydraulic Power

Hydraulic Control

Hydraulic Actuator

End of Course Comparison of Power System

Selection of Power System

6


Basic Automation System (SRD 23403)

(Study Planning)

1. Basic Pneumatic System Week 1 4 (Study week)


2. Basic Hydraulic System Week 6 9 (Study week)


3. Basic Electrical System Week 11 13 (Study Week)


Extra Assessment Attitude marks

Attendant (per/minute = 0.019%)

Cheating (per/cheat = 1%)

Attire (per/day = 5%)

Behavior (per/hour = 5%)

7


8

MSI Hydraulic System

Basic Hydraulic System

9

Introduction to Didactic Unit

Objective of Module

Why hydraulic system?

Because: hydraulic system is amazing in its strength and agility. It is uses in medium

and heavy application. It is a basic control system. Uses liquid as its medium.

Uses in medium and heavy application.

Why learn hydraulic system? Its a basic control system.

Why learn maintenance of hydraulic system? To describe the methodology of preventive and corrective maintenance technique of

Hydraulic System.


10

Basic Control System


signal

processing output

signal

input

pushbutton valve cylinder

11


Control & Maintenance

signal

processing output

signal

input

Assembly / Maintenance / Troubleshoot

12

Content of Module

CHAPTER X INTRODUCTION TO DIDACTIC UNIT

CHAPTER 0 SAFETY IN HYDRAULIC SYSTEM

CHAPTER 1 INTRODUCTION TO HYDRAULIC SYSTEM

CHAPTER 2 FUNDAMENTAL IN HYDRAULIC SYSTEM

CHAPTER 3 TANK PIPING AND COUPLINGS

CHAPTER 4 HYDRAULIC PUMPS

CHAPTER 5 HYDRAULIC ACTUATOR

CHAPTER 6 DISTRIBUTOR VALVES

CHAPTER 7 PRESSURE VALVES

CHAPTER 8 FLOW VALVES

CHAPTER 9 BLOCK VALVES

CHAPTER 10 ELECTRO HYDRAULIC SYSTEM


13

Safety In Hydraulic System chapter 0

General safety

High pressures, temperatures and forces occur in Hydraulic System. Energy is also stored, sometimes in

large quantities. A whole series of safety measures is

necessary to rule out the possibility of danger to

personnel and equipment during the operation of

hydraulic systems. In particular, the valid safety

regulations for hydraulic systems are to be OBSERVED.


14

Regulations and standards

The following safety regulations apply for the field of hydraulics:

1. Accident prevention regulations, directives, safety rules and the testing guidelines,

2. Regulations on pressure vessels, pressurized gas vessels and filling systems (pressure vessel regulations),

3. DIN standards, VDI directives, VDMA standard sheets and technical rules for pressure vessels, containing in particular, notes and regulations on dimensions, design, calculations, materials and permissible loads as well as conditions on functions and requirements.

4. Electro-hydraulic systems must comply not only with the regulations on hydraulic systems but also with the regulations on electrical systems and components (e.g. DIN VDE 0100).


15

Safety Recommendations


Install the EMERGENCY STOP push-button in a place where it can be easily reached.

Use standardized parts only.

Enter all alterations in the circuit diagram immediately.

The rated pressure must be clearly visible.

Check whether the installed equipment can be used at the maximum operating pressure.

The design of suction lines should ensure that no air can be drawn in.

Check the oil temperature in the suction line to the pump. It must not exceed 60 C.

The piston rods of the cylinders must not be subjected to bending loads or lateral forces. Protect piston rods from dirt and damage.

16

Start-up of Hydraulic System


Do not operate systems or actuate switches if you are not totally sure what function they perform.

All setting values must be known.

Do not switch on the power supply until all lines are connected.

Important: check that all return lines (leakage lines) lead to the tank.

When starting up the system for the first time, open the system pressure relief valve almost completely and gradually set the system to the operating pressure. Pressure relief valves must

be installed in such a way that they cannot become ineffective.

Carefully clean the system prior to start-up, then change the filter cartridge.

Vent system and cylinders.

In particular, the hydraulic lines to the reservoir are to be carefully vented. It is generally possible to effect venting at the safety and shut-off block of the reservoir.

Special care is needed when handling hydraulic reservoirs.

Before the reservoirs are started up, the regulations determined by the manufacturer are to be studied carefully.

17

Repair and Maintenance


Repair work may not be effected on hydraulic systems until the fluid pressure of the reservoir has been release. If possible, separate the reservoir from the system (using a valve). Never drain the reservoir un-throttled.

When repairs are completed effect a new start-up in line with the safety regulations listed above.

All hydraulic reservoirs are subject to the provisions of the pressure vessel regulations and must be inspected at regular intervals.

18

General Lab rules


1. You are prohibited from entering Hydraulic Lab without SAFETY BOOT (all time), DUST COAT (practical uses)

2. Do not be afraid to ask questions. We are here to assist you.

3. Do not step on any signal or actuator controller cable.

4. Never use your finger to align bolt-holes.

5. You must keep your work area clean and free of rubbish.

6. Never place any part of your body in an area that is considered a crush point.

7. If you break or notice any defects in the equipment you are using, immediately inform the TTO. This ensures that you will not be held responsible for repairing the equipment.

8. Do not leave tools on load frames or specimens, and at the end of the day put all tools back where they belong.

9. Work methodically and at a steady pace, and do not be afraid to ask your fellow students or Mr. FATHUL to assist you.

10. USE COMMON SENSE.

19

Introduction to Hydraulic System chapter1

Hydraulic means the generation of forces and motion using hydraulic

fluids. Hydraulic fluids represent the medium for power transmission.


Advantage of hydraulic system

Great power intensity

Precise positioning

Start-up under heavy load

Independent of load

Smooth operation and reversal

Good control and regulation

Favorable heat dissipation

Disadvantage of hydraulic system

Pollution

Sensitivity to dirt

Danger resulting from excessive pressures

Temperature dependence

Unfavorable efficiency factor

20

Application Of Hydraulic System

Stationary Hydraulic (Vise, clamp, stamping machine, injection moulding machine, and etc).

Mobile Hydraulic

(bulldozers, backhoes, shovels, loaders, fork lifts, cranes and etc).


21


Hydraulic System Overview

22

Hydraulic System vs. Pneumatic System


Drive section

Control section

Power section

23


Schematic Diagram Of A Hydraulic System

Single Acting Cylinder Double Acting Cylinder

24

The Basic Idea

The basic idea behind any hydraulic system is very simple: Force

that is applied at one point is transmitted to another point using

an incompressible fluid.

The picture below shows the simplest possible hydraulic system:


25

Working Principle

Retract position Extend position


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Fundamental in Hydraulic System Chapter 2

1. Pressure

2. Pressure Transmission

3. Power Transmission

4. Displacement

Transmission

5. Pressure Transfer

6. Flowrate

7. Pressure Measurement

8. Type of Flow

9. Friction, heat & pressure

drop

10. Energy & Power

11. Power

12. Cavitations & Throttle

point

13. Hydraulic Fluid


27

1. Pressure

Pressure (symbol: p) is the force per unit area acting on a surface in a direction perpendicular to that surface.

Mathematically: where:


A

p

F

Area of double

acting cylinder

= (d/2)

28

example


29

2. Pressure Transmission

If a force F1 acts at area A1 on an enclosed liquid, a pressure p is produced which extends throughout the whole of the liquid (Pascals Law).

This will cause a same pressure acting at every point of the closed system.


30

example


31

3. Power Transmission

If same pressure applies at every point in a closed system, the shape of the container has no significance.


32

example


Therefore

33

4. Displacement Transmission

If load F2 is to be lifted to a distance s2, Piston 1 must be displace at distance s1, at a specific quantity of liquid which lifts the Piston 2 by a distance s2.


34

example


35

5. Pressure Transfer

The pressure P1 exerts F1 force on area A1 which is transferred thru piston rod onto the small piston. Force F1 will acts on area A2 and produces pressure P2. Since piston area A2 is smaller than piston area A1, the pressure P2 will be greater than the pressure P1.


36

example


37

6. Flowrate

Flow rate is the term used to describe the volume of liquid flowing through a pipe in a specific period of time.

For example, approximately one minute is required to fill a 10 liter bucket from a tap. Thus, the flow rate amounts to 10 l/min.


38

6. Flowrate


Other derivation

Well have

39


7. Pressure Measurement

To measure pressures in the lines or at the inputs and outputs of components, a pressure gauge is installed in the line at the

appropriate point.

40


1. Laminar flow fluid moves through the

pipe in cylindrical layers

order.

8. Type of flow

2. Turbulence flow when flow velocity of fluid

rises above a certain point

the fluid particles stop to

move in ordered layers.

41


Reynolds number (Re).

A method of calculating the type of flow in a smooth pipe is enabled by the Reynolds number (Re). This is dependent on:

the flow velocity of the liquid v (m/s) (flowrate)

the pipe diameter d (m)

and the kinematics viscosity (m/s) (viscosity)

laminar flow: Re < 2300

turbulent flow: Re > 2300

42


Reynolds number (Re).

The value 2300 is termed the critical Reynolds number (Recrit) for smooth round pipes.

Turbulent flow does not immediately become laminar on falling below (Recrit). The laminar range is not reached

until (Recrit).

To prevent turbulent flow causing considerable friction losses in hydraulic systems, (Recrit) should not be

exceeded.

43


Example:

1

2

3

4 1. Draw line from piping dia. to

liquid flow velocity(1-2)

2. From point (2) draw a line to

flowrate in the pipe, (2-3)

3. The Reynolds number are on point (4)

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Guideline Hydraulic flowrate

45


9. Friction, Heat & Pressure droop

Friction occurs in all devices and lines in a hydraulic system. Mainly at the line walls (external friction and between the layers of

liquid (internal friction).

The friction causes heat. As heat generation, the pressure in the system drops and reduces the actual pressure at the drive section.

The size of the pressure drop is based on the internal resistances in a hydraulic system. These are dependent on: Flow velocity (cross-sectional area, flow rate), Type of flow (laminar, turbulent), Type and number of cross-sectional reductions in the system of lines

(throttles, orifices),

Viscosity of the oil (temperature, pressure), Line length and flow diversion, Surface finish, Line arrangement.

46


The energy of a hydraulic system is made up of several forms of energy.

Static

Potential energy

Pressure energy

Dynamic

Motion energy

Thermal energy

10.Energy & Power

47


Type of Energy

Static Potential energy: energy which a body (or a

liquid) has when it is lifted by a height h.

Pressure energy: pressurized volume

Dynamic Motion energy: when a force F acting on the

body that moves at a certain speed. (also known as kinetic energy)

Thermal energy: is the energy required to heat a body (or a liquid) to a specific temperature.

In hydraulic installations, part of the energy is converted into thermal energy as a result of friction. This leads to heating of the hydraulic fluid and of the components. Part of the heat is emitted from the system, i.e. the remaining energy is reduced. The consequence of this is a decrease in pressure energy.

48


11.Power

Power is usually defined as work or a change in energy per unit of time.

Hydraulic power is calculated from the pressure and the flow rate.

49


Example

50


Efficiency

The input power in a hydraulic system does not correspond to the output power since line losses occur. The ratio of the output power to the input

power is designated as efficiency (h).

In practice, distinction is made between volumetric power loss caused by leakage losses and hydro-mechanical power loss caused by friction. In the

same way, efficiency is divided into:

Volumetric efficiency (vol): This covers the losses resulting from internal and external leakage losses in the pumps, motors, and valves.

Hydro-mechanical efficiency (hm): This covers the losses resulting from friction in pumps, motors, and cylinders.

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Example

52


12.Cavitations & Throttle point

Refers to the releasing of the smallest particles from the surface of the material.

Motion energy is required for an increase in flow velocity of the oil at a narrowing. This motion energy is derived from the pressure energy. Because of this, pressure drops at narrow points may move into the vacuum range.

From a vacuum of 0.3bar onwards, dissolved air (Gas bubbles) are formed. If the pressure now rises again as a result of a reduction in speed, the oil causes the gas bubbles to collapse.

53

13.Hydraulic Fluid

Hydraulic fluids represent the medium for power transmission.

Function

Pressure transfer Lubrication for moving parts / devices Cooling agent: - diversion of heat produced by energy

conversion

Cushioning of oscillations cause by pressure jerks. Corrosion protection Scuff removal Signal transmission


54


Characteristic of hydraulic fluid

lowest possible density minimal compressibility viscosity not too low (lubricating film) good viscosity-temperature characteristics good viscosity-pressure characteristics good ageing stability low flammability good material compatibility

example of hydraulic fluid HLP 68

H:- hydraulic fluid, L:- with additives to corrosion protection and/or ageing stability, P:- with additives to reduce and/or increase load carrying ability 68:- viscosity code as defined in DIN 51517

55


Viscosity

can be defined as resistance to flow. The viscosity of a liquid indicates its internal friction.

Ball Viscometer

56


Tank, Piping & Coupling Chapter 3

Tank / Reservoir acts as intake and storage reservoir for the hydraulic fluid required for operation of

the system;

dissipates heat; separates air, water and solid materials; supports a built-in or built-on pump and drive motor and other hydraulic

components, such as valves, accumulators, etc.

Reservoir size, dependent on: pump delivery the heat resulting from operation in connection with the maximum permissible

liquid temperature

the maximum possible difference in the volume of liquid which is produced when supplying and relieving consuming devices (e.g. cylinders, hydraulic fluid reservoirs)

the place of application the circulation time.

57


Tank / Reservoir Reservoir shape

High reservoirs are good for heat dissipation, wide ones for air separation.

Intake and return lines

These should be as far away from one another as possible and should be located as far beneath the lowest oil level as possible.

Baffle and separating plate

This is used to separate the intake and return areas. In addition, it allows a longer settling time for the oil and, therefore, makes possible more effective separation of dirt, water and air.

Base plate

The base of the tank should slope down to the drain screw so that the deposited sediment and water can be flushed out.

Ventilation and exhaust (air filter)

To balance the pressure in case of a fluctuating oil level, the reservoir must be ventilated and exhausted. For this purpose, a ventilation filter is generally integrated into the filler cap of the feed opening.

58


Piping (Flexible Hoses)

These are flexible line connections which are used between mobile hydraulic devices or in places where there is only limited space

(particularly in mobile hydraulics).

The inner tube (1) is made of synthetic rubber, Teflon, polyester-elastomer, perbunan or neoprene. The pressure carrier

is a woven intermediate layer of steel wire and/or polyester or rayon.

This woven section (2) may consist of one or more layers depending on the pressure range.

The top layer (3) is made of wear-resistant rubber, polyester, polyurethane elastomer or other materials. The pipelines

may be additionally protected against mechanical damage by external spirals or plaited material.

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Installation of Hose Lines

60


Coupling

Hose lines may either be connected

to the various pieces of equipment or

else connected together by means of

screw fittings or quick connection

couplings.

Hose support connectors ensure that

connections do not affect operation:

61


HYDRAULIC PUMP Chapter 4

The pump in a hydraulic system, also known as a hydraulic pump, converts the mechanical energy in a drive unit into hydraulic energy (pressure energy).

The pump draws in the hydraulic fluid and drives it out into a system of lines.

62


The Basic Concept

Low pressure

High pressure

63


Hydraulic pumps

Gear Pump Rotary Vane Pump Piston Pump

External Gear Pump

Internal Gear Pump

Single Chamber

Double Chamber

Radial Piston Pump

Axial Piston Pump

TYPE OF HYDRAULIC PUMP

64


TYPE OF HYDRAULIC PUMP

External Gear Pump Internal Gear Pump Single Chamber

Double Chamber Radial Piston Pump Axial Piston Pump

65


Gear Pump: Working Principle

Volume

increase From tank

To hydraulic

system

Volume

increase

From

tank

To

hydraulic

system

Internal gear External gear

Working Operation (Gear Pump)

The suction area S is connected to the reservoir. The

gear pump operates according to the following

principle:

One gear is connected to the drive, the other is

turned by the meshing teeth. The increase in volume

which is produced when a tooth moves out of a mesh

causes a vacuum to be generated in the suction

area. The hydraulic fluid fills the tooth gaps and is

conveyed externally around the housing into

pressure area P. The hydraulic fluid is then forced

out of the tooth gaps by the meshing of teeth and

displaced into the lines.

Fluid is trapped in the gaps between the teeth

between suction and pressure area. This liquid is fed

to the pressure area via a groove since pressure

peaks may arise owing to compression of the trapped

oil, resulting in noise and damage.

66


67


Rotary Vane: Working Principle

Volume

increase

Volume

increase

From tank

To hydraulic

system

From tank

To hydraulic

system

Single chamber Double chamber

68


Piston Pump: Working Principle

compression From tank

To hydraulic

system

Radial chamber Axial chamber

From tank To hydraulic

system

compression

From tank Hyd sys

69


Pump

Specification

Assignment 2

70

MSI Pneumatic System

Working operation for: 1. Internal Gear Pump,

2. Vane Pump and

3. Piston Pump

71

There are two basic types of hydraulic actuator:

Rotary actuator

(motor / rotary)

Linear actuator

(cylinder)


Hydraulic Actuator Chapter 5

72


Hydraulic Motor (Rotary Movement)

Hydraulic motor comes various type same as hydraulic pump. It working operation

are similar.

Gear motor

Vane motor

Piston motor

73


Linear Actuator (Linear Movement)

Single Acting Cylinder Double Acting Cylinder

There are two basic types of hydraulic cylinder

single-acting and

double-acting cylinders.

74


Type of Linear Actuator

75


Type of Linear Actuator

76

Distribution Valve Chapter 6

Introduction Directional control valves are components which change, open or close flow paths in

hydraulic systems. They are used to control the direction of motion of power

components and the manner in which these stop. Directional control valves are

shown as defined in DIN ISO 1219.

Type 2/2-way valve

3/2-way valve

4/2-way valve

5/2-way valve

4/3-way valve


77


Symbols for directional

control valves The following rules apply to the representation of directional control valves: Each different switching position is shown by a square. Flow directions are indicated by arrows. Blocked ports are shown by horizontal lines. Ports are shown in the appropriate flow direction with line arrows. Drain ports are drawn as a broken line and labeled (L) to distinguish them

from control ports.

78


The switching position of a directional control valve can be changed by various actuation methods, such as push button, pedal, lever with detent, a spring is always

necessary for resetting.

Methods of Actuation

79


Port Designation

80


Type of Distribution Valve (symbol)

81


Working Principle

2/2 way valve, Normally close

Release position Press position

82


Circuit Example

Release 2/2 WV Cylinder Extend Pressed 2/2 WV Cylinder Retract

83


Basic Construction of 3/2 way valve

(3/2 way valve N.C)

84



85



(4/3 way valve, mid position pump re-circulating)

86


Basic Construction of valve

(2/2 way valve N.C)

(3/2 way valve N.C) (4/3 way valve, mid position pump re-circulating)

87


Conversion of Valve

88


Pressure Valve Chapter 7

Pressure valves have the task of controlling and regulating the pressure in a

hydraulic system.

Pressure relief valves The pressure in a system is set and restricted

by these valves. The control pressure is

sensed at the input (P) of the valve.

Pressure regulator

These valves reduce the output pressure where there

is a varying higher input pressure. The control

pressure is sensed at the output of the valve.

Symbol

2 way pressure regulator 3 way pressure regulator Pressure relief valves

89


Working Principle (pressure relief valve)

90


Working Principle (2 way pressure regulator)

91


Working Principle (3 way pressure regulator)

92


Basic Construction

Pressure Relief Valve

2 Way Pressure Regulator

3 Way Pressure Regulator

93


Flow Valve Chapter 8

Introduction Flow control valves are used to reduce the speed of a cylinder or a motor.

Type of control valve:

2. Throttle Valve

(two way flow control valve) - Restrict both direction of flow.

1. One Way Flow Control Valve - Restrict one direction of flow only.

94


Working Principle

One-way flow control valve

The one-way flow control valve where the restrictor is only effective in one direction is a combination of a restrictor and a non-return valve. The restrictor controls the flow rate in a

single direction dependent on flow. In the opposite direction, the full cross-sectional flow is

released and the return flow is at full pump delivery. This enables the one-way flow control

valve to operate.

Control Not control

95


Circuit Example (One way flow control valve)

Fluid is block

by check valve

Fluid enter cylinder

with normal flow Fluid have to flow

through throttle valve

Extend slow

96


Circuit Example (One way flow control valve)

Fluid is block

by check valve

Fluid enter cylinder

with normal flow

Fluid have to flow

through throttle valve

Retract slow

97


Working Principle

Throttle Valve

Flow control valves influence the

volumetric flow of the

fluid in both directions.

Control flow in both direction

98


Circuit Example (Throttle valve)

Extend & Retract

slow

99


Block Valve (Non Return Valve) Chapter 9

100


Check Valve

Check valves can stop the flow completely in one direction. In the opposite direction

the flow is free with a minimal pressure

drop due to the resistance of the valve.

Spring loaded Spring un-loaded

101


De-lockable Valve

In de-lockable valve, flow can be released in the closed position by pilot control of

the valve poppet. This takes place according to the following principle:

1. Flow is possible from A to B.

2. Flow is blocked from B to A.

3. In order permits flow from B to A,

signal X is produce.

102


Circuit Example (De-Lockable valve)

Signal x must

be connected to tank

In order to release

pressure at port x.

Uses when cylinder

is vertically install

103


Circuit Example (De-Lockable valve)

Change input

To suite

existing valve

with practical task

104


Shuttle Valve

This shuttle valve has two inlets X and Y and one

outlet A. If Hydraulic fluid is applied to the first inlet X,

the valve seals the opposing inlet Y, the fluid flows

from X to A. Inlet X is closed, if fluid passes from Y to

A. A signal is generated at the outlet. When the Fluid

flow is reversed, i.e. a cylinder or valve is exhausted,

the seat remains in its previously assumed position

because of the pressure conditions. This valve is also

called an OR element.

X Y

A

X Y A

0 0 0

0 1 1

1 0 1

1 1 1

TRUTH TABLE

105


De-lockable Double Non-Return Valve

The piloted double non-return valve operates according to the following principle:

Free flow is possible either in the flow direction from A1 to B1 or from A2 to B2, flow is

blocked either from B1 to A1 or from B2 to A2.

If flow passes through the valve from A1 to B1, the control piston is shifted to the

right and the valve poppet is lifted from its seat. By these means, flow is opened

from B2 to A2 (the valve operates in a corresponding manner where there is flow from

A2 to B2).

106


Circuit example

107

Electro-Hydraulic System Chapter 10

Malaysian Spanish Institute

MSI Electro-Hydraulic System

108

Schematic

Design Of An

Electro-Hydraulic

System


109


Hydraulic Pump

Pushbutton

Cylinder

Power

Supply

Pushbutton

Relay,

Timer,

Solenoid

Electro-Hydraulic Overview

From electro

110


Electro Hydraulic Automatons

Switching

control

Manual

actuation

Electrical

actuation

111

Content of Electro-Hydraulic

Safety precaution

Introduction

Advantages

Comparison

Electrical Fundamental

Electrical Input Element

Sensor

Relay

Solenoid

Electrical Timer

Sequence Control


112

Safety Precaution


1. Pneumatic safety must be apply

2. DO NOT wear sandals, wear covered shoes

3. DO NOT wear excessive jewelry

4. DO NOT wear swing-loose-long hair style, neatly tie-up the long hair or place under a proper head gear.

5. DO NOT wear shoes with heel higher than 1" (2.5 cm)

6. DO wear lab-coat all the time

7. DO NOT disturb people who are conducting experiments! (or any time)

8. NO eating or drinking inside the lab.

9. NO social gathering is allowed in the labs. The labs should not be crowded for non-working purposes.

10. In case of spilling water on a lab bench near power points, first SWITCH OFF the electrical power before cleaning.

11. TO INSPECT any electrical equipment, first turn the power off and ask for the instruction/help from the lab officer in charge. Any faulty equipment should be attended by trained personnel only. DO NOT do it on your own.

113

Introduction

Electro-Hydraulic Systems are made up of

hydraulic and electrical components:

The movements and forces are generated by Hydraulic means (e.g. by cylinders).

Signal input and signal processing, on the other hand, are effected by Electrical and Electronic

components (e.g. electromechanical switching

elements or stored-program controls).


114

Advantages


Electrical signals can be transmitted via cables quickly and easily and over great distances. Mechanical signal transmission (linkages, cable-pulls) or hydraulic signal transmission (tubes, pipes) are far more complex.

In the field of automation, signal processing is generally effected by electrical means. This enhances the options for the use of electro-hydraulic systems in automatic production operations (e.g. in a fully automatic pressing line for the manufacture of car wings).

Many machines require complex control procedures (e.g. plastics processing). In such cases, an electrical control is often less complex and more economical than a mechanical or hydraulic control system.

115

MSI Electro-Hydraulic System Comparison

116


Electrical Fundamental

The relationship between voltage, current strength and resistance is described by Ohms law. Ohms law states that in a circuit with constant resistance the current strength changes in proportion to the change in voltage:

if the voltage increases, the current strength also increases.

if the voltage falls, the current strength also decreases.

117


In the field of mechanical engineering, power can be defined in terms of the work performed. The faster a task is performed, the greater the required power. Power therefore means work per unit of time.

In the case of a consuming device in a circuit, electrical energy is converted into kinetic energy (e.g. electrical motor), light radiation (e.g. electrical lamp) or thermal energy (e.g. electrical heater, electrical lamp). The faster the energy is converted, the greater the electrical power.

Electrical power

118


A power supply unit consists of the following modules:

the mains transformer which transforms the alternating voltage of the mains supply (e.g. 220 V) into the output voltage (mostly 24 V).

a smoothed direct voltage is generated by the rectifier G and the capacitor C.

the direct voltage is then stabilized by the in-phase regulator.

Power Supply

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Electrical controls are generally supplied with a direct current of 24V. The alternating voltage from the power supply therefore has to be

stepped down to 24V and then rectified.

Conversion AC to DC

AC DC

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Electrical input elements

NORMALLY OPEN CONTACT

circuit is open when the push-button is in the normal position

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NORMALLY CLOSED CONTACT

circuit is closed when the push-button is in the normal position

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CHANGEOVER SWITCH

These contacts combine the

functions of normally closed and normally open contacts in one unit.

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Circuit example

Pressed S1, H will on

Pressed S1, H will off

Pressed S1, H will on,

Pressed S2, H will off.

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Practical (Electrical Input Element)

And

Function

Or

Function

And

Function

Or

Function

Switching ON Command Switching OFF Command

S1 AND S2 H1 on S1 OR S2 H1 on S1 AND S2 H1 off S1 OR S2 H1 off

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Sensor Limit switch

A mechanical limit switch is an

electrical switch which is activated

when a machine part or a workpiece

is in a certain position.

Normally open limit switch

1-4

Normally closed limit switch

1-2

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Sensor Pressure switch requires a pressure to activated the sensor

the pressure acts on a cylinder surface (x).

If the pressure exerted exceeds the spring

force of the return spring, the piston moves

and operates the contact set.

Normally open limit switch

1-4

Normally closed limit switch

1-2

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Circuit Example

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Relay

Relays are electromagnetically actuated switches.

They consist of a housing with electromagnet and movable contacts.

An electromagnetic field is created when a voltage is applied to the coil of the electromagnet.

This results in attraction of the movable armature to the coil core. The armature actuates the contact assembly.

This contact assembly can open or close a specific number of contacts by mechanical means.

If the flow of current through the coil is interrupted, a spring returns the armature to its original position.

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Concept of a Relay

(Electromagnet)

An electromagnet is a type of magnet in which the magnetic field is produced by the flow of an electric

current. The magnetic field disappears when the current

ceases.

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Working Principle

Relay

1 pole

Relay

2 pole

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Example

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Circuit Example

Direct Control In-direct Control

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9. Solenoids

In electro-hydraulics, valves are actuated via solenoids. It has the same concept of electromagnet.

solenoid

Directional control Valve

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Circuit Example

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Electromechanical Switching Element

(Symbol)

136


Holding Element / Latching

S1 H1 ON S2 H1 OFF

S1

S2

k1

K1

k1

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A timer is used to control the sequence of an event or process.

Two type of timer 1. Delay-On Timer

2. Delay-Off Timer

Electrical Timer

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Electrical Timer

S1 5sec H1 ON S2 H1 OFF

24V

0V

S1

S2

K1

K1

T1

K1

H1

T1

The Coil with ON delay activates its

associated contacts when current is

applied.

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Electrical Timer

S1 H1 ON

S2 5sec H1 OFF

The Coil with OFF delay deactivates

its associated contacts when current

is applied, but only after the preset

delay.

24V

0V

S1

S2

K1

K1

T1

K1

H1

T1

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Electrical Timer

24V

t

S1

0V

H1

Timer for Practical installation

Note:

For ON Delay:

Select selector to

DES.

For OFF Delay:

Select selector to

CON.

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Electro Hydraulic System

Hydraulic Circuit Diagram /

Power Circuit /

Schematic Diagram

Control Circuit Diagram /

Electrical Circuit Diagram

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D END

basic hydraulic system

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