03 basic hydraulic system v5
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Malaysian Spanish Institute
MSI Hydraulic System
v5
Assembly & Maintenance ofPneumatic & Hydraulic System
(SED 23103)
Basic Automation System(SRD 23403)
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Basic Hydraulic System
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Introduction to Didactic Unit
Objective of Module
Why hydraulic system?
Because: hydraulic system is amazing in itsstrengthandagility. It is uses in mediumand heavy application. It is abasic control system. Usesliquidas its medium.Uses inmediumandheavyapplication.
Why learn hydraulic system?Its a basic control system.
Why learn maintenance of hydraulic system?To describe the methodology ofpreventiveandcorrectivemaintenance technique of
Hydraulic System.
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Basic Control System
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signalprocessing
outputsignalinput
pushbutton valve cylinder
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Control & Maintenance
signalprocessing
outputsignalinput
Assembly / Maintenance / Troubleshoot
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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
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Safety In Hydraulic Systemchapter 0
General safety
High pressures, temperatures and forces occur in
Hydraulic System. Energy is also stored, sometimes inlarge quantities. A whole series of safety measures isnecessary to rule out the possibility of danger topersonnel and equipment during the operation ofhydraulic systems. In particular, the valid safety
regulations for hydraulic systems are to be OBSERVED.
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Regulations and standards
The following safety regulations apply for the field of hydraulics:
1. Accident prevention regulations, directives, safety rules and the testingguidelines,
2. Regulations on pressure vessels, pressurized gas vessels and fillingsystems (pressure vessel regulations),
3. DIN standards, VDI directives, VDMA standard sheets and technicalrules for pressure vessels, containing in particular, notes and regulationson dimensions, design, calculations, materials and permissible loads aswell as conditions on functions and requirements.
4. Electro-hydraulic systems must comply not only with the regulations onhydraulic systems but also with the regulations on electrical systems andcomponents (e.g. DIN VDE 0100).
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Safety Recommendations
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Install the EMERGENCY STOP push-button in a place where it can be easilyreached.
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 operatingpressure.
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 lateralforces. Protect piston rods from dirt and damage.
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Start-up of Hydraulic System
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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 almostcompletely 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 generallypossible 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 bestudied carefully.
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Repair and Maintenance
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Repair work may not be effected on hydraulic systemsuntil the fluid pressure of the reservoir has beenrelease. If possible, separate the reservoir from thesystem (using a valve). Never drain the reservoir un-throttled.
When repairs are completed effect a new start-up in linewith the safety regulations listed above.
All hydraulic reservoirs are subject to the provisions ofthe pressure vessel regulations and must be inspectedat regular intervals.
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General Lab rules
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1. You are prohibited from enteringHydraulic Lab without SAFETYBOOT (all time), DUST COAT(practical uses)
2. Do not be afraid to ask questions.We are here to assist you.
3. Do notstep on any signal oractuator controller cable.
4. Never use your finger to align bolt-holes.
5. You must keep your work areaclean and free of rubbish.
6. Never place any part of your body inan area that is considered a crushpoint.
7. If you break or notice any defects inthe equipment you are using,immediately inform the TTO. Thisensures that you will not be heldresponsible for repairing theequipment.
8. Do not leave tools on load frames orspecimens, and at the end of theday put all tools back where theybelong.
9. Work methodically and at a steadypace, and do not be afraid to askyour fellow students or Mr. FATHUL
to assist you.
10. USE COMMON SENSE.
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Safety Attitude (LAB)
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1. Pneumatic safety must be apply2. DO NOT wear sandals, wear covered shoes (SAFETY BOOT)3. DO NOT wear excessive jewelry4. DONOT 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 time7. DO NOT disturb people who are conducting experiments! (or any time)8. NO eating or drinking inside the lab /NO sitting while doing practical.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 equipmentshould be attended by trained personnel only. DO NOT do it on yourown.
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Introduction to Hydraulic Systemchapter1
Hydraulic means the generation of forcesand motionusing hydraulicfluids. Hydraulic fluids represent the medium for power transmission.
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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
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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).
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Hydraulic System Overview
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Hydraulic System vs. Pneumatic System
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Drive section
Control section
Power section
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Schematic Diagram Of A Hydraulic System
Single Acting Cylinder Double Acting Cylinder
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The Basic Idea
The basic idea behind any hydraulic system is very simple: Forcethat is applied at one point is transmitted to another point usingan incompressible fluid.
The picture below shows the simplest possible hydraulic system:
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Working Principle
Retract position Extend position
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Fundamental in Hydraulic SystemChapter 2
1. Pressure
2. Pressure Transmission
3. Power Transmission
4. DisplacementTransmission
5. Pressure Transfer
6. Flowrate
7. Pressure Measurement
8. Type of Flow
9. Friction, heat & pressure
drop10. Energy & Power
11. Power
12. Cavitations & Throttle
point13. Hydraulic Fluid
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1. Pressure
Pressure (symbol: p) isthe forceper unit areaacting on a surface in adirection perpendicularto that surface.
Mathematically:where:
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A
p
F
Area of doubleacting cylinder
= (d/2)
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example
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2. Pressure Transmission
If a force F1 acts at area A1 on anenclosed liquid, a pressure pisproduced which extendsthroughout the whole of the liquid(Pascals Law).
This will cause a same pressure
acting at every point of the closedsystem.
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example
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3. Power Transmission
If same pressure applies at every point in a closedsystem, the shape of the container has no significance.
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example
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Therefore
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4. Displacement Transmission
If load F2 is to be lifted to a distance s2, Piston 1 must be displace atdistance s1, at a specific quantity of liquid which lifts the Piston 2 by adistance s2.
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example
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5. Pressure Transfer
The pressure P1 exerts F1 force on area A1 which is transferred thru piston rod ontothe small piston. Force F1 will acts on area A2 and produces pressure P2. Sincepiston area A2 is smaller than piston area A1, the pressure P2 will be greater thanthe pressure P1.
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example
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6. Flowrate
Flow rate is the term used to describe the volume of liquid flowingthrougha pipe in a specific period of time.
For example, approximately one minute is required to fill a 10 literbucket from a tap. Thus, the flow rate amounts to 10 l/min.
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6. Flowrate
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Other derivation
Well have
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7. Pressure Measurement
To measure pressures in the lines or at the inputs and outputs ofcomponents, a pressure gauge is installed in the line at theappropriate point.
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1. Laminar flowfluid moves through thepipe in cylindrical layers
order.
8. Type of flow
2. Turbulence flowwhen flow velocity of fluidrises above a certain point
the fluid particles stoptomove in ordered layers.
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Reynolds number (Re).
A method of calculating the type of flow ina 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 < 2300turbulent flow: Re > 2300
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Reynolds number (Re).
The value 2300 is termed the critical Reynoldsnumber(Recrit) for smooth round pipes.
Turbulent flow does not immediately become laminar onfalling below (Recrit). The laminar range is not reached
until (Recrit).
To prevent turbulent flow causing considerable frictionlosses in hydraulic systems, (Recrit) should not beexceeded.
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Example:
1
2
3
41. 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
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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 ina 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.
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The energy of a hydraulic system is madeup of several forms of energy.
Static
Potential energy
Pressure energy
Dynamic
Motion energy Thermal energy
10.Energy & Power
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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. (alsoknown as kinetic energy)
Thermal energy: is the energy required toheat a body (or a liquid) to a specifictemperature.
In hydraulic installations, part of theenergy is converted into thermal energyas a result of friction. This leads to
heating of the hydraulic fluid and of thecomponents. Part of the heat is emittedfrom the system, i.e. the remainingenergy is reduced. The consequence ofthis is a decrease in pressure energy.
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11.Power
Power is usually defined as work or a change inenergy per unit of time.
Hydraulic power is calculated from the pressure
and the flow rate.
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Example
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Efficiency
The input power in a hydraulic system does not correspond to the outputpower since line losses occur. The ratio of the output power to the inputpower is designated as efficiency (h).
In practice, distinction is made between volumetric power loss caused byleakage losses and hydro-mechanical power loss caused by friction. In thesame 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 frictionin pumps, motors, and cylinders.
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Example
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12.Cavitations & Throttle point
Refers to the releasing of thesmallest particles from the surface ofthe material.
Motion energy is required for anincrease in flow velocity of the oil at anarrowing. This motion energy is
derived from the pressure energy.Because of this, pressure drops atnarrow points may move into thevacuum range.
From a vacuum of 0.3bar onwards,dissolved air (Gas bubbles) are
formed. If the pressure now risesagain as a result of a reduction inspeed, the oil causes the gasbubbles to collapse.
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13.Hydraulic Fluid
Hydraulic fluids represent the medium for powertransmission.
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
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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
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Viscosity
can be defined as resistance to flow. The viscosity of a
liquid indicates its internal friction.
Ball Viscometer
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Tank, Piping & CouplingChapter 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 whensupplying and relieving consuming devices (e.g. cylinders, hydraulic fluidreservoirs)
the place of application the circulation time.
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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 farbeneath 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 settlingtime for the oil and, therefore, makes possiblemore effective separation of dirt, water andair.
Base plate The base of the tank should slope down to the
drain screw so that the deposited sediment andwater can be flushed out.
Ventilation and exhaust (air filter)
To balance the pressure in case of afluctuating oil level, the reservoir must beventilated and exhausted. For this purpose, aventilation filter is generally integrated into thefiller cap of the feed opening.
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Piping (Flexible Hoses)
These are flexible line connections which are used between mobilehydraulic 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 carrieris 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 pipelinesmay be additionally protected against mechanical damage by external spirals or plaited material.
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Installation of Hose Lines
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Coupling
Hose lines may either be connectedto the various pieces of equipment orelse connected together by means ofscrew fittings or quick connectioncouplings.
Hose support connectors ensure thatconnections do not affect operation:
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HYDRAULICPUMPChapter 4
The pump in a hydraulic system, also known as a hydraulic pump, converts themechanical 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.
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The Basic Concept
Low pressure
High pressure
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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
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TYPE OF HYDRAULIC PUMP
External Gear Pump Internal Gear Pump Single Chamber
Double Chamber Radial Piston Pump Axial Piston Pump
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Gear Pump: Working Principle
Volumeincrease
From tank
To hydraulicsystem
Volumeincrease
Fromtank
Tohydraulicsystem
Internal gearExternal gear
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Working Operation(Gear Pump)
The suction area S is connected to the reservoir. Thegear pump operates according to the followingprinciple:
One gear is connected to the drive, the other isturned by the meshing teeth. The increase in volumewhich is produced when a tooth moves out of a mesh
causes a vacuum to be generated in the suctionarea. The hydraulic fluid fills the tooth gaps and isconveyed externally around the housing intopressure area P. The hydraulic fluid is then forcedout of the tooth gaps by the meshing of teeth anddisplaced into the lines.
Fluid is trapped in the gaps between the teethbetween suction and pressure area. This liquid is fedto the pressure area via a groove since pressurepeaks may arise owing to compression of the trappedoil, resulting in noise and damage.
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Rotary Vane: Working Principle
Volumeincrease
Volumeincrease
From tank
To hydraulicsystem
From tank
To hydraulicsystem
Single chamber Double chamber
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Piston Pump: Working Principle
compressionFrom tank
To hydraulicsystem
Radial chamber Axial chamber
From tankTo hydraulicsystem
compression
From tankHyd sys
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PumpSpecification
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Assignment 2
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Working operation for:1. Internal Gear Pump,
2. Vane Pump and
3. Piston Pump
H d li A
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There are two basic types of hydraulic actuator:
Rotary actuator
(motor / rotary)
Linear actuator
(cylinder)
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Hydraulic ActuatorChapter 5
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Hydraulic Motor (Rotary Movement)
Hydraulic motor comes various type sameas hydraulic pump. It working operationare similar.
Gear motor
Vane motor
Piston motor
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Linear Actuator (Linear Movement)
Single Acting Cylinder Double Acting Cylinder
There are two basic types of hydraulic cylinder single-acting and
double-acting cylinders.
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Type of Linear Actuator
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Type of Linear Actuator
Di t ib ti V l
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Distribution ValveChapter 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 powercomponents and the manner in which these stop. Directional control valves areshown 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
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Symbols for directional
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Symbols for directionalcontrol 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.
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The switching position of a directional control valve can be changed by variousactuation methods, such as push button, pedal, lever with detent, a spring is alwaysnecessary for resetting.
Methods of Actuation
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Port Designation
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Type of Distribution Valve (symbol)
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Working Principle
2/2 way valve, Normally close
Release position Press position
C
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Circuit Example
Release 2/2 WV Cylinder ExtendPressed 2/2 WV Cylinder Retract
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Basic Construction of 3/2 way valve
(3/2 way valve N.C)
C
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Basic Construction of 4/2 way valve
B i C i f / l
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Basic Construction of 4/3 way valve
(4/3 way valve, mid positionpump re-circulating)
B i C i f l
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Basic Construction of valve
(2/2 way valve N.C)
(3/2 way valve N.C) (4/3 way valve, mid positionpumpre-circulating)
Conversion of Valve
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Conversion of Valve
Pressure Valve
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Pressure ValveChapter 7
Pressure valves have the task of controlling and regulating the pressure in ahydraulic system.
Pressure relief valvesThe pressure in a system is set and restrictedby these valves. The control pressure issensed at the input (P) of the valve.
Pressure regulatorThese valves reduce the output pressure where thereis a varying higher input pressure. The controlpressure is sensed at the output of the valve.
Symbol
2 way pressure regulator 3 way pressure regulatorPressure relief valves
Working Principle
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Working Principle(pressure relief valve)
Working Principle
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Working Principle(2 way pressure regulator)
Working Principle
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Working Principle(3 way pressure regulator)
B i C t ti
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Basic Construction
Pressure Relief Valve
2 Way Pressure Regulator
3 Way Pressure Regulator
Flow Valve
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Flow ValveChapter 8
IntroductionFlow 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.
W ki P i i l
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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 asingle direction dependent on flow. In the opposite direction, the full cross-sectional flow isreleased and the return flow is at full pump delivery. This enables the one-way flow controlvalve to operate.
Control Not control
Circuit Example
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Circuit Example(One way flow control valve)
Fluid is blockby check valve
Fluid enter cylinderwith normal flow
Fluid have to flowthrough throttle valve
Extend slow
Circuit Example
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Circuit Example(One way flow control valve)
Fluid is blockby check valve
Fluid enter cylinderwith normal flow
Fluid have to flowthrough throttle valve
Retract slow
Working Principle
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Working Principle
Throttle Valve Flow control valves
influence thevolumetric flow of thefluid in both directions.
Control flow in both direction
Circuit Example
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Circuit Example(Throttle valve)
Extend & Retractslow
Block Valve (Non Return Valve)
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Block Valve (Non Return Valve)Chapter 9
Check Valve
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Check Valve
Check valves can stop the flow completelyin one direction. In the opposite directionthe flow is free with a minimal pressure
drop due to the resistance of the valve.
Spring loaded Spring un-loaded
De lockable Valve
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De-lockable Valve
In de-lockable valve, flow can be released in the closed position by pilot control ofthe 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.
Circuit Example
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Circuit Example(De-Lockable valve)
Signal x mustbe connected to tankIn order to release
pressure at port x.
Uses when cylinderis vertically install
Circuit Example
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Circuit Example(De-Lockable valve)
Change inputTo suiteexisting valvewith practical task
Shuttle Valve
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Shuttle Valve
This shuttle valve has two inlets X and Y and oneoutlet A. If Hydraulic fluid is applied to the first inlet X,the valve seals the opposing inlet Y, the fluid flowsfrom X to A. Inlet X is closed, if fluid passes from Y toA. A signal is generated at the outlet. When the Fluidflow is reversed, i.e. a cylinder or valve is exhausted,the seat remains in its previously assumed positionbecause of the pressure conditions. This valve is alsocalled an OR element.
X Y
A
X Y A
0 0 0
0 1 1
1 0 1
1 1 1
TRUTH TABLE
De lockable Double Non Return Valve
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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 isblocked 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 theright 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 fromA2 to B2).
Circuit example
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Circuit example
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Electro-Hydraulic SystemChapter 10
Malaysian Spanish Institute
MSI Electro-Hydraulic System
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Schematic
Design Of An
Electro-HydraulicSystem
MSI Electro-Hydraulic System
Electro Hydraulic Overview
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Hydraulic Pump
Pushbutton
Cylinder
PowerSupply
Pushbutton
Relay,Timer,Solenoid
Electro-Hydraulic Overview
From electro
Electro Hydraulic Automatons
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Electro Hydraulic Automatons
Switchingcontrol
Manualactuation
Electricalactuation
Content of Electro-Hydraulic
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Content of Electro-Hydraulic
Safety precaution
Introduction
Advantages
Comparison
Electrical Fundamental
Electrical Input Element
Sensor
Relay
Solenoid
Electrical Timer
Sequence Control
MSI Electro-Hydraulic System
Safety Attitude (LAB)
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Safety Attitude (LAB)
MSI Electro-Pneumatic System
1. Pneumatic safety must be apply2. DO NOT wear sandals, wear covered shoes (SAFETY BOOT)3. DO NOT wear excessive jewelry4. DONOT 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 time7. DO NOT disturb people who are conducting experiments! (or any time)8. NO eating or drinking inside the lab /NO sitting while doing practical.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 equipmentshould be attended by trained personnel only. DO NOT do it on yourown.
Introduction
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Introduction
Electro-Hydraulic Systemsare made up ofhydraulic and electrical components:
The movements and forces are generated by
Hydraulicmeans (e.g. by cylinders).
Signal input and signal processing, on the other hand,are effected by Electricaland Electroniccomponents (e.g. electromechanical switching
elements or stored-program controls).
MSI Electro-Hydraulic System
Advantages
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Advantages
MSI Electro-Hydraulic System
Electrical signals can be transmitted viacablesquickly and easilyand over great distances. Mechanical signal transmission (linkages,cable-pulls) or hydraulic signal transmission (tubes, pipes) are farmore complex.
In the field of automation, signal processing is generally effectedby electrical means. This enhances the options for the use ofelectro-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 lesscomplex and more economical than a mechanical or hydrauliccontrol system.
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Comparison
Electrical Fundamental
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Electrical Fundamental
The relationship between voltage, current strength and resistance isdescribed by Ohms law. Ohms law states that in a circuit with constantresistance the current strength changes in proportion to the change involtage:
if the voltage increases, the current strength also increases.
if the voltage falls, the current strength also decreases.
Electrical power
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In the field of mechanical engineering, power can be defined in terms of thework performed. The faster a task is performed, the greater the requiredpower. Power therefore means work per unit of time.
In the case of a consuming device in a circuit, electrical energy is convertedinto kinetic energy (e.g. electrical motor), light radiation (e.g. electrical lamp)or thermal energy (e.g. electrical heater, electrical lamp). The faster theenergy is converted, the greater the electrical power.
Electrical power
Power Supply
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A power supply unit consists ofthe following modules:
the mains transformer whichtransforms the alternatingvoltage 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 andthe capacitor C.
the direct voltage is thenstabilized by the in-phase
regulator.
Power Supply
Conversion AC to DC
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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 bestepped down to 24V and then rectified.
Conversion AC to DC
AC DC
Electrical input elements
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Electrical input elements
NORMALLY OPEN CONTACTcircuit is open when the push-button is in the normal position
Electrical input elements
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Electrical input elements
NORMALLY CLOSED CONTACTcircuit is closed when the push-button is in the normal position
Electrical input elements
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Electrical input elements
CHANGEOVER SWITCHThese contacts combine thefunctions of normally closed and normally open contacts in one unit.
Circuit example
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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.
Practical
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(Electrical Input Element)
AndFunction
OrFunction
AndFunction
OrFunction
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
Sensor Limit switch
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Sensor Limit switch
A mechanical limit switch is anelectrical switch which is activatedwhen a machine part or a workpieceis in a certain position.
Normally open limit switch
1-4
Normally closed limit switch1-2
Sensor Pressure switch
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Sensor Pressure switchrequires a pressure to activated the sensor
the pressure acts on a cylinder surface (x).If the pressure exerted exceeds the springforce of the return spring, the piston movesand operates the contact set.
Normally open limit switch1-4
Normally closed limit switch1-2
Circuit Example
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Circuit Example
Relay
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Relay
Relays are electromagneticallyactuated switches.
They consist of a housing withelectromagnet and movablecontacts.
An electromagnetic field is createdwhen 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 contactassembly.
This contact assembly can open orclose a specific number of contacts
by mechanical means. If the flow of current through the coil
is interrupted, a spring returns thearmature to its original position.
Concept of a Relay(El t t)
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(Electromagnet)
An electromagnet is a type of magnetin which themagnetic fieldis produced by the flow of an electriccurrent. The magnetic field disappears when the currentceases.
Working Principle
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o g c p e
Relay
1 pole
Relay2 pole
Example
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p
Circuit Example
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p
Direct Control In-direct Control
9. Solenoids
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In electro-hydraulics, valves are actuated via solenoids. It has thesame concept of electromagnet.
solenoid
Directional control Valve
Circuit Example
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p
Electromechanical Switching Element(Symbol)
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(Symbol)
Holding Element / Latching
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g g
S1 H1 ONS2 H1 OFF
S1
S2
k1
K1
k1
Electrical Timer
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A timer is used to control the sequenceof an event or process.
Two type of timer1. Delay-On Timer
2. Delay-Off Timer
Electrical Timer
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S15secH1 ONS2 H1 OFF
24V
0V
S1
S2
K1
K1
T1
K1
H1
T1
The Coil with ON delay activates itsassociated contacts when current isapplied.
Electrical Timer
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S1 H1 ONS25secH1 OFF
The Coil with OFF delay deactivatesits associated contacts when currentis applied, but only after the presetdelay.
24V
0V
S1
S2
K1
K1
T1
K1
H1
T1
Electrical Timer
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24V
t
S1
0V
H1
Timer for Practical installation
Note:For ON Delay:Select selector toDES.
For OFF Delay:Select selector toCON.
Electro Hydraulic System
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y y
Hydraulic Circuit Diagram /
Power Circuit /
Schematic Diagram
Control Circuit Diagram /
Electrical Circuit Diagram
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D END
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