03 basic hydraulic system v5

8/2/2019 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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2MSI Hydraulic System

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


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


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


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


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


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)

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.


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Introduction to Hydraulic Systemchapter1

Hydraulic means the generation of forcesand motionusing hydraulicfluids. 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


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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


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:


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


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


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.

61



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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

65

MSI Pneumatic System

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)


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


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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B i C i f / l


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(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


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




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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).


Advantages


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Advantages


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



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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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NORMALLY OPEN CONTACTcircuit is open when the push-button is in the normal position



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NORMALLY CLOSED CONTACTcircuit is closed when the push-button is in the normal position



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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

03 basic hydraulic system v5

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