Introduction to Fluid Drive System (2)

8/2/2019 Introduction to Fluid Drive System (2)

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Semester 6 Year 3

3 Credits

Monday & Friday 800 950

FKP-B-M-04

Mohamad Farid bin Mohamad Sharif


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Course SynopsisThis course introduces fluid drive system, includingfluid power component functions.

This course also design and build drive system toperform specific requirements.


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Course Outcomes Realize fluid power component functions

Design and build hydraulic system to perform specific

requirement Design and build pneumatic system to perform

specific requirement


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Assessment Methods Test 1 20%

Test 2 20%

Laboratory 30% Project 30%

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Total 100%

*Attendance less than 80% will be -10

*Door will be locked 10 min after class start.


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Fluid Drive System In automotive and construction equipment,

Hydraulic and Pneumatic a method oftransmitting power from one place to another through

the use of a fluids. Certain physical laws or principles apply to all f luids.

HYDRAULICS branch of science that deals with thestudy and use of liquids as related to the mechanical

aspects of physics. PNEUMATICS branch of science that deals with the

study and use of air and other gases as related to themechanical aspects of physics.


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Introduction The word "hydraulics" originates from the Greek word

(hydraulikos) which in turn originates from (hydor, Greek for water) and (aulos,meaning pipe).

Hydraulics can be defined as that branch of engineeringscience that pertains to liquid pressure and flow.


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Hydraulic Application


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Hydraulic Cylinder


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Hydraulic Characteristics The extensive use of hydraulics to transmit

power is due to the fact that a properly constructedhydraulic system possesses a number of favourable

characteristics, such as:1) Eliminates the need for complicated systems using

gears, cams, and levers.

2) Motion can be transmitted without the slack

inherent in the use of solid machine parts.3) The fluids used are not subject to breakage as are

mechanical parts.

4) Hydraulic system mechanisms are not subjected to

great wear.


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Hydraulic Characteristics5) If the system is well-adapted to the work, it can

provide smooth, f lexible, uniform action withoutvibration and is unaffected by variation of load.

6) Hydraulic systems can provide widely variablemotions in both rotary and straightline transmission of power.

7) The need for control by hand can be minimized. Inaddition, they are economical to operate.


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Basic Principles of HydraulicThe basic principles of hydraulics are few andsimple, such as:

1) Liquids have no shape of their own.2) Liquids will NOT compress.

3) Liquids transmit applied pressure in all directions.

4) Liquids provide great increase in work force.


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Pressure and Force The terms force and pressure are used extensively

in the study of fluid power.

Force

a total push or pull. It is push or pull exertedagainst the total area of a particular surface.

Pressure an amount of push or pull (force) appliedto each unit area of the surface and is expressed in

N/m2

or Pa or bar. Pressure may be exerted in one direction, in several

directions, or in all directions.


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Incompressibility and Expansion of

Liquids For all practical purposes, liquids are incompressible

Liquids expand and contract because oftemperature changes.

When liquid in a closed container is subjected to hightemperatures, it expands and this exerts pressure on thewalls of the container.

Therefore, it is necessary that pressure relief mechanisms

and expansion chambers be incorporated into hydraulicsystems.

Without these precautionary measures, the expandingliquid could exert enough pressure to rupture the system.


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Pascals Law Pascals law tells us thatpressure on a confined

fluid is transmitted undiminished in everydirection, and acts with equal force on equal areas,throughout the confining vessel or system.

According to Pascals law, any force applied to aconfined fluid is transmitted in all directionsthroughout the fluid regardless of the shape of thecontainer.


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Pascals Law


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Multiplication of Forces Some hydraulic systems are used to multiply force.

In below figure, notice that piston 1 is smaller than piston 2.Assume that the area of the input piston 1 is 2 sq in (1290mm). With a resistant force on piston 2, a downward forceof 20 lbs (88.96 N) acting on piston 1 creates 10 psi (68.96kPa) in the fluid.

F1 = F2

A1 A2


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Types of Hydraulic Fluids There have been many liquids tested for use in

hydraulic systems.

Currently liquids being

tested

include mineral oil,water, phosphateester,water-based ethylene glycolcompounds, and silicone fluids.

The three most common types of hydraulic fluids are;

1) petroleum-based2) synthetic fire-resistant, and

3) water-based fire-resistant


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Types of Hydraulic Fluids Petroleum-Based Fluids

The most common hydraulic fluids used in hydraulicsystems are the petroleum-based oils.

These fluids contain additives to protect the fluidfrom oxidation, to protect the metals fromcorrosion, to reduce the tendency of the fluid to foam,

and to improve the viscosity.


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Types of Hydraulic Fluids Synthetic Fire-Resistant Fluids

Petroleum-based oils contain most of the desired traits ofa hydraulic fluid.

However, they are flammable under normal conditionsand can become explosive when subjected to highpressures and a source of flame or high temperatures.

Non-flammable synthetic liquids have been developedfor use in hydraulic systems where fire hazards exist.

These synthetic fire-resistant fluids are phosphate esterfire-resistant fluid, silicone synthetic fire-resistant fluid.and the lightweight synthetic fire-resistant fluid


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Types of Hydraulic Fluids Water-Based Fire-Resistant FluidsThe most widely used water-based hydraulic fluidsmay be classified as water-glycol mixtures and water-synthetic base mixtures.The water-glycol mixture contains additives to protect itfrom oxidation, corrosion, and biologicalgrowth and to enhance its load-carrying capacity.Fire resistance of the water mixture depends on thevaporization and smothering effect of steam generatedfrom the water.The water in water-based fluids is constantly beingdriven off while the system is operating. Therefore,frequent checks are required to maintain the correct ratioof water to base mixture.


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Hydraulic System Components An arrangement of interconnected components is

required to transmit and control power throughpressurized fluid.

The number and arrangement of the componentsvary from system to system, depending on application.

In many applications, one main system supplies powerto several subsystems, which are commonly

referred to as circuits. The complete system may be a small compact unit; more

often, however, the components are located at widelyseparated points for convenient control.


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Hydraulic System Components The basic components of a f luid power system are

essentially the same, regardless of whether the systemuses hydraulic or pneumatic medium.

The basic components are as follows:1) Reservoir, 2) Strainers and filters, 3) Pumps Control

valves (directional and relief), 4)Actuating devices(cylinders), 5) Accumulators Motors Lines (pipe, tubing, orflexible hose), 6) Connectors and fittings, 7) Sealing

materials and devices Several applications of fluid power require only a simple

system; that is, a system which uses only a few componentsin addition to the basic components


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Introduction The word pneumatics is a derivative of the Greek

word pneuma, which means air, wind, or breath.

Pneumatics can be defined as that branch ofengineering science that pertains to gaseous pressureand f low.

Pneumatics is the portion of fluid power in which

compressed air, or other gas, is used to transmit andcontrol power to actuating mechanisms.


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Pneumatic Application


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Pneumatic Screwdriver1. Air tool (actuator)2. Air Hose 3/83. Oiler4. Pressure Regulator5. Filter

6. Shut Off Valve7. Lead Hose8. Coupler body and connector9. Drain daily10. 1/2or larger pipe and fitting11. Air Dryer (storage

tank/reservoir)12. 1 or larger pipe and fitting13. Air Compressor (pump)14. Auto Drain15. Drain daily


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Pneumatics Characteristics Gases differ from liquids in that they have no definite volume;

that is, regardless of size or shape of the vessel, a gas willcompletely fill it.

Gases are highly compressible, while liquids are only slightly so.

Also, gases are lighter than equal volumes of liquids, makinggases less dense than liquids.

Gases can be readily compressed and are assumed to be perfectlyelastic.

This combination of properties gives gas the ability to yield to a

force and return promptly to its original condition when theforce is removed. These are the properties of air that is used in pneumatic tires,

tennis balls, and other deformable objects whose shapes aremaintained by compressed air.


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Kinetic Theory of Gases At any given time, some molecules are moving in one direction,

some are travelling in other directions, and some may be in astate of rest.

The average effect of the molecules bombarding each container

wall corresponds to the pressure of the gas. As more gas is pumped into the container, more molecules are

available to bombard the walls, thus the pressure in thecontainer increases.

Increasing the speed with which the molecules hit the walls canalso increase the gas pressure in a container. If the temperatureof the gas is raised, the molecules move faster, causing anincrease in pressure.

This can be shown by considering the automobile tire. Whenyou take a long drive on a hot day, the pressure in the tiresincreases and a tire that appeared to be soft in cool morning

temperature may appear normal at a higher midday temperature.


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Boyle's Law When the automotive tire is initially inflated, air that

normally occupies a specific volume is compressed intoa smaller volume inside the tire.

This increases the pressure on the inside of the tire. Temperature is a dominant factor affecting the physical

properties of gases. It is of particular concern incalculating changes in the state of gases.

Therefore, the experiment must be performed at aconstant temperature. The relationship between pressureand volume is known as Boyle's law.

Boyle's law states when the temperature of a gas isconstant, the volume of an enclosed gas

varies inversely with pressure.


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Charles's Law Charles's law states that the volume of a gas is

proportional to its absolute temperatureif constant pressure is maintained.


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Pneumatic Gases Gases serve the same purpose in pneumatic systems as

liquids serve in hydraulic systems.

Therefore, many of the same qualities that areconsidered when selecting a liquid for a hydraulicsystem must be considered when selecting a gas for apneumatic system.


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Qualities The ideal fluid medium for a pneumatic system must be a

readily available gas that is non-poisonous, chemically stable,free from any acids that can cause corrosion of systemcomponents, and non-flammable.

Gases that have these desired qualities may nothave the required lubricating power. Therefore, lubrication of thecomponents must be arranged by other means.

For example, some air compressors are provided with alubricating system, some components are lubricated uponinstallation or, in some cases, lubrication is introduced into the

air supply line (in- line oilers). Two gases meeting these qualities and most commonly used in

pneumatic systems are compressed air and nitrogen. Sincenitrogen is used very little except in gas charged accumulators, we

will only discuss compressed air.


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Properties of Compressed Air1) Availability

2) Storage

3) Simplicity of design and control4) Choice of movement

5) Economy

6) Reliability

7) Resistance to environment

8) Environmentally clean

9) Safety


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The Basic Pneumatic System


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Air Production System The component parts are:

1) Compressor, 2) Electric Motor, 3) Pressure Switch,4) Check Valve, 5) Tank, 6) Pressure Gauge, 7) AutoDrain, 8) Safety Valve, 9) Refrigerated Air Dryer,10) Line Filter


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Air Consuming System The component parts are:

1) Air Take-off, 12) Auto Drain, 13) Air Service Unit,14) Directional Valve, 15) Actuator, 16) SpeedControllers


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Assignment 1What is the reason of taking Engineering?

Describe the difference between hydraulics andpneumatics.

Documents

Introduction to Fluid Drive System (2)