Post on 04-Jun-2018
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What is Fluid Power?
Fluid poweris energy transmitted and controlled bymeans of a pressurized fluid, either liquid or gas. Theterm fluid power applies to both hydraulics andpneumatics.
Hydraulicsuses pressurized liquid, for example, oil orwater;
Pneumaticsuses compressed air or other neutralgases.
Fluid powercan be effectively combined with othertechnologies through the use of sensors, transducersand microprocessors.
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The basic components of a fluid power system ,
regardless of whether the system uses a hydraulic or a
pneumatic medium are as follows:1. Reservoir or receiver
2. Pump or compressor
3. Lines (pipe, tubing, or flexible hose)
4. Directional control valve5. Actuating device
COMPONENTS OF FLUID POWER
SYSTEM
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The reservoir serves many functions
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Bafflesare used in the interior of reservoirs to
direct flow to maximize the distance the fluid
must travel between the return line and the
pump inlet line
Slows the movement of the fluid
Increases cooling
Increases separation of solid particles, air, and
water
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Typical reservoir construction
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FLUID LINES
Lines are used to transfer the fluid, and fittings are used to connect the lines to the powersource and the points of application
Pipe, tubes and hoses, along with the fittings orconnectors, constitute the conducting lines thatcarry hydraulic fluid between components
For Pneumatic Systems, no return path for thefluid, which is air, is needed, since it can be directlyreleased into the atmosphere
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Conductors must have:
Adequate strength to withstand high system pressures
Low flow resistance to assure low energy loss duringsystem operation
A design that allows economic installation and low
maintenance
Conductors must not only withstand normal system
operating pressure, but also hydraulic shock pressures
Shock pressures result from kinetic energy in the
system when:oDirectional control valves are shifted to reverse the
movement of a load or heavy machine member
oActuators encounter sudden load changes
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Tubing:
Is a relatively thin-walled, semirigid conductor
Can be bent and shaped into lines that providegood flow characteristics with a minimum of
visual clutter
Tubing can be bent, unlike pipe
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Hose is a flexible conductor made up of:
Inner tube to conduct the fluid
Middle layer of reinforcing material for strength Outer protective coating to withstand abrasion
and abuse
Hose providesflexibility
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They have the following primary tasks:
o Power transmission (pressure and motiontransmission)
o Signal transmission for control
Secondary tasks:
o Lubrication of rotating and translatingcomponents to avoid friction and wear
o Heat transport, away from the location of heatgeneration, usually into the reservoir
o Transport of particles to the filter
o Protection of surfaces from chemical attack,
especially corrosion
Hydraulic fluids - tasks
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Functional
o Good lubrication characteristics
o Viscosity should not depend strongly ontemperature and pressure
o Good heat conductivityo Low heat expansion coefficient
o Large elasticity modulus
Economic
o Low price
o Slow aging and thermal and chemical stability
long life cycle
Hydraulic fluids - requirements
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Availability
Easily stored in large volumes
Simplicity in design and control Provides linear and rotary movement
Installation
Low system cost due to low component cost
Properties of Compressed Air
Components have long working life
resulting in longer system reliability
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PUMPS
The purpose of a hydraulic pump is to supply a flow offluid to a hydraulic system.
A pump must have a continuous supply of fluidavailable to the inlet port to supply fluid to the system.As the pump forces fluid through theoutlet port, a partial vacuum or low-pressure areais created at the inlet port. When the pressure at theinlet port of the pump is lower than the local
atmospheric pressure, atmospheric pressure actingon the fluid in the reservoir forces the fluid intothe pumps inlet.