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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.