Fluid Power Application

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Fluid Power Application

Hydraulics & Pneumatics KMD 3133

By,

Mohd Shukri Bin Yob

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What is Fluid Power?

Technology that deals with the generation, control, and transmission of power using pressurized fluids.

The muscle that moves industry. Most modern machines driven by it.

Applications, fluid power steering & brakes automobiles,

drives machine tools, controls airplanes, moves earth (excavation), even drills teeth.

Power Steering

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Braking System

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Wing of an aircraft5

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Fluid Transport? or Fluid Power?

Should be realized that there are actually 2(two) different types of fluid systems.

1. Fluid transport Sole objective is to deliver a fluid from one

location to another to accomplish some useful purpose.

2. Fluid power Designed specifically to perform work.

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Fluid Power

The work is accomplished by a pressurized fluid acting on a fluid cylinder or fluid motor. A fluid cylinder produces a force. A fluid motor produces a torque. Fluid cylinders & motors provide the muscle

to do desired work.

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Fluid Power - History

Known as hydraulics & pneumatics due to the working fluid can either be liquid or gas.

Working on the Pascal’s Law “Pressure is transmitted undiminished in a

confined body of fluid” Pascal found that when he rammed a cork into

a jug completely full of wine, the bottom of the jug broke and fell out.

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Pascal’s law indicated that the pressures were equal at the top and bottom of the jug, however, the jug has a small opening area at the top and a large area at the bottom, thus the bottom absorbs greater force due to its larger area.

Pressure

Pressure Transmitted

Acting Area 2

Acting Area 1

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While Bernoulli developed his law of conservation of energy for a fluid flowing in a pipeline.

Pascal’s & Bernoulli’s law is the working principle of all fluid power applications and are used for analysis purposes.

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Fluid Power – Hydraulics

Hydraulics Systems Uses liquids such as mineral oils, water, synthetic oils,

even molten metals. Water was the 1st hydraulic fluids

Not very suitable due to several deficiencies, such as freezes, poor lubricant & corrosive characteristics.

Oils are superior and widely used. Liquids provides very rigid medium (uncompressible)

for transmitting power & thus provides huge forces moving loads (with accuracy & precision)

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Fluid Power – Pneumatics

Pneumatics Systems Uses air as the gas medium due to abundant

supply and can be readily exhausted to the atmosphere.

Other gasses are not favorable due to cost, efficiency reasons but might be considered for special/critical purposes, should there be.

Gas exhibits spongy characteristics due to compressibility of gas.

However it is less expensive to build, operate & maintained.

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Applications

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Applications

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Advantages of Fluid Power

3 basic methods of transmitting power; Electrical Mechanical Fluid Power

Efficient overall system – using combination of all above.

Fluid systems can transmit power more economically over greater distance than mechanical system. However, restricted to shorter distances compared to electrical systems

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Fluid power secret is its versatility and manageability.

Not constrain to the physical geometry of the machine compared to mechanical systems. E.g. automotive braking systems.

Power transmitted in almost limitless quantities.

Not constrained by the physical limitation of materials such in an electrical systems. (E.g. Electromagnets, depends on saturation limit of steel)

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Main advantages of Fluid Power systems are:1. Ease and accuracy of control.

2. Multiplication of force.

3. Constant force or torque.

4. Simplicity, safety & economy.

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Drawbacks of Fluid Power

In spite of all highly desirable of fluid power, it is not the answer of all power transmission problems. Hydraulics oil are messy. Leakage is virtually impossible to eliminate

completely. Safety issue – hydraulics lines might burst

resulting to injuries if proper design are not implemented.

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Applications of Fluid Power

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Pneumatic powered Dextrous articulated artificial limb

Courtesy of ,

Shadow Robot Company

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Pneumatic powered artificial muscle. Air Muscle, Courtesy of Shadow Robot Company

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Components of a Fluid Power System (Hydraulic System) 6(six) components

1. Tank (reservoir) – holding the liquid/storage.

2. Pump – force liquid

3. Electric motor -drive the pump.

4. Valves –direction, pressure & flow rate.

5. Actuators – convert energy

6. Piping – Carries the liquid

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Components of a Fluid Power System (Hydraulic System)

Figure 1-21

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Figure 1-20

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Complexity of hydraulic-depending applications Complete packaged power system containing:

1. Electric motor

2. Pump

3. Shaft coupling

4. Reservoir (oil tank)

5. Miscellaneous piping, pressure valves and

6. Other components -such as pressure gages.

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Figure 1-22

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Components of a Fluid Power System (Pneumatic System) There are also 6(six) basic components

1. Air Tank (reservoir) – storing compressed air.

2. Compressor – Compresses air

3. Electric motor –drive compressor

4. Valves – direction, pressure & flow rate.

5. Actuators – convert energy

6. Piping – distribute

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Components of a Fluid Power System (Pneumatic System)

Fig 1-23

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Complexity of pneumatic –depending applications

Self-contained pneumatic power unit is consist;

Electric motor Compressor Shaft coupling Reservoir (Air tank) Miscellaneous piping, pressure valves and Other components -such as pressure gages.

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Should be noted;

Pneumatic-air exhausted back to the atmosphere

Hydraulic- drains back to th reservoir,reused, filter

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Closed-Loop vs. Open Loop System

Fluid powerclosed-loop open-loop type.

Closed-loop System feedback. difference between command signal feedback

signals, action will be taken automatically to correct servo systemsservo systems, valves used to direct fluid are

typically called servo valves.

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Open-loop System Not using feedback. Individual components No input / output compensation occur. Most hydraulic circuits are of the open-loop type,not

complex ,precise Errors due to slippage Example,

Leakage past seals inside pumps due to viscosity change of fluid which affected to the rise of operating temperature.

Leading to pressure and speed of actuators to drop.

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Documents

Fluid Power Application