Basic Types of Compressors

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Basic Types of Compressors

Fawaz S. Al-Mozayen

M & C M EngineerReliability & Plant support


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What is Compressor ?

1- A device used for the movement of gas as per systemrequirement.

2- Compressor is a mechanical device that increases the

pressure of a gas by reducing its volume. Compression of agas naturally increases its temperature.

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Types of Compressors:

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Type of

compressor

Positive

displacementDynamic

Reciprocating Rotary Centrifugal Axial


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Reciprocating Compressor: use pistons driven by a crankshaft. They can be eithersingle or multi-staged, horizontal [lubricated] or vertical (labyrinth) [non-lubricated]or V-shape.

Rotary Screw Compressor: use two meshed rotating positive-displacement helicalscrews to force the gas into a smaller space.

Axial Flow Compressor: use a series of fan-like rotating rotor blades to compress thegasflow. Stationary stator vanes redirect the flow onto the next set of rotor blades.Axial-flow compressors are normally used in high flow applications, such as mediumto large gas turbine engines.

Centrifugal Compressor: Use impeller in a shaped housing to force the gas to the eyeof the impeller, increasing the velocity of the gas. A diffuser (or volute) converts thevelocity energy to pressure energy.

Diaphragm Compressor: used whenever there is potential of safety or environment.

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http://www.gotoppi.com/oldsite/fig1.htm


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Centrifugal Compressor:

1- Casing (volute/diffuser).2- Shaft & impeller.

3- Diaphragms.4- Guide vanes.

5- Seals.6- Bearings.

7- Balance drum.

8- Lubrication system.

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Types of impellers:

Used for high headsand small to largeflow in single stagecompressors only.

Used for large flow,usually in singlestage compressors,or as the first stagein multi-stagecompressors.

Used mainly in multi-stage compressors.

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Guide vanes:

1- To guide the flow of gas efficiently into the eye of theimpeller.

2- Adjustable type guide vanes are used to control thecapacity.

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Balancing Drum:

The pressure on discharge side is higher.

This causes an axial force that pushes the shaft towardssuction end.

Thrust bearing takes care of this axial thrust in lowpressure compressors.

When axial thrust is too great, a balancing drum is usedto equalize thrust.

Balancing drum is attached to the discharge end ofcompressors.

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Volute Casing:

a gradually widening section of the housing thatsurrounds the impeller and that gradually reduces thevelocity of the gas stream as the stream leaves theimpeller. The volute converts the velocity to pressureand directs the flow to the compressor outlet.

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Comparison:Type of compressor

/ comparison

Centrifugal reciprocating

Speed High (driver) Low (pulsating)

Maintenance time short / easy Long (valves) / difficult

Pressure Low High

Starting Need priming Self primed

Design Simple (cheaper) complicated

Noise Low high

Volume discharge High Low (fixed) / big cylinder /stages

Efficiency Less More (expensive)Flow characteristics Steady flow Pulsating (pipe design)

Maintenance Cost Less more

Discharge side Check valve Relief valve

Reliability High Less

Location / foundation Elevation Lower level / heavy12


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Thank you

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Basic Types of Compressors

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