RECIPROCATING OR PISTON COMPRESSOR

What is a reciprocating compressor?
The reciprocating compressor is classified within the positive displacement compressors since it absorbs the gas and puts it into a chamber of smaller size or volume, reducing the space it uses, increasing its pressure through a connecting rod-piston mechanism.

Reciprocating compressor

Parts of a reciprocating compressor
A compressor can have an endless number of components and each one fulfills a specific function, but this time we will only talk about the components that are essential for its operation.

Intake valve: It is in charge of absorbing the gas to be compressed
Eject valve: Ejects the compressed gas, either to a new stage of the compressor or to the outside.
Piston: This component works together with a connecting rod and is responsible for compression.
Compression chamber or cylinder: It is the space used to house the gas and to be compressed
Crankshaft: it serves for the connecting rod-piston mechanism to move back and forth.
Engine: its function is to transmit the rotary movement towards the crankshaft.
Alternative compressor parts

How does a reciprocating compressor work?
The principle of operation of this type of compressor is quite simple, since it is based on the reciprocating movement (back and forth of a piston). Although it should be noted that understanding the operation of a complete compressor is much more complicated since it incorporates components such as: sensors, valves for other operations, lubrication system, silencers, dampers, etc.

These compression machines are made up of four main stages.

Compression cycle

Compression
This stage arises when the intake and exhaust valves are closed and the piston stroke goes up to decrease the volume of the compression chamber and thus compress the gas.

This stage is the first to be executed because there is the possibility that some gas is trapped before starting operation. and thus it can be expelled before absorbing the material to work.

Compression

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When the gas in the compression chamber generates a higher pressure than in the discharge pipe, the expulsion valve opens, thus releasing the contents of the chamber.

When the discharge arises, a small space remains between the piston head and the end of the compression chamber, a little gas remains between this space and this phenomenon is known as Clearance volume or dead volume.

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Expansion
As the cylinder recoils, the dead volume expands and therefore the pressure decreases and the next step originates.

Expansion

Admission
At this stage the pressure inside the compression chamber is less than in the inlet valve pipe, this causes it to open allowing gas access. When the chamber reaches the same pressure as the intake pipe the valve closes.

Compressor intake

Types of a compressor
There are different ways of classifying reciprocating compressors.

By stages
These compressors can have more than one compression stage, each of which repeats the compression process, thus increasing the pressure of the gases.

Simple stage
They are practically the simplest compressors since they are made up of a piston, cylinder and crankshaft. Their compression level is low and they are used where the use of compressed gas is intermittent and low flow.

simple stage

Multi stage
We can find different compressors from two to six stages maximum. Each of the stages repeats the same compression process, therefore a higher pressure is generated in each phase. It should be noted that the number of stages is not proportional to the number of pistons and that between each stage the gas is cooled with either air or water.

Multistage

Single and double acting
There are compressors in which the working area is limited to one side of the piston and for each cycle (raising and lowering the piston) it only compresses once, these are called single-acting.

There are also other compressors that have two compression chambers in a single cylinder and for each cycle the piston makes it compresses twice when it rises and the other when it descends. These are known as double effects.

Simple effect