What is an Air Compressor? | What are the Types of Compressor?

compressor is a device that increases the pressure of a compressible fluid (i.e., air or gas) by reducing its volume. Gas compressors are most commonly used in different industries to transfer gas from one tank to another tank. The main objective of this article is to explain the air compressor working, types, and applications.

What is a Compressor?

The compressor is a mechanically operated machine that increases the air or gas pressure by reducing its volume. If the compressor uses gas as a working fluid, it is known as a gas compressor. However, if the air is used as a working fluid, it is known as an air compressor.

The air compressor gained worldwide recognition after its discovery in the year 1875. With the help of compressors, people could save time and money in almost every work. It was even found that these devices had a great impact on the lives of people. 

Air compressors take air from the environment and compress it. After compression, the compressed air is transferred to a storage tank.
You can supply compressed air from the reservoir wherever you need it. The air compression process requires some work; a prime mover is most commonly used to run the compressor.
Compressed air is used in a variety of applications, including air motors, jet engines, road drills, painters, starters, riveting machines, and pneumatic drills.

Air Compressor

How Does A Compressor Work?

The basic working principle of gas or air compressor can be easily understood. Basically, it works by reducing the volume of the gas or air. It uses a piston or diffuser to increase the pressure of the working fluid.

When the air enters the diffuser, it changes the speed of the air into pressure energy. In this way, a compressor compresses the gas or air.

After the compression process, the compressed air is transformed into a storage tank. Many industries have used compressors to increase production, which has led to the development of many new industries. The manufacturing of these machines was initially done using wood, but now many modern techniques and materials are being used to manufacture them.

Types of Air Compressors

The types of air compressors are given below:

  1. Positive Displacement Compressors 
  2. Dynamic Compressors

compressor types

1) Positive Displacement Air Compressor

It is one of the most famous types of the air compressor. The positive displacement compressors compress the air by sucking it into the compression chamber. It compresses the air until the air pressure reaches up to the desired level. The compressed air is then transferred to the desired area through pipelines.

The positive displacement compressors have the below-given types:

  • Reciprocating compressor
  • Rotary vane compressor
  • Rotary screw compressor
  • Scroll compressor

Positive displacement compressor types

1.1) Reciprocating Compressors

These types of air compressors use a piston or plunger that is driven by a crankshaft. This piston or plunger moves at a constant speed to suck and compress the air in the cylinder. Typically, one drive of the piston sucks the air in the cylinder, and the other drive squeezes it. The piston is linked to the crankshaft via a connecting rod.

The small reciprocating compressors have power from 5 to 30 horsepower. Such types of compressors are mostly found in the applications of automobiles and are generally used for intermittent operation. 

Large reciprocating compressors usually have more than 1000 horsepower and are commonly used in petroleum and large industrial applications. In large industries, reciprocating compressors are used for applications like chemical plants, industry, oil refineries, and natural gas processing and delivery.

Advantages and Disadvantages of Reciprocating Compressors
These are easy to maintain.These compressors produce high noise.
These are best for applications that need high pressure.It is highly vibrating equipment.
Highly efficient and flexible.It has a large size.
It has a simple design.These pumps can’t deliver constant flow.

1.2) Rotary Screw Compressors

The rotary screw compressor is one of the modern types of positive displacement compressors. In this compressor, the air is sucked into the compression chamber, closes the openings, and compresses the air with the help of two rotors that rotate continuously and run via the cavity. With each revolution, the air pressure gradually increases until it touches the desired pressure.

screw compressor

The classification of the screw compressors depends on the type of gearbox, the method of cooling, and the stage. These compressors are generally manufactured in dry variety, water, and oil-flooded types.

The rotary compressors efficiency is very dependent on the air dryer. Screw compressors have few components, high efficiency, large capacity, simple structure, voltage spikes, and low vibration, and can run at low speed to adjust power.

Advantages and Disadvantages of Rotary Screw Compressors
These don’t use a reciprocating piston.They have more costs than other positive displacement compressors.
These have higher efficiency than piston compressors.These also need high maintenance.
This compressor needs very low installation space.High precision.
It has less vibration than other types.It uses for special equipment processing.
It has high reliability.High service cost.
It has a long service life. 

1.3) Ionic Air Compressor

The ionic compressor is also called an ionic liquid piston pump. This is a liquid ionic piston-based hydrogen compressor, not a metal piston like a metal diaphragm piston compressor.

Advantages of Ionic Compressor
  • It doesn’t require a seal and bearings
  • It has a long service life
  • This type decreases energy consumption
  • It requires low maintenance

1.4) Rotary Vane Compressors

In the rotary vane compressor, two asymmetrical rotors (also known as spiral screws) are used for the compression of the air.

Rotary Vane Compressors

It consists of a rotor with a large number of vanes. These vanes are fixed into the radial groove of the rotor—the rotor fixes in a housing with a rounder or more complicated structure. 

When the rotor rotates, the vanes move inward and outward of the slot and contact the housing outside the wall. Thus, the rotor vanes create a series of maximizing and minimizing volumes. This compressor is the oldest technology of compressor.

The rotary vane compressors are used for different applications such as tire inflation in tires and wheel shops, dry cleaning and paint pumps, etc. 

Advantages and Disadvantages of Vane Compressor
It has an easy design.It uses for limited applications.
Highly efficient.They produce high vibrates during
the working
It has a low initial cost.This compressor has a high number
of rotating components.
It has a compact size.Due to many moving parts, it has a
high maintenance cost.
Simple construction. 

1.5) Rolling Piston Compressor

The rotary piston of this air compressor acts as a separation between the rotor and the blade. This piston pushes the gas toward the fixed vanes. Two of these compressors can fix on the same shaft to decrease noise and vibration and increase capacity. Rolling Piston Compressor

This gas compressor is more efficient than a reciprocating compressor because less space is lost between the piston and the compressor housing.

With a given capacity, the volume of the rolling piston compressor is reduced between 40% and 50%. It generates less vibrations and contains fewer parts than the reciprocating compressor. It is more reliable as compared to the reciprocating compressor.

Advantages and Disadvantages of Rolling Piston Compressors
It has a low maintenance cost.It has low efficiency.
It has a low initial cost.It doesn’t have a quiet operation.
Simple operation.These compressors have low efficiency.

1.6) Scroll Compressor

Scroll compressors are also called scroll vacuum pumps or scroll pumps. These types of air compressors use two offset spiral blades to compress different fluids like air or gases. The shape of the blade can be a mixed curve or Archimedean spiral.

These types of compressors work smoothly in a lower capacity limit than other types of compressors. It is quieter and more reliable.

Scroll Compressor

Usually, one scroll is rigged, but the other is eccentric and does not rotate, pumping, trap, or squeeze pockets of the available air between the scrolls.

These types are used for the applications such as residential, air conditioners, marine containers, fruit, and food refrigeration, vacuum pumps, truck transportation, etc. 

Advantages and Disadvantages of Scroll Compressors
It has low weight.  It has a low capacity.
It delivers a low pulsation gas flow.These have a high cost.
These have a quiet operation. 
It has only a few moving components. 
It has high durability. 

1.7) Diaphragm Compressor

This type of air compressor is a kind of conservative piston compressor. In these compressors, gas or air compression causes when the flexible diaphragm moves, not the intake component. 

The forward and backward motion of the diaphragm handles with the help of a crankshaft and a rod mechanism. When there is a need for gas compression then only the compressor box and the membrane makes contact with the gas. The degree of bending and the material of the membrane affect the life of the device.

diaphragm compressor

Silicone or rubber diaphragm compressors can withstand very high deflection depths. Still, due to the low strength of these compressors bounds their use in low-pressure applications and requires replacement if the plastic becomes brittle. These are used in many applications like compressed natural gas (CNG) and hydrogen plants. 

Advantages and Disadvantages of Diaphragm Compressors
They supply oil-free compression.The membrane or diaphragm of
this compressor has a low life cycle.
It provides a tight compression.It can’t self-regulate.
Low load on the crankshaft bearings.  It provides a low flow rate.
Noiseless operation. 

Read more: Diaphragm Compressor working

Types of Dynamic Air Compressors

Types of dynamic compressors are given below:

  • Centrifugal Compressor
  • Axial Compressor
  • Turbo Compressor

types of dynamic compressor

2.1) Centrifugal Compressors

The centrifugal compressor is one of the most famous types of air compressor. It uses a rotatory impeller or a disc in the housing to push the gas or air toward the blades of the impeller.

The impeller blades increase the speed of the gas. The diffuser transforms the energy of the gas speed into pressure. After that, the gas is transferred to the desired location. 

These compressors mainly utilize for constant, fixed applications in industries like petrochemical plants, natural gas, chemical plants, and oil refinery processing plants. Its applications range from 100 hp to thousands of hp. With various upgrades, high outlet pressures above 6.9 MPa (1,000 psi) can be achieved.

centrifugal compressor

These kinds of air compressors are most widely used in air conditioning systems, HVAC systems, and large refrigeration.

Advantages and Disadvantages of Centrifugal Compressor
It has low weight.Not suitable for high compression applications.
It has easy construction.It has choking, stalling, and surging problems.
Easy to maintain.  It produces a limited amount of pressure.
It has low cost than the reciprocating compressor.It has low efficiency than the reciprocating compressor.

2.2) Axial Air Compressors

The axial compressor is a type of dynamic compressor. The axial air compressors are used when compact designs or high flow rates are needed. The axial compressor uses a series of fan-shaped air blades to compress the liquid gradually. 

In this type, the wings arrange in pairs, one in a stationary row and the other rotating row. A rotating blade of air, also known as a rotor, accelerates the liquid. Fixed blades (also called vanes or stators) slow down and redirect the direction of fluid flow, arranging the rotor vanes for the next step.

Axial Compressor components

These compressor types require a large number of components. They need high-quality materials for construction. Therefore axial compressors are expansive. These types of compressors use in CNG stations and all gas turbines.

Advantages and Disadvantages of Axial Compressor
It is more efficient than other types of compressor.It has a relatively high cost.  
It has a high-pressure ratio.It has a difficult design than other dynamic compressors.
It is best for multi-staging.These compressors have a high weight.
It has low cost than the reciprocating compressor.It has low efficiency than the reciprocating compressor.

How to use an Air Compressor?

The operator of the air compressors needs basic skills and training to operate them. First, read the instruction manual and make a maintenance list according to the instructions of the manufacturer. Then, make a chart for the use of your air compressor and operate it according to that.

Following are the basic steps that will be helpful to use an air compressor. 

  1. Ensure safe operation
  2. Tight the loose parts
  3. Wear PPEs
  4. Check oil level of the fuel pump
  5. Connect pneumatic tools
  6. Expel the moisture from the air tank
  7. Inspect oil level in the tank
  8. Fill air tank
  9. Regulate the check valve
  10. Ensure more checks
1) Make Sure Safe Operation

It is very important that do not immerse the electrical components of the air compressor in water and keep them away from the water. Doing so could cause an electric shock.

Typically, the operator keeps the electric discharge valve away from wet surfaces. If pneumatic air compressors are activated, then oil changes and refueling can raise safety concerns. And also, use the machine while it cools down.

Also, do not neglect to plug the compressors into an electrical outlet equipped with a lightning rod. The fire extinguisher should also be placed in an important location near the equipment.

The inlet pressure should not exceed 90 PSI unless the internal pressure of the compressors is high. Because this higher pressure of the air may affect the functioning of the air tools. Therefore, it is very important to understand the air needs of air distribution systems, dryers, tools, and other equipment.

2) Tight the loose parts

Check and tighten loose parts in fittings and connectors because they may loose due to vibration of the compression system. Generally, vibration loosens nuts, screws, and bolts. Therefore, take a look at these parts and tighten them if they are loose.

3) Wear PPE (Personal Protective Equipment)

Always wear personal protective equipment (PPE) before operating the air compressor. Before operating the equipment, the operator should boot, goggles, hard hats, and wear gloves.

In the event of an accident at the workplace, PPEs may prevent the worker from any severe injury. Proper PPEs also reduce the risk of environmental damage.

4) Check the oil level of the Air Compressor’s Pump

It is very important to check the oil level of the oil-lubricated compressors before operating them. This will help you in the prevention of equipment damage.

In contrast, if you have an oil-free air compressor, you don’t need to perform a regular lubrication inspection. Make sure the power is turned off before eliminating the oil filter plug.

5) Connect Pneumatic Tools

When using the quick-connect accessory, pull and release the spring collar and securely connect it to the compressor.

Make sure the pneumatic tools are properly connected to the compressor’s air hose. Ensure that there should be no leakage of air from the pneumatic tool’s inlet valve.

6) Drain the moisture from Air Tanks

As the tank gets moist from the atmosphere, the compression holds the vapors. This situation often occurs with air compressors in humid weather. Therefore, it is essential to drain the moisture from the air tank for the proper working of the equipment.

After completing work, the operator can unlock the drain valve under the air tank to drain the moisturized air. It is necessary to release the air pressure in the tank before releasing the water regularly.

7) Inspect Oil Level

Inspect and replace the lubricating oil of the compressor after each use. Because oil is very important for the piston of your equipment. This oil helps the piston to move forward and backward.

If you do not adequately lubricate the piston then it may damage. The manufacturer also recommends that the operator refuel the oil lubrication pump within 500-1000 operating hours.

8) Fill Air Tank

Almost all compressors have a drain valve for the release of air or gas. Therefore, make sure the drain valve of your air compressor. If it also has a drain valve, turn it off with a wrench before filling the air tank. After closing, Turn on the power. Instead of using the compressor right away, let the pump run for a few minutes.

Check the air pressure gauge to see if the compressor will automatically shut down when the air pressure reaches 115 PSI. The extreme operating pressure can fluctuate depending on the air compressor’s model. The maximum pressure rating for some DEWALT products is 150 PSI.

9) Regulate the Air Control Valve

You can use the pneumatic power of the air tools to customize the air valve regulator according to your requirements. Typically, turning the air control valve clockwise increases the air pressure. Basically, this control valve uses to stop, decrease, or increase the air or gas pressure. 

Follow the manufacturer’s instructions in the product manual to understand the direction in which the control valve will increase air pressure. In addition, though, careful attention to the pressure gauge can provide the correct air pressure for the tool.

10) Ensure More Checks

The separator elements of the compressors can regulate excessive oil consumption. Therefore, the operator should continuously monitor the operation of the air or gas compressor. In addition, the separator element must change after the machine has been running for approximately 1,000 hours.

How to repair an air compressor?

If the air compressor starts normally at the beginning of the day but then stops and makes a loud hum on further attempts, the “unloader” valve is defective. If you want to repair your then follow the below-given steps to repair it:

  • Firstly, find the valve position on the compressor. This valve usually locates below the pressure switch. After finding this component, you can determine the type of unloader valve that can be used to replace it.
  • After finding the defective valve and ordering a replacement part, the next step is to repair the compressor.
  • For safety purposes, the device must be switched off completely before starting the repair process.
  • Next, loos the drain valve under the compression tank. When the drain valve is released, the air compressor will be depressurized and can easily repair.
  • As soon as the air compressor is switched off and safely decompressed, the replacement process can be carried out. After decompressing, remove all cables connected with the old valve. You can then install a new “unloader” valve. When installing a new valve, then secure it tightly in its position.
  • After the completion of the installation procedure, turn on the equipment to check the repair of your compressor and check the valve’s performance.

Repair Air Compressor leakage:

If your compressors are not delivering air properly and you feel leakage of fittings then follow the below-given steps to repair it:

  • For the confirmation of leakage, make a solution of soap water and pour it on the fittings. If bubbles are coming out from the fitting, it means the fitting is leaked.
  • Turn off the air compressor
  • Depressurized the air tank
  • Emilite the fitting from where bubbles were produced.
  • Get the Teflon’s plumber tape and wrapped it around the leaking fitting.
  • After this process, turn on the equipment and check performance.

Applications of  Compressor

  1. It uses in the natural gas plant for gas processing purposes.
  2. Uses in petroleum refineries.
  3. Petroleum plants.
  4. Air compressors are used in refrigerators to remove heat from refrigerant cycles.
  5. Used in gas turbines.
  6. Jet engines also have compressors.
  7. They are employed in the diving cylinder to compress and provide gas for breathing purposes.
  8. Used in heat pumps and AC units.
  9. It uses in submarines.
  10. Compressor uses in oil refineries.
  11. They are used in steam turbines.

What is free air delivery in an air compressor?

Free air delivery is a volume of air that a compressor sucks in from the atmospherecompresses, and discharges into the receiver, tanks, pipes, or air house.

The concept of free air delivery is often used to compare the fluid handling capacity of the compressor. 

For example, if you want to calculate the fluid handling capacity of several compressors, you have to compare fluid delivery at the same level (i.e., under the same conditions (pressure and temperature)). Therefore, free air delivery is the amount of air supplied at the outlet but at inlet conditions

To compare multiple compressors, you can use the NPT as an input condition and calculate the free air supply for each compressor under those conditions. These compressors have more free air delivery and, therefore, will have maximum liquid handling capacity.

The V1 is the free air delivery of the compressor.

What is the difference between Pump and Compressor?

The compressor has compressible working fluids such as air or gas.The Pump has non-compressible working fluids such as liquids.
It Increases the potential energy by compressing the working fluid.It increases the kinetic energy of the working fluid, which further raises the pressure energy.
There is a change in volume from inlet to outlet.In pumps, there is no change of volume from inlet to outlet.
There must be a pressure change during working.The pressure change is not compulsory.
It has storage capability after compression.It doesn’t have storage capacity after pumping.
Compressors have more cost than pumps.It has a low cost.
It has High ΔP and Low Q.The pump has Low ΔP and High Q.

FAQ Section

What is a compressor used for?

A compressor uses to transfer the air or gas from one location to another by increasing the pressure of air or gas through the compression process. The compressors use for different applications such as refrigerants, fertilizer industries, food industries, submarines, etc.

What are the types of compressor?

The compressors have the following types:

What is the definition of compressor?

A compressor is a machine that uses to transfer the fluids from one location to another location by increasing their pressure.

Which compressors is used in AC?

A reciprocating compressor is the most famous type that uses in AC. A piston inside the AC compressor moves forward and backward to suck and compress the air.

What is the function of a compressor in sound?

In a sound system, a compressor uses to reduce the dynamic range by compressing the sound.

Why is a compressor used for the refrigeration cycle?

All practical power-consuming or power-producing devices work on a cycle. The refrigeration cycle consists of 4 processes (heat addition, heat rejection, compression, and expansion). After combining these processes, we get continuous work (cooling in this case). Therefore, a compressor is an essential equipment for refrigeration and air conditioning units.

Basically, a compressor’s principal objective is to surge the temperature and pressure of refrigerants in the refrigeration cycle. A compressor has two objectives in the refrigeration cycle that are given below:  

  • The first objective is to increase the pressure and temperature of the refrigerants to allow the flow of refrigerants in the system. Because without pressure difference, the refrigerant can’t flow in the system. It converts the wet or dry saturated vapor to the wet, dry saturated, or superheated vapor.  
  • The second objective of the compressor is that it helps in liberating the heat gained in the evaporator to the atmosphere. Because at a lower temperature, the heat can’t be rejected to the atmosphere. Now when the pressure and temperature of the Refrigerant increase to a value greater than atmospheric temperature, the heat transfer takes place from the refrigerant to the atmosphere.

Thus, it liberates heat gained in the evaporator and also the heat gained in the compressor. Therefore, we use a compressor in refrigeration.

We can also replace the compressor with some other device in some special type of units like in the Vapor Absorption Refrigeration System (VARS). But these types of systems are not very much used practically.

In this article, I deeply explain the air compressor and its different types. So, I try my best to explain this topic. If you need any clarification, then please let me know in the comment section. I will try my best to respond to you with the right answer.

Read More
  1. Different types of Pumps
  2. Different types of Engines
  3. Working of HVAC Unit

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