Benefits of Different Types of Compressors: Which One to Pick?

Getting the right type of air compressor and the one that suits your needs is very important as in the long run it will help you save on time and money. However, it can get pretty confusing to choose from the many types and models available in the market today.

The debate of which compressor is right for you all comes down to what you want to use it for. This includes its scope of applications, the amount of air (pressure) that is required, and the flow rate of each compressor. Read our details guideline on how does air compressor work.

In addition, the ease of operation, level of maintenance, installation process the cost and operating costs plays a big role in choosing one model over the other.

In this article, we shall discuss the benefits and typical uses of the common types to help you establish which one best suit your needs.

Features and Benefits of Various Types of Air Compressors

Knowing the similarities and differences between different models will help you establish the benefits that come with each hence you will be able to select the model that best suits you. Here are some of the differences in terms of performance.

1. Reciprocating (Piston) Air Compressor

Piston or reciprocating air compressors makes use of one or more pistons/cylinders to compress air. This pistons move up and down inside the air tank allowing air in for compression which is finally discharged to the tool that is being powered.

Highlights and Benefits

• These piston compressors are usually compact in size with pressure of between 100-150 psi. They are mainly designed to be used periodically due to their low capacity as such you should consider other model if you want to use the compressor continuously.
• The compressor’s cylinder and the piston are not lubricated. Only the crankshaft bearings and pins are lubricated. This helps to reduce oil consumption and limits oil carryover which means lower costs of maintaining the system. The compression area should be kept free from air as much as possible.
• Reciprocating compressor features a control system making sure that all the required standards and codes are adhered to minimizing the risk of failures as well as simplifying the installation process.
• The compressor is mounted on a vibration isolated surface making sure that the system experiences very minimal vibration reducing noise level while in operation and also reducing the number of breakages that comes with strong vibrations.

You will find this compressor being used mainly in: garages, small businesses, workshops, and in small construction work like nailers.

2. Rotary Screw Air Compressor

The rotary screw compressor, on the other hand, uses a pair of two screws (rotors) that move in opposite direction inside the cylinder to compress air. Atmospheric air is trapped between the two screws and that’s how it is compressed.

Highlights and Benefits

• They are designed for continuous use as they have a high capacity and pressure of between 100 – 215 psi.
• The rotors and bearing of rotary screw compressors are normally lubricated to make sure that they are working properly all the time. Lubrication also helps to reduce excess heat and at the same time, it seals all the vital parts.
• Rotary screw compressors are full package i.e. you just have to install them and have them running without adding anything in the foundation. The entry cost is generally affordable and their ability to function vibration-free is an added advantage.
• For applications that may require you to work with lubricant-free compressors, rotary screw compressors offers lubricate-free compressors specifically made to suit such applications. However, they come at an extra cost in terms of maintenance and initial costs.

Rotary screw compressors are large and are ideal for powering large industrial and commercial machines.

3. Rotary Vane Compressor

Rotary vane compressors employ the same mechanism as rotary screw only that the vane version consists of blades that are aligned radially all around the rotor. As the rotor turns, the blades rotate while keeping a close contact with the cylinder wall, creating a series of increasing and reducing volumes.

Highlights and Benefits

• The vane machines comein two forms; Dry (non-lubricated) and lubricated vane compressors. The dry version operates at relatively low pressures while are the oil injected version is capable of operating at the specified volumes achieving substantial pressure levels.
• New technology in the vane compressors has improved its performance by introducing twin compressors as one unit with two rotors that work in opposite directions. This means two times performance that of a single compressor. The twin compressor is gaining popularity over its competitors as it produces less noise and fewer vibrations.
• The twin technology offers a high-efficiency level offering a wide range of operation, multiple applications, and a relatively commendable cooling capacity making them ideal for commercial applications.
• Its compact size and low costs make them a good choice for most home applications that require low capacity such as air conditioners and refrigerators.

Rotary vane compressors serve in various applications which includes; welding workshops, paper pressing cylinders, cooling various industrial operations, printing pumps among others.

4. Ionic Liquid Piston Compressor

The ionic liquid piston compressor is a hydrogen-based (takes only hydrogen part of the air) compressor that uses an ionic liquid piston instead of the common metal piston to compress air to the required pressure level.

Highlights and Benefits

• Ionic liquids have a large temperature window and their vapor pressures are not measurable. These compressors takes advantage of this property together with the fact that hydrogen gas has low solubility to compress hydrogen gas to up to 15000 psi for use in hydrogen filling stations and other hydrogen-based applications.
• Unlike other piston compressors, the ionic liquid compressor does not require bearings and seals as the ionic liquid and the gas do not mix.
• This compressor has a longer lifespan, about ten times that of an ordinary reciprocating compressor, with minimal maintenance and reduced energy consumption.
• An ordinary piston compressor requires heat exchangers to generate heat. The ionic liquid compressor does not require such exchangers as heat is produced directly from the compression tank.

This is an iconic compressor in hydrogen refueling stations and other hydrogen-based applications.

5. Rolling piston compressor

The Rolling piston features a piston in form of a roller whose shaft rotates on its own axis matching with the center line of the cylinder. This rotation causes the suction and compression of atmospheric air by reducing the volume of the cylinder.

Highlights and Benefits

• The reduced volumes and the expanding pressures make the compressor run smoothly and with tranquility facilitating a continuous flow of compressed air.
• This compressor features a lubricated design with a hydrodynamic seal to help control leakages. The effectiveness of the seal is determined by the compressor rate and the thickness of the oil.The great surface finishing further helps to eliminate interior leakages.

These compressors have wide application in air conditioners and applications whose cooling capacities do not exceed 15 kW.

6. Scroll Compressors

​​​​A scroll compressor features two spiral-shaped vanes (scrolls) whereby one is fixed and the other one moves on its own axis trapping air between them facilitating compression.

Highlights and Benefits

• The suction of air and its subsequent discharge occurs in full rotation as compared to the half rotation of the reciprocating compressors. This is due to the fact that reciprocating compressors have multiple cylinders which reduce the suction and discharge rate as opposed to scroll compressor which have only one unit.
• With about 70% fewer movable parts as compared with reciprocating compressors,  the reliability of the scroll is scroll compressors is higher which also make them use energy more efficiently while in operation. 
• The recent development allows for partial loading,unlike old model where the compressor could only operate at full capacity. This is achieved by varying the speed of the motor or having multiple compressors in place operated each at a time.
• Their compact size makes them run smoothly without necessarily having a spring suspension.This results into a considerably small enclosure which means low costs.

You will find these compressors mainly used to power air conditioners, vacuum pump and superchargers for various automobile applications.

7. Diaphragm Compressor

Diaphragm compressor is a version of reciprocating compressor. Compression of air is facilitated by the forward and backward movement of the crankshaft which brings about the movement of a special membrane inside the compression box.

Highlights and Benefits

• Diaphragm compressor features the hydraulic oil system is that ensures a uniform deflection as well as minimal vibrations, reduced knocks,translating into a  quiet and smooth performance. This system also incorporates an oil distribution mechanism that ensures that will be no pressure differentials.
• The compressor’s vital parts that come into contact with air are made to be corrosion resistant by using stainless steel. This prolongs the life cycle of the machine eliminating any risks of premature failure as well as bringing the maintenance costs down to manageable level.
• Diaphragm compressors come in multiple designs and sizes, for example, the two-stage model has the ability to significantly reduce the horsepower requirements hence reducing the energy costs.
• Most of Diaphragm compressors use static seals to prevent gas leakage to the atmosphere meaning that they are friendly to the environment.

Diaphragm compressors are used in hydrogen filling stations for vehicles, busses etc. filing gas cylinders, compressing natural gas from renewable resources among other uses. 

8. Centrifugal compressors

Centrifugal compressor is a special kind of the rotary compressor which uses an impeller (rotating disk) to suck air into the cylinder, onto a special duck where the air is converted into pressure energy.

Highlights and Benefits

• Atmospheric air is sucked into the compressor through a pipe like inlet which features a valve, which opens and closes to allow air in and prevent leakages respectively. The pipe also features vanes that are used to whirl air flow in an attractive manner. The pipe also has temperature and pressure control features.
• Centrifugal rotating disk (the impeller) rotates at very high speed which significantly increases the energy of the air. The speed of air leaving the impeller in most high advanced centrifugal compressor can be compared to that of sound. 
• The compressed air leaving the impeller is directed to the diffuser whose function is to gradually convert the high-velocity air into pressure.
• The diffused air is finally delivered into the collector which then delivers the air, now pressurized into the tool to be aired via a downstream pipe. Just like the inlet pipe, the outlet pump has valve that controls the air leaving the compressor.

Centrifugal compressors are mainly used in engines with small gas turbines but they have also been used in engines with medium-sized engines.

9. Diagonal or mixed-flow compressors

Diagonal or mixed-flow compressors employ similar working mechanism as centrifugal compressors, only that the flow of air occurs diagonally to the plane of rotation.

Highlights and Benefits

• The diagonal flow of air makes the diffuser increase the speed of air 2 times that of centrifugal compressors giving them a competitive advantage.
• The exit radius is relatively larger than the inlet which makes it possible for the air to exit in an axial manner as opposed to it exiting radially. This is important as it as it means you don’t need to have a large diameter as it is with centrifugal compressors. 

The diagonal or mixed-flow compressors have been tested and used to start aero engines worldwide.

10. Axial-flow compressors

Axial-flow compressors use fan-shaped airfoils which rotate to compress air, which flow parallel to the axis of rotation i.e. axially hence the name axial flow.

Highlights and Benefits

• The inlet and outlet features special vanes whose responsibility is to streamline the airflow and prevent any distortion as air enters and exits the compressor.
• The housing of the axial-flow compressor is designed to provide support to the vanes as well as support other compressor’s vital components. It also provides a way of extracting the air from the compressor to be used for various purposes.
• The material used for the vanes and other moving parts is resistant from corrosion and erosion. The material is also flexible enough to allow easy fastening.
• The airfoils tips are generally thin to prevent them from coming into contact with the compressor housing, this helps to prevent any damage to the compressor tank and the foils themselves. The airfoils also vary in length, a property that helps to keep the speed of the air constant making the whole process remain constant.

Axial compressors have wide application in large gas turbines like high-speed ship engines, jet engines, and aerospace engines.

So Which One Do You Pick?

It all comes down to the nature of your needs when comparing and choosing the best compressor for any application. It is all about the capacity expected, the required pressure, scope of work (tools needed), maintenance level as well the tagged price.

We hope that this article has been useful and that you have fairly a good idea of the kind of compressor that is best for you.