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There are many ways to pressurize gas from atmospheric pressure to a range of low, medium, high and ultra-high pressures. As a result of varying demands to compress the gas, whether it be air or another gas – a number of compressor designs have emerged to suit each application perfectly.
This page will serve as a guide to the different air compressor types and their common applications!
Table of Contents
- What Types of Air Compressors Exist?
- Types of Positive Displacement Air Compressors (Constant Flow Compressors)
- Types of Dynamic Compressors (Constant Pressure Compressors)
- Single Stage vs Dual Stage Air Compressors
- Oiled vs Oilless Air Compressors
- Types of Air Compressor Uses
- What Are the 3 Most Common Types of Air Compressors?
- How Do I Choose the Right Air Compressor Type?
- Reciprocating vs Rotary Screw Air Compressors: Which Is Right for Me?
- FAQs (Frequently Asked Questions)
- Additional Reading
What Types of Air Compressors Exist?
Air compressors however can be broken down into air compressor types in several ways. This probably needs a diagram to explain it more clearly.
There are 2 main categories of compressors:
- Positive Displacement (Constant Flow Compressors)
- Dynamic Compression (Constant Pressure Compressors)
Types of Positive Displacement Air Compressors (Constant Flow Compressors)
Within the positive displacement types of air compressors category, there are the following air compressors:
- Reciprocating Air Compressors (Piston Air Compressors)
- Rotary Screw Compressors
- Rotary Vane Compressors
- Scroll Compressors
Reciprocating Air Compressors
Reciprocating compressors are positive displacement piston-type air compressors that suck in air into a chamber and compress it. Read more about reciprocating air compressors here.
Rotary Screw Air Compressors
A rotary screw compressor work by generating compression continuously at the rotary screw drive air end of the compressor. Air enters the unit at the inlet port of one of the two large screws rotating against one another, also known as the rotors or rotary screws.
This air then moves down the length of the screws and compresses the air towards the outlet due to the air gaps in the rotors getting smaller and smaller. Read more about rotary screw air compressors here.
Rotary Vane Air Compressors
Typically an electric motor rotates the rotary vane shaft, the vanes draw in free air and compress it as they rotate, generating compressed air power. Read more about rotary vane air compressors here.
Scroll Air Compressors
A scroll compressor, otherwise known as a spiral compressor, is an orbital motion compressor that compresses gas with two inter-fitting scrolls. One scroll is moving whereas the second one is fixed to the compressor body. The first scroll orbits in a path defined by its mating fixed scroll and are attached to the compressor’s crankshaft.
As a result of the scroll’s movement, gas pockets are formed between the two scrolls. At the outer part of the scrolls, the pockets suck in gas and then they move towards the center of the scroll, where the compressed gas is discharged. For more information on scroll compressors visit our guide here!
Types of Dynamic Compressors (Constant Pressure Compressors)
Within the Dynamic Compression Air Compressor category, there are:
- Centrifugal Air Compressors
- Axial Flow Air Compressors
Centrifugal Air Compressors
Centrifugal compressors draw air into the center of their rotating impeller using their radial blades. The blades essentially produce a pressure variation very similar to an airfoil of a spinning propeller on an aircraft or wind turbine.
The centrifugal compressors are built in stages, and each stage has a part to play in the overall pressure increase of the system. Read more about centrifugal air compressors here.
Axial Flow Air Compressors
Axial compressors are typically made up of many alternating rows of rotating (rotors) and stationary (stators) blades. The blades are similar to that of an aircraft wing as they have small airfoil cross-sections.
Jet engines are actually extremely large examples of axial flow air compressors – in their case using compression to generate thrust. A bit more than your commercial variety axial flow air compressor! Read more about axial flow air compressors here.
Single Stage vs Dual Stage Air Compressors
The key difference between a single and two-stage air compressor is the number of times that the air gets compressed between the inlet valve of the compressor and the tool nozzle. In short, a single-stage air compressor compresses air a singular time, while a two-stage air compressor compresses the air twice for twice as much pressure.
Single-stage air compressors are known as piston air compressors and their process includes sucking air into a cylinder and then compressing it with a single stroke before moving it onwards to a storage tank.
Dual-stage air compressors have a similar process but instead of sending the compressed air to the storage tank, they send it to a smaller piston for a second stroke to increase the pressure of the air further and then pass it to the storage tank.
You can tell how many stages your air compressor has based on the size of the cylinders and the number of air intakes on the compressor. On a single-stage compressor, all cylinders will be the same size and have their own inlet valves.
If you’re interested in the effect of intake air on compressor performance, energy.gov created an informative tip sheet which you can view here!
On the contrary, in two-stage compressors, there is just one inlet, the second piston is smaller than the first, and the two are linked by a cooling tube, which brings the temperature of the air down before the additional round of compression.
For more information on this, please visit our 2-Stage Air Compressor vs Single-Stage Air Compressor guide!
Oiled vs Oilless Air Compressors
One other way to classify different types of air compressors is whether they’re oil-lubricated or oil-free systems.
All air compressors have moving parts, so, it’s important to lubricate these parts to avoid any damage to your air compressor. If you do not adequately lubricate your compressor, it is likely to fail to function correctly. Oil is the most common lubrication material used for machinery, and traditional oil-lubricated air compressors utilize this tried-and-tested medium.
Oiled air compressors are typically rugged and durable, and their oil usage makes them ideal for many industrial applications. They naturally tend to produce a lot of heat during their operation, but the oil acts as a coolant to help cool them down.
Oil-lubricated compressors are very versatile and certainly reliable, but they have some drawbacks. For one, they require a significant amount of maintenance, and operators have to check oil levels and change the oil and oil filters on a regular basis.
Oil-free air compressors use an alternative sealing, cooling, or lubrication medium, such as water, eliminating the risks and associated costs of oil contamination. Companies use oil-free compressors for applications where even the slightest bit of oil carry-over is unacceptable to ensure that the air is of the highest quality for use.
Pharmaceutical manufacturing companies, for example, must ensure they have no hydrocarbons in their products or the air in their production facilities. The same is true for food and beverage companies, such as bottling companies and food packaging manufacturers, because air comes into direct contact with their products, so, it must be pure.
For more information please visit our Oilless Air Compressors vs. Oil Compressors guide!
Types of Air Compressor Uses
|Air Compressor Type||Home/DIY Air Compressors||Workshop Air Compressors||Industrial Air Compressors|
|Rotary Screw Compressor||Y||Y|
|Rotary Vane compressor||Y|
|Axial Flow Compressor||Y|
Above is a summary table that describes what each type of air compressor is most suitable for, whether that is Home/DIY projects, workshops, or industrial purposes. This more or less depicts the size of the compressors as well, with home DIY versions being significantly smaller than those found in industrial settings.
Some types of air compressors are available as small DIY compressors as well as industrially sized, while others are specifically designed for industrial uses.
What Are the 3 Most Common Types of Air Compressors?
The 3 most common air compressor types you will come across in a wide variety of industries are:
- Reciprocating compressors
- Rotary screw compressors
- Centrifugal compressors
But, in a lot of situations, people neglect the centrifugal air compressor and focus on reciprocating compressors vs rotary screw air compressors to really decide which one is needed.
How Do I Choose the Right Air Compressor Type?
When deciding which of the above is best suited to you there are a number of factors you must consider which include:
- Air quality (oil-lubricated vs oil-less)
- Energy efficiency
- Additional features
Air Quality (Oil-Lubricated vs Oilless)
You, first of all, must consider whether you want an oil-lubricated or oil-less compressor. Using an oil-lubricated compressor may create problems in clean manufacturing environments as the fumes may contaminate the air and result in damage to manufacturing processes. Oil-less compressors significantly reduce this risk.
Though oilless compressors tend to be more expensive, they are the only option for clean manufacturing. They also boast the benefit of having a lower running cost due to parts not needing to be changed as often as oil-lubricated compressors.
Oil may still be needed to lubricate an oil-less machine but the key part is the inner workings contain a different sealing mechanism to oil-lubricated compressors so that no lubricant gets in the actual compressor.
Getting the most energy-efficient air compressor is worth the extra initial costs if you’re planning a long construction project. Now let’s look at fixed and variable speed compressors.
Fixed-speed compressors constantly churn at the same rate, the problem being that when the unit slows down, the motor continues to run until the machine comes to a full stop. This cool-down period causes energy to be wasted without power being generated.
Variable speed-driven (VSD) compressors save energy and of course money, by either increasing or decreasing output on demand.
Another option, if efficiency and energy savings are your main goals is using a natural gas unit. On top of their operational efficiency, they also boast greater heat recovery capabilities than electric compressors.
You must consider whether you wish to be able to transport or move the compressor to different locations. Small, lightweight compressors are far easier to transport and can still deliver the energy you need. They may not be as powerful as larger compressors but they’re perfect for smaller projects like tire inflation, airbrush, or other pneumatic tools at home.
Wondering how many watts a compressor uses? Visit our guide here!
Reciprocating vs Rotary Screw Air Compressors: Which Is Right for Me?
In terms of the two most popular types of air compressors, reciprocating and rotary screw compressors, there are some important differences that will help you know which is the right type for you.
Reciprocating compressors can be manufactured to work with low air pressure and very high air pressure (100 to 15000 PSI), while rotary screw compressors only work at low pressures within around 100 to 215 PSI.
Reciprocating compressors are low-capacity and typically designed for intermittent use. They’re best suited for applications that need only a small amount of air and don’t use compressed air continuously. The rotary compressor on the other hand are high-capacity and are designed for continuous-use projects. They tend to be big, industrial machines that start at 10 HP and reach up to 1000 HP, and maybe even greater!
Reciprocating compressors are suitable for workshops, garages, DIY/homeowners, small businesses, and powering some construction work while rotary screw compressors are made for the industry.
Some tools you have at home or in your workshop will require a lot more air than your reciprocating air compressor can provide, so, it is recommended to install a bigger air tank rather than buying a bigger reciprocating air compressor or a rotary screw compressor.
It’s generally advised to go for a reciprocating air compressor if the compressor is going to be sat still a lot of the time and only used intermittently. Reciprocating compressors tend to have a 50% duty cycle so they like to rest as much as possible. Rotary screw air compressors don’t like standing still as it makes them rust prematurely, they are designed to run.
FAQs (Frequently Asked Questions)
The three most common air compressors in today’s market are reciprocating, rotary screw, and centrifugal air compressors. Reciprocating and rotary screw compressors fall under the category of positive displacement compressors while a centrifugal compressor is a dynamic compressor. Centrifugal air compressors are the least popular of the 3, reciprocating compressors are the most popular for DIY and homeowners, and rotary screw compressors are the most popular in industrial applications.
It’s difficult to say which type of air compressor is best as it depends on the application or use of the compressor. For instance, reciprocating air compressors are most likely the best choice for use in workshops or projects at home if the tools needing power don’t require continuous airflow. However, in an industrial setting, they would be inadequate, so, a rotary screw air compressor that is capable of providing continuous airflow is going to be the best.
There are 6 commonly used air compressors found across the compressed air world. These include reciprocating air compressors (piston air compressors), rotary screw compressors, rotary vane compressors, scroll compressors, centrifugal air compressors, and axial flow air compressors.
The two main types of air compressors are reciprocating air compressors and rotary screw air compressors. These two are the most commonly used types of air compressors found across various industries.
If you have any questions regarding the different types of air compressors, please leave a comment below, with a photo if applicable, so that someone can help you!