What Is an Air Compressor?- Definition, Types And Working

An air compressor is a pneumatic device that can power a variety of tools. Air compressors work by putting atmospheric air under high pressure, “compressing” the air, and converting its potential energy into kinetic energy that it stores in an air tank for use.

Some of the most common uses of air compressors are in everyday items like refrigerators, air conditioners, and vehicle engines. In construction, they’re used in a variety of different tasks and settings, like inflating tires and powering HVAC systems, air tools, and industrial systems.

In this guide, we go over common air compressor uses and how to find the best air compressor for your needs.

What is an Air Compressor?

An air compressor is a pneumatic device that converts power (using an electric motor, diesel, or gasoline engine, etc.) into potential energy stored in pressurized air (i.e., compressed air). By one of several methods, an air compressor forces more and more air into a storage tank, increasing the pressure. When the tank’s pressure reaches its engineered upper limit, the air compressor shuts off.

The compressed air, then, is held in the tank until called into use. The energy contained in the compressed air can be used for a variety of applications, utilizing the kinetic energy of the air as it is released and the tank depressurizes.

When tank pressure reaches its lower limit, the air compressor turns on again and re-pressurizes the tank. An air compressor must be differentiated from a pump because it works for any gas/air, while pumps work on a liquid.

How do Air Compressors Work?

Air compressors work by forcing air into a container and pressurizing it. Then, the air is forced through an opening in the tank, where pressure builds up. Think of it as an open balloon: the compressed air can be used as energy as it’s released.

They’re powered by an engine that turns electrical energy into kinetic energy. It’s similar to how a combustion engine works, using a crankshaft, piston, valve, head, and a connecting rod.

From there, the pressurized air can be used to power a variety of tools. Some of the more popular options are nailers, impact wrenches, sanders, and paint sprayers.

There are different types of air compressors and each one has a different specialty. Generally, the differences aren’t too severe: it all boils down to the way a compressor handles air displacement.

Types of Air Compressors.

Air compressors are categorized as either positive displacement or dynamic displacement, based on their internal mechanisms. The four most common types of air compressors are:

1. Rotary Screw Compressors
2. Reciprocating Air Compressors
3. Axial Compressors
4. Centrifugal Compressors

To help you make an informed decision for your project, we’ll cover the key features of each type and explain how each one works below.

Positive Displacement Compressors

Positive displacement air compressors force air in a chamber where the volume is decreased to compress the air.

Positive displacement is an umbrella term that describes different air compressors that are power through positive air displacement. Although the internal systems vary among different machines, the method of providing the power is the same.

Some types of positive displacement compressors are better equipped for industrial workloads while others are better for hobbyists or private projects.

#1. Rotary Screw Compressors.

A common type of displacement compressor, rotary screws are some of the easiest types of air compressors to take care of, as they are equipped with an internal cooling system that doesn’t require much maintenance. They are typically large industrial-sized machines that can be either lubricated with oil or run oil-free.

Rotary screw air compressors generate energy via two internal rotors that turn in opposite directions. The air gets trapped between the two opposing rotors and builds up pressure within the housing. Because of the internal cooling system, these air compressors are designed for continuous use, and range in power from 5 horsepower up to 350 horsepower.

Best For: Large-scale jobs and industrial settings that require continuous airflow

#2. Reciprocating Compressors.

Reciprocating compressors are another popular type of displacement compressor. They are typically found at smaller work sites such as garages and home construction projects. Unlike the rotary screw compressor, the reciprocating compressor is not designed for continuous use. A reciprocating air compressor also has more moving parts, which are lubricated with oil for smoother movement.

Reciprocating compressors work via a piston inside a cylinder, which compresses and displaces the air to build pressure. Reciprocating compressors can come in single- or multi-stage variations, which affects the pressure ranges they can achieve.

When you need more power, the multi-stage compressor is the way to go. While single-stage compressors will get the job done for smaller projects such as woodworking and metalworking, multi-stage compressors provide the power needed for intense construction, such as automobile assembly and maintenance.

Best For: Home and small-scale construction projects

Dynamic Compressors

Dynamic displacement compressors utilize a rotating blade powered by an engine to generate airflow. The air is then restricted to create pressure, and the kinetic energy is stored within the compressor.

These are mainly designed for large projects, like at chemical plants or steel manufacturers, so it’s unlikely you’ll be able to find one at your local mechanic.

Just like with positive displacement compressors, there are two distinct types of dynamic displacement: axial and centrifugal.

#3. Axial Compressors.

Axial air compressors are not typically used in construction projects. Instead, they are commonly found in high-speed engines on ships and planes. Axial compressors have a high efficiency rate but are much more expensive than other types of air compressors, making them best suited for aerospace applications requiring high horsepower.

Best For: Aerospace applications and high-speed engines for ships

#4. Centrifugal Compressors.

Centrifugal air compressors slow and cool incoming air through a diffuser in order to build up potential energy. Because of their multi-phase compression process, centrifugal compressors are able to produce a high amount of energy in a relatively small machine.

These compressors require less maintenance than rotary screw or reciprocating compressors, and some types can produce oil-free air. Because they can reach around 1,000 horsepower, centrifugal compressors are typically used for more demanding construction sites like chemical plants and steel manufacturing centers.

Best For: Large-scale steel and chemical manufacturing plants

What Are Air Compressors Used For In Construction?

Air compressors are valuable in construction environments for several reasons. This industry uses various types of air compressors to complete different applications. Here are some of the most common air compressor uses in construction:

• Jackhammers and drills: Pneumatic jackhammers use compressed air to drive the hammer tool up and down to break through surfaces. These tools are essential in demolition projects, where it’s necessary to remove old concrete and pavement before creating a new surface. Air-powered drills work similarly. Contractors can drill deep into the ground with pile-driving equipment.
• Impact wrenched: Manually tightening and loosening bolts can take time and effort. Construction teams can tighten or loosen bolts with pneumatic impact wrenches in just a few seconds.
• Nail guns: Driving nails through different surfaces is necessary in most construction projects. With air-powered nail guns, nails quickly and neatly penetrate surfaces. Because these tools create more uniform results than traditional hammers, they are essential tools in construction.
• Grinders: Contractors use air-powered grinders to cut, level, and polish different materials.
• Sanders: Manually sanding down surfaces can take hours, if not days. Producing level surfaces is also more challenging when sanding by hand. In contrast, pneumatic sanders are powerful enough to sand down surfaces in much less time. Results are also far more uniform with this tool.
• Inflating tires: Air compressors can quickly inflate forklifts, loaders, scissor lifts, and other construction vehicle tires.

In addition to these pneumatic tools, you can find air-powered caulk guns, saws, ratchets, and more.

What Can You Do With An Air Compressor In Commercial Applications?

Rotary and reciprocating air compressors are also common in commercial or industrial applications.

• Powering water pumps: Air compressors serve as power sources for water pumps. They can support water delivery systems while also serving as a water-pump backup.
• Food packaging: In food manufacturing, air compressors can assist with packaging processes. They can vacuum-seal perishables to ensure freshness and prevent leakage.
• Automotive production: In automobile shops, air compressors can inflate tires, power pneumatic sprayers when airbrushing, and operate equipment like vehicle lifters.
• Sandblasting: Air compressors can power tools that clean abrasive materials from surfaces like rust. The high-pressure air provides enough force to remove rust from metals properly.
• Operating commercial cleaning equipment: Laundry pressers, steam cleaners, and pressure washers are just some types of equipment that compressed air can power in the cleaning industry.

Air compressors are also used for a variety of other commercial applications, including applications in the pharmaceutical industry.

6 Things to Consider When Choosing an Air Compressor

Physical size is not the key factor to consider when purchasing an air compressor — a larger compressor isn’t necessarily a more powerful one. You should instead evaluate your needs when it comes to:

1. Air pressure: Measured in pounds per square inch (PSI), this pressure describes how much air the compressor delivers. Higher PSI measurements mean the unit produces more air volume.
2. Air delivery: Expressed in cubic feet per minute (CFM), air delivery shows how much air a compressor can pump in one minute. Air delivery is also known as volume flow rate. The larger your application or the more complex your needs, the higher CFM you’ll require.
3. Power: Air compressor power considerations include horsepower and the power supply. Horsepower shows how much power the unit’s engine provides, and your air compressor power supply options include electric, hydraulic and gas. Electric motors often have simpler maintenance needs, lowering their operating costs. Hydraulic compressors are also cost-effective and can integrate into your existing power sources. Gas-powered models provide consistent pressure.
4. Tank size: Short tanks are suitable for intermittent compressor use, often in quick bursts. If you’ll continuously use your compressor, you’ll need a larger tank that can store more air and keep up with demand.
5. Duty cycle: Duty cycles are how often a compressor can run before pressurizing more air. This measure is often expressed as a percentage — a 50% duty cycle would require two minutes to cycle in new air after one minute of operation.
6. Configuration and air capacity: Consider your operating needs to determine the air compressor type and capacity you require. For example, reciprocating compressors, available in single-stage and two-stage configurations, have lower capacities, making them well-suited for workshops, construction sites and other needs that require intermittent use. Rotary screw compressors offer higher capacities and are designed to operate continuously, so they are often used in industrial applications.

What Is the Difference Between a Pump and a Compressor?

Sometimes the words “pump” and “compressor” are used interchangeably. They may seem similar but there is a difference between them.

Pumps move fluids between places while air compressors squeeze the volume of the gas and often transport it elsewhere. Any project involving a liquid, like pumping a pool, utilizes a pump. On the other hand, compressed air is utilized for energy to perform different tasks, such as sandblasting.

Understanding that difference between the two terms and methods of distribution can help you figure out what you need for your project.

Air compressors are useful tools in any construction project. From spray painting to fixing a flat tire, they can make a job that much easier. No two air compressors are the same, and finding out how they work allows you to make informed decisions for the project you’re working on.

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