They can drive anything from a paint sprayer to an impact wrench — but how does an air compressor work?
Found in factories, workshops, sheds, and garages, these versatile powerhouses knock out impressive grunt, allowing industrial-grade performance from their attached tools. Yet, while a crucial weapon in every serious contractor’s or ardent DIYer’s arsenal — few people understand exactly how a compressor works.
Consider this article your ultimate pneumatic 101 — lifting the veil on these essential machines, and exposing the workings beneath.
How Do Compressors Work — An Overview
Before we dive deep into the nuances of how compressors works in particular formats, let’s start with a brief overview of what these machines are and the theory behind their energy delivery.
A pneumatic air compressor is a machine that transforms a starting fuel — typically electricity, gasoline, or diesel — into potential energy in the form of pressurized air. Stored in an integrated tank, the air can be drawn upon to power tools — including wrenches, drills, paint sprayers, sanders, and riveters.
The process is surprisingly simple.
An electric or petroleum motor forces air — sourced from the surrounding room supply or through an exterior inlet pipe — into the storage tank. As more and more of this gas is squeezed inside this pneumatic reservoir, the internal pressure naturally increases.
Eventually, this will reach a factory-determined limit at which point the motor cuts out to prevent overpressurizing the tank — known as the duty cycle. This forms the potential energy component — a ready source of power that can be utilized as required.
As a tool begins to draw on the stored air, the reservoir tank will begin to slowly depressurize. As it reaches a preset level, the motor automatically kicks back in again to repressurize the unit — a process that continues while the power tool is being operated.
And that, my young pneumatic Padawan, is the basics behind how air compressors works.
For many readers, that may be a sufficient explanation. But, if you’re interested in how particular formats of pneumatic powerhouses function — and you like getting down and dirty into detailed diagrammatics and descriptions — stick with me!
Air Displacement — How Compressor Works
Time to get a little more technical in this How Compressors Work 101!
As explained above, these units require air to be sucked in and stored in a reservoir. In physics terms, this is known as air displacement. Generally speaking, there are two forms of air displacement — positive and dynamic.
Positive displacement is the most common format — due to its ability to function with a consistent flow of pressurized air regardless of the demands of output pressure. In simple terms, it provides non-fluctuating grunt for however many tools are attached.
Atmospheric air is pulled into the compression chamber or chambers. The volume of this reservoir is reduced — either through a piston, screws, or vanes — which elevates the pressure until it reaches the built-in pressure limit. The output valve then releases the air into the tool or accessory.
Dynamic displacement (sometimes referred to as non-positive displacement) relies on spinning blades and an impeller to draw air into the chamber — a kind of reverse fan. While more technically complex than the positive form — and therefore more costly and used in industrial environments — they pressurize the tank more rapidly than their counterparts. This is why they’re utilized in rapid-demand situations, such as automotive turbochargers, national gas supply pipes, and missiles.
Positive Displacement Compressor How it Works
Compressors with positive displacement can be broken down into four main systems — scroll, rotary screw, rotary vane, and reciprocating piston.
Rotary Screw Compressor
The most common format for industrial locations such as factories and automotive plants, due to their high power output and ability to run a multitude of accessories from a single unit.
So, how does a rotary compressor work?
Internally, two substantial screws — as pictured above — rotate continuously in opposite directions. As they turn, they create a vacuum that draws in air, passing this gas along their threads into a storage reservoir. The vast majority of these models are oil lubricated, although smaller oil-free models are becoming increasingly available.
That, for the casual compressor enthusiast, is all you need to know. However, if you’re a glutton for pneumatic punishment and want to understand the full process of how air compressor works with rotary screws — here it is:
- Electricity or gasoline drives the motor, which turns the rotary screws.
- This creates a vacuum that draws in atmospheric air via the inlet valve.
- Once inside, it’s atomized into a mist and combined with oil.
- This mist is pulled through the threads of the screws as they rotate.
- The air reaches the oil separator tank where it is subject to centrifugal force.
- This spinning action causes the molecules of oil to turn into droplets, become
- separated from the air, and disperse into an oil reservoir for later use.
- The remaining air passes through a filter to remove any oil remnants.
- The storage reservoir stores the compressed air for use.
- This is one duty cycle — which repeats every time air volume in the reservoir becomes depleted.
Rotary Vane Compressor
The second format of positive displacement compressors. Efficient, and with fewer components than their rotary screw siblings, they’re easier-on-the-pocket and straightforward to maintain. It’s for this reason that they’re favored in the agricultural industry — allowing engineers to effortlessly repair them literally in-the-field.
Furthermore, they can be manufactured in compact formats — making them suitable for light contractors and DIYers. And, being small in size, you find them in surprising locations — such as the power steering in your automobile.
So, how does a compressor work with rotary vanes?
- Gasoline or electricity powers a motor which turns internal vanes.
- This creates a vacuum that draws in atmospheric air through the inlet valve.
- Off-center-mounted vanes continue to spin on an internal rotor.
- The self-adjusting vane arms create cavities between each other of varying size.
- The atmospheric air spins around with the vanes.
- These vanes become closer to each other, reducing the internal volume.
- This action compresses the air.
- Pressurized air is then delivered from the output valve into your tool.
Reciprocating Piston Compressor
The most common format for home-use machines. Budget-friendly and with straightforward maintenance — they’re excellent for home use. Pancake compressors, the DIYers’ favorite, are an example of a piston compressor. The downside is, they can be noisy — so look for a machine with impressive soundproofing for comfortable use.
How does a air compressor work with a reciprocating piston? You’ll be pleased to hear that it’s ridiculously straightforward.
- The compressor unit houses cylinders that contain pistons.
- Driven by an electrical or gasoline motor, these pistons move downwards.
- This creates a vacuum that draws in atmospheric air.
- The pistons then move in the opposite direction — hence reciprocating — compressing the air.
- The compressed air is then drawn upon by a tool or accessory.
- That’s it. Simple, right?
An undoubtedly popular format of positive displacement compressor — but not in the tool, home-improvement, and DIY arenas. Almost exclusively, they feature in HVAC systems for pressurizing refrigerants.
But if you’re in the air-con or heating system industry — you probably want to know how does a scroll compressor work:
Motion of Scrolls – Cacycle, Public domain, via Wikimedia Commons
- The compressor contains two scrolls — basically, spirals of metal.
- Driven by gasoline or electrical power — one scroll rotates while the other remains stationary.
- This creates vacuum air pockets that draw in atmospheric air.
- The rotational motion forces the air towards the center of the scroll, where it experiences smaller and smaller areas of volume.
- This compresses the air, which can then be released through the output valve.
Dynamic Displacement Air Compressor How It Works
So, we’ve covered how the screw, vane, scroll and piston machines — that is, positive displacement units, work. Now to explain how does air compressor work with dynamic displacement.
As these machines are not typically for home use — and therefore unlikely to be experienced by the home-improver — this section is brief. However, to ensure this How Do Air Compressor Work article is complete — I’ve included them below.
There are three formats — centrifugal, axial, and mixed flow.
Also known as radial and turbo compressors — these tend to be absolute behemoths of machines, meaning they’re almost exclusively utilized in industrial arenas. You’re not going to be using one of these units unless you’re pumping gas from the US into Canada, or have a two-hundred-ton capacity elevator.
Here’s how air compressor work with centrifugal dynamic displacement:
- A rotating impeller with mounted radial fans draws atmospheric air into the compressor.
- Centrifugal force pulls the air into the center of the impeller.
- This elevates the pressure, which is forced through a diffuser and volute.
- The resulting compressed air can then be utilized.
Axial Compressor Movement of Aerofoils – NASA, Public domain, via Wikimedia Commons
This format is used in jet engines, cruise ship engines, and power stations. So, unless you’re an industrial or aeronautical engineer — you’re never going to use one. If you are an engineer and have come here for advice — you’re in the wrong place.
Here I’d usually include a quick explanation of how air compressors work with an axial design. However, all you need to know is that they feature aerofoils that rotate around an axis — hence the name ‘axial.’
However, if you really want to understand the working process — I’ll let NASA explain.
If you come across one of these units — and you’re not in the armed forces — then I’d be concerned.
With a ridiculously high thrust-to-weight ratio, they’re utilized for drone weapons, UCAVs, (unmanned combat aerial vehicles), and short-to-medium range missiles.
In brief, they feature a combination of axial and centrifugal components — hence the moniker mixed-flow. If you’re seriously technical-minded, and want to know how do air compressors work with a mixed-flow system — either check out this article from the Indian Institute of Technology, or watch the below video.
Air compressors are crucial powerhouses for any trade pro, home-improver, or DIYer who wants to delve into the pneumatically powered tool world.
Knocking out high power combined with reliability and serious grunt — they deliver higher brawn than standard electric hand tools. Understanding the basics behind these machines allows you to appreciate their function — and perhaps complete some of your own home maintenance.
Many of the machines described above are massive overkill for the average consumer. Instead, for contractors or home consumers looking to venture into the air arena — check out my guides to small compressors, six-gallon units, and 60-gallon machines.
I hope you enjoyed this article. If you have a buddy that you believe would also relish this How Does An Air Compressor Work 101 — please feel free to share!
Reciprocating Saw FAQs
Q: How a Scroll Compressor Works?
Scroll compressors feature twin scrolls — that is, spirals — that pressurize air. Drawn into the center of the scroll, the gas becomes increasingly compressed — then released through the outlet valve to power your tools.
Q: How To Test a Compressor?
If you’re wondering how to check compressor — it depends on what you’re testing it for. This can include leakage, short circuits, oil-contaminated air, or pressure consistency. To discover how to investigate these common areas of malfunction, together with other typical problems, check out my Air Compressor Troubleshooting page.
Q: How Long Do Air Compressors Last?
This depends on many factors, including:
- Quality of the build and design.
- Running hours.
- Correct use.
- Maintenance frequency.
However, if you want a definitive answer to the question how long does an air compressor last — a properly cared for and regularly serviced compressor should run for ten to fifteen years.
Q: How Many Amps Does an Air Compressor Use?
A typical home-style 7.5 horsepower air compressor will draw 23-24 amps. Hence, it’s important to ensure that your circuit breaker or extension cord has sufficient capacity to deal with this load. For more information on the electrical requirements of compressors and their concomitant safety, check out this link.
Q: Is It Easy to Understand How a Compressor Work?
Yes. It’s quite straightforward to grasp how a compressor work in the home-consumer market. In short, atmospheric air is drawn into the compressor and stored in a reservoir. As the amount of gas increases, the available space inside decreases, elevating the pressure to be used by your pneumatic tool.
Q: How Long Do Compressors Last if Used Every Day?
If you’re wondering how long does a compressor last when used daily — the answer can be up to 20 years. However, this assumes that you purchased a quality and durable compressor to begin with — and that you regularly maintain and service the machine throughout its life.
Q: How Compressor Work Without Electricity?
If you’re working away from power outlets — you can utilize a gasoline-driven compressor, or alternatively run a diesel generator.