With so many compressors to choose from, our guides shed light on the technology behind the most popular air compression tools to help you make good decisions about the proper functionality for your applications.

Here we’ll focus on piston compressors and run through:

  • What is a piston compressor?
  • How do they work?
  • What are the key factors in choosing a suitable compressor?

The best air compressor depends on your applications, so it’s essential to have all the facts to ensure you select the optimal tools for the job!


What Is a Piston Compressor?

Most air compressors work on a positive displacement basis. That means they draw in air and physically reduce the size of the chamber to pressurise the air.

Piston compressors are one of the most popular – so, what is a piston compressor?

These compressors come in single-cylinder models, which compress air in one stroke direction or with double-acting pistons. 

In the latter, the equipment uses both sides of the piston, compressing on both the downward and upward movement to produce a more consistent air supply.

You’ll find different functions and components in alternative piston compressors, such as:

  • Motors that drive the piston movement.
  • Cooling systems between compression stages for a two-stage compressor.
  • Air storage chambers.

There are many different piston compressors, and we’ll explain some of the standard configurations shortly – but the principle remains the same.

Single-stage, double-stage, and multi-stage piston compressors use piston movement to compress the air through positive displacement. Still, the difference is how many times they compress the air before it passes to the storage tank.


How Does a Piston Compressor Work?

Let’s break it down so you can see how a piston compressor functions:

  1. First, the piston descends. That movement is the intake phase and sucks in air through the filter.
  2. Next, the air moves through the inlet valves, reaching the compression cylinder.
  3. The discharge valves close, and the piston ascends, compressing the air in the cylinder.
  4. At the same time, the inlet valves close, and the opposing discharge valves reopen, allowing the air to discharge – this is the outlet stage of the process.

The exact construction of your piston compressor will depend on the type of model you have. For example:

  • Double-acting piston compressors have one vertical cylinder at low pressure and a higher pressure horizontal cylinder.
  • Oil-lubricated compressors use either pressure or splash lubrication.
  • Oil-free piston compressors have piston rings or sometimes toothed walls.

Valves are an integral piece of the equipment and open on both sides of the valve disc, operated by pressure differences.

You can also find larger piston compressors with seals, a crosshead, and other components to ensure oil cannot travel into the compression chamber and contaminate the air.


What Sort of Piston Compressor Should I Choose?

We’ve mentioned above some of the piston compressor options, and the best compressor for you depends on your air quality requirements, how much pressure you need, and the type of environment.

There are thousands of applications for these air compressors, including:

  • Pneumatic tools
  • Spray guns
  • Grinders
  • Sandblasting tools
  • Impact wrenches
  • Air jacks

Some of the factors to consider are the power output you need, tolerable noise levels, and the required capacity.

For smaller capacity processes, such as tyre servicing, you’ll likely need a smaller compressor of around two HP. In contrast, a four HP tool would be more convenient for running various tools.


Are Oil-Free Piston Compressors Better Than Oil-Lubricated?

To add another decision factor into the works – what is a piston compressor with oil-free functionality, and is it superior?

Oil-free compressors are primarily used in functions where air quality is imperative. That might be in food manufacturing, or pharmaceuticals, for example. 

You can select an oil-free piston compressor, which will use a Teflon or silicone coating to protect the moving parts in the absence of oil.

Piston compressors with no oil can also be managed with a closed-loop water system or use injected water. This type of compressor requires less maintenance but can be noisier.

Generally, oil-lubricated compressors are quieter and simple to maintain.

However, you will need to change the oil from time to time since oil quality is essential for reducing friction and greasing internal parts to prevent damage and breakdowns.

Oil changes are required around every 300 hours of use as a maximum, although it’s always important to check the manufacturer’s guide for any specific compressor you purchase.

Finally, you’ll also need to think about a power source.

Many piston compressors are powered by electricity – and while that option is affordable, it’s also the least powerful, particularly in single-phase compressors.

You can also choose a combustion engine compressor, which is usually only suitable for outdoor use due to the risks associated with exhaust emissions.