Reciprocating Compressors: Working Principle, Parts & Buyer’s Guide

Reciprocating piston compressors, sometimes called just piston compressors, were some of the first machines invented to compressed air. Their design is constantly being refined as technology and materials improve, and they’re widely used still to this day. Many industries rely on reciprocating compressors for their compressed air needs.

Industrial reciprocating compressors are becoming a critical part of many processes and the need for machines is growing year on year. The market is expected to be worth USD 16.36 billion by 2024. You can find them being used in Refineries, Refrigeration, Oil & Gas, Chemical Manufacturing, Automotive, Agriculture, Medical Surgery etc. Chances are that if you’re reading this you’re either a student or you work in one of these industries!

Air compressors are categorized by the working principle they use to compressed air - either positive displacement or dynamic displacement.

Reciprocating compressors use positive displacement, which is a method that relies on a law of gases called Boyle’s Law.

Boyle’s law states that the absolute pressure exerted by a given mass of an ideal gas is inversely proportional to the volume it occupies if the temperature and amount of gas remains unchanged within a closed system.

This law shows us that a gas like air will increase its pressure as it passes through an enclosed space of decreasing size. The pressure and volume relationship is inversely proportional.

The working principle of a reciprocating air compressor is to draw gas through an inlet, and then move the gas through a cavity or chamber that decreases in size.

This compresses the gas and by doing so the gas within the chamber increases in pressure.

Then once maximum pressure is achieved inside the cavity or chamber, an opened valve can release the high-pressure gas into an outlet system for industrial use.

Broadly speaking both positive displacement and dynamic displacement machines achieve the same objective - they compress and raise the pressure of gas.

So how do you know when to pick a reciprocating / piston compressor over a rotary compressor, or some other dynamic displacement machine as described in the diagram above?

You should start by making sure you’re looking for the right size of compressor.

This means knowing the amount of pressure (PSI) and flow (CFM) you need for your application.

There are various types of reciprocating compressors suitable for different needs and purposes - use our product selector to filter our range until you find your ideal product.

Notice how reciprocating compressors have very high maximum discharge pressure?

And here are some other things to consider to buying a reciprocating compressor:

• Do you need to produce clean air, dry air, or oil free air?
• How many hours per year will you be running the compressor?
• Will the compressor be running constantly during the day or will there be shifts?
• Does your air compressor demand fluctuate throughout the day?
• Will you be expanding soon? Will your requirements change in the near future?

It also depends on who’s making the purchase decision too.

At times engineers are required to make judgement calls based on what is best for the overall project not and just for the specific application of the compressor.

They may be constrained by technical, commercial and scheduling factors, as well as “off design” conditions and practical future expectations.

Here are some non-technical things to consider:

• Operating conditions (present and future)
• Quality of the equipment brand
• Available skills for maintenance
• Staff’s familiarity with the machine
• Automation and digital controls
• Availability of parts
• Delivery time
• Price and the Life-Cycle Cost

As you can tell by now there’s A LOT that goes into picking the right reciprocating compressor.

And it starts by knowing what your exact needs are or where your inefficiencies are.

That's why we recommend consulting with an Atlas Copco expert who can either guide you over email or phone, or run a FREE energy efficiency audit at your site.

Changes in molecular weight of the gas composition is a make or break factor.

Positive displacement compressors are more tolerant of changes in gas composition than dynamic compressors.

So we should identify if that is going to be an issue.

If we decide to pick a positive displacement machine then we need to be aware of the advantages that reciprocating compressors have over rotary compressors.

The working principle is simple which means that the machinery is less complicated. They are cheaper to manufacture.

The technology is well known and understood by everyone in the business. This means finding maintenance support for a reciprocating compressor is easy.

Since the machinery is less complicated and the technology is well known spare parts of reciprocating compressors are abundant and very affordable.

There are a wide range of sizes that are suited for small businesses as well as larger facilities.

Smaller reciprocating compressors are also portable which is useful for site-specific applications.

And as you can tell from the table above reciprocating compressors have a relatively high maximum discharge pressure.

Headquartered in Sweden and operating in over 180 countries, Atlas Copco has been providing industrial solutions since 1873.

Our vision has always been to be First in Mind—First in Choice as a supplier of compressed air and gas solutions in UAE and worldwide.

And over the years we’ve discovered that being interactive, committed and innovative, is the key to offering them the best value.

Our clients are the beneficiaries of the consistent break-throughs we’ve made in optimizing our products for energy savings.

Did you know that air compressors use anywhere from 12-40% of a facility's yearly industrial electricity consumption?

But of all the energy that’s being supplied to your air compressor a lot of it isn’t even being used!

Energy is wasted in a number of ways:

• Heat production
• Air leakage
• Friction between screw compressor parts
• Bad compressor design

Our reciprocating compressors are market leaders in terms of energy efficiency and innovation.

Our Atlas Copco product range includes efficient reciprocating compressors that are suited for a variety of applications.

And they come in Belt Driven, Direct Drive, Dental Air, PET Blowing and Compressed Natural Gas variants.

We suggest that you get an expert to walk you through the type of reciprocating air compressors and its parts that would work best for your facility.

And remember to take advantage of our FREE energy efficiency audit when you get in touch with us.

We can arrange to send one of our experts to your site

The audit can be a visual inspection, or a full system overhaul, where we solve for leaks, pressure drops and energy savings however possible.

Our customers maintain a long term working relationship with us because we give them peace of mind and do everything in our power to make sure their production processes run smoothly at all times.

We promise to continue to design products that provide tangible benefits in terms to you of productivity, energy efficiency and lower life cycle cost.

Founded in 1953, ORTA is an industry-leading denim manufacturer in Bahrain. Its weaving plant has six units of Atlas Copco 250 kW 2-stage oil-free screw air compressors.