Guide to Reciprocating Compressors

A reciprocating compressor works by converting power into potential energy stored in pressurized air. It achieves this through a piston driven by a crankshaft. The piston moves down to draw air into the cylinder, then moves up to compress it. This simple yet effective mechanism is why reciprocating compressors are favored for many applications.

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 remain 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.

• High Pressure and Efficiency: Reciprocating compressors can achieve high pressures, making them suitable for heavy-duty applications. Their efficiency in compressing air also means they consume less energy compared to other compressor types.

• Durability and Longevity: Built to withstand tough conditions, these compressors offer long service life with proper maintenance. Their robust construction ensures reliability even in demanding environments.

• Versatility: These compressors are used in various industries, from manufacturing and construction to automotive and food processing. Their ability to handle a wide range of pressures and flow rates makes them incredibly versatile.

• Low Initial Cost: Compared to other types of compressors, reciprocating compressors generally have a lower initial cost. This makes them an attractive option for businesses looking to maximize their return on investment. 

Reciprocating compressors are indispensable in multiple sectors. In the manufacturing industry, they power pneumatic tools and equipment. In the automotive sector, they are crucial for tasks such as tire inflation and painting. The food and beverage industry relies on them for packaging and processing operations. They are also used in HVAC systems, refrigeration, and more.

Modern reciprocating compressors incorporate advanced technologies to enhance performance and sustainability. Features such as variable speed drives (VSDs) help optimize energy use, reducing operational costs and environmental impact. Additionally, improvements in materials and design have led to quieter and more compact models, broadening their applicability.

Regular maintenance is key to ensuring the longevity and efficiency of reciprocating compressors. This includes routine inspections, timely replacement of worn parts, and keeping the compressor clean and well-lubricated. Many manufacturers offer comprehensive service plans to help users maintain optimal performance.

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?

1. Air Quality Requirements:

   • Do you need to produce clean air, dry air, or oil-free air?

2. Operating Hours:

   • 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?

3. Demand Fluctuations:

   • Does your air compressor demand fluctuate throughout the day?

4. Future Expansion:

   • Will you be expanding soon?
   • Will your requirements change in the near future?

5. Decision Factors:

   • Engineers often need to make judgment calls based on what is best for the overall project, not just 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.

• 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 Life-Cycle Cost

As you can tell, there is a lot that goes into picking the right reciprocating compressor. It starts by knowing your exact needs or identifying where your inefficiencies are.

That's why we recommend consulting with an Atlas Copco expert who can guide you via email or phone.

Changes in the molecular weight of the gas composition can be a critical factor. Positive displacement compressors are more tolerant of these changes than dynamic compressors. Therefore, it's important to identify if this will be an issue for our application.

If we decide to choose a positive displacement machine, we need to be aware of the advantages that reciprocating compressors have over rotary compressors:

1. Simplicity of Working Principle: Reciprocating compressors have a simple working principle, which means the machinery is less complicated. This simplicity makes them cheaper to manufacture.

2. Well-Known Technology: The technology behind reciprocating compressors is well known and understood within the industry. This ensures that finding maintenance support is easy and convenient.

3. Abundant and Affordable Spare Parts: Due to their less complicated design and widespread use, spare parts for reciprocating compressors are abundant and very affordable.

4. Wide Range of Sizes: Reciprocating compressors are available in a wide range of sizes, making them suitable for both small businesses and larger facilities.

5. Portability: Smaller reciprocating compressors are portable, which is useful for site-specific applications.

6. High Maximum Discharge Pressure: Reciprocating compressors typically have a relatively high maximum discharge pressure.

By considering these factors, we can make an informed decision about whether a positive displacement compressor, specifically a reciprocating compressor, is the right choice for our needs.

Reciprocating compressors remain a cornerstone of industrial operations worldwide. Their efficiency, durability, and versatility make them a preferred choice for various applications. With continuous advancements and a focus on sustainability, these compressors are set to remain a critical component in the industrial landscape.

For more information on reciprocating compressors and how they can benefit your operations, visit Atlas Copco's comprehensive guides and product pages.