What is a Piston Compressor and How Does it Work?

What is a Piston Compressor?

A piston or reciprocating compressor is a type of air compressor that uses one or more pistons to compress air. Piston compressors work on the displacement principle. As the piston moves downward in the cylinder, it draws air into the cylinder through an inlet valve. Likewise, as the piston moves upward, it compresses the air and forces it out through an outlet valve into an air tank.

Piston compressors can be oil-lubricated or oil-free. There are also single-stage, double-stage or multi-stage configurations. Many industries use piston air compressors because of their reliability and high-pressure output. These characteristics make them suitable for applications with a high demand for compressed air.

How Does a Piston Compressor Work?

1. The process starts with the piston moving down in the cylinder, which reduces the pressure inside the cylinder and allows ambient air to enter through the inlet valve.
2. As the piston reaches the bottom of its stroke, the inlet valve closes and traps the air inside the cylinder.
3. The piston moves up, reducing the trapped air’s volume and increasing its pressure.
4. This compression stroke continues until the air pressure exceeds the pressure in the tank or storage vessel.
5. The outlet valve opens, and the compressed air is pushed into the air tank.
6. The valve system manages the airflow into and out of the cylinder with the valve discs opening and closing as the piston moves, which is crucial for the compression process and overall efficiency of the compressor.

Single-Stage and Multi-Stage Piston Compressors

• Single-stage compressors use one cylinder and piston to compress the air.
• Multi-stage compressors use two or more cylinders to compress the air to higher pressures.

Oil-Lubricated and Oil-Free Piston/Reciprocating Compressors

• Oil-lubricated piston compressors use oil to lubricate the moving parts to reduce wear and tear.
• Oil-free piston compressors use special materials and coatings to achieve the same effect without oil and are suitable for applications where oil contamination must be avoided.

Piston compressors are popular because of their high-pressure output, reliability, and versatility for industrial applications.

Parts of a Piston Compressor

Piston compressors usually have several components that work together to compress the air:

• Piston(s): move up and down in the cylinder to draw in and compress air.
• Cylinder(s): the pistons are inside the cylinders, where the air compression occurs. They can be single or multi-stage.
• Valves: inlet and outlet valves control the airflow into and out of the cylinders. When the inlet valve opens, the air is drawn in. When the outlet valve opens, the compressed air is released.
• Crankshaft: converts the rotary motion of the motor or engine into a reciprocating motion that moves the piston(s).
• Connecting rods: connect the piston(s) to the crankshaft. The crankshaft powers the piston(s).
• Electric motor or engine: provides the power to drive the crankshaft, which, in turn, moves the piston(s).
• Air tank: stores the compressed air for use when needed.
• Lubrication system: lubricates the moving parts, using oil or special coatings to reduce friction.

These parts ensure piston compressors work efficiently to produce high-pressure compressed air for various applications. Reciprocating compressors can be classified into low-speed integral (200 to 600 rpm) and high-speed separable (900 to 1,800 rpm) types, each with different operational characteristics and maintenance requirements.

Different Types of Piston Compressors

There are several types of piston air compressors.

Single Acting Compressors

A single piston compresses air on one side of the cylinder. They are used for lower-pressure applications and are known for simplicity and reliability.

Double Acting Compressors

Double pistons compress air on both sides of the cylinder and are suitable for applications that require a continuous and high-pressure air supply.

Oil-Lubricated Compressors

Oil lubricates the piston and cylinder to reduce wear and tear and extend the compressor’s life. They are used for heavy-duty applications and require regular maintenance to manage oil levels and prevent contamination.

Oil-Free Compressors

Special materials and coatings help reduce friction and wear; they have lubricated bearings and grease-free piston rings. They are suitable for applications where oil contamination is a concern, such as in the food and medical industries.

Multi-Stage Compressors

Multiple stages of compression achieve higher pressures. A multi-stage piston setup compresses air in successive stages, with each stage increasing the pressure further. They are suitable for applications that require air at very high pressure.

What are Piston Compressors Used For?

Piston/reciprocating air compressors are very versatile. Various industries use this industrial air compressor because it efficiently produces high-pressure compressed air.

• Manufacturing, automotive, and construction industries use piston compressors to power pneumatic air tools, spray painting equipment and other machinery.
• Auto workshops use them to inflate tyres and provide air for cleaning and maintenance.
• The food and beverage industry uses piston/reciprocating air compressors for processing and packaging.
• The medical industry uses compressed air to power dental tools, respiratory ventilators, other medical devices, and anaesthetic gas carriers.

Different types of air compressors are suitable for specific tasks. However, piston air compressors are generally more affordable than higher-spec models, which is why they are widely used.

Advantages of Piston Air Compressors

Piston air compressors have several advantages:

• Can produce high-pressure compressed air suitable for applications that require high power.
• Suitable for various industries, from automotive to manufacturing to power pneumatic tools and machinery.
• Durable piston compressors can withstand heavy use and provide consistent performance over time.
• Oil-free piston compressors are suitable for applications where oil contamination is a concern, such as food and medical industries.
• Generally cheaper than other alternatives, it is a cost-effective solution for businesses.
• The simple design makes them easy to maintain for long-term efficiency.
• Can be configured in single-stage or multi-stage setup to suit application-specific pressure requirements.

These benefits make piston air compressors a reliable and efficient compressed air source for many industrial applications.

How to Choose the Right Piston Compressor

The best piston compressor is one that matches your needs. Below are some things to consider.

Factor	Considerations
Pressure Requirements	Determine the pressure level needed for your applications. High-pressure needs may require a multi-stage compressor.
Air Flow Rate	Verify the compressor’s cubic feet per minute (CFM) rating to ensure it can deliver the necessary air volume for your tools or machinery.
Oil-Lubricated vs Oil-Free	Decide between an oil-lubricated compressor for durability or oil-free compressors to prevent contamination in sensitive applications.
Size and Portability	Consider the compressor’s size and whether you need a portable model for easy movement around your workspace.
Noise Level	Evaluate the noise output, especially if the compressor will be used in a noise-sensitive environment.
Power Source	Check compatibility with your power source, whether electric or gas-powered.
Budget	Fix a budget that includes the purchase price as well as maintenance and operating costs.

Considering these factors will help you select a piston compressor that matches your specific requirements and will provide reliable performance.

Where to Buy a Piston Compressor

Control Gear stocks a wide range of super-efficient, reliable compressors suitable for most industrial use cases.

Our Atlas Copco oil-lubricated LE & LT models deliver compressed air up to 30 bar. And the LF, LFx, and LZ models are compact, quiet, and supply 100% oil-free air.

Need help choosing the best piston air compressor? Contact Control Gear today and let our experts help you find the best solution for your compressed air needs.