The basics of a piston or reciprocating compressor

The piston compressor is the oldest and most common of all industrial compressors. As opposed to rotary screw compressors, these machines are relatively simple in terms of mechanical components. They're typically made up of a piston, crankshaft, and cylinders. It operates by using the reciprocating motion of the piston to compress air.

Usually, people think of a piston air compressor first when considering pressurized air equipment. As you might know, there are two basic principles of air compression. One of those is the principle of displacement compression.

With this, there are a lot of compressor types that classify as displacement compressors. The piston compressor is one of them and comes in oil-lubricated or oil-free models.

Cylinder configuration:

The number of compression stages is often related to how the cylinders are arranged. For example, a compressor with vertical cylinders, where the cylinders are placed one above the other, always compresses air in a single compression stage. Whereas a V-design compressor has cylinders arranged in a V-shaped pattern which allows for two-stage compression. In this case, the first compression occurs in a large cylinder, followed by the second compression in a small cylinder. In addition, you can also find W-shape and Star-shape cylinder designs which allow for three or four compression stages respectively.

Lubrication:

Oil-lubricated compressors normally work with splash lubrication or pressure lubrication. The oil is used to lubricate the crankcase and cylinders and the pistons have oil-scraper rings to reuse iol and reduce the oil-use to a minimum.

Oil-free piston compressors contain pistons made from specific materials like PTFE, Teflon, and Carbon, so lubrication is not needed. Compared to an oil-lubricated machine, they have fewer piston rings for example, they do not have the oil-scraper ring

Since oil in oil-injected machines cools and lubricates the motor, oil-free compressors implement alternative methods. One way of keeping temperatures regulated is with an internal fan.

With this, there are ways to ensure smooth operations with oil-free equipment. This includes direct drive and a one-bearing motor. The latter helps reduce friction.

The main reason for choosing an oil-free reciprocating compressor is if your application(s) require Class 0 "oil-free" air quality. This is determined by the International Organization for Standardization (ISO) 8573-1 standards.

A piston compressor works by coordinating its piston, crankshaft, and cylinders. Let's see how they relate to each other. 

1. Piston: The piston is a cylindrical shaped component that moves back and forth inside the cylinder during combustion. The repeated up-and-down movement of the piston creates a reciprocating motion.
2. Crankshaft: A connecting rod connects the piston to the crankshaft. An electric motor drives the crankshaft to rotate. The rotation of the crankshaft moves the pistons up and down so they can compress the air
3. Cylinders: The cylinders are cylindrical chambers in which the piston moves. They are closed at one end and open at the other. Air enters the cylinder through intake valves during the suction stroke when the piston moves downward. During the compression stroke when the piston moves upward, air is compressed and released through outlet valves.
4. Valves: Most compressors have self-acting valves. A self-acting valve opens and closes through the effect of pressure differences on both sides of the valve disk. They allow air to enter the cylinder during the suction stroke and prevent it from escaping during the compression stroke.

In summary, the crankshaft drives the piston. As it moves within the cylinders, it creates alternating high- and low-pressure areas, which compress air. As a result of these components working together, piston air compressors can produce a pulsated flow due to the up-and-down movement.

Thanks to their simple yet robust design, piston compressors are well-suited to heavy-duty environments and easy to maintain. The maintenance procedures are straightforward, which reduces downtime and associated costs. Compared to other types of compressors, piston air compressors are generally more affordable and have lower investment costs.

In industries where compressed air is a critical component, piston compressors are known for their capability to meet high-pressure air demands. This enables compressed air to be used effectively in various applications that require substantial pressure, providing sufficient power and force to accomplish specific tasks.

They do not require a large volume of air or power to meet the compressed air requirements. A piston compressor can operate with a small airflow of less than 4 litres per second and a power range of less than 1.5 kilowatts. 

As a result, piston air compressors are cost-effective and energy-efficient solutions for applications with low air demand. Their ability to operate efficiently with limited resources makes them an ideal choice. They can also be easily integrated with other machines as original equipment manufacturer (OEM) components.

However, it's also worth noting that piston compressors usually come with runtime limitations and may require cooling periods.

Depending on what you need, you can choose to buy a reciprocating (piston) compressor directly from our e-store. If you're just researching options, feel free to browse our oil-free and oil-lubricated equipment.

Still not sure where to begin? Ask us any questions and we will be happy to answer them for you. Contact us today to get started.