Understanding Compressor Pistons: What They Are and How They Work
The piston compressor is one of the most common – and oldest – compressor types. This machine uses principles of displacement to boost the pressure of an enclosed volume of air or gas.
This article is about understanding compressor pistons, what they are, as well as how they work.
What is a Piston Compressor?
A piston compressor is a mechanical device that utilizes one or more pistons for compressing gas or air. This machine compresses air or gas in intervals and is highly suitable for users that require smaller compressed air needs.
In other words, a piston compressor uses the positive displacement principle to compress air or gas via pistons and cylinders.
There are at least 4 sub-types of piston compressors, with different configurations. Some piston compressors fall in the ‘oil-lubricated’ compressor category, while others are ‘oil-free’ machines.
How a Piston Compressor Works
Piston compressors generally come with one or more cylinders and pistons powered by a motor. When the piston moves down, vacuum forms over it. Atmospheric air is sucked in and fills the area above the piston within the cylinder.
When the piston moves up, the air is compressed in one – or more – compression stages, depending on the compressor used. This action occurs simultaneously with the closing of the inlet valve while the outflow valve gets opened.
Every piston stroke draws more air or gas into the reciprocating compressor, increasing pressure.
The Sub-Types of Piston Compressors
There are 4 sub-types of piston compressors that exist today, namely:
- One-Stage Compressor
This compressor type has one or more cylinders. Each of the cylinders efficiently compresses air from atmospheric pressure into operational pressure.
- Multi-Stage Compressor
This type of compressor also has 2 or more cylinders, generally connected in series. Air is compressed gradually to the required pressure level within the cylinders.
Between each step of the compression process, the compressed air is sufficiently cooled with ambient air or water. This significantly boosts efficiency while accomplishing much higher pressure levels than its counterpart, i.e., the one-stage piston compressor.
- Low-Speed (Integral) Piston Compressor
This compressor type comes with its driver mounted into its frame, hence the ‘integral’ that is part of its name. Low-speed piston compressors are generally heavier and larger than high-speed compressors.
They also require add-ons such as pulse and noise suppressors due to how loud they operate. They also require lower maintenance since they generally function at 200 to 600 rpm speeds.
- High-Speed (Separable) Piston Compressor
Compressors in this category are ‘separable’ since they are dissociated from their energy source. They are usually powered by motors of engines. High-speed compressors are easy to transport or move from one point to another. They are available in different sizes and are fairly low-cost.
The Most Important Component of a Piston Compressor
A piston compressor’s mode of operation relies heavily on this machine’s most crucial component, i.e., the piston. As you may have deduced, the piston primarily compresses air.
As a result, pistons are required to have strength and weight. In addition, it should be highly compatible with air or gas to be compressed.
The piston also transmits the energy from the crankcase to the air or gas within the cylinder. This prevents the refrigerant from leaking through this gap. This vital component is also covered with piston rings between the cylinder walls and the piston.
Pistons are often made of cast iron or aluminum. It is designed to travel vertically, i.e., upwards and downwards within the cylinder. This movement results in the compression and suction of the refrigerant.
Another crucial component is piston rings which are wound on the piston. The piston rings usually come in direct contact with the cylinder walls as the piston travels up and down. As a result, they need to be replaced more often than other components on a compressor.
The primary function of piston rings is to minimize wear and tear between the piston and cylinder. Piston rings are available in metallic and non-metallic forms, though it is important to have rings softer than the inner wall of the cylinder for seamless performance.
Uses of Piston Compressors
Piston compressors are highly suitable for several compressed air requirements. For instance, one-stage reciprocating compressors can generate pressures up to 8 bar while multi-stage compressors produce as high as 15 bar.
This type of compressor has found excellent uses in several industries, such as:
- Chemical industries
- Gas processing
- Refineries and oil plants, etc.
The availability of a wide range of piston compressors makes them suitable for nearly every work setting. However, experts recommend intermittent operation if you want your equipment to last long.
Every air-cooled compressor’s load level should never exceed 60 to 70 percent. Therefore, after compressing air or gas for at least 2 minutes, the machine must rest up to 1.5 minutes. Ensure the total compression period on a daily basis does not exceed 4 hours.
Most piston compressors come with more than a few maintenance requirements. However, they are energy-efficient as they can be used in workshops, auto repair shops, and DIY settings.
The Benefits of Piston Compressors
One of the most significant benefits of piston compressors is the inherent optimization for intermittent performance, especially with the load rate ranging from 40 to 60 percent.
Another benefit of using this compressor type over other versions is its availability in mobile and stationary models. As a result, potential users enjoy more flexibility as these machines can be used almost anywhere.
Moreover, since piston compressors are available in a wide range of models, finding the right one for your needs is possible. As long as you have the specifics you require, you will always find the perfect piston compressor suitable for your own needs.
Piston compressors are one of the most common and oldest machines today. They compress air by the action of pistons within cylinders and are used in various industries.
However, they must be used intermittently in order to ensure longevity. They also require regular maintenance for optimal performance.