What Is a Reciprocating Compressor?
A reciprocating compressor is a device that compresses air using the reciprocating motion of a piston.
Reciprocating compressors are also referred to as piston compressors in Japan. One of the advantages of this type of compressor is its ability to achieve a higher pressure ratio compared to other compressors.
They have a relatively simple structure, making them easy to maintain and repair. However, they are also known for their high vibration and noise levels.
Applications of Reciprocating Compressors
Reciprocating compressors find applications in various industrial and commercial settings. Here are some examples:
1. Pneumatic Systems
Reciprocating compressors are widely used in pneumatic systems to supply compressed air. They are used in factories for instrumentation air piping, as well as in machine shops to power tools and machinery, and for drying equipment.
2. Refrigeration and Freezing Equipment
They are employed to compress refrigerants in freezing and refrigeration equipment, commonly found in commercial refrigerators, freezers, refrigeration trucks, and air conditioners.
3. Gas Supply Systems
Reciprocating compressors are also utilized in gas supply systems to intake, compress, and raise gas to the required pressure before pumping it into pipelines or tanks. An example is the liquefaction and transportation of liquefied propane gas (LPG), which is then used for various purposes including natural gas supply, pipeline maintenance, and pressure control.
Principle of Reciprocating Compressors
The working principle of a reciprocating compressor involves compressing gas through the reciprocating motion of a piston. This compression process occurs in a continuous cycle of intake, compression, and exhaust, driven by a power source (engine, motor, etc.) that provides the reciprocating motion.
1. Intake Process
As the piston moves downward in the cylinder, the cylinder volume increases, causing the intake valve to open and allowing gas to be drawn into the cylinder. During this phase, the pressure inside the cylinder decreases.
2. Compression Process
As the piston begins to move upward within the cylinder, the cylinder volume decreases, and the intake valve closes. Compression of the gas in the cylinder takes place, resulting in an increase in pressure within the cylinder.
3. Exhaust Process
Once the piston reaches the top position, the pressure in the cylinder is at its maximum. At this point, the exhaust valve opens, and the compressed gas is expelled from the cylinder. As the piston moves back down, the cylinder volume increases again, causing a decrease in pressure.
Types of Reciprocating Compressors
There are two main types of reciprocating compressors: oil-injected and oil-free.
1. Oil-Injected Type
Oil-injected reciprocating compressors use oil for lubrication during the compression process and to reduce friction between the piston and cylinder. This results in reduced wear, heat generation, and noise levels. However, the released gas may contain a small amount of oil.
2. Oil-Free Type
The oil-free type does not use oil for compression or lubrication but employs alternative methods to manage friction and lubrication. Since the released gas is free of oil, it is suitable for industries such as medicine and food where oil contamination is a concern. However, the oil-free type may require additional design considerations for cooling and durability, and it is primarily used in high-capacity and high-pressure applications.