Whenever most people think about a compressor, they probably have a piston compressor in mind. You might already know there are two basic principles of air compression. One of those is the principle of displacement compression. There are a lot of compressor types that classify as a displacement compressor. The piston compressor is one of them, oil-lubricated or oil-free.
The piston compressor is the oldest and most common of all industrial compressors. It is available in single-acting or double-acting, oil-lubricated or oil-free variants, with various numbers of cylinders in different configurations. With the exception of very small compressors having vertical cylinders, the V-configuration is the most common for small compressors. On double-acting, large compressors the L-configuration with a vertical low pressure cylinder and horizontal high pressure cylinder offers immense benefits and has become the most common design.
Oil-free piston compressors have piston rings made of PTFE or carbon, and alternatively, the piston and cylinder wall can be profiled (toothed) as on labyrinth compressors. Larger machines are equipped with a crosshead and seals on the gudgeon pins, and a ventilated intermediate piece to prevent oil from being transferred from the crankcase and into the compression chamber. Smaller compressors often have a crankcase with bearings that are permanently sealed.