Reciprocating Gas
Compressors Explained

Reciprocating compressors pull vapor into a cylinder through a suction valve by drawing back a piston to create a low pressure area in the cylinder and pressurize the gas by pushing the piston back up into the cylinder to squeeze the gas out through the discharge valve.

A compressor valve consists of four parts: a seat, bumper, disc and spring. The spring rests against a bumper and pushes the disc against the seat. The disc seals off the flow passage through the seat. If more pressure builds up on the seat side than the bumper side, the disc is forced away from the seat so gas can flow through the valve.

In order for compression to take place, the piston must be sealed against the wall. This seal is made with several piston rings. To avoid contaminating the process gas with lubricating oils, the piston rings must be made of a self- lubricating material. Corken’s piston rings are usually made of glass-filled PTFE. The gas pressure in the cylinder presses the piston ring against the cylinder wall. Ring expanders help push the piston rings towards the cylinder wall so high pressure gas may flow behind the ring.

Although piston rings form a good dynamic seal, they are not tight enough to seal all the pressure and gas inside the cylinder so additional piston rod packing is required. The piston rod packing is located at the bottom of the cylinder and composed of several parts. The most important component of packing is the self-lubricating PTFE V-rings that seal against the piston rod. A spring is included in the packing assembly which allows a slight amount of float to reduce friction. The piston rod packing also helps keep oil from the crankcase from entering compression chamber.

Depending on the type of gas, there will be one to three sets of packing per piston rod. One set of packing controls leakage and oil contamination of the vapor to a satisfactory level for most commercial LP gas and ammonia applications. When leakage and contamination must be held to an absolute minimum, three sets of packing separated by two distance pieces must be utilized. Corken manufactures vertical and horizontal compressors with single (planin style), double (D-Style), and triple packing (T-Style) options.

The crankcase converts rotary motion from the motor to reciprocating motion at the piston. With the exception of the model 91, all of Corken’s compressors have an oil pump that pressure lubricates the bearings and wrist pins. The oil pump is a gear type that runs in either direction. A Corken compressor can be turned in either direction.

For more information on Corken’s reciprocating gas compressors, click on one of the links below.

Vertical Reciprocating Compressors (Single Packed)
Vertical Reciprocating Compressors (Double & Triple Packed Oil Free)
Horizontal Reciprocating Compressors (Single Packed & Triple Packed Oil Free)