Reciprocating compressors – the most common form, which is known as piston compressors – are positive-displacement mechanical devices designed to compress and deliver high-pressured gases via the use of a plunger or piston. Gas transmission pipelines, refineries, and many other applications use reciprocating compressors to deliver or transfer oxygen, hydrogen, and other gases.
Piston compressors have sliding pistons inside a cylinder containing the gas about to be compressed. A piston rod is directly attached to the piston and is frequently pivoted around a horizontal axis.
The Different Types of Reciprocating Compressors You Should Know
Different types of reciprocating compressors exist, namely:
- Single-acting reciprocating compressor
- Double-acting reciprocating compressor
- Diaphragm reciprocating compressor
Reciprocating compressors are also available as single-stage compressors or multi-cylinder multi-stage – i.e., multiple cylinders – reciprocating compressors.
Let’s get into more detail on each reciprocating compressor type, arranged in no particular order.
Single-Acting Reciprocating Compressor
A single-acting reciprocating compressor is a mechanical device with several valves set at the top. There is only one compression cycle for each revolution of this machine’s crankshaft.
The piston in this reciprocating compressor can reach a topmost position – known as the Top Dead Center or (TDC) to the Bottom Dead Center or (BDC). Then, the piston moves from the TDC to the BDC and back again within one crankshaft revolution.
As the piston travels from Top Dead Center to Bottom Dead Center, the pressure within the cylinder plummets to a value below the atmospheric pressure. Owing to the significant pressure difference across the suction valve, the latter overcomes the spring force and then opens up in order to grant air access into the cylinder.
As the piston journeys from BDC back to TDC, the air is gradually pressurized while the spring-loaded suction valve closes. Finally, as the piston moves closer to the TDC, the pressure of the air is enough to readily get the better of the spring force of the outlet discharge valve.
Therefore, this discharge valve opens up, so that air from the cylinder leaves with increased pressure. The cylinder empties itself while the discharge valve closes readily, and the piston is again ready to move to the BDC.
Double-Acting Reciprocating Compressor
A double-action reciprocating compressor is a machine with 2 sets of valves. The first set of valves is located at the top of the cylinder, while the other set is found at the bottom.
This reciprocating compressor has 2 compression cycles for each revolution of the crankshaft. When the piston compresses air or gas from one side, the gas or air is sucked right into the cylinder on the other side of the piston.
As the piston moves from TDC to BDC, the pressure within the cylinder, especially at the top, falls below the atmospheric pressure. The significant pressure difference across the suction valve at the top results in the suction valve overcoming the spring force and opening up. This allows the air or gas to enter the cylinder.
As the suction action takes place at the top section of the piston, the air or gas becomes compressed almost simultaneously in the bottom chamber. As the piston draws closer to the BDC, the air pressure on the bottom section becomes sufficient enough to readily overcome the spring force of the discharge valve at the bottom. This cause the bottom discharge valve to open up and discharge the high-pressure gas or air.
As the lower discharge valve closes, the piston moves immediately from the BDC back to the TDC.
The air or gas on the upper section of the piston becomes gradually pressurized, closing the upper suction valve. As the piston draws closer to the TDC, the air pressure on the upper section of the piston becomes sufficient to readily overcome the spring force of the discharge valve at the top.
The top discharge valve opens up in order to discharge the air or gas from the cylinder under increased pressure. The cylinder empties itself as the discharge valve closes, and the piston moves immediately towards the BDC.
In the meantime, the bottom suction valve is already opened, and fresh air enters the compressor’s bottom section. The gas becomes ready for compression as the piston draws away from the TDC to the BDC.
It is not surprising to see that double-acting reciprocating compressors are typically more efficient than its counterpart, the single-acting compressor. Nevertheless, a double-acting reciprocating compressor vibrates much more than its counterparts, requiring an excellent or strong foundation and vibration isolation.
Diaphragm-Type Reciprocating Compressor
A diaphragm-type reciprocating compressor is a variant of the prototype reciprocating compressor. Gases undergo compression as a result of the up-and-down movement of a membrane or diaphragm, hence the name ‘membrane compressor.’
The diaphragm travels up and down due to its connection to a piston that a crankshaft and connection rod drives.
The piston of this reciprocating compressor pulls down the diaphragm instead of moving inside a cylinder. The diaphragm contracts in order to create suction and push up the diaphragm in order to create discharge.
The life of the diaphragm, as well as the volume of air or gas compressed, depends primarily on the material of the diaphragm.
Diaphragm-type reciprocating compressors are generally used for applications that require leakage- and contamination-free processes.
Diaphragm-type reciprocating compressors come in two varieties: single-stage reciprocating compressors and multi-stage reciprocating compressors.
Single-Stage Reciprocating Compressor
This reciprocating compressor has one – or multiple – cylinders connected in a parallel way. As a result, air or gas is only compressed once before getting transported to the final storage tank.
The design of the single-stage compressor limits its discharge pressure. The maximum pressure achieved with this reciprocating compressor is about 125 PSI. Any value beyond this increases the temperature of the cylinder.
Multi-Stage Reciprocating Compressor
The multi-stage reciprocating has multiple stages, i.e., more than one cylinder, and successfully compresses gases or air in multiple stages.
However, noted that not every multi-cylinder compressor is a multi-stage reciprocating compressor. Instead, there are single-stage compressors with multiple cylinders.
The best way to differentiate a multi-stage reciprocating compressor from a multi-cylinder single-stage compressor is by checking out the cylinder size.
All the cylinders used in a single-stage multi-cylinder compressor are the same size. But the second-stage cylinder in a multi-stage reciprocating cylinder is of a smaller diameter than the others.
Reciprocating compressors are among the most widely-used industrial equipment in nearly all settings. They are available in single- and multi-piston models and are capable of providing highly effective and long-term gas compression.
From industry standards like Ariel compressor parts to Ingersoll Rand and Cooper Bessemer compressor parts, we carry compressor parts you can trust and the service you can count on.