Single-stage and two-stage compressors perform the same air compression job, but slightly differently!
The primary variance is that the air is compressed once between the inlet valve and the tool nozzle in a single-stage compressor.
What is a 2 stage compressor?
It’s a similar piece of equipment but compresses the air twice, generating double the pressure.
The advantage here is that, with more cylinder stages and more significant pressure, the compressor works more effectively, recovers faster, and can manage more tools simultaneously.
Let’s explain a little more what is a 2 stage compressor used for, how it works, and when this type of air compression is most valuable!
How Does a Two-Stage Air Compressor Work?
A 2-stage or multi-stage air compressor has cylinders of varying diameters. The first cylinder is low-pressure, and the next smaller and so higher pressure.
Air passes through the heat exchanger to be cooled between each compression. Cooling that air is crucial since it means less work is required to compress it even further.
Two-stage compressors then transmit the air into the next chamber for increased pressurisation.
As a popular option, reciprocating piston and rotary compressors, both positive displacement air compressors, come in two-stage models.
Here’s how it works:
- Step One: ambient air is drawn into the lower pressure cylinder through the inlet filter. The piston compresses the air, usually from 40 to 70 PSI.
- Step Two: the inter-cooling system then reduces the temperature to remove stress on the compressor and improve efficiency.
- Step Three: cooled air moves onto the higher pressure cylinder with a shorter piston. The increased pressure can reach between 175 and 200 PSI.
- Step Four: the pressurised air is cooled again and passes to the storage reservoir.
You will find 2 stage compressors in drinks manufacture, aerospace industries and automotive applications.
What is a 2 Stage Compressor Used For?
The best air compressor depends on the applications. Single-stage compressors are more suitable for smaller work environments since they are quieter and cheaper to buy.
Single-stage compressors are designed for intermittent use rather than continual airflow, so a lot depends on the processes you need your compressor for.
Most factory or industrial applications require a 2 stage compressor since they are more reliable, less prone to condensation, and more compact.
A multi-stage air compressor can handle large numbers of pneumatic tools and are best suited to high powered applications, such as painting or sanding.
What Are the Benefits of a Two-Stage Compressor?
Let’s run through the advantages of opting for a two-stage compressor.
Lower temperature air compression is thermodynamically more efficient. Two-stage compressors cool air between cylinders, requiring less energy to produce high pressure.
Two-stage compressors are, therefore, more energy-efficient and cost less to run.
They can also produce high CFM, with the operating capacity you’ll need for most industrial applications.
The inter-stage cooling prevents overheating and reduces the potential for mechanical damage and maintenance.
Lower maintenance costs mean higher productivity and increased reliability compared to a single-stage alternative.
Reduced moisture build-up.
Water vapour in air compression is responsible for premature equipment wear and even mechanical failures.
The cooler air compression produces less moisture content, with reduced potential for vapour to build up.
Downsides to a Multi-Stage Air Compressor
As we’ve discovered, single-stage and multi-stage compressors are valuable tools, although with different applications and uses.
There are some potential downsides to be aware of:
- Two-stage technology is a little limited in HP ranges, usually from 125 HP and above.
- Initial purchase prices are higher for two-stage compressors. For example, a 2 stage rotary screw compressor can be around 30% higher than a comparable size single-stage option.
- Multi-stage equipment comes with similar control schemes as a single-stage compressor, but there are limitations in terms of placement. Sizing also depends on the type of compressor you have, and a two-stage option can be larger, with designs ranging from over/under compressors to tandem designs.
Generally, two-stage compressors are slightly smaller, but as we’ve mentioned above, that depends on the type of compressor you have.
The benefit is that, even with the higher initial cost, a multi-stage compressor is simply more efficient, requiring less HP to deliver the same airflow requirements.
Over time, that substantially reduces the cost difference, and the smaller footprint is ideal for manufacturing facilities where space is at a premium.
As with all air compression choices, it’s all about the applications you need your air compressor to deliver, access to adequately ventilated compression rooms, and the output required to produce the proper functionality.