Which Type of Air Compressor Is Best for Your Application?

Built almost like an automotive engine, reciprocating compressors have a crankshaft driven by an electric motor. As the shaft turns, it pushes a piston up and down, drawing air into a chamber as it moves in one direction, then compressing it when the piston reverses direction.

Often called piston compressors because of their construction, reciprocating compressors are very practical for small applications. They are rugged and durable, holding up well when properly sized. Unfortunately, they need to be oversized, because they have a low-duty cycle, needing time to cool off. Heavy use or a high-duty cycle is not recommended. Single-stage models have only one compression chamber and come in sizes from .25 to 5 HP. They are better for low-pressure applications.

Recips are also available in a multi-stage design that uses more than one stage to compress air to the final discharge pressure. Multiple cylinders each perform a different stage of compression. An interstage cooling device reduces the air temperature between the stages of compression, decreasing the work required and the risk of mechanical failure due to excessive heat. Multi-stage compression is more energy-efficient than single-stage compression for high-pressure applications.

Double-acting reciprocating compressors have compression chambers on both sides of the piston and can get much larger, up to 1,000 HP. But while double-acting reciprocating compressors have water cooling that addresses the duty cycle issues, they are becoming less common because they are expensive, require reinforced foundations to handle vibration, and need more extensive maintenance.

Most recipes in use in industrial applications today are two-stage compressors, which are much more durable and can deliver greater pressure and flow, according to Air Compressor Guide. 

As mentioned above, reciprocating compressors have a limited duty cycle, working best with intermittent or partial duty. They typically run best at 50% duty cycle or less. That’s 30 minutes in an hour. Run it longer, and you risk damaging your compressor and shortening its life. As a result, to properly size a recip, you need to consider a compressor with a larger horsepower rating to give the pump time to cool down.

Pistons produce larger air pulses than rotary screws. And, because they just have wiper rings between the air and the oil, they do not have systems in place to prevent oil slugs from passing through. Those are huge disadvantages for painting applications where you want a smooth, even flow of high-quality air to produce the mirror finish your customers want.

And they are noisy. Because pistons are generally open, with loud valves and no acoustical enclosures, reciprocating compressors are noisy, with sound levels usually over 85 dBA, requiring hearing protection mandated by OSHA. In fact, many companies want to isolate them in rooms that become hot and stuffy. Or move up to rotary screw air compressors to reduce the noise and vibration.