2 Considerations When Shopping for a Reciprocating Air Compressor
Reciprocating air compressors offer a multitude of compelling benefits, especially when compared to their primary alternative: rotary screw compressors. Reciprocating compressors tend to carry lower price tags; however, they need to be sized correctly to avoid premature failure. Most reciprocating compressors are air-cooled and need to have time to cool properly. Generally, this means they should be fully loaded no more than 60–70% of the time.
Reciprocating compressors also excel when it comes to performance. The piston-driven nature of a reciprocating compressor allows it to provide a continuous flow of pressurized air. When it comes to maximizing both power and pressure, a reciprocating air compressor simply can’t be beat.
Yet reciprocating air compressors can vary greatly from model to model. Unless you buy a compressor with the right set of features, you may find that it fails to meet your needs. This article will prepare you for your next air compressor investment by discussing two key considerations to be aware of when selecting a reciprocating compressor.
1. Single-Stage Vs Two-Stage
Reciprocating air compressors can be broken down into two main types, known respectively as single-stage and two-stage compressors. The distinction between these two varieties has to do with the number of times intake air is compressed before entering the storage tank. As you can likely guess, a single-stage reciprocating compressor only compresses the air one time.
Another way to state this is that a single-stage compressor only contains one piston. A two-stage compressor, by comparison, contains both a low-pressure and a high-pressure piston. After being compressed by the first piston, air travels through the intercooler into the high-pressure area, where it is compressed again by the secondary piston.
Two-stage compressors have a number of advantages over single-stage compressors. For one thing, they tend to be much more powerful, both in terms of the pressure they can generate (measured in pounds per square inch, or psi) and in terms of the flow rate (measured in terms of cubic feet per minute, or cfm).
Despite being capable of handling higher workloads, two-stage compressors also tend to boast lower operating temperatures, thanks to the cooling that takes place in between the two pistons. As a result, a two-stage reciprocating air compressor can run for longer periods of time without the risk of overheating.
For heavy-duty applications, a two-stage compressor simply can’t be beat. Yet single-stage compressors may still be advantageous for those with lighter workloads and for pressures below 90 psig. For one thing, single-stage compressors will consume less energy. For another, their smaller footprint and lighter weight makes them ideal for on-the-go use.
2. Oil-Flooded Vs Oil-Free
All reciprocating compressors require some form of lubrication in order to function properly. Otherwise, friction in the crankcase and cylinders would lead to excessive temperatures and premature damage. Traditional reciprocating compressors — often referred to as oil-flooded compressors — use oil to lubricate not only the crankcase but also other moving parts, such as the pistons.
Yet depending on the application, the use of lubricating oil in certain areas of a compressor can have serious drawbacks. That’s because a small proportion of oil will migrate outward into the air stream. Such renegade oil can have serious repercussions for compressors used to power painting equipment, among other things.
In such cases, an alternative exists in the form of oil-free reciprocating compressors. Don’t let this name fool you: these compressors still utilize oil to lubricate the crankcase. Because the crankcase can be fully sealed, oil migration isn’t an issue. However, the cylinders and pistons won’t contain any oil.
Instead, these parts of the compressor receive their lubrication from the use of Teflon or related substance piston rings. In addition, oil-free compressors must contain either an air- or water-based cooling mechanism in order to prevent overheating.
Nonetheless, oil-free compressors tend to have much shorter life spans, meaning they are only suitable for applications where an oil-flooded compressor simply won’t work.
To get the best results for powering your equipment or tools, you must be sure to select the most appropriate type of reciprocating air compressor. For more information about which model and style would best suit your needs, contact the compressor experts at Compressor-Pump & Service, Inc.