Air compressors are some of the most necessary appliances found at construction sites, as they can be used as a power source for electric tools. There are many different types of air compressors, each with their own unique capabilities and drawbacks.
Air compressors are categorized as either positive displacement or dynamic displacement, based on their internal mechanisms. The four most common types of air compressors you will see are:
- Rotary Screw Compressor
- Reciprocating Air Compressor
- Axial Compressor
- Centrifugal Compressor
We’ll cover what each is best used for below, so you can make an informed decision for your project.
Positive Displacement Compressors
Positive displacement compressors encompass a variety of different air compressors that generate power via air displacement. Air compressors in this category work with different internal mechanisms, but the principle for each is the same. A cavity inside the machine stores the air brought from outside, and then slowly compresses the cavity to increase the air pressure and potential energy.
Rotary Screw Compressors
A common type of displacement compressor, rotary screw compressors are some of the easiest types of air compressors to take care of, as they are equipped with an internal cooling system and don’t require much maintenance. They are typically large, industrial-sized machines that can be either lubricated with oil or run oil-free.
Rotary screw air compressors generate energy via two internal rotors that turn in opposite directions. The air gets trapped between the two opposing rotors, and builds up pressure within the housing. Because of the internal cooling system, these air compressors are designed for continuous use, and range in power from 5 horsepower up to 350 horsepower.
Another popular type of displacement compressor is the reciprocating compressor. These are typically found at smaller work sites such as garages and home construction projects. Unlike the rotary screw compressor, the reciprocating compressor is not designed for continuous use. A reciprocating air compressor has more moving parts than a rotary screw compressor, and these parts are lubricated with oil for smoother movement.
These types of air compressors work via a piston inside a cylinder, which compresses and displaces the air to build pressure. Reciprocating compressors can come in single or multi-stage variations, which affects the pressure ranges they can achieve.
When you need more power, the multi-stage compressor is the way to go. While single-stage compressors will get the job done for smaller projects such as woodworking and metalworking, multi-stage compressors provide the power needed for intense construction, such as auto assembly and maintenance. Multi-stage reciprocating compressors can reach up to 30 horsepower.
Dynamic air compressors generate horsepower by bringing in the air with rapidly rotating blades and then restricting the air to create pressure. The kinetic energy is then stored as static within the compressor.
Axial air compressors are not typically used in construction projects but are instead found in high-speed engines on ships or planes. They have a high-efficiency rate but are much more expensive than other types of air compressors, and can get up to many thousands of horsepower, which is why they are mainly reserved for aerospace research.
Centrifugal air compressors slow and cool the incoming air through a diffuser in order to build up potential energy. Because of the multi-phase compression process, centrifugal compressors are able to produce a high amount of energy in a relatively small machine.
They require less maintenance than the rotary screw or reciprocating compressors and some types can produce oil-free air. They are typically used for more demanding construction sites such as chemical plants or steel manufacturing centers, as they can reach around 1,000 horsepower.
How Do I Choose the Right Types of Air Compressors?
In addition to the power-generating mechanisms and energy output levels discussed above, there are several other factors to consider when choosing the right types of air compressors.
Consider the Air Quality of Oil-Free Compressors
In clean manufacturing environments, using oil-powered air compressors can create a problem. Most air compressors rely on oil to lubricate the inside mechanisms, and the fumes may contaminate the air, which could result in damage to products or manufacturing processes. With an oil-free air compressor, this risk is greatly reduced.
Though oil-free compressors are generally more expensive, they are the only option for facilities that guarantee clean manufacturing. Oil may still be necessary to lubricate the machine, but the inner workings of oil-free compressors contain a different sealing mechanism to ensure that no oil gets into the actual compressor. In addition to clean air, oil-free compressors often have lower running costs as parts do not need to be changed as frequently.
Use Energy Efficiently
If you’re working on a long construction project, getting the most energy-efficient air compressor can be worth the extra cost in the long run. Below are a couple of types of air compressors that are energy-efficient.
Fixed Speed Compressors vs Variable Speed Compressors
Variable Speed-Driven (VSD) compressors save energy and money by either increasing or decreasing output on demand. In comparison, the motors in fixed-speed compressors are constantly churning at the same rate. This is fine while the compressor is in use, but as the unit slows down, the motor continues to run until the machine comes to a full stop. Energy is wasted during this cool-down period as the compressor is still running, but no power is being generated.
Natural Gas Air Compressors
In certain industrial settings, a natural gas compressor works well to power tools and equipment. Examples include chemical processing plants, petroleum refineries, and manufacturing facilities. These units run on natural gas instead of diesel or electricity. Natural gas air compressors often operate more efficiently than other options, even at partial loads. They also have better heat recovery capabilities than electric compressors. If efficiency and energy savings are your main goals, a natural gas unit may be a better option.
Figure Out Portability Limitations
If you transport your air compressor between sites, a portable unit is a good option. Small, lightweight units can still deliver energy, but in a compact package. Though they won’t be as powerful as larger units, portable compressors can be ideal for smaller construction projects. Certain units can even be plugged into a car’s power adapter to fuel an airbrush painting tool or tire inflation tool!
Determine the Need for Additional Features
There are a variety of add-ons and additional features you can use with different types of air compressors. For example, multiple couplers or air hose splitters allow you to hook up multiple tools to your air compressor, so you don’t have to connect and disconnect when you’re changing tasks constantly. Air compressors with thermal protection add-ons keep track of internal heating and stop motor damage if the machine is overloaded.
Some air compressors have belt-drive systems rather than direct-drives, which allow for quieter operation. If you think you will need any of these additional features, you will want to make sure that the types of air compressors you choose will be compatible with these tools.
If you don’t want the commitment of purchasing an air compressor for your construction job, BigRentz has several types of air compressors ready for you to rent for your next job. From small and portable to industrial-scale, you’ll now have all the information you need to make the best choice for you.