Now that you know your compressor size, you have to decide which type of compressor would be best for your application.
To help you with that search, let’s look at the two most popular types of compressors available.
However, before we explore your options, you first have to ask yourself these questions:
What is the application?
How much flow does my facility/workshop use?
What pressure is needed within the facility?
Do I need clean/dry air (use of dryer and filters)?
How many hours per year does my compressor operate?
How many shifts do I run per day?
Is there a fluctuation in flow demand between shifts? (if so, a compressor with variable speed drive would be best. You can find out more about them below)
Do you expect to expand any time soon?
With the answers to these questions in hand, you can now figure out which type of compressor best meets your needs.
Piston compressors
Rotary screw compressors.
Piston compressors, which are sometimes also called reciprocating air compressors, are the most economical and least expensive air compressors available. They are very simple and robust machines that can often be found in workshops, machine shops, body shops, tire shops and small manufacturing facilities. High-pressure compressors generally also rely on piston technology.
One of the benefits of piston compressors is that they are relatively easy to maintain. In addition to their low investment cost, they are economical to operate. In other ways, they are a great “starter compressor” and well-suited for operations with a limited compressed air demand.
Obviously, their simple design and low cost also means there are some drawbacks that should be taken into account prior to making an investment decision.
Piston compressors are mainly designed for intermittent use, meaning that the compressor can only work at about 50-60% of its duty cycle. The duty cycle refers to the amount of time a compressor can be operated at a standard ambient temperature.
In this case, that means a piston compressor will run 30 to 35 minutes per hour and then have to cool down. If you operate it longer than that, it may overheat and fail.
In addition, piston compressors also use a lot of oil and, if the compressed air is not properly treated, it could damage the downstream equipment and, if applicable, contaminate end products.
While piston compressors are easy to service, maintenance cost are higher than for screw compressors as reciprocating units contain more moving parts (pistons, piston rings, in- and outlet valves) that are prone to wear and tear.
Lastly, piston compressors tend to be loud. As a result, they can be hard on anybody working in close proximity to where it is set up.
Rotary screw compressors are often the ideal choice for operations that require a constant compressed air supply. Unlike piston compressors, they can be used for applications that require up to a 100% continuous duty cycle. Rotary screw compressors are built for a long lifetime of reliable operation.
They come in different types and sizes, so there is a rotary screw air compressor for any need and budget.
You can also enhance them with other equipment. For example, by integrating a dryer, you get a compressed air system that is ideal for applications requiring clean and dry air. And smaller screw compressors can be tank-mounted. This adds storage capacity which, coupled with an integrated dryer, allows for plug-and-play installation.
This makes the system ideal if you have limited space at your facility and if you want to save on installation costs.
Atlas Copco has invented and refined an innovative drive concept for compressors. We call it the variable speed drive (VSD). As you now know, energy expenses are by far the greatest factor in determining a compressor’s total cost of ownership. That also means that they contribute a great deal to an operation’s environmental footprint.
A VSD compressor can do something about that.
While traditional compressors run at full speed whenever they are turned on and regardless of how much compressed air is required, VSD compressors adjust their motor speed to the air demand. For example, on slow days or during shifts where a facility operates with a skeleton crew, they produce much less air and, therefore, also require a lot less energy. In fact, they can reduce the energy consumption of a compressor by up to 60%.
Sure, their initial investment cost is higher than that of conventional compressors but this is quickly recouped. Depending on the compressor size, VSD technology can achieve savings that range from $100s to $10,000s annually or more.
