How Do I Size an Industrial Air Compressor?

Editor's Note: This post was originally published in 2019 and has been updated for accuracy, comprehensiveness, and new information.

Sizing a new air compressor can be a difficult task. It requires a thorough knowledge of the pressure and flow needed for the application, a solid understanding of how frequently jobs are performed & how many jobs are being completed at once, and the ability to plan for upcoming changes in the application or in upcoming business needs. This may seem like a substantial amount of work; however, the benefits of correctly sizing your compressor are multifold and include improving your business’ productivity, decreasing existing compressor room inefficiencies, and improving your bottom line.

Keep in mind that sizing your compressor doesn’t necessarily mean the physical size of the compressor. Rather, this idea refers to making sure that your compressed air system is sized to deliver the air your production needs across your entire compressed air demand profile at peak efficiency. Many new air compressor technologies today are incredibly energy efficient and can provide the ideal flow and pressure in a smaller compressor package.

Wait - How Do I Know if My Current Industrial Compressor is Sized Correctly?

First, let’s address your current air compressor system. Do you know if your current compressor is sized correctly, or is it undersized or oversized? To help you determine this, we highlight a few common signs that indicates your compressor may be undersized or oversized for the application(s) it powers:

Undersized Compressor. If your compressor is undersized, it’s likely running at all times! Keep in mind that this can be a bit difficult to distinguish with rotary compressors, as they are intended to run virtually 24/7. However, this would be noticed right away with piston compressors, as they aren’t intended to run 24/7. So, if you’re experiencing pressure drops and the inability to complete a task (as in the application can’t be completed due to the lack of compressed air supply), chances are that an undersized compressor is the issue.

Oversized Compressor. Is your compressor constantly stopping and starting (commonly known as loading and unloading)? It could be oversized! This means that your compressor will start-up, immediately meet the demand, and then stop; it then realizes that demand is present and will start-up again. This will lead to huge energy bills, largely caused by the spike in energy produced when the compressor starts up. The excessive start/stop cycle can also result in motor burnout, future mechanical problems and potential failure of the compressor.

How Do I Correctly Size a New Industrial Compressor System?

There are a few key steps to take in order to appropriately size a new industrial air compressor:

1. Know Your Flow (CFM). The CFM, or flow rate of your compressor, is application-dependent, which means that having a good understanding of your plant's demand profile is critical to sizing a compressor and uncovering any potential energy efficiency opportunities. If you are trying to determine the flow requirements for a new plant, be sure to have accurate flow requirements for all equipment and estimates for the duty cycle of that equipment. For an existing operation, we recommend reaching out to a local compressed air expert to assist with this calculation. Your local expert can also guide you through planning for future expansion and make sure your air flow and quality are appropriate for your applications. Learn more about CFM, ACFM, ICFM, and SCFM here.

2. Know Your Pressure (PSI). Pressure is measured in PSI, or pounds per square inch, and refers to the amount of pressure required by the tools/equipment used by your application. This is typically between 90 and 100 PSI but can also be higher or lower. While you may want to add a little padding to this pressure so that your new machine can handle any extra requirements that may be throw its way, be wary of increasing the pressure beyond what is absolutely necessary. Increased pressure means increased power bills and loss due to unregulated uses. Learn more about PSI, PSIA, and PSIG here.
   
   
3. Check Your Voltage & Phase. Your industrial compressor will require a sufficient energy source to operate, so knowing the available voltage and phase of your compressor’s new “home” (whether this is inside a building out outdoors) is essential. If you’re unsure, consult with an electrician! They’ll be able to tell you whether the electrical supply is single-phase or three-phase, as well as the voltage.

One of the best starting places for determining new compressor specifications is by conducting a compressed air audit. Knowing your system’s compressed air demand, and subsequently determining how to deliver the right amount of compressed air at the lowest cost, will help you avoid choosing a compressor that is undersized or oversized for the job that it needs to complete.

Need assistance? Reach out to us at www.atlascopco.com/air-usa!