Centrifugal Air Compressors: How Do They Work?

Centrifugal air compressors are one example of dynamic style air compressors. The dynamic type of compressors have a continuous flow of air that has its velocity increased in an impeller that is rotating at a higher speed. The kinetic energy of the air is increased due to the increase in velocity and then becomes transformed into pressure energy through the use of a volute chamber, or a diffuser. The volute chamber is a curved funnel that increases in surface are as it approaches the discharge port. This converts the kinetic energy into pressure by allowing the velocity to reduce while the pressure increases. Approximately 1/2 of the energy is developed in the impeller and the other half is developed in the volute chamber or diffuser.

1 – Basic Centrifugal Air Compressor

The most common centrifugal air comppressor has between two and four stages in order to generate pressures up to 150 psig. A water cooled inter-cooler and separator is placed between each stage in order to remove condensation and cool the air down prior to being passed on to the next stage. These compressors still have advantages and some disadvantages. The list below showcases just a few.

Advantages:

  • Lubricant-free air is generated
  • Complete packages up to 1,500 hp
  • Initial costs decrease with increase in compressor size
  • No special foundations or reinforcements needed

Disadvantages:

  • Specialized maintenance requirements
  • Higher initial investment
  • Unloading/waste of air required to drop system pressures

To determine which type of compressor may be best suited for your facility, we suggest to locate and contact a compressor sales company in your geographic area. When it comes to determining the volume of air required to operate the EXAIR products and even some other point of use compressed air applications, EXAIR’s Application Engineers can help you determine the volume you will need to ensure the compressor is sized appropriately. If you would like to discuss any other point of use application, please contact us.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF

1 – Dugan, Tim PE – Basic Centrifugal Air Compressor, Compressed Air Best Practices; retrieved from https://www.airbestpractices.com/technology/air-compressors/centrifugal-air-compressor-controls-and-sizing-basics

A For Ingenuity, F For Performance

Over the past month or so, I have had several customers taking advantage of the EXAIR Efficiency Lab.  This one that came in really stood out to me though.  This is a 48″ long Steel pipe that was custom designed and made by the customer.  The unit has slots that we believe were EDM’d into the pipe.

IMG_3269IMG_3270

The customer was using this to blow debris off sheets of steel.   Once we got the pipe hooked up and set to run we were only able to generate 3.5 psig inlet pressure to the pipe.   The measured consumption was 176.55 SCFM at 3.5 psig inlet pressure.  They were utilizing 80 psig inlet pressure, needless to say it was slightly overkill for the application.    At 80 psig the pipe would consume over 1,400 SCFM of compressed air.

We were able to replace the pipe with a 48″ Super Air Knife Kit that still produced the necessary force to remove the debris from the steel, and only consumed 139.2 SCFM at 80 psig.   The customer was able to save 1,252.8 SCFM and reduced the noise level drastically.   The amount of air saved is equivalent to a little more than a 300 HP compressor.   The amount of air saved is equivalent to 31.3 cents per minute of operation.

We get surprised (still) every now and then at the amount of compressed air customers are willing to use for applications. This example was a surprising one. But, now we have a customer who knows that EXAIR knows how to save compressed air and keep the plant running…while staying OSHA compliant…while reducing noise levels.

These guys took some time and spent some money to make this custom homemade blow off pipe. Needless to say, something that costs more and is custom, isn’t always better.  If you have a compressed air application in house and would like to see how you can optimize it, contact us.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF