Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here


Compressed air system

Compressed air system

Compressed air system

I need help to design/size compressed air system that includes compressor, air dryer and receiver tank. Given data are the air demand, air pressure and running time to start an engine. It would be great, if you direct me an example on how to size air compressor, air dryer, and receiver tank.

RE: Compressed air system

The first, second, and third thing you need to do is to understand flow numbers into the compressor, demand, and how they relate. Terminology alone will kill you if you don't have rigor on your side. My approach is to convert the STUPID numbers you get from compressor manufacturers and pneumatic tool manufacturers into mass flow rate before anything else.

Air compressor manufactures want to rate their machines in ACF, which (if you filter through the cultural BS) means "actual cubic feet per minute at suction conditions". If you are at sea level and air temperature is always 60°F then that number is SCF/min. If you are at 7200 ft elevation and normal suction temperature is somewhere between -40°F and +100°F, it is not so much SCF/min. Determine the mass flow rate at the least favorable temperature.

Now figure out what your Maximum humidity will be. Convert the water vapor flow rate to a mass flow rate and subtract that number from the compressor mass flow rate.

Pneumatic tool demand is often stated as "CFM", but the definition of that number is quite murky. The main confusion is that they rarely say what inlet pressure they are using to calculate a cubic foot at actual conditions is. You have to dig it out.

Sum your loads, add a 50% safety factor for leaks (many people prefer 100% for leaks). Your air receiver should be big enough to carry you through 3 shifts without a compressor. You can do that with receiver size or with receiver pressure. You choose, you're the engineer.

If your compressor runs more often than once per shift it will be obnoxious. Size the compressor to give you 8 hours of air in less than 2 hours.

I don't have a clue if this is what you were looking for or not, but the canned "size a compressed air system" lead to bad systems (in my experience) since they never ensure that you are comparing apples to apples, not apples to lug nuts.

David Simpson, PE
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Research Report: State of IoT Adoption in Product Development 2019
This research report, based on a survey of 234 product development professionals, examines the current state of Internet of Things (IoT) adoption by product design teams, its perceived importance, and what features and capabilities teams consider important when making decision about adding IoT functionality to their products. Download Now
Research Report: Augmented Reality for Maintenance, Repair and Overhaul (MRO)
The term Industry 4.0 denotes a cluster of technologies that’s poised to fundamentally reshape manufacturing and bring about a new industrial revolution. These include 3D printing (AM), the Industrial Internet of Things (IIoT), artificial intelligence (AI) and mixed reality technologies, more commonly known as virtual reality (VR) and augmented reality (AR). Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close