Contact US

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!

*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

Natural Gas Pipe Sizing?

Natural Gas Pipe Sizing?

Natural Gas Pipe Sizing?

What size pipe would be needed to supply a piece of equipment, given the following information:
Utility Gas Source is 40 psig
Equipment - min press 8" WC @ 30 SCFM, max press 75psig, max flow 30 SCFM

RE: Natural Gas Pipe Sizing?


Piping in general is selected so that the actual volumetric velocity is approx 10 m/s. (Most gasses, there are exceptions like H2). If the velocity is bigger you get too much pressure drop, if the velocity is smaller you pay to much for your piping. For smaller length of pipe you can go higher in velocity if the pressure drop is not an issue.

If your gas temp is 70F, your pressure in the pipe 40 Psi and your ID of the pipe is 1" you get a actual velocity of 7.5 m/s. If you go for an ID of 3/4" pipe you get a velocity of 13.34 m/s. I would select the 1".

Best regards,


RE: Natural Gas Pipe Sizing?

How did you calculate the 7.5 m/sn actual velocity?

RE: Natural Gas Pipe Sizing?

Hi Musafa,

Flow=30 SCFM (S=Standard so refered to 70F and 760 mmHg(a))
Pressure=40 Psig
Temp=20 C (Assumed)

To calculate to Volumetric (SCMF is Normelized (Could be refered to as Mass flow although confusing))

Law of Boyle/Gay-Lussac: (P*V)/T=Constant (T in degrees K, P in Abs pressure)

Volumetric or Actual flow is than: 8.029 CFM

Area 1" ID pipe: 0.785398 Sq Inch

Average velocity = Actual flow/Area

Average velocity = 7.49 m/s (After conversion)

(Average velocity is not taking flow profile into account)

Best regards,

Paul de Waal
Sierra Instruments

RE: Natural Gas Pipe Sizing?

Thanks Sierra,

I have an electrical background and have to work in other disciplines on projects - this information was helpful.


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! Already a Member? Login


Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. 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