Q: What is the typical natural gas pipe velocity, and what is the maximum gas pipe velocity?

A: For underground installations, 20 m/s is normal. Maximum velocity in a pipeline, on the other hand, is defined by available pressure, but in control and safety valves, it can be allowed up to 100 m/s.

Q: Thanks for the information. I noticed from the calculator on PipeFlowCalculations.com, for two-inch pipe with 1,500 feet length, 90 psi in and 10 psi drop, it gives a result of 337 CFM gas flow with a 44 FPS and 50 FPS velocity. Shouldn”t the velocity of this be 257 FPS (based on that 337 CFM flow and two-inch pipe).

A: It would only be 257 FPS if pressure is at standard conditions at 1.013 bar, but since the pressure is 90 psi (cca 6 bar) it is about 6 times less (257/6=44 fps – approx.)

Q: So it”s acceptable to have a 20,000 cfh gas flow in a two-inch pipe with 90 PSI with a drop of 10 PSI? (yielding m/s pipe velocity)?

A: Yes, it is just about perfect.

The preceding Q&A is based on an exchange on PipeFlowCalculations.com, a website featuring calculators and a forum that focuses on fluid flow.