Hi,

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,

Paul

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

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
www.sierrainstruments.com

Thanks Sierra,

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

cgap