Air Only Calculation

(not verified)
Posted in: , on 25. Aug. 2008 - 18:43

Hello all,

I open this thread because I need some help for an air only calculation.

In our plant we have air supply net (5 bar) that we use for conveying.

I need to calculate the volumetric flow in order to size the air venting for the receiving hopper in case the inlet valve is completely open.

The line consists of 25 m. of DN50 pipes, 5 90º bends and the discharge point is 7 m higher than the air inlet.

Based on the book of Dr. Mills, "Pneumatic conveying design guide" I made the calculations, but I obtained a 340 m/s outlet air velocity, that to my understanding does not make much of sense. The inlet pressure is quite high, but I am not sure that the oulet velocity can be this high. Is it possible?

In the attached file you can find my calculation.

Thank you,


air only relationship (ZIP)

Air Only Pressure Drop

Posted on 28. Aug. 2008 - 11:07

Terminal velocity depends upon the system pressure drop and the air flow rate. Since your pressure drop is fixed, you have to control the velocity by controlling the air flow rate.

Calculation method for air only pressure drop is quite simple. It is given in most fluid flow text books.

Let me know if you need this method. I will be glad to send it to you.


Amrit Agarwal

Consulting Engineer

Pneumatic Conveying Consulting


Ph and Fax: 304 346 5125

(not verified)

Re: Air Only Calculation

Posted on 29. Aug. 2008 - 11:44

Dear Armit,

I have already made the calculations for the air only pressure drop( see file attached to my first message), which in my case is fixed and I obtained 340 m/s outlet velocity. I do not know if this value is realistic or not. The pressure drop is about 5 bar and I would like to know if the equations are valid for such a big pressure difference.

Kind regards,

Re: Air Only Calculation

Posted on 29. Oct. 2009 - 11:17

Dear gerpega

Why do u use density = 5,5 kg/m^3 ?


Andrés Miller V. PRDW-Aldunate Vásquez Consulting Port and Coastal Engineers