3 replies to this topic

[samue.warner]

Hi, I am trying to calculate the SCFM for a compressor used for pneumatic filling of chemical tanks. • I know that there is 15 psi of losses in the line from the truck to the tank, the max pressure is 25-30 psi and that the desired flowrate of the chemical is 180 gpm. I initially thought the volume of air would be the same as the volume of chemical transferred and just did a conversion from gpm of air to SCFM, but the answer I got seemed unreasonably small (~40 SCFM). Then I was thinking perhaps the calculation would be based on mass flowrate instead, but I didn’t reach an answer with my calculations. Can anyone help me out with the calculations here? Apologize if this is a relatively basic question, I am a junior wastewater process engineer and don’t have experience with pneumatic filling. If this isn't the correct place on this forum could someone point me to where I should post the question? thank you.

[latexman]

180 U.S. gpm = 24.0625 acfm of displacement for transfer.  Let's assume 30 psig air is required (worst case) and temperatures do not change.

 

24 acfm x ((30+14.7 psia)/(0+14.7 psia) = 73 scfm

 

You have to use absolute pressures in gas equations.

Edited by latexman, 16 August 2017 - 04:48 PM.

[Art Montemayor]

Sam:

 

Your written description of what you are proposing to do is very deficient and hard to understand.  Please refer to the enclosed workbook and look at the sketch I have provided.  Is that something like what you are proposing?  If not, then provide your own sketch.  An engineering drawing is worth a thousand words - and less subject to erroneous interpretations.

 

​The method to calculate the required air capacity to effect the specified liquid transfer is relatively easy to calculate.  What is the Liquid that you are transferring?

 

 

 Liquid Transfer with Compressed Air.xlsx   14.34KB   13 downloads

[samue.warner]

That drawing is correct, thank you. Sorry for not being specific enough. So then latexman, it looks like my original approach was right after all just not my execution? Thank you.