Thanks David. I have a clearer understanding now. You kinda nailed it because we use this criteria side by side with the allowable velocity for certain services. Btw, in our company, we also use this criteria for liquids.
Thanks for your very prompt replies.
@Artisi: Yes, I am referring to pressure drop for fluid thru a pipeline.
@Latexman: I'm sorry but from what I see in the hydraulic calculation results, this value is a lot higher than the "plain" pressure drop. If I do multiply this pressure drop per unit...