I have a filter press than needs to gravity drain filtrate to a 0.15 psig holding tank. Per the vendor, "The filtrate is effectively a gravity drain. If the pipe is set up so that it builds pressure back to the filtrate discharge, a check valve should be installed.
When there is pressure build up at the filtrate discharge, the slurry feed pumps will move the filtrate at a much lower pressure than what is seen at the head of the press. This would require a pump with a much higher output pressure than the filter press would require. This can have a detrimental effect filter cake as well."
How important is it that I meet the criteria in Hills paper of Froude < 0.3 in the vertical sections (see attached)? The filter press has a flow of nearly 400 gpm. This results in a a 10" sch 10 pipe (for me in the chemicals industry, this is huge even 4" is big). Obviously, if we need a 10" pipe, we will run a 10" pipe, but I don't want to overkill this because I am meeting an unnecessary criteria. The filtrate should only be draining for less than 10 minutes every 3 hours.
According to the International Plumbing Code equation (attached), Qw = 27.8*rs*D^(8/3), assuming 1/3 full for rs according to "Selecting the Optimum Pipe Size" by Randall W. Whitesides (even though I think he might have messed up transposing the equation), I only need a 4" sch 10 pipe.
I don't see how the IPC equation can allow so much more flow or which one I should use (Hills vs IPC). I don't necessarily trust the IPC equation since it has a very poor explanation of how to use the equation and what the terms are, but since it's supposedly used by plumbers worldwide, I would think it's semi accurate.
If you have any questions for me or the vendor, please ask me .