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More pressure across the sheet will definitely increase throughput
but as one member pointed out the sheet can only take so much. No a
plastic barrel would be worse. And no the size of the pump is not so
much of a factor. I can implode a steel drum with an aquarium pump,
although it will take a little time, it will be just as exciting! A
good vacuum (say 750 mm of mercury or roughly 29 inches) results in
atmospheric pressure on one side and essentially zero on the other.
Atmospheric pressure is roughly 14.7 pounds per square inch (PSI). Say
15 psi. If the lid of a drum is 24 inches in diameter, it has an area
of about 450 square inches. A good vacuum would therefore place 450 x
15 = 6785 pounds or roughly 3 tons of force on the ends of the cylinder
and a hell of a lot more radially inwards on the sides of the
cylinder. Even a wimpy partial vacuum of 2 inches mercury would put
roughly 450 pounds force on the drum head. What I have been considering doing is using gravity as a motive force for filtering. If I can raise a bucket of water in the air with a hose attached to the bottom, I get roughly 1/2 psi for every foot of height. Now oil is a little lighter than water but it is roughly the same. If I can raise my drum with a block and tackle 40 feet up to the roof of the barn I get about 20 psi of pressure on the end of my hose where my filter housing is. I would use a standpipe in the drum as well so that the majority of the gunk stays in the bottom of the barrel and doesn't clog my filter. Also a very coarse prefilter or fine mesh screen ahead of the actual filter will help tremendously. If you want to make a home job vacuum filter using bed sheets or whatever, large surface area will help a lot in filter life but go for a long narow cylindrical shape with smallish ends. Cylinders take force very well in a radial direction but not so well axially. For vacuum use, I would construct a filter by using a pipe with tons of holes drilled in it and wrap it with the sheet or felt or what have you, Then place this pipe inside a larger pipe as a housing. The inlet would be to the outer pipe and then the pipe with the holes becomes a mechanical support for the filter media. The outlet then becomes the end of the inner pipe. A pipe reducer then adapts the inner pipe to the outer one. You would have to ream out the reducer so the smaller pipe can go right through before you glue it. Use a peice of rubber tire inner tube that fits the outer pipe with some hose clamps as a seal. Check the touchless processor on the JTF site for pics of this type fliter. PS this filter won't work with pressure, only vacuum. Cheers Joe Kurt Nolte wrote: True. What if it were more of a pulsed vacuum, based upon rate of flow? A little vacuum assistance here, a little vacuum assistance there; what I was operating off of was the principle behind a little piece of lab equipment we used in high school, in which running water was used to generate suction to draw thick or particle-heavy fluids more rapidly through filter paper. The vacuum doesn't have to be huge, large or even moderate, just enough to create a difference in pressure between the atmosphere and the inside of the barrel. |
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