The problem with vacuuming up large quantities of very fine dust from sandblasting is that the filter in the shop vac gets rapidly clogged, restricting air flow and causing a loss of suction:
You can of course restore suction by cleaning or replacing the filter at frequent intervals, but this can get to be a major hassle over time. As you might expect, this is a common problem in industry, and it was solved decades ago with the invention of cyclonic separation:
Particulate-laden air enters a cylindrical chamber at a tangent, causing it to swirl around in a circular fashion and throwing the particles toward the outside wall. Clean air leaves at the top center of the chamber, while the particles fall to the still air at the bottom for collection.
You can buy dust collector/separators for sandblasting, but they cost a fortune. There’s nothing high-tech about them, so I set about to make my own. Here’s what I came up with in spring 2007, for a total investment of about $15:
It is exactly what it appears to be: two five-gallon plastic pails, duct-taped face-to-face, and a couple of PVC pipe stubs for inflow and outflow. Air enters in the tangent pipe, and exits through the elbow at the center of the top pail; from this exit fitting, a 12-inch standpipe extends down into the enclosure, giving the particles a chance to migrate to the edge of the pail and drop to the bottom before the air gets drawn up.
And it works fantastically well. Too good, in fact. I have a confession to make: my original intent was merely to salvage the still-usable blasting sand, while allowing the fine dust and blasting debris to be drawn into the shop vac; blasting sand ain’t cheap. But the separator works so good that it’s collecting the extremely fine dust as well as the good sand: when this reclaimed stuff is put back in the cabinet, blasting work throws up a dense, opaque cloud. The good news is that the shop vac’s filter doesn’t get plugged anymore.
Questions? Comments? Email me!
©2006, Mitchell P. Patrie