The selective type oil skimmer is always motor driven and operates by introducing to the oil—a surface (metal or plastic) that the oil is attracted to and sticks to. This surface, being a belt or mop or tube or drum or disc is then rotated around (by the motor) to an oil removal spot, and then—wiped or wrung or scraped off, allowing the oil to run off by gravity flow to a sump or tank or trough or somewhere else for eventual removal.
Case in point: our floating drum skimmers float on the surface of the water/oil—the drum (air or hydraulic driven) rotates slowly thru the oil, getting covered with oil, then rotating around then scraped off by a “doctor” blade allowing the oil to flow into the sump where it collects until it's pumped away. On these floating drum skimmers it's very important to pump the oil out of the sump as it's coming in—otherwise the floating skimmer turns into a submarine. If you're skimming—you gotta' keep pumping it off.
These floating drum skimmers are the most efficient way of moving a LOT of oil FAST!
Even our smallest industrial drum skimmer “the steelmax” which is only 2.5' x 3.5' can skim an amazing 20 gallons of oil per minute—now you can see why you have to keep pumping it out! Very few people have this much oil to skim—but it also is deadly efficient at 1 gpm, giving you very little water to deal with and that's what separates these selective skimmers from the non-selective type—the water does not like (very much) the plastic or metal rotating element.
Now onto the non-selective type skimmers which do give you a lot of water to deal with. These floating weir type skimmers create a low spot or depression on the surface of the water that you can pump from—allowing everything on the surface near it—to run into that floating low spot. Think of it as a stand pipe or floating manhole on the water surface. These skimmers don't have any motor driven rotating elements, BUT they do require use of a pump to pump away everything that's running into that surface manhole. Make no mistake these will give you a lot of water to deal with if you have little surface oil—but they are FAST and flow rates can range from a few gpm up to hundreds of gallons per minute.
The floating weir skimmers are also used to skim or remove floating stuff other than oil—such as floating fly ash in power plants, floating duck weed in ponds, grass/ plastic pellets and anything else that floats on the surface and that can be influenced by the motion of water moving across the surface. If this floating weir skimmer is sitting in pure oil—you can move huge amounts of oil fast without getting water along with it!
Here are some general application thoughts and ideas about which skimmer to use where.
Hook a hose to it and put it into the water—capable of high recovery rates—usually measured in gallons per minute.
Floating drum skimmers—for removing a lot of oil without water—FAST or use with very heavy oils—the toughest and most effective skimmers made. Hydraulic or air powered.
Floating disc skimmers—same as above but somewhat more delicate—probably not so good where it gets moved around a lot. Hydraulic or air powered.
Floating weir skimmers—real workhorse-type skimmers, the only skimmer that will remove sheen or floating stuff other than oil. Works great with a vac truck or AOD pumps.
Low recovery rate—usually measured in gallons per hour.
Belt skimmers: electric, great for reaching down into a pit or well or tank and lifting the oil to the surface. Requires no pump. Usually rather lower recovery rates—low maintenance.
Rope mop wringer skimmers: have a LOT more surface area than belts; the rope usually looks like a squirrel tail, often used/stretched across a pond or tank, has wringer rollers—won't tolerate high solids content. Electric, air or hydraulic powered. Higher maintenance
Tube type skimmers: same idea as above—uses a hose-like tube that dances on the surface to gather oil. Recovery rates to 40 gph. Low maintenance.
As always—experience helps with skimmer applications.
SkimOil, Inc. has all the skimmer technologies known to man.
This is what we do all the time, so we can bring highly specialized knowledge and experience to your requirement—giving you the right technology so we can get it right—the first time. We love oil! Call SkimOil at (314) 579-9755 or e-mail: firstname.lastname@example.org
“Roscoe” J. McWilliams
Skimoil Inc./Separator Systems—Carrboro, NC / Carrboro, NC - USA
Phone (314) 579-9755—fax (314)558-9253