We have previously talked about velocity (date) and how it’s really a combination of air flow and the added power of velocity that moves things around. Similar things happen to air flows in a dental piping collection system. At a given level of vacuum (‘’Hg) a certain flow of air can be moved through a specific diameter of pipe. A pipe is defined by its diameter just like a hole. A good chart for finding air flow is at www.basvacdental.com

Most dry vac manufacturers want larger diameter pipe 4 and 6 inch. The idea here is that a high flow suction pump needs a large pipe to move its large volume through. OK, I agree but only if you can get that much air into the pipe through the tiny holes of the suction tools. Velocity, remember, needs a higher vacuum to really create excitement and movement. The large flow big pump systems tend to be 5-9’’ Hg vacuum energy systems.

What happens then is as the air enters a big pipe from a small inlet pipe the air velocity slows down. Little to big air slows down, big to little air speeds up.

As the air slows down it loses energy and starts to drop the water and debris along the way. This isn’t good as the debris stays in the pipe hardens and never makes it to the amalgam or air water separator. A smaller pipe with a stronger suction maintains a higher velocity or excitement and keeps the water and debris moving in the pipe.

So velocity does matter in a piping system if we want to keep the liquids and solids moving. A high vacuum system 15-25’’Hg even with a smaller volume can keep the air velocity high. A side note, I have had installations of the BaseVac (high vacuum/velocity) system installed on old piping only to have the first hour of operation emptying years of sediment left by the old pump. So air flow and vacuum and the resultant velocity have a significant effect on how a piping system works.