Published by Jeremy Poague of Resource Conservation Group, Inc. (May 2016)

I can write about this for a couple of hours but let me sum it up. Better, more gentle filter cleaning. In a Scientific Dust Collector (SDC) bag-house, there are less parts. There is no venturi! Yes, you heard me, NONE! The idea of the venturi is to take your compressed air and induce more cleaning air. The venturi does a good job of that. It actually induces 3-4 times the amount of air from the initial pulse. Here lies the issue. The issue seems to be a lack of focus on velocity, as in there is too much. There is also a lack in focus on consistency. SDC has done some extensive testing in an effort to illustrate what is actually happening. They have found out that the top 16-22″ of a bag using the venturi system is actually seeing a negative pressure. This negative pressure pulls on the bag, thus eventually pulling dust through it and into the clean air stream. No Bueno! (Unless of course you are trying to see if you can get a Notice of Violation). Additionally, the consistency is almost non-existent.

In the early 80’s, SDC wanted to be the company that offered something different, appealing, and efficient while maintaining competitive pricing. From this desire, a supersonic nozzle was born. In order to get a more even flow of air, they knew the burst of air had to be gentle and consistent. They also knew that the venturi had to be eliminated. Air naturally expands at approximately 15 degrees. It was then decided that if a focused pulse of air was shot toward the mouth of the filter bag, we could somehow obtain an even flow of cleaning air. They then do this thing called trigonometry to find out that a good spot to start is pulsing air from 18″ above the tube sheet via a blow tube. Finally, we add a supersonic nozzle into the mix. Throughout the years, the supersonic nozzle has been improved time and again. Through more extensive SDC testing, we can confidently say that the supersonic nozzle induces 12 times as much cleaning air (3-4 times more than the venturi), but at a lower velocity. More testing was then done to see how various compressed pressures would affect the cleaning cycle. To SDC’s surprise (but not really), we learned that 80 PSI was all that is required to achieve the desired benefits. That’s exciting stuff since a lot of plants struggle to get 90 PSI or greater,

Can it get any better than a supersonic nozzle? Yes…as a matter of fact. Another fact that is widely known is that in a blow tube the orifice farthest away from the source sees the pressurized air first, this taking away from the rest. SDC continues to amaze by making simple, common sense improvements. They now have made it a standard to use balanced blow pipes. The current model has three zones, each zone with a slightly different sized supersonic nozzle. This allows a more consistent cleaning across the entire baghouse, not just a localized area of filters.

I spent a few moments letting you know about the supersonic nozzle. The result is no negative pressure spike on the bag (much less emissions), more usable filter media, much longer filter life, less parts, and lower PSI required. This has allowed SDC to give 3-4 year service life guarantees for the filter media of a new bag-house. That’s the most exciting thing to talk about. However, there are several other very important factors that set SDC aside from the “rest”. In upcoming blogs, I will talk more about bag spacing, high inlets vs. hopper entry, low velocity inlet plenums, interstitial can velocity, smaller air-to-cloth ratios, smaller footprint, smaller pressure losses equal hp (energy) savings, and much more. Feel free to ask me for SDC’s 120 page 2nd edition on dust (it’s free), supporting white papers on the studies mentioned above, and other references that back our claims.

“SDC has the best dust collector system in the market because of its cleaning system. You want to buy collectors by the pound, you do not need us. Do you want a 3+ year of media life and more efficiency than required by your state DEP agency? If so, we are your guys.” – Steve Cocks, an industrial air expert with nearly 50 years’ experience.