What’s “Static” about Static mixers?
In his article, “Disposable Static Mixers: A Maturing Industry,” Paul Gossi charts a course from the classic, helical static mixer of the mid to late 1960s, a phase in which each manufacturer custom-made and individually tailored static mixers to a job’s specification, to the large-scale production of plastic, disposable static mixers of which we are perhaps more familiar today.
The classic, helical static mixer was composed of metal, and was, not surprisingly, far more exacting to manufacture than what is made possible nowadays by advances in machining technology. And while there are numerous reasons for why the static mixer came to be, one here suffices: its advantage over a mechanical mixer. Even though manufacturing a static mixer out of metal was not-so-easy an undertaking, the static mixer still proved advantageous because it did not rely on moving parts to create a controlled turbulent fluid flow. Though more powerful pump systems were required to counter the increased resistance, a more efficient use of space plus low operating and maintenance costs put the helical static mixer in competition with machines such as the stirred tank reactor.
At first glance, a static mixer (whether handmade from metal or machine made from plastic injection molding) seems to do little more than strategically turn the two parts of an epoxy or polyurethane and allow them to react. Whereas a machine with moving parts mixes dynamically, a static mixer mixes (wait for it) statically or without moving parts. Installed in a pipe or a duct, for instance, adding air in an aqueous system or dispersing two liquids in food processing, the original static mixer’s fixed position was still able to yield the predictable results that were previously possible only through dynamic, machine mixing. In other words, the static mixer was able to produce the results of a machine without either the hassle or the requisite investment of a machine. What’s remarkable about the static mixer is its deceptive simplicity, its capacity to produce a dynamic mixture while itself being static and, as a result, nearly maintenance free.
Originally, the static mixer worked by means of two metal strips that were placed at a 90° angle and then twisted 180° into one another, forming what is called a “mixing element.” The mixing element’s “twist” is devised to fold and re-fold a liquid into itself as it passes from one helix to the next. Each helix not only splits the liquid but also forces its rotation to change direction, thus spurring on a series of self-canceling vortices that (as we say in the industry) “stretch” the liquid.
Remember: here at BTmix, we not only sell quality static mixers, but can accommodate all your mixing elements needs as well: along with our industrial line of mixing elements we also produce both food grade mixing elements and mixing elements for medical applications. (Check out the last blog post on a client to whom we provide just mixing elements.) If you’re interested, contact us for some free samples.