Pop Fisher: "You know my mama wanted me to be a farmer."
Roy Hobbs: "My dad wanted me to be a baseball player."
Pop Fisher: "Well you're better than any player I ever had. And you're the best … hitter I ever saw. Suit up.”
- Wilford Brimley & Robert Redford in Tri-Star Pictures “The Natural”, 1984
If you’re a baseball fan, December & January are the time of year for leaks. Rumors and innuendo about trades and free agent signings are everywhere. Every GM is out looking for position players who can not only hit but play defense, too. Rotary valves are a lot like that elusive player that fills multiple rolls.
WHAT CAN ROTARY VALVES DO?
1. They create a seal
2. They meter material
3. They create a seal WHILE they meter material
Truth be told, they only do a so-so job of the first 2 things. They create a seal, but because they are machined with clearances, by definition they leak. If you only need to seal something, butterfly valves or knife gates can do a much better job. Rotary Valves also meter material but because of their deep pockets and lack of agitation above, they are nowhere near as precise as a screw feeder or belt feeder (at least not on small rates, anyway).
But if you are talking about doing both at the same time, they are the greatest thing since sliced bread (maybe better, since Wonder Bread seems to be going “adios”). That is why they have remained the workhorse of the pneumatics industry for over 60 years. In spite of extended efforts by Venturii / Eductor manufacturer’s to wipe rotary valves from the face of the earth, they can’t change the fact that Eductors can’t meter material and have a huge pressure drop. Pressure vessels/blow pots create a seal too, but they have to be cycled and can take up a tremendous amount of height, especially in higher rate systems.
So if you need a dual purpose solution, much like baseball, mom’s apple pie & jazz music, rotary valves are an iconic fix that never gets old. The good news is, that unlike a utility infielder’s yearly salary these days, they still cost a lot less than $2M to add to your plant’s arsenal (at least until “Super Agent” Scott Boras starts signing them, anyways).
For more information on Rotary Valves Click Here
Submitted By: Larry Eagan | Regional Sales Manager