A: Doug Kitch, CPM Roskamp Champion, says:
It’s no secret that the energy to grind can be one of the more expensive processes at your facility. Making sure your equipment is running efficiently to keep operational expenses at a minimum is imperative for the long-term success of an operation. Keeping your hammermill maintenance expenses low starts before the hammermill is installed at your plant. By carefully selecting the hammermill’s wear parts and determining the best way to operate the mill in your application, you can minimize required maintenance while ensuring that the mill provides top grinding performance. To speed and simplify maintenance, you also should select wear parts designed for easy replacement.
Selecting the screen area. The hammermill should have at least 14 square inches of screen area per horsepower for most applications. Too little screen area will make the mill inefficient and cause your material to heat up during grinding. Too much horsepower per screen area can also lead to premature hammer wear. When using a very fine screen (with holes less than 1/16 inch), you may need to use more screen area per horsepower because the screen has less open area.
Selecting the hammer pattern. The number of hammers in your mill is called the hammer pattern. The ratio to keep in mind is the horsepower per hammer ratio. For many applications, this ratio is typically one hammer per every 1.7 to 2.0 horsepower. Not enough hammers in a pattern can lead to excessive pin wear and hammer hole elongation. This wear can dictate a hammer change before the hammer’s hard facing has been worn. Too many hammers in a pattern can lead to an increase in fines produced.
Setting the tip-to-screen clearance. In most applications, the clearance between the hammer tip and screen has only minor influence on grinding performance. Generally, a larger tip-to-screen clearance provides the greatest grinding capacity and efficiency. For a fibrous or other tough-to-grind material, however, setting the hammer tip near the screen can achieve a finer grind, but this can also increase screen and hammer wear.
Setting the proper tip speed. The majority of the grinding done in a hammermill is at the initial point of impact when the material meets the hammers. A faster tip speed can more efficiently reduce the material size allowing it to leave the grinding chamber quicker, leading to reduced hammer and screen wear. A mill with a lower tip speed and smaller screen hole will typically produce a more uniform grind than a hammermill with a higher tip speed and larger screen hole diameter.
CPM Roskamp Champion, Waterloo, IA, supplies grinding, pelleting, and cooling process technology equipment for the animal feed, food processing, and biofuel industries.