Magnetic protection is necessary in order to realize the best life of the working components of the
mill. Tramp iron that enters a hammermill can knock holes in the screen, break hammers, and create
undesirable sources of ignition. Mills that routinely operate with excessively worn or failed hammers
will vibrate badly and promote bearing failures. The vibration monitor switch on a hammermill is
intended to be used as an emergency shut down measure and not as an indication that lost tools
have been found.
Always buy the best possible magnetic protection that is reasonable for a specific system and make
sure the magnets are routinely cleaned. Nothing in the process plant is less productive than magnets
that are covered with tramp iron.
Many types of feeders can be equipped with VF drives or other means to permit easy adjustment
of the feed rate. In many plants these will be integrated with a process control system that automatically
adjusts the feed rate to match motor loads or process flow rates. While not as uniform as rotary
pocket feeders, variable speed screw feeders can also be employed to regulate the flow of materials
into a hammermill grinder. While simple slide gates may be less costly to install initially, the improved
service of the mill and working components, lower operational costs, and improved product quality
are all good reasons to invest in a quality feeding system.