| This
article is based on a presentation by Greg Alles, sales manager
for Bliss Industries, Inc., Ponca City, OK. He spoke at the 2004
International Association of Operative Millers (IAOM) Conference
and Trade Show, held at the Century II Convention Center in Wichita,
KS, May 15-19.
Hammermills, used in most flour mills for grinding screenings and
bran, are complex pieces of equipment that must be maintained properly
to operate at maximum efficiency.
Problems with excessive vibration, using worn parts, and failing
to diagnose irregularities in the grinding process can lead to costly
repairs and operational inefficiences.
Milling operations that try to cut corners end up paying for it
for the entire life of the system.
The following steps are suggested as ways to help mills prevent
this from occurring.
Finding the Vibration Source
Excessive vibration is one of the most common problems in hammermills.
To locate the vibration source, you should first remove all hammers,
hammer rods, and spacers.
Then, start the hammermill, and run it at operating speed. If the
vibration disappears, then the source is your hammers and/or rods.
If the vibration still exists, stop the hammermill, and check the
tightness of the stabilizing bars and spanner nuts. You should also
check the welds on the rotors, if applicable.
Next, start the hammermill again, and run it at operating speed.
If the vibration still exists, have the rotor rebalanced.
Finally, check the rotor for excessive wear. See if the rotor plate
hammer rod holes are worn.
If the rotor is worn, it will have to be replaced.
Replacement Parts
Replacing parts before they become too worn is another preventive
measure that can be taken.
Here’s a look at three critical components of a hammermill
and when they should be replaced:
- Screens: When the edges become rounded.
- Hammers: When the corners become worn.
- Wear plates: When the thickness has been reduced
by 50%.
Once the replacement parts are installed, you can take the following
steps to maximize their longevity:
- Reverse the rotation of the hammermill rotor on at least a weekly
basis, if not daily. Doing this will increase the life of both
the hammers and screens.
- Make sure product is being fed uniformly into the mill. Too
much material in one area and not enough in another will cause
screens and hammers to wear unevenly. Hammers that wear unevenly
will cause excessive vibration.
- Make sure adequate air volume is used. Air flow will help uniform
feeding and grinding.
Too little air flow will cause premature wear on the main rotor
plates and force you to change hammers and screens, before they
normally would need to be changed.
The Grinding Process
Finally, it’s important to troubleshoot the grinding process
on a regular basis, to make sure the system is operating properly.
One way to accomplish this is by using the following checklist:
- Confirm capacity.
- Check hammers and screens.
- Check temperature of the grinding chamber.
- Check the air volume.
- Check the feeding device.
- Check for possible discharge obstructions.
- Make sure you’re not using excessive horsepower.
Arvin Donley, editor
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