One Design, Many Applications
The basic design of the industrial hammer mill is really quite simple:
- A steel chamber containing a shaft to which rectangular steel hammers are affixed.
- Replaceable plates lining the mill’s interior to reduce wear caused from grinding abrasive materials.
- Steel screens or bar grates cover the mill’s discharge opening.
Material is fed in through the top of the mill. Once in the grinding chamber, it is reduced by a combination of repeated hammer blows, particle on particle impact, and contact with the walls of the mill. The material will remain in the grinding chamber until it is reduced to a size that is able to pass through the screen covering the mill’s discharge opening.
The simplicity of this design makes it a very versatile hammer mill, one that can be adapted to suit a wide variety of materials, such as:
Similar, Yet Different
The same hammer mill for fishmeal and coal? Well, yes and no. The basic framework of the mill is the same. However, the configuration of the variable components is how they differ. That determination is based on the following criteria:
- Material being processed – Material characteristics such as: friability, flowability, moisture content, and in-feed size
- Desired finished particle size – Gravel, granules, powder?
- Desired production rate – 10 lbs/hr, 10 tph, etc.
With this information, the following can then be determined:
- Hammer mill size – Rotor diameters between 6″ and 44″, and internal mill widths of 6″ to 72″.
- Hammer size and style – Number of hammers, size, style and metallurgy.
- Screens or bar grates – Style and thickness of screen or bar grates, and size of openings.
- Choice of proper RPM
It’s Optional
Finally, once the the mill is configured, the last determination is whether or not any optional peripheral equipment is needed. For this, the following questions must be answered:
- How will the material be fed into the mill? By hand, auger, or belt conveyor?
- How will the material be taken from the mill? Heavy materials such as stone or metal may evacuate via gravity, while light or low density materials will require pneumatic suction.
- Is dust a concern?
Answers to these questions will help to determine the best types of optional equipment such as belt conveyors, augers, rotary feeders, and dust collection, as well as the most efficient design of the in-feed and discharge chutes.
