The Long Gap Mill

Rotormills are referred to as “long-gap mills” because of the long annular gap between the inlet and discharge sites on the mill. Long-gap mills provide enhanced milling characteristics when particle-to-particle collisions are occurring during material processing.

In 1984, IPEC began manufacturing Rotormills, and in 2021 Prater Industries acquired IPEC and its quality product lines. The acquisition enabled Prater to build on IPEC’s legacy of outstanding machines and to reach a broader spectrum of industries.

Features and Highlights

  • Eight models are available, ranging from 15 to 750 horsepower
  • Long gap design eliminates the need for screens that can choke or wear
  • Compact, heavy-duty construction with carbon or stainless steel fabrication
  • No specialized foundation is needed
  • Heavy-duty, top and bottom rotor bearings
  • Dynamically balanced rotor
  • Large access doors to the mill interior
  • Hassle-free adjustment or replacement of internal parts
  • Hardened grinder internals available for abrasive materials

Key Benefits

  • Reduced cost and time of processing because several operations such as de-agglomeration and surface coating take place simultaneously
  • It can be used with materials, such as abrasive products and less-friable materials, which may not be handled well by a fine grinder or classifying mill
  • Continuous fine milling at high production rates
  • Simultaneous coating and mixing during milling
  • Fiber fluffing capability

Operational Theory

Particles are pulverized to small sizes by inter-particle collisions induced by very high turbulence within the mill. The pulverizing action is generated by an internal rotor that spins at high speeds. Heavy-duty bearings provide stability during the pulverization process. These bearings are housed outside the grinding chamber to prevent product contamination.

The rotor consists of two sections:

  • A Lower Section that functions as a material distribution fan 
  • An Upper Section, where the material is finely ground.

Grinding occurs at several stages within the upper section. A series of grinding plates accelerate the air and particles against the grooved lining on the interior of the Rotormill. Miniature pockets of highly rotating air are set up within the mill during operation. This high-velocity turbulence causes particle-to-particle collisions and pulverizes the material. Internal heat is absorbed by the continuous flow of air.

Because of the unique design, which allows for varying airflows, the adjusting of the grinding plates, and the type of grinding plates, a wide variety of materials and sizes can be accommodated and rapidly processed. Heat-sensitive materials can be milled without cryogenic processing.

We Are Here To Help

Let us know how we can serve you. We can custom-build almost any milling product needed for your application. If you require anything specific in a Rotormill, we will design and manufacture what you require. Similarly, if you already own a Prater Rotormill that needs maintenance or upgrading, contact us for immediate service.