Plant and Machinery

High-pressure grinding rollers (HPGR)

During the high-pressure comminution process, rather than being crushed between the roller surfaces, individual grains or particles are in effect compacted to a dense flake through exposure to relatively high pressures. After de-agglomeration, the flake normally shows a substatial amount of completed or incipient cracking emanating from the particle surfaces. This highly efficient comminution process requires considerably less energy compared to conventional crushers and mills, due to:

  • relatively uniform loading of the material in the compression zone
  • very short retention time
  • minimal enrgy requirement for material transport in the HPGR.

The movement of the floating roller constitutes the basic principle of high-pressure comminution with a roller press. In HPGRs, the roller gap adjusts itself automatically when subjected to a given pressure between the rollers. The extent of the roller movement at the gap is a function of the 'stiffness' of the hydraulic system in relation to the reaction forces exerted by the processed material, and therefore varies accordingly. This design feature guarantees that during the comminution process, all the feed material passes through the roller gap under the same process conditions, thus ensuring that the HPGR output quality remains constant. 

The applied specific pressing force influences the ease with which the comminution process can be controlled and the ability of the machine to respond quickly to operator adjustments. The HPGR drive system is made up of electric motors and planetary gear boxes installed at the drive end of each roller. The gear boxes are connected to a system of torque arms. Depending on the application, an HPGR may be laid out for constant-speed operation or fitted with a variable-speed drive.

The main parameters for controlling the comminution process and press throughput are:

  • the process-specific pressing force generated by the hydraulic system
  • roller speed (when a VSD is fitted).

In addition to these parameters, the throughput of an HPGR also depends on:

  • machine width
  • the operating gap, which is a function of...
  • ...the roller diameter
  • feed material characteristics and particle size distributions.

Machine Frame
Köppern has developed and patented different hinged-frame designs in order to facilitate the rapid exchange of rollers and minimize maintenance shutdowns.
Read more about the different hinged press frame designs

Wear Protection
Today, almost all HPGRs for grinding applications of minerals are equipped with tires. Tire-shaft solutions are used in combination with well-proven wear protection systems such as hardfacing or Köppern’s own HEXADUR® and HYBRIDUR® systems.


Click on the illustration for more details
HPGR for comminution of ores
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original Main drive Hydraulic system Material feeder Press frame Rollers