OK™ Vertical Roller Mill

Designed for economically grinding a variety of cement types, this roller mill is much more than OK

OK Vertical Roller Mill_FLSmidth
  • The basics
  • Maintenance

Key benefits

  • 20-50% less energy use than ball mill systems
  • For portland cement, slag and blended cements
  • High productivity with stable, reliable operation
  • Design optimized for maintenance 
  • Effective drying when grinding blast furnace slag or blended cements with wet components
  • Consistent cement quality with easy-to-adjust quality parameters
  • Modification of PSD (particle size distribution) curve possible
  • Long lifetime
  • Simple, compact layout
  • Proven technology

Design advantages

  • Only grinding mill in the market designed as a cement grinder and not a modified raw mill
  • Simple layout and fewer machines in the mill circuit ensure high run-factor and low maintenance costs
  • Roller and table profile improve operating stability and reliability
  • Special design features for iron removal during slag grinding minimise wear
  • Optimal wear protection on all internal surfaces extends lifetime
  • Flexibility to operate with reduced number of rollers guarantees long-term availability
  • Segmented roller wear parts made of the hardest possible material without the risk of cracking; very suitable for hardfacing

How it works

The OK™ mill combines the drying, grinding and separation processes into just one unit, which simplifies the plant layout. And because it operates at a low noise level, outdoor installation is feasible – substantially reducing civil construction costs and improving the working environment. Compared to ball mills, the OK™ mill can produce better or equivalent cement quality.

An ounce of prevention

Even though the OK™ mill is very sturdy, you should still be sure to:

  • Stop wear from air blasting in good time
  • Keep seals in good condition to avoid wear and false air
  • Change filters and keep lubrication systems in good condition
  • Adjust roller stoppers to avoid roller table contact
  • Change nitrogen pressure in hydraulic accumulators according to grinding pressure
  • Fix oil spills/leakages and change hoses as needed

Rollers and wear liners

The rollers and the wear liners of the grinding table are segmented and therefore easy to replace when worn out. Roller wear segments can easily be reversed or replaced while inside the cement grinding mill – that is, without taking rollers out of the grinding mill. The separator reject cone is provided with rail and trolley for that purpose.

By reversing the wear segments of the rollers to use both sides of the segments, you can achieve higher utilisation.

Normal maintenance

We recommend visually inspecting the cement grinding mill every two weeks, both while running and stopped.

Major maintenance

Major jobs include reversal/change of segments and/or hardfacing. A full hardfacing usually takes 3-4 days. For a cement clinker grinder, hardfacing is usually required annually; for slag grinding, expect to hardface every 3-4 months.

The grinding mill’s swing-in/out roller support system makes it easy to maintain the rollers and suspension system.

Swinging one roller out and changing the seals takes 24 hours, while changing a hydraulic cylinder takes 10-16 hours.

The cement grinding mills have 2 access doors for ease of maintenance, and entry is possible as soon as the grinding mill is stopped. Any jobs done inside the grinding mill have to wait until it is cooled down – typically 3-4 hours.