OK™ cement mill

Designed for the most energy-efficient and reliable grinding of all cement types, this roller mill is much more than ok. With more than 150 mills sold, the OK™ cement mill has proven to be the most reliable and efficient cement vertical roller mill (VRM) available.

OK cement mill
  • The basics
  • Maintenance

Key benefits

  • Energy-efficient
    The mill uses five to ten percent less energy than other vertical roller mills and 30-50% less energy than ball mill systems
  • High run factor
    Operating time availability is typically 90 to 95 percent
  • Easy to operate
    Allow easy switch between different cement types and adjustment of PSD (Particle Size Distribution)
  • High capacity
    The mill is offered in a broad size range with the largest cement VRM available
  • Operating flexibility
    Achieve 60 to 70 percent of nominal output with a reduced number of rollers in operation
  • Easy maintenance
    Wear liners can be replaced or rewelded inside the mill or the roller swing-out feature can be used for maintenance work externally from the mill
  • Low Total Cost of Operation
    Single large mill size gives lower total installed and Cost of Ownership per tonnes cement produced
  • Concrete mill stand
    Concrete mill stands have faster installation time and reduced cost of installation
  • One mill, many products
    Efficient grinding of Portland cement, slag, and blended cements

Design advantages

  • The modular design has parts commonality with OK raw mill, resulting in reduced spare parts inventory and consistent maintenance practices
  • The patented cement grinding profile is the only one in the market designed specifically for cement grinding
  • The integral separator ensures the mill’s energy-efficiency, stability and reliability
  • Concrete mill stands allow standardization of the mechanical parts of the mill and reduced vibration at the foundation
  • Operation with half of rollers out of service, allows for continued operation at 60-70 percent of nominal output
  • Simple layout and fewer machines in the mill circuit ensure high run-factor and low maintenance costs
  • Optimal wear protection on all internal surfaces extends lifetime
  • Segmented roller wear parts made of the hardest possible material without the risk of cracking; very suitable for repeated hard-facing
  • Proven technology


How it works

The OK™ mill combines the drying, grinding, material conveying and separation processes into just one unit, which simplifies the plant layout. Its low noise level makes outdoor installation feasible – substantially reducing civil construction costs and improving the working environment. Because of its highly effective drying performance, the OK mill is a natural choice for grinding blended cements with one or more wet components.

An ounce of prevention

Even though the OK™ mill is very sturdy, it is important to:

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

Reduce maintenance turn-around time

FLSmidth has incorporated the following features:

  • The rollers and the wear liners of the grinding table are segmented and easy to replace when worn out
  • Roller wear segments can easily be reversed or replaced while inside the mill – without taking rollers out of the mill
  • The wear segments of the rollers can be reversed to use both sides of the segments, enhancing higher utilization
  • Swinging one roller out and changing the seals takes 24 hours, while changing a hydraulic cylinder takes 10-16 hours
  • The mills have two access doors for ease of maintenance, and entry is possible as soon as the mill is stopped. Any jobs done inside the mill have to wait until it is cooled down – typically three-four hours.


Rollers and wear liners

The separator reject cone is provided with rail and trolley for that purpose.

Normal maintenance

We recommend visually inspecting the mill every two weeks, both while in operation and stopped.

Reduce maintenance turn-around time

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

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

Take a tour inside and around the OK mill
OK mill