Our cost-saving Vertical Roller Mill (VRM) exhibits a modern design approach. We continuously improve our solution with the latest updates to enhance grinding performance and overall productivity. The success of the OK™ Mill highlights the reliability of its technology and a contribution to the cement industry amidst rapidly emerging trends of greater variation in feed materials and larger production capacity.
Our OK Mill grinding solution skilfully comminutes raw material, cement and slag. You can easily adjust it to grind any feed material and produce multiple cement types in the same mill.
Due to its highly effective drying performance, the OK Mill is the natural choice for grinding blended cements with one or more wet components. A design for optimal efficiency ensures your operating costs are minimised while profitability is maximised.
Our OK Mill with its patented roller and table design delivers the best power efficiency of any cement vertical roller mill. It uses five to ten percent less power than other vertical roller mills. In addition to efficiency, the unique design also makes the vertical roller mill more stable in operation than other vertical roller mills, offering higher availability and the capability to grind the finest products and highest Blaine cement.
With a modular design, the OK Mill offers the best possibility for low long-term total cost of ownership (TCO) and minimal spare parts net working capital. Parts commonality leads to greater flexibility in sharing spare parts across vertical roller mills, regardless of size and application. It also simplifies spare parts inventory, saving you costs and improving parts delivery times.
The segmented wear parts can be maintained inside the mill or if needed, the rollers can be removed from the mill using the swing out feature for external maintenance. The roller wear parts are made of the toughest material that is suitable for repeated hard-facing.
The OK Mill combines the drying, grinding, material conveying and separation processes into one compact unit, requiring fewer machines in the mill circuit and therefore, simplifying plant layout. Concrete mill stands replace the traditional steel structures, reducing installation time and costs. Using concrete also means lower mill vibration at the foundation.
The high-performing vertical roller mill generates minimal noise during operation due to the lower level of mill vibration. This makes installation without a building feasible. This substantially reduces civil construction costs and improves the working environment for your plant employees.
Our OK Mill offers a high run factor of typically 90 to 95 percent availability. And because the OK Mill can continue to operate with a reduced number of rollers, you can achieve 60 to 70 percent of nominal output in emergency or low demand times.
Selecting a single large vertical roller mill size gives you lower total cost of ownership per tonne of cement produced. Common parts increase equipment availability, lower maintenance and parts inventory costs and help keep the machine in operation while parts are being repaired.
The industry best in energy-efficient grinding, the OK Mill uses five to ten percent less power than other vertical roller mills and 30 to 50 percent less energy than conventional ball mills.
Worn roller grinding surfaces can either be replaced or re-welded inside the vertical roller mill. If needed, the roller swing-out feature allows easy removal of rollers to perform maintenance work externally. Sharing of common parts is possible across different vertical roller mill sizes for both cement and raw applications. This offers you more opportunities in the use of standard component combinations, along with maximal spare part flexibility and reduced spare parts inventory.
With the OK Mill, easy switching between different cement types is possible, along with adjustment of particle size distribution (PSD) to match or to improve products made in existing mills.
The OK™ Mill was originally designed for cement grinding. In 2017 we released the OK™ vertical roller mill for raw materials grinding. The OK™ Mill’s modular design comes with unique flexibility, showcasing parts commonality, where spare parts can be shared between vertical roller mills regardless of size and application. Equipment longevity is assured with durable wear protection on all internal surfaces. The main difference between cement and raw OK™ Mills lies in the roller grinding profiles, with the raw mill rollers bearing a spherical shape that is more suitable for grinding cement raw materials.
We have replaced the conventional steel stand with a simplified concrete stand for the OK™ Mill. This allows standardisation of the mill’s mechanical parts, along with the use of the same construction procedure. Replacing the steel with concrete also minimises vibration in the foundation. A simple layout with fewer machines in the mill circuit and eliminating the need to transport steel stand parts helps keep civil construction costs low.
The OK™ Mill’s patented roller and table design uses a swing lever and roller assembly. This enables easy roller removal for maintenance and replacement. The rollers are made with the toughest material, offering increased longevity and efficient raw and cement grinding. This vertical roller mill uses a hydro-pneumatic system to press its grinding rollers against the material bed on the rotating grinding table.
The OK™ Mill is offered in a complete size range, including 3-, 4- and 6-roller mills, and the largest vertical roller mill size available with installed power over 11 500 kilowatts. This ensures the ability to meet all possible capacity requirements in a single vertical roller mill solution. Reliable large-sized mills help reduce the project CAPEX investment and the total cost of ownership per tonne of cement produced, while increasing total plant productivity.
Engineering for a 50% Clinker Future
Kiranmai Sanagavarapu, Fuller Technologies Denmark A/S, explores the practical challenges of reducing clinker content, with a focus on grinding system design and variability management. This article first appeared in the April 2026 issue of International Cement Review.
Webinar: Grinding technology - best practices for operation and maintenance
This 45-minute webinar briefly reviews grinding theory before delving into an exploration of operations and maintenance best practice. The discussion includes real world case studies that show how our customers are improving product quality and profitability through a combination of solutions, services and best practice. Ahmed Seaf, Process Specialist leads the discussion and Nick Litzenberger, Design Engineer, serves as the moderator.
Gaining ground on SCM use
Increasing energy efficiency through advanced digital tools is helping cut carbon by reducing power consumption. However, there are some emissions that are much harder to deal with: those which occur with the calcination of limestone and formation of clinker.
Greener cements – what are we waiting for?
John Terembula, Fuller, discusses options to reduce the clinker factor using existing technologies and materials.
New OK™ raw mill increases productivity and efficiency at CalPortland's Mojave plant
At CalPortland Cement’s Mojave plant, kiln production was being limited by the raw mill, which couldn’t cope with the increasing demand of a hot market. The company made the decision to invest in a new mill, and settled on an OK™ raw mill 48-4 from Fuller – the first OK raw mill to go into operation in North America.
OK™ Mill - Working Principle
Fuller's OK™ Mill use 30-50% less energy than ball mill systems, and a simple layout and fewer machines in the mill circuit ensure high run factors and low maintenance costs.
Making gains with the OK™ mill
As cement producers continually seek reduced energy consumption and lower maintenance costs, two emerging trends are changing the face of cement production: the use of grinding stations that support variable feed materials and more widespread use of vertical roller mills (VRMs). Cement producers in India, Nepal and Bangladesh demonstrate the success of using VRMs.
The How, What, and Why of Grinding SCMs
In recent decades, the cement industry has made great strides towards reducing its carbon emissions. But while the utilisation of alternative fuels is increasing and new technologies are driving efficiency in the cement manufacturing process, a sticking point remains: The calcination of limestone is the industry’s largest source of emissions. To address this, cement manufacturers must reduce the quantity of clinker in the mix and replace it with supplementary cementitious materials, or SCMs.
Brochures
Fuller has introduced a new simplified bearing conversion kit for separators installed on certain FRM, ATOX® and OK™ mills between 1998 and 2021. This upgrade significantly reduces maintenance and risk for RAR, ROKS, RAR-L, RAR-LVT, RAR-FS, and some ROKS-H separators.
17.08.2026 |
1.72 MB |
English
First published in Oct 2025 by Global Cement, Ahmed Seaf looks at why vertical roller mills (VRMs) get ‘angry’... and how to calm them down.
01.10.2025 |
1.06 MB |
English
07.04.2026 |
601.53 KB |
English
The OK™ mill has been our standard cement VRM since 1993. Since its introduction, the OK mill has proven to be the most efficient cement VRM available, with the highest reliability and ease of operation. In 2017, we introduced the OK raw mill, which is designed with the same proven technology and modular design as the OK cement mill.
07.04.2026 |
3.10 MB |
English
The OK™ raw mill is designed with the same proven technology and modular design as our standard OK™ cement mill.
07.04.2026 |
4.38 MB |
English
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