Mining industry products and services supplier Multotec reports that its Hawkeye monitoring system, which monitors the life cycle of mill liners, has been met with great enthusiasm by the com- pany’s customers.

In the past, customers have encountered problems with monitoring the life cycle of mill liners, owing to their rotation, which sees liners in a uniform pattern around the circumference of the mill. This means no specific reference liner is seen when the mill is stopped to measure the liners.

Another problem is that the liner to be assessed could be under tons of grinding balls when the mill is stopped for an inspection.

The liners are designed to protect the steel of the mill from wear and impact abrasion that would be caused by the movement of the ore and grinding media.

They are designed to provide a specific trajectory to the charge, specifically the grinding media and the ore, in order to increase the grinding of the ore. This means that the grinding media falls for the maximum distance – from near the top of the mill onto the toe of the charge – so that maximum energy is transferred from the grinding ball into the ore particle.

The charge, which is anywhere from 12% to 40% of the volume of the mill, forms a kidney shape as it is dragged and lifted up the side of the mill by the lifters, while the bottom corner is referred to as the toe.

The company notes that the longer the life of the liners, the more cost effective they are and the longer the grind remains constant and does not drop off as the lifters wear down.

“Hawkeye is a visual, simple and easy to understand wear-based monitoring system which will enable end-users to monitor mill liner life cycles,” explains Multotec Rubber MD Spike Taylor.

Following a survey in early 2011, the company found that most of the feedback from its customers focused on the issues around accurately determining mill liner wear, which led the company to enhance its Web-based Hawkeye monitoring product to overcome the inherent difficulties associated with mill liners. The resultant system reduces the aggravation and costs associ- ated with mill liner shutdowns.

“This first-of-its-kind monitoring programme for mill liners has been developed in a manner that allows a progressive visual display of the liner profile. The replacement profile is clearly shown in red in this visual display and it facilitates the accurate planning of the scheduled shutdown for replacement of the liners,” says Taylor.

While the Hawkeye monitoring system has been running successfully for years on screen panels in both South Africa and Australia, the development of a system for mill liner wear monitoring posed a number of challenges.

“It was an exceptionally complex process to arrive at this simple solution,” says Taylor, adding that it is easy to monitor screen panels as they remain in a specific position.

“However, this is not the case with a mill liner. One needs to consider that, because of the rotation of the mill, there is a lack of a specific base point for the recording of wear.”

After extensive engineering and testing, the design of Hawkeye was perfected to the point where it will display lifter bar and shell plate wear profile results that are easy to understand.

Hawkeye allows the profile measurements to be related directly to the tonnages treated from data accumulated on the end- users’ high-level supervisory control and data acquisition system. “This is an important factor when assessing the liner life cycle, as changes in throughput will have an impact on the replacement timeframe,” he says.

Recording the liner life cycles will also result in predictable shutdown scheduling and eliminate the unplanned shutdowns typically associated with unpredicted liner failure. This greater level of predictability, in terms of maintenance requirements on the mill, results in a more productive and profitable environment.

“Additionally, this accurate recording of the life cycle will facilitate discussion of liner design changes between Multotec Rubber personnel and the end-user, resulting in an improved life of the mill liner. This high level of monitoring allows accurate information to be retained and mill-specific liner solutions to be provided,” says Taylor.

“Because it is a Web-based system, end-users have ready access to the mill liner data. The system allows the customer to set predetermined levels of access according to individual plant needs. For instance, the plant personnel can have access to plant data while management could have access to data in more than one plant or even all the plants across a group,” says Taylor.

The item descriptions are fully, but simply, displayed and include the installed quantities. They are cross-referenced between the Multotec Rubber item number and the customer stock code number. “This allows for ease of ordering, and we are currently enhancing the system to allow the cus- tomer to automatically request quotations. This will result in far simpler stocktaking and will eliminate much of the human error that occurs,” he says.

A close relationship between Multotec and its customers has culminated in many long-term fixed price contracts being instituted. With the advent of Hawkeye for mill liner monitoring, the company is able to provide customers with the advantage of access to a high level of liner consumption data.

“This data allows the customer to more accurately forecast and control budgets while simultaneously ensuring maximised plant uptime,” Taylor concludes.