Kaltech brings high-tech to mill relining

The world's foremost mill relining company, Kaltech International, has reinvented the painstaking yet necessary task of mill relining with innovations that lessen downtime, improve safety and increase profitability.

Kaltech Sentinel, the company's latest line of state-of-the-art mill relining products, includes smart bolts and sturdy cameras that provide an unprecedented look inside an operating mill.

"Producing products that will benefit the mining industry is a goal of Kaltech, it is necessary to continually improve not only its own valuable final product but those of our clients," Dan Steed, research and development, Kaltech, told Metal Tech News. "The benefits these revolutionary products bring to mining will allow for safer operation and relines for years to come."

Kaltech traces its roots back to the 1980s, an era when the price of gold hit record highs and many large low-grade ore deposits suddenly became commercially viable.

Because of the advantages in terms of capital and operating costs, autogenous grinding (AG) and semi-autogenous grinding (SAG) mills, became the natural choice for mines to crush and grind larger quantities of lower grade ore.

Both mills are basically giant drums that pulverize ore by tumbling it, a process that also wears the inside of a mill by the thousands of tons of rocks bouncing around inside. The difference is AG mills accomplish this as the rocks beat against each other. SAG mills on the other hand have steel balls as an added grinding medium.

As these mills grew in size and number, so too, did the enormity of the linings required. This increase in liner size created a maintenance problem, because the changing out of worn liners was a task that required specialized equipment.

There were also new problems for production staff. As a SAG mill was often the only primary grinding mill, a stoppage of the mill to change out worn linings meant that all production for that concentrator stopped.

Australia-based Kaltech began filling this growing need for a unique group of individuals equipped and able to safely and efficiently reline mills – establishing itself as an industry leader, a position it retains to this day.

While originating from Australia, Kaltech established itself in the United States in 2002 and has set up shop in Salt Lake City, Utah, one of the preeminent mining cities in America.

It is here that this innovative company began the arduous task of redefining the mill relining business and changing the process from preventative to predictive maintenance with high-tech.

Tough business

Mill relining is an unavoidable maintenance process and is one of the primary reasons for mill or plant shutdowns at mines.

While the cost of relining a mill is factored in, the loss of production can be far more costly for any mining company using these massive rock grinders.

Generally speaking, and depending on current ore prices, the loss of production from a large SAG mill being down for maintenance or repairs can cost a mining operation between US$30,000 and US$250,000 per hour.

The high-wear liner components of a large SAG mill can take anywhere from 40 to more than 120 hours to replace, depending on worn liner condition, support equipment, tooling, and the depth of experience of the reline crew.

So, doing this task less frequently and more efficiently can save a mining operation millions of dollars in lost production.

The relining of mills, however, is a tough business that requires working in a confined space potentially with suspended loads because of cracked liners or broken bolts, typically on an uneven and slippery work surface. To accomplish this work safely and efficiently requires comprehensive job specific safety training, meticulous planning, the right tooling, and an experienced team is critical in getting the job done efficiently and incident free.

Currently, the largest SAG mill in operation has a diameter of 42 feet, so it can be imagined how massive such equipment is. The protective lining within one of these mills contain roughly 400 metal plates or liners that can weigh in excess of 8,000 pounds.

With typical preventative maintenance measures, these linings wear out after 30 weeks of constant use, dependent on a number of factors including ore type and quantity, and need to be replaced, manually, by a crew of experienced reliners.

To ensure these plates are secured, large bolts are threaded from the outside and welded to ensure stability as any of the plates coming loose during operation would be disastrous.

The difficulties and costs involved with shutting down a mill to replace all the linings, whether they were worn or not, led to an ingenious solution by Kaltech.

Necessity breeds innovation

To provide mining companies with a better way of knowing whether liners need to be replaced, Kaltech's research and development team developed the iBolt, a simple yet effective method of predictive maintenance for mill relining.

The iBolt is an ingenious but simple bit of technology that involves boring a hole through an anchor bolt and installing a specialized sensor to indicate wear.

Simply put, it is a wear indicator bolt.

Before the iBolt, SAG mill operations lacked the means to intelligently determine mill liner replacements, other than the "blind" option of shutting down production, clearing the feed chute and doing a full, physical inspection of the mill lining and its wear depth.

Thanks to Kaltech's iBolt sensors, maintenance engineers outside the mill can determine how the liners are wearing. This is accomplished by a LED light which can be configured according to the end user needs.

For example, the trigger points can be set to activate at: 50% wear (green light), 65% wear (orange light) or 80% wear (red light).

These bolts are built to the specifications of any mill and liner and are positioned in high wear areas in accordance with a facility's wear prediction requirements.

As the iBolt is intended for placement in high-wear spots, installation of a few strategically placed bolts in a mill is all that is required.

Paired with Kaltech's rugged MillWatch system, a monitoring camera built to endure the inside of the crushing space of the mill, operators have a means to continuously monitor the inside.

This enables remote monitoring of the mill charge and grind behavior while the mill is running, as well as observation and measurement of the charge level and composition and the condition of the shell and discharge liners when the mill is stationary.

Kaltech is also collaborating with Rio Tinto's Kennecott Utah Copper to develop new plugs, named the iBung, that can seal leaks from spare bolt holes.

Previous designs to seal spare bolt holes involve inserting plugs from outside of the mill, which often work their way loose causing unnecessary mill downtime to replace missing or leaking plugs.

The Kaltech iBung has been designed to be easily and quickly fit into the spare bolt hole from the inside during the reline process. The liners themselves lock these plugs into place, which ensures they cannot work loose and leak.

This advanced design also means the iBung does not have to be removed during a liner change.

This not only eliminates the time-consuming process of manually prying a standard bung from the spare bolt hole from the outside of the mill but, as a bonus, eliminates any potential hazards associated with the manual removal and replacement of traditional bungs.

Furthermore, once an iBung has been set in place it need not be removed and is easily reusable, as just the neoprene seal needs replacing before things can go back to business as usual.

Kaltech has even reinvented the liner bolt as a simple and clever two-piece design that decreases mill reline times and increases installation safety.

Kaltech Sentinel

Kaltech has now packaged the next generation of its mill reline technology into Kaltech Sentinel, a complete package system that further improves upon their previous generation designs.

This includes the addition of eBolt, a new electronic bolt; an upgraded version of MillWatch, known as the Sentinel camera unit; the newly developed iBung; and the newly designed liner bolt.

"The idea behind the development of our products such as the Sentinel camera unit, iBolt, eBolt, iBung and our new two-piece liner bolt is to achieve safer relines, greater efficiency and improve mill availability for mine operations," said Steed.

The new eBolt can report up to 16 predetermined wear events in each bolt through a wireless communication system to Kaltech Sentinel software while the mill is still running.

It provides live remote monitoring of the thickness of liners in SAG mills, ball mills, rock boxes, feed chutes and similar applications.

"By collecting information in real time, we can assist mines in projecting more accurate reline schedules, predict wear life of liners and improve the overall downtime during liner changes," said Steed.

Where the iBolt provides a simple notification of wear, the eBolt embodies a true smart system for managing mill linings.

"Ultimately the three main objectives are to protect people, plant and production by getting necessary data that will serve the interests of all involved in mining," Steed said. "The bolts will get information to operations so that they can better understand how the liners wear and when the liners need to be changed."

The new Sentinel camera is engineered to inspect the mill at any time. Using the latest technologies available in high-definition imagery, it is permanently affixed to the feed chute to provide live video and still images from inside a running or stationary SAG mill, which equates to more inspections with less downtime.

Together, the Kaltech Sentinel components provide high-tech yet elegant solutions for production, maintenance and above all, safety.

Mines in countries all around the globe are now applying the mill relining solutions and expertise offered by Kaltech.

The demand for these time and money saving solutions is expected to grow as more precious, base and critical metals are required to continue fulfilling the needs and wants of consumers around the globe.