Published in the March 2006 American Longwall Magazine

Equipment supplier JH Fletcher & Co has developed a fully commercial system for its line of industrial minerals roof bolting machines and is working with West Virginia University to develop a complementary system for its line of coal roof bolting machines.

Roof control engineers have long sought ways to identify when geological features change at a certain location but to do so they need to know in advance the geology within the bolted horizon, from bolt row to bolt row. The only way to do this in realtime is to map changes in geology from bolt hole to bolt hole using information from the drillhole.

Since 1992, JH Fletcher & Co has used electronic technology on its roof bolters to both identify and react to changes in the roof strata to optimize the machine’s safety and drilling performance. The progression of this drilling technology has produced a means of collecting sensor data that can be analyzed and interpreted as changes in roof strata.

At the same time, West Virginia University’s Department of Mining Engineering was doing similar work with roof mapping. A partnership was formed for the university to complement its current research to further correlate this sensor data to the roof strata and rock strength.

A Fletcher model DDR roof bolter equipped with a patented drill control unit (DCU) was dedicated to the university to facilitate this research. The test bolter was used to record drilling parameters in experiments in which more than 1000 roof bolt holes were drilled in laboratory conditions and at eight underground mines.

This research, led by Syd Peng, the department’s chairman, resulted in the development of a set of computational rules that have been built into a software package known as MRGIS (Mine Roof Geology Information System). The MRGIS software package is scheduled to be tested during production on a second roof bolter at Foundation Coal’s Emerald mine. This roof bolter will be used both as a production machine and as a test machine.

JH Fletcher & Co also uses the electronic feedback system on its line of roof bolters that service the industrial minerals market. In 2002, the Graymont Pleasant Gap mine (limestone) purchased a roof bolter with the feedback system and was very interested in monitoring voids (strata separations) in the mine top. After many borescoped test holes were analyzed, software was developed and successfully tested to map voids from the machine data. This software was expanded to also graph changes in the strata’s relative material hardness (RMH).

After the accuracy of this software was demonstrated to the mine engineer, he asked for the information to be displayed to the operator in realtime. If the mine engineer decides to make a change after the production area was originally bolted, then the area would have to be bolted a second time. Being able to make changes during production means less repair bolting and ultimately a safer roof.

West Virginia University was again called upon. With the aim of complementing the two related projects, WVU was contracted to aid in the development of the software to display the mapped holes in realtime.

In April 2004, the realtime software was successfully tested. To use this software during production clearly required the installation of a robust computer in the cab of the drilling machine. Fletcher partnered with New Hampshire-based supplier of rugged computer technology Glacier Computer to produce the first production models.

In May 2004, the computer used to test this realtime software was replaced with a more rugged touchscreen computer from Glacier. With the information now displayed in realtime, the operators are working with the mine engineer to actively change their bolt lengths when anomalies are realized in multiple neighboring holes above a certain critical depth.

Since then, every production hole drilled at the Graymont mine has been recorded and stored. This mass of information has both led to further refinements and to new applications. The archived data files revealed the hydraulic drill feed motor was starting to lose its hydraulic efficiency. The mine was notified and the drill motor was replaced during scheduled maintenance with little machine down time.

Now that placing a computer on a machine can be justified, its application can be expanded.

The realtime mapping system was expanded to be a realtime information display that contains electronic parts book, operator’s manuals, circuits and trouble shooting information.

Since implementation of this system, other industrial minerals mines have shown interest. The system was originally developed for a rotary drill but the software has now been expanded to work with a percussive (hammer) drill.

A limestone mine in Tennessee, which uses a percussive drill, uses the mapping software to track a soft seam of shale to adjust the mining depth when it face drills. The mine personnel use a data recorder since the percussive drill mapping software was not originally available in realtime, (though it is now).

To date, the mapping system has been used in production at three different limestone mines with the realtime display currently only being used in one.

A further three Fletcher machines are being fitted with the new technology.

The technology has been thoroughly tested, but Fletcher project engineer Craig Collins, said because every mine has its own unique roof conditions for which the system may or may not have been tested the system’s level of accuracy would have to be demonstrated and verified for each new operation. As data is collected and analyzed for new roof conditions, the software’s accuracy and versatility will only be improved.

“I feel that making information available in realtime at the location that it is most needed is one of the system’s biggest benefits,” Collins said. “The biggest challenges for this system will be user interface. Technology is not always embraced underground. This system must be simple to operate and easy to understand or it will never work underground no matter how accurate its results.”

JH Fletcher & Co has plans to display the MRGIS system in realtime on its coal machines. Dealing with the electrical approvals poses additional obstacles that did not have to be dealt with on the industrial minerals application. The field experience and feedback gained from the industrial minerals application is being applied as the coal mine mapping display hardware is designed.

In addition to the hardware, the field experience from the mapping software will be used to ultimately make both systems better.

This is not Fletcher’s first cooperative effort, he said. “Working in conjunction with other companies is very much an important part of how Fletcher conducts its business.”

As a custom builder of mining equipment, Fletcher is accustomed to working together with others from throughout the industry, and is currently involved with and supports various research endeavors.