Some 15 years of research and around $20 million in funds have been spent on efforts to automate roof bolting. None have been successful. In September this year, around 20 representatives from various Australian and Japanese research, mining and manufacturing organisations met at the Brisbane offices of CSIRO Exploration and Mining (CEM). The meeting was to nail down conceptual details in the lead-up to construction of Australia's first automated roof bolting machine as part of the Rapid Roadway Development project. Coal mining co-ordinator for CEM, Mick Kelly,
spoke to ILN about the latest developments.
At their last meeting in June, representatives from CEM, Hydramatic Engineering, the Japan Coal Energy Centre (JCOAL), and others agreed to shorten the length of the Autonomous Conveying Bolting Module (ACBM) machine by 2m. This was achieved by narrowing and repositioning the roof bolt box and feeding the bolts alongside the narrowed section.
Previously, bolts were feeding into a carousel and the bolter was returning to pick up bolts. Now the carriage will feed straight into the bolter, meaning less opportunity for things to break down, Kelly said.
The outcome of the September meeting has been finalisation on almost all the parameters of the ACBM, designed to travel behind a miner inserting roof and rib bolts as it moves forward. Construction of a prototype is expected to begin in November through to July 2001. Initial trials are expected to begin in September that year to test the capacity of the bolter followed by a full production trial beginning in early 2002.
According to Kelly, the four crucial elements that had to be worked through in the last two years were the use of a self-drilling bolt, automation of the feed system, making the bolter autonomous, and the control/system issues.
"The first primary target was to use a self-drilling bolt. Two years ago, BHP had a bolt still under development and if that had fallen over we doubted if we could go down this particular development path."
Kelly likens the adoption of the new self-drilling bolt to the development of the revolutionary nail-gun; for the nail-gun to succeed the consumable had to be changed.
Says Kelly: "When we started this process we looked at what people had done before us and it was obvious that people were trying to automate something that was not amenable to automation. The reason is because they're trying to automate a manual process."
BHP has since decided to spin off part of its steel business. This newly formed company is called OneSteel and is committed to the commercialisation of the Self Drilling Ezybolt. Trials of the self-drilling bolt are under way with full commercialisation expected next year.
Having identified a suitable bolt, the next challenge was automating the feed system.
The aim is to bolt continually during a shift at an advance rate of around 15
metres/hour. Under most conditions, bolting will be a 4 bolt pattern at 1.2m spacing.
At the start of each cycle, the bolting machine will be loaded with two 3-tonne cassettes. The Roberts Group is currently designing a jib system to pick up 3T off an EJC130. Each cassette will contain 180 roof bolts, 90 rib bolts and enough chemical to feed both installations.
Kelly said at a capacity of about 40t, the bolts will be about 25% stronger than other
bolts currently on the market. The bolts utilise a special patented bolting head which
drills into the roof and rib, followed by chemical being pumped up through the bolt
itself. This chemical installation system means these types of bolts will always be
machine installed. One of the advantages is no capsule gloving or chemical mixing
A major design challenge is the control system, which is the part of the work CEM is
involved with. The machine will incorporate around 150 solenoid valves, installed by
three to four manufacturers and have to be able to interface and be compatible.
"The control system on the valves is quite challenging at a maintenance level," Kelly
The market for the bolters will probably be small. Kelly's conservative estimate is a
market in Australia of 15 machines plus. The automated bolter has been designed for
Australian height conditions of between 2.8m to 3.6m. This means it is unlikely the
design in its current form will find its way to the US where parameters are typically
2.1m. For one, American researchers would need to rethink the bolt loading
mechanism, which currently occurs vertically. This would not be possible under more
constrained operating heights.
Kelly said three suitable sites from a big list of hopefuls would be identified for
trialing the machine. "We've had a lot of interest from newer Bowen Basin mines with
good conditions. Then a lot of NSW mines are using place changing which would be
ideal for this type of system."
Another aspect of the work is to assess different stand-up times at different mines to
enable researchers to design different bolting patterns. The drilling will also be
monitored to show the hardness of the roof and any breaks before it becomes a
problem. The Japanese researchers are developing the software to show the integrity
of the roof.
An area of the design yet to be finalised is the installation of a remote bolting facility
onto the miner itself. Kelly said in general conditions 12m cut-outs were fine but in
poor conditions additional support was necessary. The bolter on the miner will be a
much smaller, simpler version of the one on the roof bolter, and capable of installing
two bolts every 2m in poor conditions.