One of the requests most often voiced by drill operators is for automated and remote-controlled drilling machines capable of drilling an entire work session before being removed for the blasting operation. But while control systems might theoretically enable this, new solutions are necessary for consumables to practically allow it.

Flexible and fast to set up top hammer drills are ideal for narrow and short boreholes in hard rockFlexible and fast to set up, top hammer drills are ideal for narrow and short boreholes in hard rock

"The traditional drilling bits can't last long enough, but Robit developed special bits with diamond coated carbides that can perform in the desired way. That means one drill bit being able to drill typically about 3,000 - 3,300ft (900 - 1,000m), and it will be able to maintain the drilling performance well all the way towards the end of its life without sharpening," says Vuojolainen. "While the diamond bit unit cost is clearly higher than a usual TH bit, it does offer an extremely good total cost per metre payback."

Together with the general improvements in the durability of drilling consumables, operators' ever prevalent desire to improve efficiency and the consequent continuous increase in drilling power are also creating new demands to the drilling string, especially the threads. As a response, the market is seeing new thread designs, like for example shoulder supported male/female thread, that many operators have found an improvement to the traditional thread designs.

However, it is not one specific innovation or application which will decide the efficiency and profitability of top hammer drilling on a specific project. Rather it is, stresses Vuojolainen, the old skill of adding up all cost-determining factors and establishing the total drilling cost (TDC). "TDC is a sum of productivity cost of drilling in terms of time and cost per metre (drill string endurance)," he explains.

Energy saving is another key factor as sometimes drilling is set-up to drill with highest pressures, while not necessarily needed. In short, Vuojolainen concludes, what needs to be focussed on is what can be done to increase productivity by increasing drilling speed, avoiding downtime and managing the lifetime of wear products.

On top of this, top hammer drilling allows for a larger number of smaller holes enabling more accurate and controlled blasting, something which is usually highly critical in underground operations.

Lastly, top hammer drilling is also required for bolting operations to secure tunnels, and, although the drilling machines used for bolting and production drilling can be slightly different, they share the same drilling methodology and require the same skillset from operators.