Roof Bolter

Overview

A roof bolter is the machine that keeps an underground mine from caving in. Behind a continuous miner, the freshly cut roof is unsupported; the bolter drills holes up into it and installs steel bolts with bearing plates that clamp the rock layers together so they span like a beam instead of falling in slabs. It is one of the most safety-critical machines underground, and the rule of work is strict: the operator stays under already-supported roof while the machine reaches forward to support the new ground.

The drilling end is the Drill Boom & Feed and Rotary Drill Head: a boom that aims the drill at the roof and a rotary head that spins the steel while a hydraulic feed pushes it up. The support end is the Temporary Roof Support, an automated temporary roof support (ATRS) that presses a canopy against the new roof to protect the work area until the permanent bolts are set.

How it works

To drill, the Drill Boom & Feed positions the Feed Frame against the roof, and the Feed Motor drives a chain that advances the Rotary Drill Head. The head's Drill Rotation Motor turns the spindle through a sealed gearbox and chuck, spinning a hollow Drill Steel & Bit tipped with a carbide bit. Cuttings are cleared through the centre of the steel, drawn off by the Dust Collector, whose vacuum fan and filter capture the respirable silica dust that is a serious health hazard when drilling dry.

Once a hole is drilled, a resin or mechanical bolt is inserted and tensioned, pinning the strata. Every cylinder on the machine, boom positioning, feed thrust, and the Temporary Roof Support props, is fed by the Hydraulic Power Pack, a motor-driven hydraulic pump and valve bank. The machine moves itself between bolting stations on the Chassis & Tramming, a low-profile carrier driven by tram motors through reduction gearing to the Wheel Assembly sets. The operator runs drilling, bolting and tramming from the Control System, a panel of valve controls, interlocks and a display, with the 12 V Battery holding up control power.