Products - Spin to Stall Resin system
In South Africa it has been recognised that improved bond strength and consistent high installation standards will lead to improvements in roof control and a reduction in falls of ground.There are also pressures to install bolts rapidly and at minimum cost. This has led to the development of the 'spin to stall' system of resin roofbolting. The bolt is spun to mix the resin and spinning continues until the gelling resin increases the resistance, resulting in torque nut breakout. The nut runs up the thread and is tightened against the bolt plate until the roofbolter stalls. This method allows the bolt to be installed in approximately 10 seconds using a very simple procedure. The length of exposed thread provides an indication of the standard of installation.
Conventional wisdom is that resin should not be spun into the gellation phase, called overspinning', as this permanently damages the setting resin. Spin-to-stall systems violate this principle. Spin-to-stall works because strength increase during gellation is so rapid that the break-out torque of the nut is reached before significant damage is done. The resin is made with a reserve of strength so that residual strength is sufficient even after some unavoidable damage.
Modified short encapsulation pull testing indicated that spin to stall installation gives comparable results to the spin and hold system previously used. Spin to stall is in regular use on an increasing number of collieries in South Africa. Its success depends on tight control of the quality of the materials and equipment used and adherence to good operating practices. Work is continuing to optimise the spin to stall installation technique to maximise bond strength. Development includes the setting characteristics of the resin and achieving the desired torque break-out with consistent accuracy.
