Using polyurethane in mining and quarrying industries.

In the mining and quarrying industries, however, polyurethane is being used for many other applications with advantage and replacing rubber or even hard steel. In general these applications are connected with movement of very abrasive slurries of relatively small particle size such as in the ball and rod mills, flotation plant, hydrocyclones and piping.

Ball or rod mills have generally been lined with manganese steel replaceable linings, but in recent years the use of rubber replaceable linings has been developed. Dependent on the condition existing in a given mill these rubber linings can last several times longer than the manganese steel, and polyurethane linings can last considerably longer than the rubber linings. Further advantages are that the tooling cost with polyurethane are less and the fact that, due to the availability of the harder grades, the polyurethane can be used as a structural material and does not require reinforcement by metals.

Similarly in flotation plant the impellers, rotors, stator and scrapers are made of steel centers often covered in conventional elastomers. Polyurethane again can be used in certain cases and will generally outlive natural rubber. The main precaution to be observed are limitation in temperature and also extremes in acidity or alkalinity of the slurries.

Hydrocyclones used in the separation of ores and cray are also subjected to harsh abrasive condition, and polyurethane have been successfully used in these conditions.

In mines there is often a considerable fire risk, and comprehensive precaution are taken to avoid spark which can start a fire or explosion. For this reason the use of track laying vehicle with metal tracks is prohibited. Covering of the tracks with natural rubber goes only part of the way to solving the problem due to highly abrasive conditions causing relatively rapid breakdown. The polyurethane track pad do not wear so rapidly and are being used successfully. A further advantage of polyurethane as opposed to metal is the increase in traction obtained which enable the vehicle to climb steeper slopes.