Modern Mining July 2020

to fix holes and cracks. Historically, this has been done using hot-work to weld metal plates into place over the defect; however, this is being matched by the advent of cold-bonding practices which allow metal plates to be bonded onto the equipment using cold-curing, polymeric materials. Once the repair has been completed, providing protection of the main impact zones is crucial to pre- venting further damage. This can be achieved by an array of sacrificial barriers or linings, which help to absorb impact and abrasion from the mining materi- als. More recently, ceramic-filled abrasion resistant linings have become common place in order to pro- tect chutes, hoppers and pipework. Solvent-free and cold-curing, these linings can be applied in situ with- out the need of specialist tools, which allows for safe and easy applications in confined spaces. Pumps Pumps are used throughout the mining industry from the transport of slurry, to the pumping of sub- soil water. As these materials are pumped along through the process chain, they each carry with them a variety of problems, threatening the service condi- tion of the equipment. The consequence: abrasion and erosion-corrosion damage, as well as chemical attack, occurring on main pump components such as impellers, casings and shafts. Initially, this damage will lead to rough and pit- ted surfaces, which will increase friction and lead to a drop in the efficiency of the system as well as increased running costs. However, if not tackled in time, erosion-corrosion and abrasion problems may jeopardise the integrity of the component, ultimately causing failure of the equipment. While replacement of the damaged components might be an obvious solution, it is usually associated

surface profile. There are many solutions available to the mining industry which requires dismantling the equipment to remove the shaft. However, this creates excessive downtime periods which are expensive and unnecessary. Some instead utilise orbital welding, that operates 360 degrees around the shaft, welding to the static workpiece in a contin- uous motion. Fundamentally, these once again can require a great amount of equipment being brought to site, increasing downtime and potential hazards. Conversely, cold-applied, metal repair, polymeric composites are available to restore shafts in situ to their original dimensions. Once cured, these mate- rials provide erosion and corrosion protection; in some instances, their self-lubricating properties help to safeguard against vibration and wear. In addition, these composite repairs offer very high compressive strength, being able to cope with significant load- ings. Solutions such as Belzona 1111 (Super Metal) and Belzona 1131 (Bearing Metal) offer these perfor- mance benefits over traditional methods. Chutes and hoppers Chutes and hoppers are among the most heav- ily threatened pieces of equipment in the industry. Much like conveyor belts, solid handling equipment is exposed to extensive erosion and abrasion from excavated materials of varying sizes. Not only that, but the impact, trajectory and volume with which some of the material is transported through the chutes and hoppers can have detrimental effects on their structure. This can often leave equipment affected by cracks, holes and wall thickness loss as a result of the intense abrasion, erosion, corrosion, impact and sliding abrasion. Initially, in order to return chutes and hoppers and other such apparatus back to service, it is necessary

An increasing number of pump operators are turning to cold- curing polymer technologies to repair and protect their equipment.

July 2020  MODERN MINING  33