It’s not uncommon to have various problems that could be associated with machinery and equipment in the mining industry. The environments in which they operate can be incredibly harsh, often leading to the need for repair and maintenance. The most common issues associated within the mining industry include abrasion, chemical attack, corrosion, impact and wear. These can all have a major impact on processing and productivity. Ultimately, they can lead to shutdowns and costly downtime.
How Vibration Causes Wear
A common cause of wear can be vibration. This can cause eventual fatigue, resulting in cracks and a loss of material. Inherent vibration from the operational equipment can cause premature failures in areas such as concrete foundations and their anchoring systems. Generally speaking, concrete can be considered too brittle and weak to absorb such constant impact and vibration transferred from the equipment. Once the concrete has failed, anchor bolts in the foundations can loosen, further aggravating the effects of the vibration on the foundation.
A copper mine in Marabá, Brazil, found this to be the case with its primary crusher. The base of the primary crusher needed to be rebuilt due to being weakened by vibration. The primary crusher weighs 336 tonnes and is 9.5m high and 5.6m wide, contributing further to the amount of stress being put on the foundations. The crusher processes over 3,000 tonnes of copper ore per hour. Being one of the biggest copper crushers in South America, and with copper being traded at around US$6,000 per tonne, every hour of shutdown can result in a loss of almost US$20 million.
Continuing under such damaged conditions would have eventually led to serious consequences, including a significant financial loss. A solution was required that could rebuild the foundation and bases of the primary crusher, whilst being able to withstand high dynamic and impact loads without shattering and breaking. Excellent mechanical properties and a fast curing time were also critical in ensuring the primary crusher would return to service in as little time as possible. The solution used was Belzona 4111 (Magma Quartz), a high-performance concrete repair and rebuild composite.
Repairing The Concrete & Rebuilding Composite
Using an impact hammer drill, the first two layers of concrete were removed to reach the steel reinforcement structure. Particularly with concrete repairs, surface preparation is critical in its success. The substrate needs to be free from contamination, free from excess moisture and any loose material needs to be removed. The area was therefore cleaned and degreased with solvent and compressed air was used to remove the entire repair area of loose debris and dust. A conditioner was then applied to ensure an optimum bond between the substrate and repair materials.
The perimeter of the repair area was initially built up, later acting as a mould for a slurry mix of Belzona 4111. The material was able to level evenly to recreate a foundation at the base of the primary crusher. The implemented solution offered resistance to high vibrations and dynamic loads due to its high mechanical strength. The system adhered to both metal and old concrete allowing for a homogeneous load distribution, without weak spots during the anchoring/grouting procedure and service.
The assembly of the machine commenced in as little as four to six hours after application and a full return to service was possible in approximately 16 hours. The fast turnaround time allowed the copper mine to continue its processes without a majorly disruptive or costly downtime.
John Hutchinson is with Belzona