Spare pulleys are often vital to a mining operation, but if not stored properly, can degrade rapidly. David Molesworth, Director at Elastotec, explains how to keep them in the best possible condition.
When a pulley needs replacing, it is often key to do so quickly. This is especially true in an emergency changeout due to catastrophic pulley failure, but also helps in planned maintenance shuts.
To provide a level of speed and efficiency in this process, spare pulleys are often held in inventory. In both cases it is essential that the spare is completely serviceable and ready to be used – any deterioration of the lagging in storage presents a major problem.
Spare pulleys are usually held on site where storage conditions can vary substantially from mine to mine. They should be packaged in such a way that the lagging is protected from direct exposure to sunlight, as this will protect the rubber portion of the lagging from degradation over time.
Additionally, packaging should be designed so that the pulley will not ‘sweat’ due to moisture or condensation developing inside the packaging. This increases the risk of corrosion and lagging adhesion problems. Ideally, spare pulleys are stored inside a warehouse in dry conditions, but this is not always possible.
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In some situations, like one that a major Queensland coal terminal faced, more of the maintenance budget is spent on spare pulleys than operational pulleys due to the deterioration of spares during the typical storage time of five to 10 years.
The coal terminal had found that replacement of the cold bonded lagging on the spare pulleys was a significant part of this cost.
Some of the common signs of deterioration of cold bonded lagging during storage include:
- Lifting of the lagging at the edges of the pulley
- Lifting of the lagging along the joint between two strips
- Opening up of the joint between two strips (this allows water to penetrate the lagging and start corroding the pulley shell).
Hot vulcanised lagging offers significant advantages over cold bonded lagging when pulleys are held in storage for extended periods and in less than ideal conditions. The advantages of hot vulcanised lagging are due to the much better adhesion between the lagging and the pulley shell (100 per cent rubber tear adhesion is the standard) and also to the elimination of any joins between the lagging strips.
The cover image shows how hot vulcanised lagging eliminates the problems of lagging lifting at the pulley edge and of separation of the lagging along the joints between strips.
Hot vulcanised lagging helps give maintenance personnel peace of mind, as their spare pulleys in storage will have the lagging ready for operation when needed.