Friday 17th Jul, 2020

Lagging solutions

When a major conveyor maintenance company needed to replace damaged pulley lagging at an iron ore export port in the Pilbara, it turned to Elastotec for specialist support.

Unplanned downtime and equipment failure have the potential to cost bulk handling companies millions of dollars in lost productivity, on top of hefty repair costs.

This is particularly the case for the mining industry, where conveyors transfer thousands of tonnes of ore every hour and operated 24 hours a day, 7 days a week.

Elastotec Managing Director David Molesworth says that conveyor systems operating round the clock like this will inevitably suffer wear and/ or damage. High tension bend pulleys in contact with the dirty side of the belt are particular prone to wear and damage – this is due to the presence of carry back and also high localised shear forces that are generated in the centre of the pulley due to wear of the belt top cover that changes the belt profile. The more the belt cover wears the greater the localised shear forces and the greater the damage/wear of the lagging

As a result, mining companies install pulley lagging onto their conveyors to help protect the pulley and the belt from damage and build- up. However, the lagging is also subject to the same conditions. If it gets damaged, it can expose the pulley shell and lead to further problems.

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This is what a major iron ore port facility in the Pilbara, Western Australia, encountered on one of its high-tension bend pulleys (Pulley 3 in Figure 1). The port operates 24/7 year round, with a handling capacity of around 180 million tonnes of iron ore per year, meaning the reliability of its conveyor system was critical to achieving the maximum ore throughput.

At the time, hot cast polyurethane lagging was specified for all non-
drive pulleys by the port operator, however this requires removal of the pulley from the conveyor, and in this instance this was not possible. The lagging specification had recently been revised to nominate polyurethane lagging in place of the previously used Direct Bond Ceramic Lagging (DBCL) because of its ability to resist build-up.

Build-up from carry-back has been a problem on ceramic-lagged, non- drive pulleys in the region, causing belt tracking problems and damage to belt and belt splices.

The conveyor maintenance company contacted Elastotec to discuss the lagging options for on-site application. Elastotec’s recommendation was to install its 20-millimetre Plain Polyurethane (PU) lagging, which can be manufactured with bonding layers suitable for cold bonding or hot vulcanised applications. This was discussed with the port operator and the cold bonded 20-millimetre PU was selected because it could be applied with the pulley installed on the conveyor.

The 20-millimetre thickness was selected to provide a service life that would exceed the existing mechanical components, such as bearings and locking elements.

In December 2017, during a planned shut, the damaged ceramic lagging was removed and replaced with the Elastotec 20-millimetre PU lagging. In December 2019 a follow up check showed that the 20 millimetre PU lagging was still in service and was operating satisfactorily.

Molesworth says the company believes that rubber backed polyurethane lagging can successfully be used as an alternative to hot cast polyurethane.

“It can provide comparable service life with the added advantage of being suitable for on conveyor replacement of damaged or worn lagging,” he says.

“Hot vulcanised application of the Elastotec PU Lagging is always preferred as it ensures 100 per cent rubber tear bonding to the pulley shell and no joints between strips, however, like hot cast PU lagging, the pulley must be removed from the conveyor for this type of application.”