Monday 16th Dec, 2019

Vale’s Vargem Grande conveyor lagging challenge

When the fourth-largest iron mining operation in the world wanted to increase the service life of its pulley lagging, it turned to Elastotec for specialised support.

When the fourth-largest iron mining operation in the world wanted to increase the service life of its pulley lagging, it turned to Elastotec for specialised support.

Vale’s Vargem Grande mine site, located in the state of Minas Gerais, Brazil, contains 2.53 billion tonnes of proven and probable iron ore reserves, making it the world’s fourth-biggest iron-ore mining operation.

The Vargem Grande site maintenance personnel wanted to increase the service life of the lagging on a number of non-drive pulleys installed on a belt turnover conveyor.

Severe localised belt wear was evident in as little as three months and the cost of conveyor downtime to replace the worn lagging was a serious concern. Initial attempts to address this by installing ceramic lagging in high-wear areas fixed the lagging wear, but transferred the high wear to the bottom belt cover.

As the steel cord ST3500 belt is a far more expensive component than the pulley lagging, the use of ceramic lagging was not a viable option. Vale began looking for a lagging solution that would extend the service life past that of the rubber lagging but would not wear the conveyor belt covers.

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One such solution was Elastotec’s Polyurethane (PU) lagging. Two factors made the PU lagging a competitive option to increase the lagging service life.

The PU lagging has a much higher abrasion resistance than rubber lagging (DIN 53516 Abrasion Resistance Natural Rubber has around 100 cubic millimetres of volume loss compared with PU’s 35 cubic millimetres of volume loss) and has a much lower co-efficient of friction than rubber, making the surface slippery.

This slippery surface allows the belt to slide over the PU lagging, minimising any shear force that would cause wear and helping resist the build-up of material from the dirty side of the belt.

A decision was made to trial the PU lagging on two non-drive pulleys, each with a diameter of 1250 millimetres and a face width of 1600 millimetres. Elastotec supplied 12-millimetre diamond PU lagging in strips to suit the pulley face width. The PU lagging can also be supplied in rolls up to 85 metres long but, in this case, strips were preferred.

Elastotec supplied the PU lagging for both pulleys in December 2014. The lagging was manufactured with the Elastotec buffed CN bonding layer for cold vulcanised application.

The PU lagging was applied to the pulleys and put into service in April 2015. Compared to the lagging being used previously, the PU lagging dramatically improved service life, increasing from three months to 18 months.

Vale maintenance personnel said that in this environment, a normal bend pulley that typically lasts one year would last at least three years with the PU lagging. Based on this result, Vale is adding the Elastotec PU lagging to their general specification for all pulley applications with this type of operating conditions.

An additional benefit to the longer service has been the effect on the bottom cover of the steel cord belt, where no additional wear has been observed. Given the high cost of steel cord belts, this is possibly a greater cost saving than the extended life of the lagging.

Elastotec has been able to provide a solution to Vale’s lagging service-life problems and sees this as an integral part of their role in helping their customers reduce conveyor operating costs and improve production performance.