Crushing

Chute liner performance tested

In particular, the sliding and impact abrasion experienced at the transfer point chute is one of the most common problem areas on conveyor systems. Once the conveyed material has left the discharge end of the belt, it independently gathers velocity due to gravity to a subsequent part of the structure.

It is at this precise moment that the material trajectory becomes turbulent and almost uncontrollable, with changes in horizontal and vertical forces acting on it.

Depending on what the rock is made of, or how it is performing in regard to a particular set of circumstances (for example, weather conditions, percentage of clay and fines present, moisture content or change in product flow altogether), the material will present itself differently.

This may lead to many different issues arising in the transfer chute, including material hang-up, excessive wearing of components, tracking issues from change in load distribution and cleanliness of the plant due to spillage and material carry-back.

All these issues are somewhat caused by materials flow and chute layout. Reducing the time in which the rock material is uncontrollable and turbulent, and promoting laminar flow, is possible. However, this requires use of controlled linear cascading drops and sacrificial materials known as “wear liners”, which manage the product deflection and optimise production.

More recently the design phase of plant construction has been focused on the transfer chutes, and the selection of the most effective wear liners to meet the needs of flexible production objectives.

Wear liners don’t just contain the asset and direct it to the next stage in the process. They now also have a function of promoting flow; flow reduces the occurrence of hang-up, rat-holes, bottlenecks and blockages, which result in unnecessary stoppages, downtime and wasted money and production time.

The reactive maintenance model that relied on simple and “quick fixes” is fast becoming unacceptable because hindsight is proving that reactive repairs are more costly in the longer term.

REDUCED WEAR LIFE {{image2-A:R-w:300}}Take, for example, the experience of a quarry in Melbourne’s southeast peninsula region. Its granite business has been in operation for more than 80 years, producing 650,000 tonnes per annum, with a further 30 years of reserves planned for the site.

To transfer the conveyed 400mm sized granite rock for screening, the existing transfer point at the site incorporated a chute made of conventional steel, with a drop height of 2.5m and an impact angle of 60 degrees from horizontal (see Figure 1). The wear liner used was a 16mm bisalloy plate, considered as having high ballistic performance.

However, due to the weight of the rock and the drop height and impact angle, the chute still experienced significant abrasion and damage, with the bisalloy plate offering a wear life of only five days before it had to be replaced with further bisalloy “quick fix” plating patches.

The knock-on effect of this repetitive maintenance was an accumulation of unsatisfactory labour and manual handling costs. Where access to the inside of the chutes was extremely difficult, both thorough and extensive conveyor shutdowns would be necessary. This led the quarry to consider searching for a better wear liner solution.

NEW LINER ALTERNATIVE {{image3-A:R-w:300}}K-Redi-Liner is a modular lining system that is well-suited to this application.

It is lightweight in comparison with the bisalloy patches and needed only to be bolted into place as opposed to being welded (see Figure 2).

Being able to reduce labour and associated repair costs would provide an opportunity for the maintenance team to complete other tasks towards improving production.

However, the convenience appeal of the K-Redi-Liner needs to be matched by its wear resistance potential.

Lining selection requires consideration of both the “science” of wear and environmental factors, so with the speed of the conveyed granite (350 tph with a velocity of 1.8m/s), the ideal configuration is the newest edition to the K-Redi-Liner range – K-Redi-Liner KP Dual Duro – as it incorporates ceramic cubes with dual durometer suspension formulas: 63 Shore A bottom + 93 Shore A Duro top (51 + 51mm).

After installation in January 2013, the wear life of the K-Redi-Liner KP Dual Duro has been impressive.

As opposed to the previous bisalloy patch’s wear life of five days, the K-Redi-Liner KP Dual Duro provided effective material control and turbulence reduction in the transfer chute area for more than 14 months before it needed to be replaced. The end result was not only a significant reduction in replacement liner product costs but in costs associated with reactive maintenance labour.

A challenge for potential users of new lining alternatives is to be able to predict the likely performance of the increasing range of chute liners – rock boxes, manganese, mild steel, duoplate and HDPE, to mention a few; all have their uses.

Field trials with customer case studies provide a reference point on performance but Kinder & Co recommends consultation with an engineering expert on the best options to suit specific application and site conditions prior to any “quick fix” expenditure. New alternatives are often not costly in the long term. 

Sean Kinder is a sales engineer for Kinder & Co, Melbourne.

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