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Successful screen optimisation program

Quarry manager Matt Neil had used 20mm thick cross-tensioned rubber screen cloths on the top deck of a 5m x 2m primary screen.

Installation of the heavy cross-tensioned rubber screens was quite difficult, with a mobile crane required to lift 60kg-plus, 20mm screen cloths up to the working platform before being manhandled into position.

Removal of the worn cloth was equally difficult, requiring several men to wrestle with and lift the cloths out of the screen box.

Neil’s primary concern was his workers’ health and safety. This prompted him to investigate safer, lighter options. He subsequently chose Nepean Rubbers’ Eazi-fit modular system because he could convert his screen to a modular arrangement without costly frame modifications.

Each cross-tensioned rubber cloth was subsequently replaced with four smaller, 40mm Eazi-fit rubber panels, each weighing less than 20kg. The lightweight panels could be easily and safely carried up to the screenbox without heavy lifting equipment.

The screen optimisation program was completed in two stages:

  • Stage 1. Changes to the crushers and screen media on the primary screen resulted in increased throughput and significant reductions in screen media maintenance.
  • Stage 2. Through improved screening efficiencies, product specifications were tightened, thus eliminating continual screen cloth blinding and unwanted carry-over. To achieve the required results, Neil substituted the standard woven mesh and standard self-cleaning wire screens used on screens two and three with high performance Flex-mat 3 self-cleaning screen cloths.

On screen one, the modular rubber panels replaced cross-tensioned rubber screens. The panels provided three times the wear life of the cloths, as well as offering easier and safer installation/removal.

On screen two – a 5m x 1.5m triple-deck – Flex-mats replaced woven mesh cloths on the top and middle decks, and rubber was installed on the bottom deck. The future plan is to fit Easy-Fit rubber panels to the top deck to enable easier access to the middle deck. From an OHS perspective, there will be no need for cranes or heavy lifting.

On screen three, Flex-mats replaced some self-cleaning screens. The former screens required regular cleaning, whereas the new screen media has had consistently accurate gradings, and its wear life has been up to three times longer.

Flex-mats were also installed on screen four to replace self-cleaning screens, resulting in a 30 per cent increase in throughput.

“Since the change to Flex-mats, screen two has had no carry-over and there’s no longer a need to clean the blinded screens,” Neil said. “The Flex-mats always stay clean.

“The goal is to optimise our production mix to best suit market demands. We aren’t increasing our production rate, we are simply moving material from one specification and sending it to another where we want it through the use of a more efficient screen media. After the screen cloth switch, the plant has seen an 85 per cent change in our 10mm material and 30 per cent in the 14mm, which is what we were looking to achieve.”

Indeed, the aggregate sampling contractor remarked that the first batch to come off the Flex-mats was the cleanest sample the quarry had ever submitted for testing.

Screen three – a second 5m x 1.5m triple-deck – previously used self-cleaning screen cloths on the top and middle decks, with the bottom deck being wedge wire panels. Flex-mats have now replaced the self-cleaning cloths on the top deck.

“There has been a 30 per cent increase in throughput from the top deck Flex-mats to the middle deck, all of which carried over into our 10mm product,” Neil said.

Flex-mats will also be installed on the middle deck when its self-cleaning screens reach the end of their practical service life.

There are many benefits over and above production improvements to be enjoyed through the use of Flex-mats. All of these production gains are extremely critical to the profitability and success of the operation, but of paramount importance to Neil is the safety and wellbeing of his team.

“Halve the frequency of screen cloth change-outs and we halve the potential safety risk straight up,” Neil said.

The competency and life expectancy of the Flex-mats means there is no need to clean blinded screens with chains and hoses – a real win for the maintenance team.

“Screen cloth change-outs are no one’s favourite job,” production manager Dave Saville said. “When the fitters comment how much lighter the Flex-mats are, they are easier to install and go straight in without the need for trimming or cutting, and with no sharp edges, you know you are on a good thing. What was once a job to be dreaded, the guys get straight in and do it now, plus they comment how much easier it is.”

Stage two optimisation benefits through the changed screen media included:

  • Reduced risk exposure for installation, removal and cleaning.
  • Greater screening efficiency and increased throughput.
  • Longer screen cloth wear life.
  • More accurate and consistent sizing.
  • Cleaner in-spec product.
  • Easier, lighter installations.
  • Faster installations through good fit and no trimming.
  • A happier, more productive workforce.

Neil and his team have worked hard and smart to reduce exposure to potential safety hazards. Their aggregate specifications are now where they want them and, thanks to the product’s strict manufacturing tolerances on aperture size and shape, Neil can now proceed with confidence, knowing the screen media he orders next time and every other time will produce the same results in terms of throughput and sizing as the screen media he is using now.

Source: Nepean Rubber

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