UK success for modular screen media

Havering Aggregates new D10 screen from Metso Minerals was the first UK application for the recently introduced Trellex modular screen system. It has solved ‘pegging’ problems, saving several hours of lost production each day.

The operation at Wennington in Essex screens and separates soft sand, sharp sand and stones from ballast excavated in nearby Upminster. Trucks haul the ballast from the South Hall quarry to the unit.  “We process 110 t/h through a ten hour day operation,” says Site Foreman David Proctor. “The problem we had was that we were regularly being faced with pegging. This meant that twice a day we would have to stop and clear the stones caught in the screen. This could take more than an hour every time.”

Havering opted for a more pliable screen but again this kept pegging. “We have now had the Metso screen in operation for more than six weeks and it hasn’t had a single pegging problem,” Proctor said.

The Metso Minerals Trellex modular screen media can be fitted to almost any installation in the world. Its modular components have been designed to upgrade systems currently using other manufacturers’ standard fittings. This proved invaluable for Havering Aggregates as the rest of the installation was working well.

“We separate then wash and bag the products here,” said Proctor. “The rest of the washing plant was operating effectively. Now the top deck is really making a difference.” The top deck separates the oversize stone – the natural uncrushed gravel used for footings, drainage and hardcore, allowing the 25-mm stones to pass through the holes of the screen.

“Previously we were getting stones ‘pegged’ in the screen which meant a number of smaller stones were being rejected” Proctor said. Once through the top mat, the stones go into the log-wash and are separated into 20 mm and 10 mm. Meanwhile the sand is washed and separated into sharp and soft grades.

“We work ten-hours a day here and it is important to keep the plant working,” says welder-fitter Paul Edwards. “It was pretty frustrating having to stop work every four or five hours to clear the screen. Fitting the Trellex step has been a great success.”

The new system has been designed with many positive features, including lightweight rubber or polyurethane modules, easy snap-on connections and an emphasis on recycling. One of the other benefits is that the Trellex range has an improved open area compared with other solutions on the market, giving better performance.

The strips to which the modules are fixed are narrower than the ones traditionally used on existing modular installations. This means there will be a smaller blind area at the intersections between panels.

The Trellex Modular Screening Solutions is the family name for a system that includes a full range of components. Existing successful products such as stepped modules will remain a very important part of the Trellex Modular Screening Solutions family. They are joined by new additions that will enable Metso’s products to be directly compatible with the other standard sub-frames used around the globe. The new range is easily retrofitted to existing systems with no need to weld or cut steel rails. A new profiled strip simply fitted to the rail and it is then ready to take Trellex modules. 

Metso Minerals Screening Media Product Line Manager Claes Larsson said, “Customers will even be able to opt for a special tapered strip to allow them to mimic our existing system by introducing a step to the deck. This is particularly recommended for applications with a lot of fines.” 

The new Metso range is divided into three families, depending on the spacing, between fixings of 300 mm or 305 mm and whether they are snapped on transversely or longitudinally. There are many options, including material, size and aperture arrangement. The range also includes optional fittings such as deflectors to steer the flow.

Havering was also interested in the better wear life that the Metso system promises. This is the biggest factor that has been encouraging customers elsewhere in the world to move from custom-made steel wear cloths to rubber or polyurethane modules. “In extreme cases, a woven wire cloth might need to be changed every week; the rubber equivalent could last eight months or more,” said Larsson. He added that there are also environmental benefits in using rubber or polyurethane products, as they can reduce noise. Sections can be rotated or replaced as they wear out, instead of discarding an entire steel cloth.