The evolution of the heavy duty trommel

• 
• 30th September 2009
• Quarrying
 

Nigel Moreton examines the evolution of the heavy duty Trommel and the recent upsurge of interest generated by quarry operators looking at more sustainable ways to maximise their profitability by reworking their waste stockpiles, so extending the life of existing quarry sites or reclaiming good rock from disused ones.

Demand for good quality stone in the UK has been rising steadily and although in many areas the quarrying industry is in the middle of reduced outputs, operators are still looking at maximising their potential reserves in order to make their operations both economic and profitable.

Restrictions on the opening of new quarries and development of existing sites has meant that matching production to demand as become a challenging balancing act..Companies  are now looking at the often vast hidden reserves of waste which have been left behind as the quarrying of more easily accessible good rock became the prime objective. As the good rock reserves grow less abundant new methods, both in cleaning and sizing, have had to be developed to capitalize on these material assets.

The development of the heavy duty Trommel screen by Stelex Construction of Whitchurch, Shropshire, has spearheaded this recent trend and has resulted in very high recovery rates of good, clean rock from overburden waste, which in turn have led to an increase in company operating profits.

History

Trommel screens have been used since mechanized quarrying began in the late eighteenth century. Then the screens consisted of circulate steel meshes bolted together to form a single barrel which rotated around a long, central shaft set with a slight inclination. Crushed material travelling down within the cylinder was graded out according to the size of the apertures that made up the barrel. These screens were used extensively until the 1950s when vibrating flat bed types started to come onto the market. Developments in bigger, more robust, heavy duty, high capacity Trommels in the 1980s, for the production of rip rap and armour stone, led the way for heavy duty Trommels purposely built to handle high tonnages of material and lump sizes of up to 1.0m.The rolling action of the barrel breaks up any unwanted clays to produce a clean product. Also the barrel is self cleaning and the unit can operate unmanned.

In 2006 Stelex, with over fifteen years of experience in the manufacturing of this type of screen decided to redesign and expand the Hercules product range to greatly improve the machine, both in built quality and operating performance. This new generation of Trommels feature a "live drive barrel" drive which eliminated the need for gear wheels and chains and offered a smoother, more reliable and maintenance free drive to the barrel.

Other features include a hard steel feed hopper with high wear resistance internals , which can accommodate up to 160 tonnes. A variable speed reciprocating feed table, which is supported on rollers, moves material into the barrel via hydraulic rams. All barrels are manufactured from high grade steel bars welded to form segments which are bolted together. Aperture sizes are made up to suit individual customers product requirements.

As well as cleaning dirty and contaminated feed material Trommels have been use in both the quarrying and mining industrys for taking out fines prior to material being fed to a crushing station.

Other duties include the high volume production of sea/river defence rock and sized material to make up Gabian baskets for road and rail cutting support. 

Case Study: Qatar

Duty - to provide 30 million tonnes of rock for the construction of a new breakwater to provide additional deep water facilities for large container vessels at the Ras Laffan port.

The machines supplied were two model HT232s, each with a barrel diameter of 2.3m and capable of through putting as dug rock at a rate of up to 1000 tonnes/h. Working 24 hours per day, seven days per week, reliability and low maintenance was the key to this successful project. Both machines supplied clean sized rock to a fleet of transport vehicles for delivery to the construction yards. Drive for both the feeder and barrel was provided by a separate remotely stationed electric/hydraulic power pack. As part of the contract the machines were specified to work in temperatures of up to 50^oC. These machines are the largest Hercules Trommels operating outside the UK.

Case Study: Southern USA

Duty - To clean as dug quarrying materials to produce rip rap sizes of 12 in, 18 in and oversize at a rate of 500 tons an hour. The machine, a model lHT182M is the latest generation of the fully mobile Trommel, designed to be brought in, set up quickly and put to work, then towed to another site to repeat the operation. The clean graded rock was loaded from the quarry into large river barges which each carry 10,000 tonnes. The barges are linked together to transport the material down the Mississippi river to New Orleans to repair the levees damaged by hurricane Katrina. The contract called for over two million tonnes of rip rap to be supplied.

Case Study: Germany

Duty - Quarry operator needed a machine to clean and size as-dug materials from waste in a large limestone quarry in preparation for cement manufacture.

A mobile HT182M with a 1.8m diameter barrel mounted on a special support frame to segregate products was supplied.

Recycling

Duty - Two customers in France with recycling plants were experiencing very high wear rates on their existing screens and were not able to cope with heavy builders' waste, including bricks and concrete, from industrial and domestic skips.

For primary sorting Stelex installed heavy duty Trommels fitted with heavy duty perforated plate segments, together with chutes and bin walls to eliminate contamination and enable screened materials to be conveyed away for secondary sorting.

This year, Stelex launched a new design of recycling barrel which features easily replaceable punch plate aperture panels. The panels slide easily into the barrel and are locked in place by heavy duty lifters. The benefits of such machines lie in the recycling market where operators need a well engineered/compact , yet heavy duty machine with a switch on and forget reliability.

Future

The increasing requirement to reclaim and recycle a greater proportion of primary rock, and the need to clean materials containing heavy soils and clays will ensure that heavy duty Trommels will continue to play a major role in a wide spectrum of applications within the extractive industries. The latest machines have proved to be extremely efficient in delivering clean rock products and will pay back the investment involved.

Stelex Construction Equipment Ltd
Unit 2 Elms Lodge Barns
Melton Road
Barrow Upon Soar
Leicester
Leicestershire
LE12 8HX
UK

T: + 44 (0) 1509 416101
F: + 44 (0) 1509 413754

www.herculestrommels.co.uk