True to its commitment to continuous innovation, US family-owned group Derrick Corporation has several new product developments up its sleeve, most notably a Super Stack Sizer™, which is currently undergoing plant trials.

The Super Stack Sizer™ is a fine particle wet sizing screen, which offers up to eight individual screen decks, operating in parallel, positioned one above the other. The machine, which is 1.5 m wide, is designed to increase the capacity of Derrick’s five-deck Stack Sizer™ by up to two-and-a-half times on a similar footprint.

The new screen will find favour in high capacity plants, such as copper processing facilities, where tonnages frequently exceed 1 000 t/h.

The Super Stack Sizer™ is currently undergoing plant trials at strategic locations around the world and is expected to become commercially available in 2019.


The Stack Sizer™ screen, which, amongst other applications, replaces cyclones in a milling circuit, is one of Derrick’s most popular technologies.

Derrick Solutions International Africa, is the exclusive authorised distributor of the US group’s mineral processing equipment in Africa, says the installation of Stack Sizer™ screens reduces circulation load, improves recovery rates and increases capacity through the mill.

“The test to establish if one of our screens will work for a particular task, other than closing of a mill circuit, is to determine quality by size fraction. If an upgrade is evident, then the Stack Sizer™ needs further investigation,” says Derrick Solutions International Africa Vice President Nic Barkhuysen.

He adds that panel openings as fine as 38 micron in non-blinding, long-life urethane surfaces are employed on the Stack Sizer™ screens.

Derrick also offers a Hi G Drier technology, which is used for dewatering or desliming of fines.

Combining a radially mounted set of cyclones above a high frequency dual motor screen, the technology will recover up to 80% of fines and ultra-fines from a slurry, capturing particles as fine as 20 micron. The oversize from the screen is stackable and conveyable and the screen underflow is returned to the feed continuously. Cyclone overflow is used as process water or sent for further treatment.

“This technology is an ideal precursor to expensive thickening, filtration or centrifuging, and/or reducing the load on tailings disposal dumps,” says Barkhuysen.

The group’s dry screening technology is the third leg of its fine screening technology and is used extensively in the mineral sands, coal and chrome industries.

“Dry screening of coal is notoriously difficult owing to the inherent retention of moisture. At Derrick, we have developed successful screening techniques from single deck to four double deck configurations that can efficiently screen at apertures as fine as 100 micron with capacities of up to 375 t/h,” explains Barkhuysen.

New Developments

Besides the Super Stack Sizer™ currently in development, Derrick is also working on front-to-back dry screens and three-dimensional (3D) synthetic surfaces on its Hyperpool™ screens.

Front-to-back dry screen involves a revised fastening technique that allows for rapid panel changes. Barkhuysen says it takes less than one minute to change a panel, while the front-to-back dry screen also improves utilisation and increases efficiency and capacity.

The 3D synthetic surfaces is a technology developed for the oil and gas industry, but adapted for the mining industry. It allows for capacities as high as 500 m3/h through a 1.2 m w x 3 m long screen fitted with 0.7 mm poly-pyramid surfaces.

Barkhuysen says Derrick’s pioneering spirit is best demonstrated by its research and development team’s long-term commitment to innovation. “This mindset dates back to our founder’s invention of the first integrated vibratory motor and sandwich screen technology.”

Derrick is an US family-owned business established in 1951. The group’s US manufacturing capabilities include robotic welding, laser cutting and the third-largest interconnecting crane assembly in the world, after Caterpillar and Boeing.

The group’s universal presence comprises of partners in countries around the world. Derrick Solutions International Africa, based in Centurion, Gauteng, was appointed as distributor in 2014.

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