Kleinkopje Colliery.
Five main seams that are numbered in order of deposition from No.1 seam to No. 5 seam are present at Kleinkopje Colliery, this being typical of the Witbank Coalfield1. The coal- seams are separated by sediments of shale, sandstone and siltstone.

Kleinkopje Colliery is an opencast mine that uses strip and shovel method to mine the remainder of pillars left during underground mining.

Kleinkopje Colliery has five Wemco drums that were installed and commissioned in 1978. Over the years, there have been remarkable changes in mining and geological conditions at the colliery. First, an increase in the percentage of fines was recorded, which resulted in an uneven split or an imbalance in silo levels between material feeding the cyclone (-12 mm) and Wemco drum (+12 mm) sections respectively. This problem was solved by doing modifications around the banana screens to allow finer material to the drums. The imbalance challenge was then followed by spontaneous combustion that takes place in situ and results in low product yield. The results obtained from efficiency tests indicate that although there is a limit in the percentage of -6 mm material in the feed, Wemco drums are still very efficient and applicable to the current mining conditions. These results also suggest that it is essential to lower the throughput when the drums are treating low yielding coal.

The washing plant is primarily subdivided into Wemco drum, cyclone and fines sections respectively. Feed from run of mine (ROM) is subjected to banana screening to separate at 12 mm cut size. The oversize is fed into a drum feed silo while the undersize reports to a different silo, from which it is fed into a DSM cyclone plant. The final product from the three sections is combined and sent to the rapid loading terminal (RLT) and railed to Richards Bay Coal Terminal (RBCT) at calorific value of 27.40 MJ/kg on air dry basis, top size of 50 mm and total moisture of 8%.

The layout of Kleinkopje plant commences at the raw coal tipping area, where coal can be tipped either on the A, B or C tip. The tipped material is then sized down to 150 mm through primary crushing Bradford breaker. The oversize is then subjected to a jaw crusher that also reduces the material size to a top size of 150 mm.

The stockpiling is done in chevron pattern to allow proper and even blending of raw material. The bucket-wheel reclaimers are then utilized to reclaim raw coal from the stockpiles through the banana screens which classify coal for the drum plant and cyclone plant silos.

The Wemco drum section is divided into five modules, namely, module 3, 4A, 4B, 5A and 5B. The oversize material reports to Wemco drum plants from which separation according to gravity takes place. After separation, the product and discard material report to their respective drain and rinse screens where medium recovery takes place before the material is transported either to a product or discard silo.

A single compartment Wemco drum is a separation bath that consists of a steel shell typically supported from four rollers in a longitudinal operating position. Inside, the shell is equipped with a set of lifting scoops that are perforated to allow drainage of medium as it rotates. In addition to the lifting scoops, the internal part of the drum consists of a feed chute, sinks launder, steel and rubber skirtings and medium addition points.

Raw coal enters in the feed end, into the magnetite-water mixture known as medium. Separation starts taking place immediately, with the heavier material sinking to the bottom of the shell and the lighter material floating. As the drum rotates, and the lifters fitted inside carry the discard to the sinks launder from which it flows onto a drain and rinse screen. The product floats with the medium out on the discharge end of the drum. The maximum size of coal that can be handled in the Wemco drum depends on the size of the whole shell, the inlet and outlet diameters as well as lifting scoops. A top size of 250 mm has been treated in the coal industry, whereas 150 mm seems to be more common (Wills, 2006). The Wemco drum can handle as much as 400 ton per hour feed, with approximately 20–25 ton per hour per m2 pool area with very good separation efficiencies.

Wemco drums present several advantages that make it a separator of choice over other dense medium washing baths. These include amongst others the following:
- A sharp separation can be obtained at various relative densities.
- High efficiencies are achievable with large amount of near gravity material.
- The operating density can be easily reached and controlled.
- A large range of particle size can be handled very efficiently.
- Changes in feed rate and quality can be treated with a high level of confidence.
- The drum can handle large quantities of feed per square metre per hour.