The quotation and the method statement for furnace and industrial service provider Dickinson Group’s cleaning of a Mpumalanga coal mine’s storage silo has been agreed upon, says Dickinson Group silo-cleaning division manager Marius Steyn, noting that the company is waiting for the mine to make the silo available for cleaning.

Maintenance has to be performed on some of the flow components of the storage unit, such as valves, which is a legal requirement; therefore, the silo needs to be completely empty, he explains.

Cleaning such a big silo that is quite dirty can take up to two weeks, says Steyn, adding that such a job can curtail a company’s production because of the vital role that a silo plays in the production line.

He emphasises, however, that neglecting to clean a silo can be more detrimental to production in the long term, as moisture causes the material to harden and to form lumps. The lumps can block the valve outlets and can create a build-up of hardened material along the walls or at the base of the silo, restricting the flow of materials and slowing down production.

Since 2013, Dickinson Group has been providing cleaning services for clogged-up and contaminated bulk storage containers, the demand for which has been on an upward trend, says Dickinson Group CEO Trevor Dickinson.

“It is our impression that companies are becoming more focused on the efficiencies of their operations. Furthermore, with the continued labour costs and higher safety standards in the mining industry, our customers are adopting safer and more efficient methods for cleaning their silos and bulk storage containers.”

In addition, Dickinson notes that, to the group’s advantage, there are only a few other companies providing this service in Southern Africa.

Meanwhile, Steyn says there is significant demand from the mining sector for this service, as most mines store crushed ore or fine ore in bulk storage bins or silos.

He explains that most of the material is mined in wet conditions and the moisture causes the material to bind. Rainfall during transportation in open trucks and carriages or during storage, owing to some of the silos and bins not always being totally covered, is a common source of moisture.

Steyn notes that, depending on the material, as little as one rainy season can block up a silo so much that it has to be cleaned.

Cleaning Equipment

Dickinson Group ventured into silo cleaning with the silo whip and the Cardox system – equipment provided by bulk industrial cleaning solutions provider Cardox International.

Steyn explains that the silo whip is “like a giant weed-eater” that is mounted to the top of the bin. The head is lowered into the bin or silo and its rotating chains strike dried lumps of material off the wall of the container.

The silo whip uses a hydraulic motor and the power pack, which converts the electric energy to hydraulic energy, is situated outside the bin, he adds.

Steyn further explains that the Cardox system is a patented technology consisting of a tube of about 40 mm in diameter in various lengths. Attached to the tube is a reservoir of liquid carbon monoxide (CO). The CO is released into the tube towards the outlet where it meets the small rupture disk.

A small heater heats the gas, rupturing the disk, which increases the volume of the CO gas 600 times, subsequently increasing the pressure by about 3 000 bar. The high pressure is then used to blast away any material stuck to the wall of the container.

Dickinson notes that this is a safe method of cleaning which uses a highly controlled explosion.

Choosing either the Cardox system or the silo whip depends on the type of blockage, says Steyn, adding that the silo whip is most appropriate when there is clogging on the sides and there is a passage through which to pass the head, while the Cardox system is used when the silo is completely blocked and requires bottom-to-top cleaning.

Dickinson Group sent some of its staff to Europe to receive training in the use of the equipment, as knowledge

thereof is critical, concludes Dickinson.