Johannesburg-based mining solutions provider Aveng Manufacturing Dynamic Fluid Control (DFC) – the largest valve factory in the southern hemisphere – is still successfully meeting the requirements of the harshest valve operating environments in Africa.

“We provide technical advice on the correct valve for any application free of charge,” says DFC mining division executive director Pat Stander, adding that Africa does not need to look to Australia, South America or the Far East for valves, “because we make them closer to home, here in South Africa”.

Stander notes that DFC strives to meet “truly African” concerns, combining local manufacturing with distribution channels across central, southern and eastern Africa. Channels to West Africa are advancing through logistics development in Ghana.

DFC has three main valve ranges for mining applications, namely Saunders, Insamcor and RF Valves. Product development for all these ranges is ongoing, with RF pinch valves recently having undergone an upgrade to replace fabricated valve bodies with castings that support the curve of the sleeve at all points, leading to improved valve closure.

With the Insamcor knife-gate valve range, DFC has introduced a bidirectional design that delivers superior sealing. The new design has applications in mining as well as the manufacture of fertiliser and pulp. Stainless steel models have been developed for acid-intensive applications in the Central Africa-based Copperbelt’s copper leaching plants.

The Saunders product line has also been extended to include a stainless steel option on all models, allowing the valves to be effective in corrosive environments. As with the other two brands, the valves use local components, such as rubber linings, which are manufactured in DFC’s own rubber plant.

Stander admits that valve selection remains a problem for many users, owing to uncertainty caused by the multitude of valve types and brands available.

“The fact that a particular type of valve was installed in a mine during the development phase does not mean that it is the correct valve for the application,” he explains.

“There are different types of slurries at a typical mine, including pebble-containing slurries, fine slurries resulting from mineral extraction, chemical slurries and dirty water, among other types.

“It is therefore necessary to match the correct valve to the application and then determine the correct configuration in terms of valve size, the type of liner best suited to the medium passing through the valve and the correct type of actuator,” he points out.

Selecting the correct actuator is also becom- ing increasingly important in African mines looking to automate production, owing to the need to increase process efficiencies and extract the highest possible mineral quantities from the ore during the first pass.

An actuator needs to deliver sufficient torque for valve operation, with a valve in a dirty water application requiring substantially less torque to close than the same valve would need in a slurry application.

Similarly, owing to the diaphragm’s area, a diaphragm valve requires more torque to close than a knife-gate valve, which slices through the medium.

“However, it’s not just torque that must be considered, as there are different methods of actuation, such as electric, hydraulic, pneumatic and, of course, manual.

“Therefore, one must look at the overall process to select the correct type of valve and the right method of actuation. From that point of view, DFC has a substantial knowledge base that we make available to our customers at no cost through our technical advisers,” Stander comments.

Local Quality

Meanwhile, Stander criticises the supply of valves that are typically mass-produced in factories in the East, where there is an overreliance on high production volumes to deliver the lowest possible price.

In South African mines, the result of this lowest-price approach has often been that the user who has tried a product from the East has suffered production losses caused by premature valve failure.

Consequently, the growing trend among South African mines is a return to reputable local manufacturers with a history of successful, durable valves used in harsh mining conditions.

Stander says developers throughout Africa often want to commission mines as quickly and as cheaply as possible, resulting in the installation of cheaper valves from the East. After the mine starts producing, however, profits are used to replace inferior valves with valves from a reputable manufacturer when the warranty period reaches its expiration date.

Stander says DFC’s rubber plant produces linings that it has developed over several years for different applications, which will outlast Eastern equivalents.

“DFC manufactures a product that is going to outperform rather than underprice, delivering the lowest lifetime cost to the customer rather than the lowest initial purchase price,” he concludes.