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Quality valves save on maintenance costs
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6th March 2009
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Slurry equipment solutions provider Weir Warman Africa is supplying a pro-duct offering to the mining sector that includes knife gate valves and pinch valves.

Weir Warman Africa process engineer responsible for valves and cyclones Moses Coetzee tells Mining Weekly that the com- pany, which is generally associated with slurry pumps, rubber mill liners and other rubber wear-resistant mill liner components and hydrocyclones, has more than 300 valves operating successfully in installations throughout Africa.

With the level of emphasis being placed on reducing costs throughout the mining sector, it has become increasingly important to look at the whole picture, and this is especially so when buying valves for slurry pipeline applications. More often than not, the material being transported in pipelines is abrasive and can cause high levels of wear not only in the pipeline, but also within valves fitted along the pipeline.

“Weir Warman Africa’s refer- ence base of mining valves is across the minerals sectors with the most recent installation being at a gold and uranium mine in South Africa,” says Coetzee.

He comments that there is a vast difference between buying a cost-competitive product and a cheaply produced one.

“A quality slurry valve is designed to withstand the extre-mely abrasive, and often corrosive, conditions found when transporting slurry,” he says.

The Isogate valves available from Weir Warman Africa are engineered to deal with these harsh operating conditions without compromising on slurry flow.

This valve incorporates a heavy-duty stainless steel gate, which is lowered into the slurry flow stream, creating an airtight bubble seal. When in the open position, only the thick elastomer sleeves of the Isogate valve are in contact with the slurry. Manufactured from a specially formulated rubber compound, these sleeves offer increasingly efficient wear life even in the most abrasive applications.

Coetzee says that none of the metal parts of the valve touch the slurry at any stage while the valve is in the open position, and there are no internal cavities where solids can collect and cause gate interference. This ensures reliable operation of the knife gate valve at all times.

“Minimum maintenance is on everyone’s lips today and the Isogate valve is engineered with this in mind,” Coetzee says.

The sleeves are easily replaced without the need to disassemble the valve itself, which makes maintenance simple and more time efficient. It also features a packingless design, which eliminates the need for gate or stem packing. A double sealing mechanism, which forms an integral part of the Isogate valve, prevents leakage, again reducing main-tenance requirements.

“Yet another important feature is the technology used in the design configuration, whereby the valve bottom remains open and solids can be purged from the bottom. This eliminates the build-up of solids within the body of the valve. Being able to offer the industry the option of knife gate valves or pinch valves is a major advantage,” says Coetzee.

While in the past pinch valves were imported, Weir Warman Africa has recently completed the first 600-mm pinch valve built and assembled at its Isando facility.

The decision to manufacture this pinch valve locally was based on the cost factor as well as the need to supply the component within a very short lead time. The date of order receipt to delivery took just six weeks.

The range of Isogate valves starts with the WS series, which caters for pipeline diameters of 50 mm to 400 mm, while the WB series is suitable for pipeline diameters of 450 mm to 1200 mm. The WS series and the WB series both have improved pressure ratings of 10 bar. Also available is the Isogate WH range, which has been engineered for applications that have a markedly higher pressure and this knife gate valve is capable of operating at pressures of up to 20 bar.

The correct selection of a valve, be it a knife gate valve or a pinch valve, is critical to ensure the most appropriate balance of performance for a particular load in a slurry pipeline, and for this reason, Coetzee says, it is advisable to secure the technical assistance of a company that is able to offer the necessary expertise and experience in the application of valve technology.

Options for valves include selection of the most appropriate materials of construction, as well as the method of actuation. All Isogate valves can be actuated pneumatically, manually, electrically, hydraulically or through a gear drive system, allowing vast flexibility in application.


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Weir Warman Africa’s reference base of mining valves is across the minerals sectors with the most recent installation being at a gold and uranium mine in South Africa
Picture by: Weir Warman Africa
MOSES COETZEE Weir Warman Africa’s reference base of mining valves is across the minerals sectors with the most recent installation being at a gold and uranium mine in South Africa