Valves manufacturer AZ-Armaturen (AZ) South Africa delivered a total of 22 high-pressure plug valves to a mineral sands operation near Richards Bay, in KwaZulu-Natal, over two occasions, once in June and once in July, says AZ GM Erich Ermel, adding that the valves ranged in size from 50 mm to 500 mm nominal bore for the mining company’s sand slurry application.

AZ supplied plug valves to the same mineral sands operation in 2007, where the valves were used to control sand slurry being pumped from the pit to the plant. Ermel enthuses that AZ’s valves delivered excellent performance and exceeded the client’s expectations, adding that the plug valves’ resistance to abrasion makes them suitable for this application.

Ermel notes that the initial mine reached the end of its life in 2014 but that a new deposit is currently in the commissioning and testing stages and operations should get under way in 2016.

“We believe that nobody has ever manufactured self-lubricating plug valves in these sizes and pressure ratings worldwide,” he says, adding that AZ-Armaturen Germany – the headquarter of the AZ Group – has since requested the same valve design to be manufactured for an application elsewhere in the world.

Ermel further highlights that, owing to the novelty of this project, it was challenging to meet the size and pressure rating requirements. He explains that, typically, these plug valves are made for chemicals and petrochemicals processes and are not primarily designed for high-pressure applications, such as the sand slurry being pumped at the mineral sands mine. Ermel adds that the size and pressure rating of the valves also made mounting the valves and pressing the gaskets a demanding task.

He further notes that handling the valves was a challenge for the machines operating at AZ’s South African plant, as these machines were not initially bought to handle the sizes of the valves that AZ needed to manufacture.

Ermel points out that, because the valves will be used in corrosive coastal conditions, the exterior of the plug was covered in a special heavy-duty, corrosion-resistant coating. He adds, however, that it was challenging to achieve these painting specifications, as it is difficult to apply these high-quality coatings.

Nevertheless, despite the numerous challenges facing his team, Ermel highlights the project as a success for AZ, owing to the suitability of the product for its application.

He further emphasises the absence of internal cavities in the plug valves as an important factor that contributes to the reliability of AZ plug valves, which eliminates damage to internal parts. In terms of the plug valves’ application in Richards Bay, the absence of cavities in the design of the plug valve ensured a smooth slurry flow.

Ranging between 2" and 20", the castings for the new valves were manufactured by local foundry Steloy Castings. This company has been producing castings for AZ for many years and has the ability to meet AZ’s quality standards, states Ermel.

The plug valves comply with an American National Standards Institute, or ANSI 300, to 600 pressure rating to a maximum of 100 bar.

In addition, the design of AZ’s plug valves complies with internationally accepted standards, while its factory complies with ISO 9001 standards.

All AZ plug valves are fitted with a polytetrafluoroethylene (PTFE) sleeve. This allows for AZ’s valves to operate in the harsh sand slurry environment without failure.

Further, because the PTFE sleeve is self- lubricating, the plug will not seize, even after not being used for extended periods. In these instances, the valve can be operated without risk of damage.

Meanwhile, Ermel proudly boasts that these plug valves are almost 100% locally manufactured, which is in line with South Africa’s designated valve policy.

For users of sleeved plug valves in South Africa, AZ offers the advantage of local manufacture and support, backed up by a substantial inventory of spare parts.

Improved Design

AZ announced this month that it had further improved its plug valve design, concentrating on the shaft and cover sealing of the valve.

The new modular valve design provides enhanced flexibility, so that the basic valve can easily be modified according to customer requirements.

“After an extensive and successful development, test and implementation phase accomplished by our German headquarters, AZ-Armaturen South Africa is going to supply the new valve design to the sub-Saharan African market from early 2016,” says Ermel

Meanwhile, AZ marked its 30-year anniversary in September.

“The company is proud to celebrate three decades of progress, success, development and commitment to manufacturing sleeved, self-lubricating plug valves in sub-Saharan Africa,” says AZ.