Pinch valves from Benoni-based valves and pumps company Flowrox South Africa (SA) are being used at Namibia-based uranium producer Swakop Uranium’s Husab mine.

Flowrox was awarded a R54-million contract to supply 83 pinch valves of 550 mm diameter to the mine, which is the second-largest uranium mine in the world.

“Tailings applications are usually very abrasive environments, and Husab’s being located in 23 km2 of desert adds to the harshness of the environment in which Flowrox valves are required to operate,” says Flowrox SA MD Henlo Blignaut.

Swakop Uranium ordered the hydraulically actuated pinch valves during the first half of 2015 and they were delivered in August 2015 as part of the mine’s greenfield tailings operation. The contract included the supply and delivery of valves, actuators, spare parts and valves, as well as the training of Swakop Uranium’s valve operating personnel.

Flowrox SA conducted theoretical and practical training sessions at its Benoni office, including correct pinch valve sleeves replacement techniques – the most critical component to ensure sleeve longevity. “The most common cause of pinch valve failure is the implementation of incorrect sleeve change procedures,” Blignaut says.

When valve technicians are not skilled in exchanging pinch valve sleeves, their actions can significantly impact on the life of the replaced sleeve, owing to incorrect seating, besides others, he adds.

Custom Actuating
The pinch valves in use at the Husab mine are operated through a unique actuator solution using two mobile petrol-powered hydraulic power packs.

Owing to the vast distances between each valve, Flowrox SA suggested mobile power packs to increase efficiency and ease of operation, instead of manual operation. These mobile power packs (similar in appearance to small, portable generators) enable valve operators to load the power packs onto a vehicle, drive to each valve, start the power pack and quickly operate the valve by either shutting or opening it.

The power packs represent a significant advantage, as the valves weigh 3 t each, thereby making it difficult to actuate them by conventional methods. The alternative method of actuating the valve involves valve operators turning a large hand-wheel, which requires significant labour and, thereby, more time to operate the valves.

Using hydraulic power packs allows for the valves to be shut or opened within three minutes. “Because of the size of the valve – operating at 16 bar – it would require 2 600 hand-wheel revolutions to shut the valve,” Blignaut highlights, adding that if each of the 83 valves had to be operated simultaneously, it would take the whole day to do so manually.

The Husab mine operator insisted on using the best technology available for the project, which he says is evident in Flowrox’s “own in-house blend” – an elastomer sleeve technology comprising a mixture of the styrene and butadiene monomers. Although competitors have tried to copy the blend and composition of Flowrox’s sleeves, they have been unsuccessful to date, Blignaut says.

The project also grants Flowrox SA the supply contract for all required strategic valve spare parts to empower Husab staff to perform thorough maintenance and repairs as needed. The strategic spare parts include spare sleeves, service kits for the hydraulic power packs and spares for the actuators.

Flowrox SA will also provide service exchange valves to ensure steadfast serviceability. A service exchange valve is a complete unit that can be installed in place of a faulty valve – which would otherwise necessitate the removal of a faulty valve, and its repair and reinstallation – thereby reducing downtime.

Using service exchange valves also assists in ensuring repairs are undertaken in workshops and not in the field, where contamination is more likely to occur and technicians can possibly become frustrated with having to work in a nonconducive environment.

The wear parts of Flowrox pinch valves have a typical life span of about five years in slurry applications, but a Flowrox pinch valve is being used for about 23 years without having to be replaced in a flow control application, in Sweden, owing to the non-abrasive conditions, concludes Blignaut.