Materials handling company Clyde Bergemann Africa (CBZ) is installing its dome valves on the fly ash conveying systems at State-owned power utility Eskom’s Matla Unit 3 coal-fired power station, in Mpumalanga.

CBZ engineering manager Keitumetse Molamu tells Engineering News that installation started in February and CBZ will supply about 240 of its new-generation dome valves, as well as associated equipment, such as multiple pressure vessel denseveyor pumps, control panels and piping, collectively valued at about R130-million.

“The first installation of the new-generation dome valves took place in 2011. The timeline for the initial installation was very tight and we had six months from order placement to complete the design, manufacture and installation of Unit 6’s dome valves. In the years since then, CBZ has successfully installed valves on Units 1, 2 and 5,” she notes.

Molamu states that the CBZ dome valve’s simple and proven design offers full bore unobstructed flow of the conveyed material and forms a pressure-tight seal when closed. It is capable of handling pressure of up to 30 bar. The valves, which range from 50 mm nominal bore to 500 mm nominal bore, are also able to cut through moving or static material columns.

“The dome valves can handle material temperatures from –20 °C to 480 °C. With fewer moving parts, their on-site maintenance is easy and cost effective. The valves have an operating life of up to one-million cycles between major overhauls with most materials. They also require limited maintenance and generally require that only the seals be changed once a year,” she highlights.

Molamu points out that 126 of CBZ’s older-generation dome valves are currently in use at Matla power station, having been installed in the 1990s.

CBZ has supplied more than 3 000 dome valves across Southern Africa in the past 30 years; the valves are used in pneumatic conveying systems that convey a wide range of materials in the mining and power generation industries.

Dome valves are installed in most power stations worldwide and play a pivotal part in fly ash conveyor systems, owing to the airtight seal when in the closed position. The unique inflating seal on the dome valve allows the valve to form a tight seal even if fine particles of the conveyed material are caught in the seal. In other valve types, any material caught in the seal degrades the valve, creating grooves in the materials and, therefore, leading the valves losing sealing capabilities.

Dome valves are also ideal for use in conveyors at smelters and process plants, where lime, coal, concentrate and various other corrosive materials are moved.