Steinmüller Africa: SA’s welding innovator
At Mondi’s Richards Bay paper mill, Steinmüller Africa is leading an 18-month boiler construction project, Vuselela, that showcases a powerful blend of engineering excellence and cutting-edge technolo- gies, marking a major milestone for the paper and pulp sector and Africa’s broader industrial progress. Steinmüller Africa: South Africa’s strategic welding innovator
Steinmuller’s senior welding engineer, Friedrich Schwim.
C ontracted to erect a new boiler to meet the future needs of a Mondi paper mill in Richards Bay, Stein- müller Africa is currently engaged in Project Vuselela, a welded-assembly project for an imported process steam boiler for Mondi’s Paper Mill in Richards Bay. “We have a team of approximately 130‑200 skilled professionals onsite, includ- ing 28 welders. We are responsible for the full mechanical installation, including the welded assembly and installation of all the steel structures, pressure parts, fans, flue gas ducts, tanks and critical systems such as the air preheater and flue gas damper,” says Steinmuller’s senior welding engineer, Friedrich Schwim. The process steam boiler is being built as an eventual replacement for four very old boilers on the site that are currently delivering process steam to the mill. Thou- sands of metres of continuous welding are required. “The new Mondi boiler is known as a circulating fluidised bed (CFB) boiler, a more modern design that is cleaner, more cost-effective and fuel-flexible,” Schwim
Orbital welding requires a squarer prep, which would not have been possible without changing the length of each pipe section,” he explains, adding that for the capping runs on tubes with larger wall sizes, stick electrodes are used following the TIG root runs. A lot of the welding, however, involves long, continuous plate-work welds that do not have to hold pressure. “Here, we have developed and qualified some advanced, deposition-efficient procedures based on using a metal-cored welding consumable,” says Schwim. The process was initially qualified using a Miller welding machine, where the RMD mode – a modified short-arc process with superior puddle control – could effectively control the fusion of the weld root. In con- trast, a pulse mode was qualified for the fill and capping runs. “We are still using the two original Miller machines we bought for this work, but we have now found other brands with similar short-arc and pulse modes that offer equivalent weld quality,” he says. On the gas side, the metal-cored wire enables higher CO 2 levels in the gas mix, delivering better penetration. “For these long structural welds, we are using a univer- sal gas mix with between 20 and 25% CO 2 . This gives us a good combination of weld stability and penetration,” says Schwim. The use of advanced, modified short-arc and pulse modes on Mondi’s Vuselela boiler project has increased productivity by 2-3 times while maintaining weld integrity. This is projected to cut welding time by at least 50%. “By strategically reengineering proven technologies, we are achieving a perfect balance between speed and qual- ity,” says Schwim. “This level of efficiency is crucial for fast-paced, large-scale projects like this,” he adds. Safety first solutions Mondi is very strict on safety requirements, continues Schwim, especially with respect to lifting gas bottles into a boiler under construction. “Gas cylinders have to be
tells AF , adding that while some compo- nents are being manufactured locally, most are being imported as pre-fabricated and prepped sub-assemblies and sections for assembly onsite. “We started with the first components in October 2024, and we expect to be pressure testing by February 2027, in time for the handover in about June,” he says. Steinmüller uses various welding processes for its construction projects, including conventional stick and tungsten inert gas (TIG) welding, as well as advanced metal- cored welding processes that have recently been qualified. “On this project, most of the boiler tubing is small bore – 45 and 51 OD – with a relatively thin wall thickness, typically 4.0 mm, so these are all completed using the TIG welding process for both root and capping runs. We wanted to use some orbital welding for these, but all the tubes are precut to length with a V-preparation. Welding process choices and innovations
Steinmüller Africa is leading an 18-month boiler construction project for the pulp and paper industry. Shown here is the pre-fabricated steam drum, the heart of the boiler, being lifted into place.
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November-December 2025
AFRICAN FUSION
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