Revolutionising Fluid Dynamics: Closed vane impeller redefines industry standards
Among the exceptional projects in this year’s awards, one stands out as the special merit winner, showcasing ground-breaking advancements in the manufacturing of closed vane impellers – a crucial component used to boost fluid pressure and flow. This project, spearheaded by Venter Consulting’s team of visionary engineers, skilled machinists and expert metallurgists, not only met its ambitious goals but also redefined industry standards, setting a new benchmark for innovation and excellence in the field.
Inspiration and objectives
The project was inspired by successful manufacturing of open vane impellers from a single stainless steel billet as a monolithic part. This earlier success spurred the team to push the boundaries further – this time focusing on closed vane impellers. The primary objective was to replicate the benefits of open vane impellers, such as enhanced structural integrity and longer lifespan, in closed vane impellers, which present a more complex design and manufacturing challenge.
Venter Consulting Project Manager Doks van Tonder emphasises the driving force behind this endeavour: “We knew we were onto something significant with the open vane impellers and the logical next step was to tackle the closed vane design. Our main goal was to optimise the design and machining process to create a stronger, more durable impeller that could withstand the rigours of demanding environments”.
Enhanced performance
One of the key features of this project is the impeller’s monolithic construction. Traditionally, closed vane impellers were fabricated by welding together separate sections – a process that introduced several inherent weaknesses. The welding process, especially where the vanes meet the base, created heat-affected zones prone to stress corrosion cracking due to chrome depletion at the corners.
By manufacturing the impeller from a single billet of stainless steel, these weaknesses were effectively eliminated. The result is a component with superior structural integrity, capable of withstanding higher stress levels without the risk of corrosion-related failures. This innovation not only enhances the impeller’s lifespan but also improves its overall performance, making it a more reliable choice for applications in corrosive and high-stress environments.
Overcoming challenges through collaboration
The most significant hurdle on the journey to achieving these results was the sheer size of the impeller with a diameter exceeding 850 mm. This necessitated re-design and modification of the tooling needed to machine the deep pockets and sharp angles integral to the impeller’s design.
Van Tonder highlights the importance of teamwork in overcoming this challenge: “This project was a true collaboration. Engineers, machinists, technicians and our tooling supplier all worked closely together to develop the tools we needed. It was a continuous process of trial and error but, ultimately, we succeeded in creating the precise tools needed”.
Another challenge was selecting the appropriate stainless steel grade for the impeller’s demanding operating environment. The team’s metallurgists conducted an extensive investigation to identify a grade that offered the right balance of high strength as well as resistance to stress corrosion cracking and hydrogen embrittlement. The choice, 1.4418 stainless steel, proved to be the perfect solution, providing the necessary properties to ensure the impeller’s durability and performance.