Machined "Pocket" for Stellite Cladding.
This recessed pocket will be filled with the wear-resistant alloy to reinforce the area against cavitation and erosion.
Unlike modern Pelton turbines, which typically feature nozzle offset angles between 75 and 80 degrees for optimal runner water entry, this unit – part of a third-party installation – has a much narrower 45-degree nozzle offset angle. As a result, the water jets interfere with one another - one striking the runner while the previous jet’s water has not yet exited. This jet interference causes severe flow disturbance and, over time, massive wear on the runner buckets.
These runner inflow irregularities led to a phenomenon known as cavitation. Cavitation occurs when local pressure in a liquid drops below vapor pressure, causing vapor bubbles to form. When these bubbles collapse, they release energy in the form of shockwaves that impact surrounding surfaces. In turbine applications, this can lead to pitting, material erosion, and, ultimately, functional failure.
Recognizing the persistent challenges faced by the plant operator, Global Hydro took on the task of finding a reliable long-term solution. At our Innovation and Manufacturing Center in Austria, we combined decades of expertise in hydraulic design, engineering, manufacturing, and digitalization with the latest research from our in-house R&D department, HydroLab. Close collaboration between these departments ensured a fully integrated approach tailored to the specific challenges of this project.
The applied solution was the result of a step-by-step optimization process, developed to systematically address the root causes of wear. Through a combination of proven surface technologies and precise application, specific zones most affected by cavitation and erosion were effectively reinforced. The choice of materials was based on long-term field experience: Stellite offered outstanding protection against cavitation, making it the ideal choice for runner areas exposed to concentrated, high-velocity water jets. In contrast, Elastomer coatings were applied to components like splash guards, where flexible, impact-absorbing surfaces are required to withstand high flow velocities and abrasive sediment - without compromising mechanical stability.
This coordinated use of specialized materials reflects Global Hydro’s ability to deliver technically sound, field-proven solutions for even the most demanding hydropower applications.
After 1,862 hours of operation, the treated zones showed no signs of wear or cavitation - a clear and measurable improvement. Untreated areas, in contrast, exhibited renewed material degradation. Based on these convincing results, the operator decided to extend the Stellite application to all runner buckets.
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In parallel, another recurring issue was resolved: Excessive wear on the turbine’s splash guards, which deflect the water jet after it leaves the runner and protect surrounding structures from direct impact. Exposed to both sediment impact and turbulent water flow, these components were coated with a highly elastic elastomer material. Its shock-absorbing properties help to minimize cavitation effects and mechanical stress from coarse particles like sand or gravel.
This measure also proved highly effective, further enhancing the plant’s resistance to wear and improving long-term performance with minimal maintenance effort.
What began as a focused refurbishment effort quickly turned into a benchmark project. The outstanding results achieved through Stellite and Elastomer applications have laid the foundation for further improvements and reinforcements in similar installations. Global Hydro continues to apply these proven solutions in other projects - building on extensive experience and delivering reliable protection in demanding operating environments.
Behind this success is Global Hydro’s unique setup: Development, engineering, and manufacturing all under one roof at our Austrian headquarters. Combined with in-house R&D and insights from over 1,500 turbines delivered worldwide, we create precisely tailored solutions that maximize component lifetime, reduce maintenance costs, and optimal efficiency.
Hydropower plants operating under challenging conditions - such as turbulent flow patterns, high sediment loads - are particularly prone to wear and cavitation. Over time, these effects can severely impact components. Without effective protection, material erosion and surface degradation can reduce overall efficiency, increase maintenance needs, and lead to more costly downtimes.
Global Hydro develops custom-fit solutions that effectively tackle the underlying causes of wear. With a deep understanding of hydraulic behavior and decades of field experience, we apply advanced surface technologies where they’re needed.
Whether it's sediment erosion, high flow velocities, or cavitation effects, by applying targeted coating technologies, vulnerable areas are effectively reinforced. This extends the lifetime of key components, lowers maintenance demands, and ensures more predictable, efficient operation - resulting in long-term cost savings and improved operational security for plant owners.
Both applied technologies - Stellite and elastomer coating - are part of Global Hydro’s WearShield program, which focuses on protecting components in harsh environments.
Whether you're facing persistent erosion on runners, outdated flow geometry, or looking to aim durability of critical components- we're here to help. With our proven technologies and expertise, we deliver tailored solutions for long-term performance and protection.
Get in touch with our experts today and find out how we can revitalize your hydropower plant.
Roland Fleischmann
Senior Sales Manager Revitalization
+43 (7285) 514 0055
roland.fleischmann@global-hydro.eu Contact
