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Hydropower: sealing for sustainability

Diving deep into seals for hydroelectric plants

When you think of renewable energy sources, monolithic wind turbines most likely spring to mind. While you wouldn’t be mistaken, it is in fact hydroelectric power plants that are responsible for producing most of the world’s renewable electricity – and 16 percent of global electricity. On top of that, it’s the fastest growing source of electricity.

Let’s open the floodgates to hydroelectric power and highlight some of the most common sealing applications found in dams.

Feeling the flow

All renewable electricity sources carry their own unique advantages and challenges. Yet, it has to be said that hydraulic turbines and many other components that make up hydropower plants are exposed to some of the most perilous operational conditions in industry. In certain cases, during heavy rainfall, the inbound flow of water can reach 72,000 cubic meters per second. That means each section is exposed to enormous pressure, particularly between generator and turbine – and accordingly, should be fortified to the max.

But that’s not all hydropower systems have to deal with. Naturally, rivers, reservoirs, and other bodies of water are home to all kinds of flora and fauna, large branches or logs, and, unfortunately, plastics and other pollutants. Dam barriers are often deployed to prevent such debris from entering the system’s inner workings. However, particles can often slip through several barriers of defense and affect the heavy equipment within. Then the reliability of industrial sealing solutions becomes the difference between seamless and smooth production or long periods of downtime, disruption, and in severe cases, destruction.

Massive failure of the runner, shaft, head cover, turbine, and generator bearings at the now infamous Sayano-Shushenskaya Dam in 2009 took the lives of 75 people. Load rejection was the cause, likely triggered by inappropriate or damaged seals.

Machined seals capabilities

As is the case in the wind energy industry, hydropower also requires the deployment of large-diameter seals for many functions. Fortunately, SKF has the capability to machine seals in-house for these applications. The company is now able to produce seals up to 15 meters in diameter, yet larger seals can be made for unique applications. However, any seal with a diameter over four meters will arrive on location split and the material needs to be welded together at the cross section during assembly. This is done by utilizing a special welding technique. On-site assembly and installation of seals are always performed by well-trained and experienced SKF service engineers.

G-ECOPUR, a special cast polyurethane, comes highly recommended for most instances in hydropower. Not only can it be easily welded if large-diameter seals are required, but it is highly resistant against hydrolysis (breakdown of chemical compounds due to contact with water), flexible, and robust. SKF G-ECOPUR seals are also compatible with most operating media – mineral oils, HFA and HFB fluids, or biodegradable hydraulic fluids – even at high to extreme operating temperatures.

Applications in focus

SKF-engineered designs for hydropower range from flexible lip seals to O-ring and X-ring solutions. Many applications, such as rotor blades, wicket gates, and spherical valves all use compact seals. Other applications include upper and lower ring gates and butterfly valves.

Rotor blades, as the name suggests, are propeller-like blades arranged radially around a center axis which activate a rotor when continually struck with water. Wicket gates are responsible for making sure the desired amount of water is entering the turbine at any time, which effectively controls the power of the turbine. If for example the power requirement in the electricity grid is low, wicket gates narrow to prevent excessive water usage. This works the other way round when there is high demand. Ring gates can isolate water pressure entirely, also eliminating any leakage to the wicket gates.

Ensuring operators are provided with the most appropriate sealing solution for such critical applications requires extensive knowledge of the operating conditions that bearings and seals are exposed to. Fortunately, SKF’s multi-disciplinary teams across the world are well-versed in hydropower solutions. Not only are they happy to consult and assist in selection processes with on-site analysis but they also provide standard or customized solutions in good time via a global logistics network. This way, new hydropower plants have a dependable and long-lasting seal from the get-go, or if replacing or upgrading seals, can limit downtime and minimize maintenance costs.

Interested in learning more about how SKF supports the burgeoning hydropower industry? Refer to our capability brochure here or get in touch with a local SKF representative.