Optimizing geothermal turbines: Best practices and innovations

The harsh realities of geothermal engineering

The global production of geothermal energy is expected to soar to 98.74 billion kWh by the end of 2024, growing 1.68% annually over the next five years. But it’s going to be far from plain sailing.

Every geothermal plant – whether dry steam, flash steam, or indirect cycle – needs to follow best practices to optimize performance, safeguard equipment, and extend lifecycles. This means leveraging assets to gain the most value possible – vital to increased reliability and saving on cost.

But regardless of which OEM is involved, turbines always face steam conditions and chemistry at each installation that needs to be addressed.

With geothermal resources easily capable of eroding conventional materials at an alarming rate – including very damaging short-term spikes in pH – even small variations in hardness and chemistry can have a significant impact on your turbines.

With some clever thinking and preparation ahead of time, you can ensure your turbines run efficiently. Proactive steps include:

●        Appropriate material selection – choosing the right materials to withstand harsh conditions

●        Robust shutdown and moisture removal processes – proper procedures during outages

●        Periodic steam path monitoring – regular checks and repairs

●        Steam chemistry control – strict regulation to prevent erosion and corrosion

●        Steam path retrofits – redesigns to match current steam conditions and flow rates

Combatting challenges with state-of-the-art solutions

At EthosEnergy, we always believe in staying one step ahead and being prepared for anything. We offer a full range of independent and OEM-approved solutions for your turbines, generators, and transformers, perfectly tailored to tough geothermal conditions.

Let’s take a look at some of the specifics.

Moisture

Moisture problems are incredibly common in geothermal plants, often causing wear-and-tear damage to the tenons (the protruding parts used to attach shrouds to the blades on the turbine rotor), due to harsh conditions like corrosive steam.

Combine that with the risk of chemical deposition and it can be a recipe for disaster if left untreated.

To tackle moisture and tenon erosion in geothermal turbines, we provide a Stellite^™ shield or solid coupon, and to reduce tenon erosion change to integral covers.

Integral covers are specially designed to eliminate tenons, as the shroud is machined integral with the blade using accurate geometry to ensure proper blade damping. Blades with integral covers can either be retrofitted to existing turbines or installed on new turbine designs for life extension.

Another of our design improvements includes control stages with integral covers made from titanium. The material density lowers the stress on the wheel and blades, while the titanium’s material properties minimize fouling, which can decrease the turbine’s flow capacity and, in turn, diminish output.

By implementing these solutions, we can ensure that turbines operate more efficiently and have longer service intervals, ultimately reducing downtime and maintenance costs.

Tall blades

In geothermal turbines, tall blades are particularly susceptible to harsh operating conditions, including high moisture content and corrosive steam.

To enhance the durability and performance of these blades, we offer advanced material options well-known for their strength and corrosion resistance, including:

●        403 SS/X15 – 403 Stainless Steel (SS), well known for its solid mechanical properties and corrosion resistance. The X15 variant is often used for its superior strength and durability in corrosive environments.

●        M152 (Jet Heat) – this advanced alloy is known for its high-erosion resistance and resistance to oxidation and corrosion.

●        17-4 PH – this precipitation-hardening stainless steel also provides high strength and hardness, as well as excellent corrosion resistance.

●        Titanium – renowned for its exceptional strength-to-weight ratio and excellent corrosion and erosion resistance.

We also provide treatments to enhance the durability of tall blades, such as laser hardening, flame hardening, and various coatings like metallic layers to provide additional protection.

By using this combination of advanced materials and treatments, we can ensure that tall blades in geothermal turbines can withstand the extreme conditions they face.

This means you improve efficiency and reduce maintenance costs over time, with fewer replacements and less downtime required.

Analysis

Now that your blades are prepared for the elements, you also need to know how they perform.

Analysis is key to understanding the natural frequencies of blade dynamics:

●        Vibratory stresses at resonance

●        Blade and rotor centrifugal stress

●        Blade fixation issues

With EthosEnergy, you can use our experienced team’s technical expertise to help you analyze these blade dynamics at your geothermal plant, helping you to stay within allowable limits.

Repair, reblade, redesign

To keep your geothermal plant running as it should, our repair, reblade, and redesign solutions ensure the best outcomes for your turbines, whether it’s wheel welds or reconfiguring blades based on failure analysis, erosion issues, or control systems.

Inspections

Regular inspections – including visual, magnetic particle, and other forms of non-destructive testing (NDT) – are also vital for your geothermal turbines. They can highlight any issues like surface cracks, blade and shroud damage, erosion, and corrosion, which all need to be addressed as soon as possible to avoid further issues.

EthosEnergy provides ongoing solutions to follow on from your inspection, making any repairs or replacements right away to avoid costly downtime.

Our solutions include:

●        Improved materials, coatings, and steam quality for blade issues

●        Stainless steels upgrades

●        Inconel weld repairs to inner and outer diaphragm rings

●        Improved moisture separation features

●        Wheel replacements with improved materials and lower stress designs

Full steam ahead for geothermal plants

We understand geothermal energy inside out. In the exciting race towards renewable power, we offer the expertise and solutions you need to maximize equipment efficiency and production, regardless of your location, OEM, or lifecycle stage.

Our team is on call and ready to support the growing geothermal sector with proven capabilities and innovative, independent approaches to address challenges such as moisture and corrosion.

As geothermal energy becomes an increasingly vital element in the global energy mix, we see this as a massive opportunity to help our customers achieve more.

Get in touch today for more information on our geothermal offerings.