Thermal Power Generation Process: Control Valve Problems and Solutions

Thermal power plants have been the backbone of electricity generation for over a century, yet they still grapple with persistent challenges like cavitation and pressure surges. At the core of these issues are control valves, which play a crucial role in maintaining operational efficiency and safety. Despite advances in technology, the harsh conditions in thermal power generation continue to push these valves to their limits, making it essential to address these ongoing challenges with innovative solutions.

Control valves need to be able to withstand severe conditions, from cavitation in boiler feedwater systems to the precise modulation required in desuperheating applications. At the same time, they must constantly perform at the highest level.

At Trimteck, we’ve spent decades addressing these challenges, helping power plants maintain high performance while mitigating common issues that can compromise safety and efficiency. In this blog, we’re going to look into some of the most problematic control valve applications in thermal power generation and then we’ll share how precision-engineered, custom control valves can resolve them.

Problem #1: Cavitation in boiler feedwater systems

Cavitation occurs when a rapid pressure drop causes vapor bubbles to form in the liquid within the valve. As these bubbles collapse, they generate powerful shock waves that erode the valve's internal components. Due to the high pressures and temperatures involved, this is a common problem in boiler feedwater systems. Cavitation leads to premature wear, leakage, and reduced efficiency, often resulting in costly unplanned shutdowns.

To combat cavitation, Trimteck equips its OpGL globe control valves with multi-stage anti-cavitation trims, such as the ST-2 trim. These trims gradually reduce the pressure through a series of restrictive channels and expansion areas, preventing the formation of vapor bubbles. For example, at the FPL Martin Boiler Feedpump Recirculation Valve installation, our custom-engineered valves have proven effective at mitigating cavitation under severe conditions, thanks to our CVD-5B hardening process that improves valve durability.

Problem #2: Pressure surges in anti-surge applications

Thermal power plants often experience pressure surges, especially during startup, shutdown, or rapid load changes. These surges can create significant mechanical stress, leading to cavitation, mechanical failures, and eventual system instability. Unchecked pressure surges can damage both the valve and surrounding equipment, resulting in costly repairs and extended downtimes.

Trimteck engineers its high-performance control valves with multi-stage trims to manage these pressure surges effectively. By gradually reducing the pressure through restrictive passages, our valves help prevent mechanical stress and cavitation. This ensures stable operation even under the most demanding conditions. Additionally, incorporating Class V shutoff capabilities ensures tight sealing, which prevents leakage that could further damage the system. Our custom-engineered solutions help power plants maintain operational stability even during rapid pressure fluctuations.

Problem #3: Erosion and temperature control in desuperheating

In desuperheating applications, operators must control steam temperature precisely to prevent turbine damage. However, large pressure drops and high-velocity flows expose superheater and reheater attemperation systems to erosion and cavitation. Over time, these conditions cause significant valve wear, leading to failure and inefficiencies in the steam generation process.

Trimteck’s OpGL Globe Control Valves, equipped with ST-2 or ST-3 trims, ensure precise steam temperature control while preventing cavitation and erosion. Our noise attenuation technology and multi-stage trims effectively manage pressure drops, allowing for long-lasting operation in severe service conditions. In plants like Indiantown Cogeneration, these valves have consistently improved operational performance, even under low-load conditions where cavitation risk is highest.

Problem #4: Thermal cycling and fatigue due to load variations

With the integration of renewable energy sources, many thermal power plants now operate in cycling mode, where frequent startups, shutdowns, and load changes introduce thermal cycling and fatigue. Valves that were not designed for these fluctuations often crack, experience thermal stress, and fail prematurely, especially when subjected to high-pressure and high-temperature variations.

At Trimteck, we offer valves engineered to withstand the stresses of cycling operations. Our valves, featuring multi-stage trims and durable materials, are built to handle frequent temperature and pressure changes without compromising performance. By implementing control strategies like the 80/20 rule, where 80% of the capacity is handled by the startup valve and 20% by the regulating valve, we ensure smooth transitions and extended valve lifespan, reducing the effects of thermal fatigue.

Problem #5: Inconsistent flow control in recirculation valves

Maintaining a consistent minimum flow is essential in recirculation valves to prevent pump overheating and cavitation, especially during low-load conditions. Oversized valves, however, tend to operate below their optimal throttling range, leading to inconsistent flow and cavitation damage to the valve’s internal surfaces.

Trimteck’s OpGL-XT Angle Control Valve, featuring the ST-2 multi-stage trim, ensures precise flow control and protects pumps by managing high-pressure drops effectively. Additionally, ensuring the correct valve size and, in some cases, using a two-valve system (one for startup and another for normal operations) can optimize performance. This reduces the risk of cavitation and ensures consistent flow control, protecting pumps and minimizing inefficiencies.

Problem #6: Valve leakage in critical systems

Valve leakage, particularly in feedwater systems and other high-pressure applications, can lead to system inefficiencies and erosion of internal valve components. Operators often install valves with lower shutoff classes, which allows leakage even when the valve is closed. Over time, this leakage erodes components, reduces efficiency, and leads to valve failure

Trimteck ensures tight shutoff in critical systems by specifying Class V shutoff for all valves used in high-pressure applications. This ensures minimal leakage, reducing the risk of erosion and improving the overall efficiency of the system. Some of our valves are also equipped with soft valve seats for positive shutoff, further reducing the risk of leaks. Regular valve diagnostics and maintenance also help maintain shutoff integrity over time.

Problem #7: Improper valve sizing

Improper valve sizing is one of the most common issues in thermal power plants. Oversized valves operate inefficiently, particularly during low-load conditions, often leading to cavitation and premature valve wear. Conversely, undersized valves may not handle peak load conditions effectively, causing operational inefficiencies.

At Trimteck, we ensure that our valves are correctly sized for each application to avoid issues associated with oversizing or undersizing. By analyzing the plant’s actual operating conditions—such as load variations, pressure, and temperature fluctuations—our engineers provide custom valve solutions that match the plant’s unique requirements. This helps prevent cavitation, ensures smoother operations, and extends valve life.

Customized control valves for optimal performance

The right valve design and materials are crucial for ensuring long-lasting performance and minimizing maintenance. Trimteck designs custom-engineered solutions to meet the specific needs of demanding thermal power generation applications, helping power plants maintain operational efficiency and safety.

We pride ourselves on our ability to provide advanced control solutions that not only meet but exceed industry standards. Whether you’re dealing with cavitation in a boiler feedwater system or need precise steam temperature control in desuperheating, we have the expertise and products to help you achieve optimal results. Contact our Applications Engineers today to discuss your needs and discover how we can help resolve your most challenging valve applications.