Combined cycle power plants are a popular choice in the power industry for electricity production. They offer better efficiency than other options like gas turbines or steams turbines alone. The combined cycle power plant (CCPP) involves two cycles, the topping cycle (gas turbine) and the bottoming cycle (steam turbine), which are connected by a heat recovery steam generator (HRSG).
The HRSG is a vital part of the combined cycle power plant. It is essentially a boiler with water and tubes. Instead of releasing exhaust straight into atmosphere, like a simple cycle gas plant, the HRSG acts to convert as much of the heat as possible from the gas turbine exhaust into steam which drives the steam turbine, providing additional power and making the plant more efficient.
Because there is a strong interdependence between the topping and bottoming cycles, any failure or fault can spread quickly and cause a drastic reduction of efficiency, accidents, and equipment damage. With the HRSG in a combined cycle plant, there’s a fair amount of maintenance needed due to thermal fatigue, cycling, and other processes. Some components inevitably end up failing because they are metal parts. Repairing, replacing, or upgrading these parts during planned outages helps eliminate downtime due to failure and keeps plant efficiency high.
HRSG Components That Commonly Need Repair, Replacement, or Upgrade
In a combined cycle HRSG power plant, there are two types of components to consider, gas path or non-pressure parts, and steam generation or pressure parts, where repair may need to be performed.
The gas path parts involve the flow of the turbine exhaust through the ductwork. As it flows through the ductwork, it’s being directed through systems, one being the boiler tubes themselves. This optimizes the heat transfer to get as much heat into the water as possible to drive the steam turbine.
Other components in the gas path, such as emissions control systems, often require attention and repair. Newer CCPP sites are required to have emissions control, which you may hear referred to as an FCR and/or a CO system. In the gas path, this is a separate system that interacts with the gas flow to mitigate emissions, ensuring the plant is within its permitted emissions levels.
Additionally, within the gas path, other parts help direct the flow to optimize performance to consider. Besides the boiler tubes and emissions systems, you’ll find aerodynamic flow conditioning elements in the gas path that may need repair or replacement to prevent failure.
Liners are another component where repairs are commonly needed due to the turbulence from the turbine exhaust and thermal fatigue and heat. Liner systems must be in good repair because they maintain the proper OSHA casing temperatures, helping to keep power plants operating within compliance.
Silencers, also called parallel baffles, absorptive baffles, or splitters, are another component of the gas path that may require repair or replacement. While simple cycle systems are much louder at the static exit than combined cycle systems because the flow is attenuated by HRSG boiler tube rows, reducing the need for silencing, large CCPPs have big, noisy turbines, as a result, there’s often still the need for some sort of silencer.
In the steam generation area, which includes pressure parts, various components must be maintained. The tube rows (harps), piping systems, pressure tanks, vent silencers, and valves all have components that can fail, resulting in loss of efficiency and unscheduled downtime. Pressurized components must meet ASME standards, so a repair source that can do ASME pressure part work is critical for CCPPs.
SVI Dynamics – Your Go-To Source for Combined Cycle Power Plant Repairs
At SVI Dynamics, we are dedicated to providing exceptional services to our industrial plant clients, including those with combined cycle HRSG power plants. We understand that optimizing all parts of the system is essential to the efficiency and profitability of your plant. Whether you need repairs, replacements, or upgrades, our expert team of technicians and engineers can help. They are knowledgeable in even the most complex maintenance situations.
We are available to test and analyze your plant’s performance and help put together a plan to mitigate any issues that are found. As always, we will work to minimize downtime and increase your plant’s efficiency while ensuring that plant equipment operates safely, complying with all applicable regulations.