The demand for flexible operations creates challenges for owners of combined-cycle plants installed prior to 2010. Due to recent shifts in the industry, including flattening demand and the prioritization of renewables and new gas generation, operational flexibility is gaining momentum, leaving owners with the challenge of adjusting their approach to equipment operations, maintenance and service.
These combined-cycle plants were typically designed to perform 50 start/stops per year and included design plans for baseload operation with regular maintenance intervals. As new technologies have emerged and been implemented, some plants are experiencing additional cyclic operation of up to 250 start/stops per year.
This operational approach can cause higher rates of equipment damage, reduce performance and increase operation and maintenance costs – particularly for piping and boiler equipment.
Costly Wear and Tear
Constant cycling and long shutdown periods causes wear and tear on power island equipment and combustion turbines. With frequent unit cycling, inadequate pipe support will lead to overstressed piping and failure of the mechanical loading design of the equipment. For example, some of Kiewit’s clients are experiencing issues with their high-energy piping systems due to pipe support misalignment caused by failed supports or slide plate erosion and deterioration.
To mitigate these issues, it is imperative that plant personnel perform frequent visual inspections of pipe runs and pipe supports for (a) misalignment, (b) binding and (c) gaps between pipe shoes and slide plates.
Boiler Chemistry Precision
Another common challenge associated with increased cyclic operation is unstable boiler chemistry. Boiler operators have experienced difficulty maintaining precise chemistry in this unique operating environment. A frequent on/off operational approach commonly results in scaling and fouling, ultimately leading to excessive pipe corrosion and increased equipment maintenance costs.
To alleviate these concerns, Kiewit water specialists work with plant personnel to perform a thorough review of the water chemistry program utilizing the steam and water sampling systems to diagnose and help minimize these problems.
Staying One Step Ahead of the Unexpected
Kiewit’s team of experienced engineers are frequently called upon to troubleshoot common issues related to the cyclic operational nature of plants. As the leader in gas-fired generation and with decades of extensive experience in the detailed design and construction of new plants, our engineers have a broad understanding of these challenges and their weaknesses under these new base conditions. Operating a plant beyond its original design basis will ultimately lead to costly repairs, forced outages, and potential safety hazards. To avoid unintended shutdowns and trips, we offer insight and solutions to implement strategic measures and maximize plant performance.
About the Authors:
Tony Jaime is the Senior Vice President of Engineering Services with over 15 years of service at Kiewit. He has extensive experience in power plant design including EPC projects, as well as conceptual and detailed design. Tony brings over 20 years of combined project management/structural design experience on power and industrial projects.
Dan McGee is Director of Plant Services within Kiewit’s Engineering Consulting group. His career in power and energy over the past 25 years includes extensive experience in implementing studies, environmental reviews, detailed engineering, facility evaluations, operational support and predictive diagnostics for a variety of clients. Dan is responsible for Kiewit’s market expansion in existing plant services retrofit work and small consulting projects.