CASE STUDY | CCGT Maintains Competitive Edge with HotSense™
Lead-free materials and sensors with low temperature capability for extreme environments
Key Deliverables/Value
- Gas turbine power plant secured its competitive edge in the energy market with optimised availability through automated ultrasonic thickness (UT) monitoring, allowing proactive maintenance to maximise uptime.
- Correlation of wall loss rates with operational factors such as cold starts, Gigawatt output, pressure, and flow rate to extend asset lifetime.
- Improved maintenance planning by shifting from calendar-based assessments to event-based tracking, reducing unnecessary inspections and minimizing downtime.
- Early identification of conditions leading to accelerated erosion, enabling the plant to adjust operations to avoid high-risk scenarios.
Overview
A combined-cycle gas turbine (CCGT) power plant sought to improve its ability to bid competitively in the energy market by achieving faster cold starts and ensuring plant availability. In this highly competitive landscape, plants must offer the lowest price and shortest startup times to secure a position on the grid, with all selected providers ultimately receiving the same market rate. However, the aggressive thermal cycling required for rapid starts was suspected to be contributing to accelerated wall loss in critical steam lines.
Previously, the plant relied on manual ultrasonic testing (UT) every two years, which provided only a snapshot of wall thickness and correlated loss rates with calendar time rather than operational cycles. This approach left the maintenance team with limited insight into whether specific plant conditions were exacerbating erosion. To optimise performance, the plant required a continuous monitoring system that could provide real-time data, correlating wall loss with actual operating conditions to prevent failures and extend asset life.
The Challenge
The plant was experiencing significant wall loss in both the smaller 3” warming lines and the main 24” steam feed line. Both lines, which are cold during startup, were particularly vulnerable to condensation formation, leading to droplet erosion and accelerated thinning. Water accumulation due to pressure and temperature drops at the injection points in the warming lines further exacerbated the issue.
- A previous repair of the location had resulted in the installation of a patch plate. However, space constraints between butt welds limited future repair options.
- Manual UT was infrequent and ineffective in linking wall loss trends to specific operational conditions, leaving maintenance teams unable to take proactive action. Surface temperatures exceeding 550°C and insulated pipes made on-stream inspections impossible.
- Surface temperatures exceeding 550°C and insulated pipes made on-stream inspections impossible.
- High thermal cycling due to frequent cold starts increased the risk of rapid erosion, making it essential to continuously monitor these lines.
The Solution
To address these challenges, Ionix deployed its HotSense high-temperature ultrasonic thickness monitoring system, integrated with Field Data Logging Kit (FDLK for automated data collection and analysis. This solution was delivered as part of the Apave CEMS monitoring-as-a-service, ensuring seamless implementation and ongoing support.
- HotSense™ sensors were installed on the critical steam lines, providing continuous, real-time wall thickness measurements.
- A combination of straps and welded stud deployments were used, see Figure 1.
- Data was collected and processed through FDLK, offering high-frequency monitoring and trend analysis.
- Wall loss trends were correlated with plant operational data, including temperature, Gigawatt output, pressure, and flow rate.
- The system was configured to alert maintenance teams to high-risk conditions, enabling proactive intervention.
Figure 1: An NDT inspector installs a HotSense™ transducer using welded studs on an NPS 24” line.
Execution
- The HotSense™ monitoring system was deployed across key steam lines, tracking wall loss trends in real time.
- A rapid wall loss event was detected and directly linked to cold start conditions, validating the plant’s initial hypothesis, see Figure 2.
- Data analysis also revealed a previously undetected leaking valve, which was contributing to unexpected erosion.
- Maintenance teams used the insights provided to adjust startup procedures and schedule repairs based on actual degradation rates rather than estimated timelines.
Figure 2: Sanitised data from one of the HotSense™ sensors showing the detection of 0.6mm wall loss over a number of hours, caused by the conditions of the specific cold start routine.
With the implementation of automated UT monitoring, the power plant can now optimise maintenance planning, extend the life of critical assets, and improve operational efficiency. By shifting from calendar-based inspections to condition-based maintenance, the plant has enhanced reliability and minimised unplanned downtime, securing its competitive edge in the energy market.