BLOG | High-Precision Wall Thickness Monitoring in a Nuclear Power Plant

A solution was sought by a European nuclear power plant to monitor high-pressure steam lines in proximity to the electricity generating turbines. Previous assets had been experiencing wall loss due to steam condensate causing erosion at piping T-junctions and as such had been replaced. The operator suspected that the wall loss rate and location was accelerated due to process conditions and so sought to collect data at increased frequency to allow wall loss rate to be correlated with specific process parameters. The operator was also advised that the greatest wall loss may occur during the first year of operation of the new piping and so a solution which could be installed immediately was required. The non-standard steel 21” and 25” NPS diameter steam lines, with surface temperatures above 230 °C, were located across several levels up to 30 m high in an area that is restricted to personnel during operation.

The Challenge

There were a number of challenges around the deployment which required a flexible monitoring solution.

• A high-temperature wall thickness monitoring solution was required which could operate over 230°C continuously.
• The pipe geometry was non-standard and the monitoring locations were distributed around two T-sections.
• The piping is lagged, and the location is inaccessible during normal operation.
• The wall loss was thought to be process dependent, requiring a high-frequency of measurements.
• Wireless/RF systems are restricted in proximity to sensitive electricity generating plant.
• The equipment needed to be installed very short notice before the end of a shutdown as subsequent access would not be possible.

The Solution

• 16 x HotSense™ 380 sensors were deployed around each T-junction to provide a sensor which could operate continuously above 230 °C and provide a stable and reliable thickness measurement.
• The HotSense™ strap deployment system allowed for fast installation during the limited shutdown and offered flexibility to place sensors in the expected pattern to detect wall loss.
• Initially, all sensors were connected to Measurement Hubs for manual data collection from a lower platform using a GE flaw detector.
• The CALIPERAY automated monitoring system was inspected by the local electrical engineering team and the radio output found to be of no concern to the safe operation of the site.
• The Measurement Hub was subsequently upgraded to a fully automated CALIPERAY WirelssHART node with Field Deployment Logging Kit (FDLK) for simple implementation and data collection.