Detection of Corrosion and Geometrical Anomalies Within DH Pipework Using High Resolution, Low Risk, Ultrasonic Inline Inspection Tools
Abstract (Case study is available here in PDF format)
Recently, within a coastal community in Western France, Quest Integrity completed the cleaning and inline inspection of two operationally critical sections of district heating pipework for Salines Energies Service (part of ENGIE Solutions). The inspected sections formed part of a localized district heating network providing heating and hot water for approximately 4,500 residents in 2,500 properties on the outskirts of the City of La Rochelle.
The network was constructed in 1971 and was comprised of a main carbon steel hot water feeder and cool water return pipe with distribution offtakes. The piping was laid within concrete ducting supported every 7 meters by steel crossmembers. The sections identified for inspection consisted of 1km of the main hot water feeder pipework departing from the boiler plant and the parallel 1km of return pipework terminating inside the boiler plant. The pipework had a nominal diameter of 406mm (16 inches) and constant wall thickness of 8.8mm (.346 inches).
Following an unexpected interruption of service in the winter of 2020 due to a major water leak, it was concluded during the emergency repair work that a breakdown of the concrete ducting allowed underground water to infiltrate the system, causing severe external corrosion of the main pipework. Although the repair recovered service, it raised the question as to whether additional corrosion cells were present and possibly growing at different locations and with similar or possibly worse severity.
Critical to the success of finding a solution to resolve this concern was the selection of a proven technology with capabilities to accurately detect, quantify, locate, and discriminate corrosion defects while minimizing operational downtime and ensuring safe passage within the pipework during operations. A cross array of inspection technologies were reviewed, and Quest Integrity’s InVista™ ILI (inline inspection) technology was determined to be the most accurate and lowest risk inspection solution due to its high-resolution ultrasonic detection, identification, sizing and discrimination capabilities packaged within a compact, lightweight single-bodied tool design with up to 30 percent inline collapsibility. These characteristics, coupled with a minimal execution window of opportunity, were all crucial aspects of the risk assessment prior to executing the inspection campaign.
Following a progressive cleaning program, the InVista™ UT ILI tool was launched and received, achieving 100 percent sensor data capture and greater than 99 percent valid internal radius and wall thickness measurements. The downloaded tool data and analysis results provided defect type, severity, precise locations and an engineering assessment, empowering Salines Energies Service to develop a repair or replacement strategy easily and quickly.
The final engineering report provided by Quest Integrity enabled Salines Energies Service to rapidly re-establish the network’s operational integrity by prioritizing repairs to the immediate high risk corrosion areas identified. Furthermore, the report and its findings substantiated the decision to repair the pipework (as opposed to replacing it) and underpin the integration of a Network Integrity Management Strategy to safeguard future operations.
The utilization of an inline inspection service within a district heating network provided precise, actionable data, empowered the operator to assess risk and identify a robust future operational strategy. Utilizing this approach realized a cost saving of approximately 85 percent compared to the cost of a systematic and
non-conditional replacement of the pipework.
A PDF presentation of this case study is available here.
*Winner of the 2022 ENGIE Innovations Award within the Operational Performance Category