ULTRASONIC MONITORING OF FLAW GROWTH AT 600 ̊C (1110 ̊F) IN AN OPERATIONAL POWER PLANT
Flaw growth monitoring at operational temperatures in high-temperature plants has long been recognised as a highly desirable inspection goal, particularly in regard to effective outage management and lifetime extension of existing plants, and increasing the reliability of future plants through the incorporation of active monitoring systems. However, despite considerable efforts in the area of high temperature inspection, practicable solutions for implementing long-term continuous flaw growth monitoring in operational power plants have proved elusive. KANDE International and E.ON have worked together over a number of years to develop a viable means of performing long-term monitoring of known flaws in operational fossil-fuel power plant components, where operating temperatures can be as high as 600°C (1110°F), and we have previously reported on the development and laboratory testing of permanently installed high temperature ultrasonic probes and associated testing techniques. In this paper we report on the progress made to date in a new study that is investigating the wider problems associated with performing remote monitoring of real flaws in a main steam line in an operational plant. We discuss the approaches used to address a range of issues including: the permanent attachment of probes close to known flaws; designing an instrumentation system capable of recording data and transmitting it to an off-site location with minimal operator intervention; and the development of software tools to display and analyse the resulting data so that flaw growth can be identified and measured. We comment on the lessons learned to date and on how the experience gained will influence the future development of the technology.
Ultrasmart: Developments in Ultrasonic Flaw Detection and Monitoring for High Temperature Plant Applications
Plant in the power generation, petrochemical and metals processing industries is subject to increasingly onerous operational and regulatory requirements. Where plant that operates at high temperature is involved, the costs associated with shutdown for planned or unplanned inspection to meet these requirements can be particularly high. The ability to perform condition monitoring or flaw detection at on-line plant temperatures would enable plant to remain in operation for longer periods, reduce the risk of damage from thermal cycling associated with periodic shutdowns and allow shutdowns to be completed more quickly. The associated minimizing of the loss of revenue caused by frequent and lengthy shutdowns is a highly attractive proposition to the plant operators. This paper reports on progress in the Ultrasmart Project, which is being undertaken by a consortium of UK companies and aims to address the problems associated with performing ultrasonic inspection on pressure vessels and piping at temperatures exceeding ∼350°C. A brief review of the state of current industry capabilities is given and then details of the developments investigated within Ultrasmart are reported and discussed. These include: • Liquid cooled transducers and automated scanning mechanisms suitable for deployment on components with surface temperatures up to ∼500°C. • Permanently mounted piezoelectric transducers suitable for long term flaw growth or component thickness monitoring at temperatures up to ∼750°C. • Techniques, procedures and protocols necessary to achieve reliable and quantifiable inspection capability at high temperatures. • Use of a novel non-resonant thin film Aluminum Nitride (AlN) transducer for in-situ component monitoring.© 2007 ASME
Ultrasonic thin film transducers for high-temperature NDT
Ultrasonic thin films have advantages over conventional transducers for non-destructive testing, especially at high temperatures. We have demonstrated thin film ultrasonic devices in operation at temperatures over 400°C. Pulse-echo and through-transmission modes have been used, with standard ultrasonic pulser-receivers. The films are deposited directly onto the test components, thus eliminating problems with acoustic coupling at high temperatures. Transducers formed in this way are low-profile, unlike water-cooled transducers or those requiring thermal isolation via buffer rods. It is possible to deposit the films onto curved surfaces and extensive surface preparation is not required. Pulse-echo tests have been carried out on aluminium and mild steel components, showing that back-wall echoes and simulated defects can be detected through several centimetres of material. There are clearly important potential applications in non-destructive testing at high temperatures including detection of defects in hot components and monitoring pipe-wall thickness in high-temperature plant.