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In this paper, a sensing device specifically for measuring deformations of high temperature pipes is designed, and its applicability is verified both experimentally and theoretically. First, the design procedure and the working principle of the sensing device are described in detail. Then, experiments are carried out to prove the accuracy and the long-term stability of the sensing device. To verify the accuracy of the device, numerical simulation of the deformation of a pipe model is carried out using finite element method. Results from the experimental measurements are in good agreement with results from the numerical simulation. The long-term stability of the device is validated by monitoring the deformation. Conclusions are drawn that the designed sensing device has high accuracy and excellent stability and can be used for measuring deformations of high temperature pipes in power plants.

To accurately detect deformation and extend the component life beyond the original design limits, structural safety monitoring techniques have attracted considerable attention in the power and process industries for decades. In this paper an on-line monitoring system for high temperature pipes in a power plant is developed. The extension-based sensing devices are amounted on straight pipes, T-Joints and elbows of a main steam pipeline. During on-site monitoring for more than two years, most of the sensors worked reliably and steadily. However, the direct strain gauge could not work for long periods because of the high temperature environment. Moreover, it is found that the installation and connection of the extensometers can have a significant influence on the measurement results. The on-line monitoring system has a good alarming function which is demonstrated by detecting a steam leakage of the header.

In this paper, an extensometer was specifically designed for online deformation monitoring of high temperature pipes and its applicability was verified experimentally. The design procedure and the installation of the extensometer were described in detail. Experiments were carried out to prove the accuracy and the reliability of the extensometer. The laboratory test at room temperature was performed. The reliability of the extensometer at high temperature was validated by on-site monitoring of the deformation of a main steam pipe operating at 540 °C in a power plant. It was demonstrated that the designed extensometer has a high accuracy and an excellent reliability for measurement of the deformation of the high temperature pipes.