The Application Of Modal AE Testing Techniques To Water Pipes

Leak in pipe is one of the major problems in the oil, chemical, and other industries. Investigation of the theories and technologies of leak detection, precisely locating the leak is significant in maintaining the safely running of pipeline and avoiding waste of resource. Modal acoustic emission (MAE) is a new NDT technology, which based on traditional acoustic emission, has an advantage on long range testing. In this paper, leak of water-filled pipe was researched in laboratory by means of modal acoustic emission and modem signal processing technologies.The main work in this paper is as follows:Designed and set up a system of Acoustic Emission (AE) pipe testing, include pipe leak simulated equipment and Acoustic Emission Testing equipment. With the changing of the pressure of water-filled pipe, diameter of leak hole, distance of propagation, the energy and spectrum of pipe leak signal will change. Based on this system, these laws were researched by means of experiment.Based on the theories of wavelet and MAE, the experiments of lead break in thin plate and water-filled pipe were researched in detail. By use of Gabor wavelet transform and MAE technologies, the arrived time to sensors of transient AE signals of specific guided mode can be precisely obtained. As the result, the precision of leak location was improved. The disperse characteristics of thin plate and pipe can also be found.Considering the multimode and disperse characteristics of water-filled pipe, the leak location arithmetic model was constructed. Based on this model, a method was developed to obtain certain guided mode signal form AE signals. The final results showed that the method could reduce the multimode and disperse influence to AE signals effectively and locate the leak source correctly.