Study On Mechanism Of Ultrasonic Testing Scanner For Pipeline Welds

The in-service inspection of reactor pressure vessel and pipeline welds is of great importance in the operation of nuclear power plants, which huge workload and hard environment require the device some of necessary characters such as simple structure, convenient mounting, enough stability and light mass etc. Series of automatic ultrasonic testing devices for large-sized vessel and pipeline welds in the dissertation utilize wheel device with permanent magnet to perform the adsorption and circular motion of the scanner in cylinder's working surface, and additionally mount different special scanning modules to perform corresponding automatic inspections on different working surfaces.According to the actual work requirements and environment, this dissertation chooses appropriate adsorption mode and drive scheme, on the basis takes advantage of modular design method, respectively represents various general planning designs suitable for inspecting corresponding working surfaces, represents various modules design such as the main body of the scanner, the scanning arms etc in detail. The scanner mounted by the main body and the appropriate arm can achieve every trace motion of the ultrasonic wave detector.This dissertation studies the static stability of the scanner with the ultrasonic testing scanner for pipeline loop welds as the study object: firstly sets up the global coordinate system, the pipe coordinate system and the scanner's object coordinate system, introduces the pipe's slope angle and round angle, converts the scanner's gravity to three component forces in the scanner's coordinate system, therefore studies all kinds of unstable situations at random positions in the scanner's operation and obtains respective mathematic models;secondly converts the scanner's destabilization problems to the problems of the magnetic wheel's allowable adsorption force in order to keep the stabilization, and then deals with some numerical simulations about each model of the allowable adsorption force;at the end detailedly analyzes various destabilizing forms and reasons, brings forward corresponding settlement measures, and builds the quantitative relationship between the stability of the scanner and the magnetic adsorbing force, and then obtains the adsorbing force quantity to offer a gist for the design of magnetic circuit structure.According to the regular rule of static magnetic circuit design andrequirements of the device's operation, the paper calculates the basic structure sizes of the magnetic wheel, then verifies the magnetic forces by a series of simulation of the design in FEA software and perfects the structure design. In addition, we select rubber to encapsulate the permanent magnet structure so as to improve the safe operation level and avoid being rusted.In the end the dissertation analyzes the dynamical balance model of the scanner crawling in the circumstance of the pipeline at a uniform velocity and gain maximum friction moment to offer a gist for selecting driven motor.The ultrasonic testing scanners for pipeline welds designed by the project have simple structures, good reliability and applicability. The study methods in the paper have some universalism in some sense and can be used for reference for some similar design.