Inner Inspection of Butt Welds in Layered High-Pressure Hydrogen Vessels Using the Phased Array Ultrasonic Total Focusing Method

Abstract

Abstract Layered high-pressure hydrogen vessels have been widely used in hydrogenation stations in China. The structure of the butt weld at the head of the vessel is complicate, and it is difficult to effectively detect internal defects of the butt weld from the outside surface of the vessel due to the air-filled gap in the double-layer hemispherical head. Inner inspection conducted with the phased array ultrasonic testing method has been proved to be effective in detecting defects of the butt weld, however the inspection area is not large enough to cover the entire butt weld without moving the probe, and the signal-to-noise (SNR) of the inspection image is low. Total focusing method (TFM) performs better inspection results than conventional phased array methods. In order to verify the feasibility of TFM imaging in inspection of the butt weld, a special test block consistent with the material and structure of the head of the vessel has been customized, and the TFM inspection simulation and experiment have been carried out. The results show that the feature of defects located at the butt weld can be recognized conveniently in TFM images, and the TFM inner inspection method can be expected to be an effective means of periodic inspection of layered high-pressure hydrogen vessels.