Ultrasonic Testing for the Seam of In-Service Liquefied Petroleum Gas Sphere

During the periodical testing for in-service liquefied petroleum gas sphere, a lot of cracks were detected out by ultrasonic testing method. Three typical crack defects were chosen to the wave form analysis, and the crack height testing method by ultrasonic max end echo was verified for its possibility, and the method how to prohibit the subsurface defect undetected was proposed.