Acoustic Emission Testing and Structural Evaluation of Seamless, Steel Tubes in Compressed Gas Service

Tube trailers are used in the distribution of industrial gases. The tubes, which are of seamless steel, measure 22-in. diameter, about 1/2-in. wall, and 34 ft long. The U.S. Department of Transportation mandates periodic re-tests of tubes every 5 yr. Acoustic emission re-tests have been substituted for hydrostatic re-tests. This paper presents an analysis of flaws using fracture mechanics methods and establishes a maximum allowable flaw depth. It describes the acoustic emission test method and presents some typical results. Also, some discussion of the hydrostatic re-test is included.