5.1 General—This procedure is used for evaluation of the structural integrity of atmospheric storage tanks. The AE method can detect flaws which are in locations that are stressed during pressurization. Such locations include the tank wall, welds attaching pads to the tank, nozzle attachments, and welds attaching circumferential stiffeners to the tank. Among the potential sources of acoustic emission are:
5.1.1 In both parent metal and weld associated regions:
5.1.1.1 Cracks,
5.1.1.2 The effect of corrosion, including cracking of corrosion products or local yielding,
5.1.1.3 Stress corrosion cracking,
5.1.1.4 Certain physical changes, including yielding and dislocations,
5.1.1.5 Embrittlement, and
5.1.1.6 Pits and gouges.
5.1.2 In weld associated regions:
5.1.2.1 Incomplete fusion,
5.1.2.2 Lack of penetration,
5.1.2.3 Undercuts, and
5.1.2.4 Voids and porosity.
5.1.2.5 Inclusions:
5.1.2.6 Contamination.
5.1.3 In parent metal:
5.1.3.1 Laminations.
5.1.4 In brittle linings:
5.1.4.1 Cracks,
5.1.4.2 Chips, and
5.1.4.3 Inclusions.
Note 1: Not all of these sources are typically encountered in field examination, some are detected under laboratory conditions.
5.2 Accuracy of the results from this practice can be influenced by factors related to setup and calibration of instrumentation, background noise, material properties and characteristics of an examined structure.
5.3 The outcome of this practice is t