Claddings and Weld Overlays

Visual indications that deteriorating claddings or weld overlays are resulting in corrosion of the pressure vessel shell must be further investigated. Hammer testing can provide a useful indication of the integrity of the lining. A “solid” or “resonant” sound indicates that the lining has not separated from the vessel shell, and that cracks have not developed. On the other hand, a “hollow” or “tinny” sound indicates that the liner has disbonded or that cracks have developed. Bulging or wrinkling of the lining may also occur. However, indication of deterioration of the liner does not necessarily indicate that the vessel shell is corroding. Corrosion of the vessel shell can be determined by removal of a section of the deteriorated lining and visually examining (VT) the shell, or by ultrasonic examination (UT) using a longitudinal wave procedure from the O.D. surface of the vessel to determine the remaining wall thickness.

Corrosion of a shell resulting from deterioration of the lining should be evaluated as discussed above. Deterioration of the lining that has not resulted in corrosion of the shell need not be repaired, unless continued deterioration may to lead to corrosion of the shell before the next scheduled inspection, or the integrity of an internal attachment may be compromised.

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