Indications of Cracks

Indications of cracks are usually of considerably greater concern than corrosion. They predominantly occur at weld joints and may propagate during operation. However, cracks that exceed the acceptance limits for radiographic examination in the ASME Code do not necessarily compromise the integrity of a pressure vessel.

The acceptance limits for linear indications (including cracks) in the ASME Code are “workmanship” criteria used to establish quality standards that should not be exceeded with good fabrication shop practices. It should not be inferred that cracks exceeding these limits, detected after a pressure vessel has been placed in service, always jeopardize reliable operation and require immediate repair. Flaws that are larger than the acceptance limits in the ASME Code will not always result in failure during startup, nor will they necessarily propagate so rapidly at the operating pressure and temperature that they cause failure before the next planned shutdown.

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