Inspection of storage tank floor welds with ACFM

摘要

The Alternating Current Field Measurement (ACFM) method has become well established in the oil and gas industry for routine in-service weld inspection. It offers many advantages over conventional inspection methods by avoiding the need for extensive pre-cleaning. It has recently been applied to the inspection of lap and fillet welds inside steel storage tanks and has, in some cases, outperformed the standard methods for internal weld inspection such as magnetic particle inspection or vacuum box testing. This paper focuses on recent experience in both Europe and Central America in the use of the technique for the inspection of welds in the floors of cylindrical steel storage tanks. The inspections used conventional ACFM probes as well as new array probes recently developed to speed up inspection of these welds. Results from ACFM are compared with those from the conventional methods, including examples where through-wall cracks giving rise to measurable leaks were not detected with the conventional methods, but were found using ACFM. Conclusions are drawn as to the benefits this technique offers in terms of cost and time savings and inspection reliability.