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Defect Assessment

AFAA undertake defect assessments using a structured approach. The approach starts with an initial screening assessment using simplified methods. Increasing levels of complexity, removing various levels of conservatism, are gradually introduced until a defect can be shown to be acceptable for the proposed operating regime. By adopting this approach considerable savings on unnecessary excavations and repairs can be made.

AFAA undertake the various assessments using industry leading software.

Corrosion

Corrosion is one of the main causes of pipeline failure around the world. At AFAA we have experience of using traditional deterministic approaches such as those documented in corrosion specific standards such as ASME B31G, DnV RP-F101 and those in fitness-for-service standards such as API 579 and BS 7910.

In situations where a defect is found to be unacceptable using a deterministic approach, AFAA can offer a more accurate defect assessment. One approach would be to use a probabilistic approach. This is a very powerful method for assessing corrosion defects, as it is able to take account of the uncertainty in how the defect will grow. This approach will allow the operator to plan a more cost-effective repair strategy and decide the optimum time to inspect in the future.

Dent and Gouges

At AFAA mechanical damage defects such as dents and gouges are assessed using industry standard methods. In situations where the defect is found to be unacceptable, AFAA are able to provide a more detailed assessment of the defect using FEA. This approach will allow the operator to decide with confidence which defects require repair.

AFAA have been involved in the development of a new limit state function for assessing dent/gouge defects.

Cracks

Cracks occur due to poor workmanship levels and the inability of NDE to detect small crack-like defects. The detection of such defects only become apparent in-service when they have grown due to fatigue.

AFAA have significant experience of performing simple screening assessments to more detailed assessments. Typical assessments performed by AFAA include Level 2A approach in BS 7910 and Level 3A approach in API 579.

When a defect is found to be unacceptable using these approaches, AFAA are able to perform FEA or probabilistic fracture mechanics. At AFAA accurate and definitive solutions are provided that allow the operator to schedule an appropriate NDE inspection or repair strategy.