Which condition disqualifies the use of corrosion averaging in API 510 for a locally thinned area?

Which condition disqualifies the use of corrosion averaging in API 510 for a locally thinned area?

• A. If the corroded area has notches
• B. If erosion/corrosion damage is present
• C. If the inside diameter is less than 60"
• D. If the corroded area has 75% remaining wall thickness

Answer: (A)

The use of corrosion averaging in API 510 is disqualified when the corroded area has notches. Notches can significantly affect the mechanical integrity of the pressure vessel because they disrupt the stress distribution across the material. The presence of notches typically indicates a more serious local geometric alteration, which can lead to stress concentration points where failure could initiate. Corrosion averaging is intended for areas where uniform corrosion has occurred across a surface, allowing for the calculation of remaining wall thickness based on a broader average condition. In cases with notches, the localized reduction in wall thickness can create stress risers that would not be accounted for in an averaging approach, potentially leading to unsafe conditions. Therefore, recognizing notches signals a need for a more conservative assessment rather than relying on an average thickness calculation. The other conditions listed do not inherently prevent the application of corrosion averaging. For example, erosion/corrosion damage can still be averaged across larger areas unless it results in notches. Similarly, the size of the inside diameter being less than 60 inches does not disqualify the use of averaging, nor does having 75% remaining wall thickness, as these factors do not inherently compromise the integrity assessment methodology like the presence of notches does.

The use of corrosion averaging in API 510 is disqualified when the corroded area has notches. Notches can significantly affect the mechanical integrity of the pressure vessel because they disrupt the stress distribution across the material. The presence of notches typically indicates a more serious local geometric alteration, which can lead to stress concentration points where failure could initiate.

Corrosion averaging is intended for areas where uniform corrosion has occurred across a surface, allowing for the calculation of remaining wall thickness based on a broader average condition. In cases with notches, the localized reduction in wall thickness can create stress risers that would not be accounted for in an averaging approach, potentially leading to unsafe conditions. Therefore, recognizing notches signals a need for a more conservative assessment rather than relying on an average thickness calculation.

The other conditions listed do not inherently prevent the application of corrosion averaging. For example, erosion/corrosion damage can still be averaged across larger areas unless it results in notches. Similarly, the size of the inside diameter being less than 60 inches does not disqualify the use of averaging, nor does having 75% remaining wall thickness, as these factors do not inherently compromise the integrity assessment methodology like the presence of notches does.