Nov 23, 2015

Hydrostatic Exemption Evaluation of API 650 Storage Tank

After storage tanks undergo repair, API, 653 Tank Inspection, Repair, Alteration, and Reconstruction, may require a hydrostatic test to provide assurance that the repairs are sound. This is required for “major repairs” (as defined in API 653) and for repairs at or near the bottom shell-to-floor joint due to the more complex nature of the stresses at this location. API 653, section 12.3 permits the use of an engineering evaluation and NDE in lieu of a hydrostatic test. The logic for the engineering evaluation approach is to show that flaws that could lead to failure (brittle fracture) are detectable using NDE rather than hydrostatic testing. If limiting flaw sizes are detectable by NDE and the weld in question is inspected 100% and found to be defect-free, hydrostatic testing is not required.

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