Frequently asked questions
Guidance on the assessment of corrosion damage in internally pressurized pipes or pressure vessels from the viewpoint of plastic collapse of the corroded ligament is given in Annex G of BS7910  . Alternative rules for the assessment of corrosion damage in pipes and and more complex geometries are given in API 579  though it is not known how thoroughly the assessment procedures for complex geometries have been validated. Simple assessment procedures are given in the ASME B31G procedure  . Using the assessment procedure recommended in BS7910, the yield and tensile strength of the component material, the length and depth of corrosion, the pipe diameter and operating pressure are required as input information.
Alternatively, corrosion can be assessed using finite element analysis  (FEA). However, FEA is normally recommended for high value components in situations where it is inappropriate to use simpler assessment procedures.
Particular care must be taken to avoid the risk of brittle fracture. Further guidance is given in ref  , together with a comparison of the different methods. The methods described here refer to generally smooth corroded regions or locally thinned regions and the topography of the corroded region should be considered in applying the assessment technique.
TWI has world renowned experience in the structural assessment of corrosion damage, probabilistic assessment of corrosion damage, non destructive inspection and finite element analysis. TWI can also advise on the selection of materials and appropriate joining technologies, for metallic and non metallic systems, plus mitigation measures through surfacing and coating technologies.
- 'A critical review and comparison of various methods to evaluate the static strength of corroded pressurised components', TWI Members Report 707/2000, May 2000. Only available to industrial Members of TWI.
FAQ: How can I assess corrosion damage at nozzles in steel pressure vessels?
FAQ: How do I assess the structural integrity of corroded regions at welds?