Dear Richard,

we run a B31.4 line with the option "All Case Corroded" as "False". The system passed.

Then we run the same system enabling the "All Case Corroded" as "True" and the system failed miserably in operating, expansion and sustained load cases.

Considering your words, my conclusion is that B31.4 does not consider a reduced section modulus due to less thickness in normal condition ("All Case Corroded" as False). Is my understanding correct?

If I'm right, the option must be always enabled if we are designing the pipeline for 30 years.

How does it work for B31.8?

Please advise.

Thanks in advance