Acceptance criteria for pitting corrosion 2

[ahmadire]

Dear experts,
I would be grateful if you could help me if we have acceptance criteria for pitting corrosion on steel plates used in pressure vessels?

 

[XL83NL]

None

 

[metengr]

Use API 579 locally thin area evaluation.

 

[weldstan]

Are you asking about pits in new plate to be used for PV fabrication? Or PV's in service?

 

[wsu1975]

In addition to API 579/ASME FFS-1 Part 6 Pitting evaluation, try the National Board Inspection Code methodology, If it is still in the NBIC.

 

[r6155]

It´s simple. If all pitting depths are less than corrosion allowance the pressure vessel can return to normal service. if not see API 579. Allways see API 579
Regards
r6155

 

[ahmadire]

weldstan, what I meant to say was about new plate before fabricating of pressure vessel

 

[metengr]

For new plate you refer to the material specification and associated tolerances and workmanship.With that said, you have to inspect the incoming plate and ensure the wall thickness of the new plate beneath the pitted surface, which should be removed, still remains above the required minimum design thickness. Otherwise, I would reject the plate.

 

[weldstan]

See metengr.

 

[ahmadire]

metenger are we allowed to repair pitting discontinuities by welding and grinding? either above min thk. or beneath.

 

[metengr]

Yes, if you have accepted the plate with pits, you issue a nonconformance and weld repair, as necessary. Why in the world would you accept such material?

 

[ahmadire]

because those are supplied in a difficult way and our company doesn't want to discard them as much as possible.