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In the inspection of material for construction of a boiler drum I found some pittings on the surface of A516-grade70 which are not very serious. but I don't have any accept or reject criteria to evaluate this problem. Please tell me a standard for acceptance.

RE: pitting

API-510 has a very specific criteria for acceptance of pitting on pressure vessel components.

Steve Braune
Tank Industry Consultants

RE: pitting

If this is a boiler drum, I would defer to the National Board Inspection Code (NBIC). There is pitting criteria referenced in the NBIC in RB-9130 (j). Also, we list API 579 as a reference document in the NBIC. API 579 contains specific information to evaluate pitting damage.

RE: pitting

I also just realized that if this is new construction of a boiler drum, you are bound by the rules for the Code of Construction. In this case, you need to evaluate the depth of the pits to determine if the remaining wall thickness of the shell material is below the required minimum wall thickness for the drum by the Code of Construction rules.

RE: pitting

Your pit's may also be mechanical rolling marks from manufacturing. Most heavey plate is hot rolled which can leave pit-like impressions on the surface. Where are the pit's? random or in a given area.

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