API 510 8.3.1 Permanent Repair Techniques

[mariolucas75]

API 510
Question one:
8.3.1 Permanent Repair Techniques
Typical permanent repair techniques include the following.
a) excavating the defect and blend-grinding to contour in accordance with API 579-1/ASME FFS-1 (also refer
to ASME PCC-2, Article 304 for guidance on flaw excavation and weld repair);

This reference is to what section / paragraph in API 579-1/ASME FFS-1 ? I have gone through the the API 579 and really could not find place guiding for excavating the defect and blend-grinding to contour...

Question two:
8.3.3 Filler Metal Strength for Overlay and Repairs to Existing Welds
It says in there:

"The repair thickness shall not be more than 50 % of the required thickness of the base metal (this excludes
corrosion allowance)"

What if defect in existing weld goes beyond 50 % of the thickness of the base metal, or even goes through the weld thickness ?

 

[Trestala]

I have gone through the the API 579 and really could not find place guiding for excavating the defect and blend-grinding to contour...

The profile or contour requirements are what is defined in API 579-1. This would depend on the kind of defect you have. There are cases in which the defect is shallow (e.g. a shallow crack) and based on the assessment you would not require any weld repairs. However, that crack can propagate under cyclic loading for example. In that case, you can just excavate the area and contour it to lower the stress intensification around the crack so that it would fit the requirements of API 579-1 and that flaw is transformed and now acceptable.

What if defect in existing weld goes beyond 50 % of the thickness of the base metal, or even goes through the weld thickness ?

This is a condition/requirement if you are using a filler material with lesser tensile strength of the base metal. If the defect is more than 50% of the thickness, just use a weld filler that has the same or greater minimum specified tensile strength.

 

[mariolucas75]

If there is a vessel under cyclic loading conditions and it has a crack-like flaw near one of the nozzles - which paragraph of 579 will guide me to have excavating the defect and blend-grinding to contour in accordance with API 579-1/ASME FFS-1 ?

 

[r6155]

Do not expect that every defect situation is explained in API-579 or similar. A welding supervisor is supposed to know how to repair any welding defect in pressure components.

Regards