Pressure vessel - weld corrosion assessment.

[HenryT200]

Hello,

According API 510, "5.10.1 Inspection for [highlight #FCE94F]weld quality is normally accomplished as a part of the requirements for new construction[/highlight],
repairs, or alterations."

however it is common to find a pitting/corrosion/MIC (Microbiological Induced corrosion) on in service welds pressure vessel, what would be the assessment code for this?
if follow clause API 510: accomplished as part of requirement for new construction, mean whatever defect greater than design code eg: ASME VIII div 1 have to be repaired?

this doesn't make sense, even crack also can be assessed with API 579, let say just a 2mm pitting found on welding, it required to repair the vessel immediately due new welding requirement does not allowed it to be happened.

Please correct me.

Billion thanks.

 

[mk3223]

If I understood the question correctly, the vessel constructed in the shop needs to be inspected per API-510, and any weld defect found requires to be repaired before put it in service.
The API-579 assessment is for the existing vessel in operation, but not used for the new construction.

 

[weldstan]

API 510 is for repair/alteration. The repair weld or additional welds are to be inspected per the original Code of construction.

 

[HenryT200]

dear mk3223 & weldstan,
Thank for your reply, as a summary of my question is: how to assess the pitting corrosion on weld for in-service pressure vessel,

however, after discussion with my colleague, "5.10.1 Inspection for weld quality is normally accomplished as a part of the requirements for new construction" this referring to weld defect such as porosity, undercut, excessive roof penetration and etc which is not applicable for pitting corrosion assessment.

for pitting corrosion assessment on weld should follow "API 510 section 7.4" by using construction efficiency (E) for Trequired calculation.

please correct me if i was wrong.

Thanks

 

[mk3223]

The API-579 also has the guidelines to assess the pitting corrosion on the existing equipment. Basically, the assessment is to determine the extent of the corrosion or damage on the equipment due to the service, and to decide if the equipment needs a repair immediately, or is safe for continuous operation for how long.

 

[weldstan]

API 510 does not deal with assessing corrosion in service. When it is determined by the Owner's engineer (per API 579 or through experience or other analyses) that the specific corrosion requires repair by welding, API 510 defines the inspection requirements for the completed REPAIRED weld.

 

[HenryT200]

Dear Weldstan, i agree with you statement regarding "API 510 defines the inspection requirements for the completed REPAIRED weld". which is follow ASME VIII or BS 5500.

Dear Weldstan & mk3223.
As a conclusion of my discussion with my colleagues.
Example cylindrical shell thickness required for circumferential stress calculation:

​

Treq = PR/ (SE − 0.6P)

​

(E = assume to be 1 for metal lost on shell always from weld distance of greater of 2x Treq or 1"

​

(E = Construction Efficiency as per RT1, 2, 3, Eg: E = 0.85 for metal lost on weld of within 1" or 2x Treq)
api 510 7.4.5 Joint Efficiency Adjustments
therefore Treq calculated for shell will be greater than Weld region.

if assesment above failed under section 7.4 then only proceed to API 579 for more rigorous calculation.

hahaha. cheer.