Rewelding Existing Weld Joints

[napster385]

Hi Everyone,

When an API 650 tank is dismantled and relocated to a new location, can it be welded on its existing weld joints? Or is it required to cutoff the Heat Affected Zones (approx 2in) on each sides/edges of the plate before rewelding? The API 653 only states that "the existing weld joints shall meet the requirements of the as-built standard."

Appreciate any advise. Thanks.

 

[metengr]

The plate containing the previous weld joints should be prepared for welding by use of a new weld prep followed by surface NDT before re-welding.

 

[napster385]

Thank you for your reply metengr.

Does this mean that we don't need to cut off the HAZ area? We will just clean and prepare the plate edges to undergo a new welding process?

 

[metengr]

Yes, if the carbon equivalent (CE) is equal to or less than 0.45 for the plate material, there should be no concern with excessive hardness of the heat affected zones.

 

[napster385]

Ok. Thank you.

Follow up question: What if I weld a high strength steel plate for pressure vessel application? Will there be any special requirements for rewelding? Especially if the plate thickness is over 36mm.

 

[metengr]

I would qualify a WPS with similar plate material where the edges have been welded, the weld has been removed, NDT and re-welded.