Toe Cold cracking of welds

[TANKO]

Good afternoon to all,
i have a question for you. During maintanace operations of a tank, it's necessary to open a temporary door in the 1° shell course.
After 2 months that door was welded and regularly checked with RT and MT with with no defect, some toe cold cracking appeared in the horizontal seam at 2/3 mm of depth (tk plate 45mm).
What could be the causes of such defects?

Thank you

 

[mk3223]

Could be resulted from the improper weld procedure or PWHT...
Suggest to have a Material Specialist to conduct a failure analysis for the weld defect.

 

[IFRs]

How does one "regularly RT" the weld? - the tank was taken out of service regularly?

It would help to know the grade of steel, the product stored, the temperature of the product.

Perhaps not enough preheat and moisture was not driven off during welding, possibly low hydrogen weld consumables were not used or not kept dry. Perhaps caustic attack.

For the original weld, was the back-gouged surface of the root pass and final pass (each side) examined for its complete length by magnetic particle or liquid penetrant methods and 100% RT also?

 

[TANKO]

Thank you to all for your replies, and, as you said, we think that is a problem of improper welder procedure.. cleaning weld seam, temperature maintenance during welding,moisture elimination etc etc..
I will inform you..
Thanks