CobusvanJ
Mechanical
- Dec 6, 2008
- 45
Hi,
A fabricator has welded some rectangular support pads to the shell of a tank for a client of ours, but did not adhere to specified weld clearances and has now submitted a non-conformance for us to review. The tank is designed in accordance with API 650 and 620 (conical bottom) and fabricated from SA-516 Gr. 60N (Group IIIA). In our engineering specifications it was specified that any welds must clear the main seam welds by 75mm or the requirement of API 650 5.7.3 whichever is greater.
To determine whether the non-conformance can be accepted, I have been looking at the requirements of API 650 and waiving those of our own specification.
Now when I read section 5.8 of API 650 I cannot find any specific weld restrictions for our tank, as the requirements given in 5.8.1.2 only applies to Group IV, IVA, V and VI materials. Does this imply that there are no restrictions on shell attachment weld clearances on tanks fabricated from other groups (such as Group IIIA)? In other words, can attachment welds be welded over main seam welds without angle on incidence / weld clearances issues?
For instance the fabricator welded a pad over a horizontal seam where the bottom edge of the pad runs parallel to the main horizontal seam. The pad extends over the seam by 5mm. Can this be accepted without violating API requirements?
Other pads clear the horizontal seams by 15 to 69mm and vertical seams by between 110 and 136mm.
Any advice would be greatly appreciated.
A fabricator has welded some rectangular support pads to the shell of a tank for a client of ours, but did not adhere to specified weld clearances and has now submitted a non-conformance for us to review. The tank is designed in accordance with API 650 and 620 (conical bottom) and fabricated from SA-516 Gr. 60N (Group IIIA). In our engineering specifications it was specified that any welds must clear the main seam welds by 75mm or the requirement of API 650 5.7.3 whichever is greater.
To determine whether the non-conformance can be accepted, I have been looking at the requirements of API 650 and waiving those of our own specification.
Now when I read section 5.8 of API 650 I cannot find any specific weld restrictions for our tank, as the requirements given in 5.8.1.2 only applies to Group IV, IVA, V and VI materials. Does this imply that there are no restrictions on shell attachment weld clearances on tanks fabricated from other groups (such as Group IIIA)? In other words, can attachment welds be welded over main seam welds without angle on incidence / weld clearances issues?
For instance the fabricator welded a pad over a horizontal seam where the bottom edge of the pad runs parallel to the main horizontal seam. The pad extends over the seam by 5mm. Can this be accepted without violating API requirements?
Other pads clear the horizontal seams by 15 to 69mm and vertical seams by between 110 and 136mm.
Any advice would be greatly appreciated.
