welding over a cracked weld... sounds wrong
welding over a cracked weld... sounds wrong
(OP)
Hey guys!
A friend of mine (yea right) was talking about a cracked weld that was found on an offshore platform flair boom during a shut down. I don't know the details but this is one of the structural welds and I am assuming it is one of the welds that connects one of the diagonal tube members to a horizontal tube member on the boom truss. I am not sure if the welds are full penetration welds but I am assuming they are. Anyhow, a 40mm crack was found and in the end they decided to just weld over the crack as a repair. Something about this just sounds really sketchy. Should they not have gouged out the old weld material and just done a brand new weld?? It will be a while before they do another shut down so a new repair will not happen for at least a year. Would love to get some feed back.
A friend of mine (yea right) was talking about a cracked weld that was found on an offshore platform flair boom during a shut down. I don't know the details but this is one of the structural welds and I am assuming it is one of the welds that connects one of the diagonal tube members to a horizontal tube member on the boom truss. I am not sure if the welds are full penetration welds but I am assuming they are. Anyhow, a 40mm crack was found and in the end they decided to just weld over the crack as a repair. Something about this just sounds really sketchy. Should they not have gouged out the old weld material and just done a brand new weld?? It will be a while before they do another shut down so a new repair will not happen for at least a year. Would love to get some feed back.





RE: welding over a cracked weld... sounds wrong
Steve Jones
Materials & Corrosion Engineer
http://www.linkedin.com/pub/8/83b/b04
RE: welding over a cracked weld... sounds wrong
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RE: welding over a cracked weld... sounds wrong
Thanks for the insight!
RE: welding over a cracked weld... sounds wrong
On thick vessels, the cracked surface is excavated about 3/8" down and a total width of 3/8" [3/16" either side of the crack, and past the ends of the crack about 3/8". The mechanism is that when this partial-penn weld is made [in a specific sequence, with specific heat inputs [bead widths], the weld shrinkage will pull the edges of the crack togather. Saves a deep excavation that would cause PWHT to have to be used.
Problem is that the crack has to be FULLY mapped using a highly skilled UT tech, and a lot of Finite Element analysis done of the stresses in the region of the crack, and a fair ammount of specific, weld bead-by-bead Weld Engineering. Then everly 1-2 years [every opportunity] that crack has to be fully resurveyed, using that highly qualified UT tech. This is very Engineering intensive $$$, and adds one more mandatory inspection area for every shut-down $$.
The other Embedded Flaw technique is simpler, and only applies to socket-welds. The weld is peened shut, while in operation, using a center-punch until the [water] flow stops. A root of E-6010 is woven over the peened crack. Then the same ammount of weldmetal is applied to that weld as was initially required. Thus if the socket-weld size was 1/4-inch, there will be the original 1/4-inch weld, the 6010 'root', and another *full* 1/4-inch of weld layered onto the socket fitting and pipe. It makes a horrible looking knot of weldmetal, but it is EPRI approved and seems to work well.
Do not attempt the second one with onstream-flammable [or combustible] fluids.
RE: welding over a cracked weld... sounds wrong
quite intersting stuff! do you have any references that explains the processes further?
RE: welding over a cracked weld... sounds wrong
Me, I'm a "gouge the crack ALL the way out" guy. I would use the "peen it shut" technique for a *temporary* repair, to limp along until the plant can be shut down.
RE: welding over a cracked weld... sounds wrong
RE: welding over a cracked weld... sounds wrong
RE: welding over a cracked weld... sounds wrong