Weld Terminology
Weld Terminology
(OP)
I am writting a report to the customer regarding repair methods of cracked fillet welds and butt welds found in the belly pans of steam drums. Carbon steel to carbon steel.
Cracked welds of this nature are fairly common. I know how to fix it the correct way, however the contractor typically does nothing more of a repair than simply welding over the cracks. (again and again and again)
The question:
Is there a definition of this type of weld repair? Where as the the cracked weld remains as-is and simply covered up with more weld. The closest I come up with is calling it a plug weld.
Cracked welds of this nature are fairly common. I know how to fix it the correct way, however the contractor typically does nothing more of a repair than simply welding over the cracks. (again and again and again)
The question:
Is there a definition of this type of weld repair? Where as the the cracked weld remains as-is and simply covered up with more weld. The closest I come up with is calling it a plug weld.





RE: Weld Terminology
RE: Weld Terminology
I am not sure whether the question was regarding the liner repair. I have the similar problem with our steam drum and would like to have more input to it. Apparently during fabrication, heat treatment was not effective and now we have cracks in almost all the nozzles. Each shutdown these cracks are measured for compared with critical size which is a very expensive proposition. Does any one have similar experience of having this problem, and the behavior of these cracks with time. Do these cracks also grow in size and instensity and what is the mechanism (the shell material is carbon steel.)
regards
RE: Weld Terminology
The nozzle cracks are probably corrosion fatigue, based on what I have seen from prior steam drum nozzle cracks on one of our B&W units some time ago. This unit was cycled, which really drives the crack propagation rate.
The cracks are not necessarily self limiting in depth as you would expect from a thermal fatigue damage mechanism because you have corrosion that helps propagate the cracks. The corrosion fatigue cracks normally initiate along the toes of the nozzle attachment welds.
Repairs should be performed (remove the cracks and weld repair using one of the NBIC alternative welding methods) along with blend grinding to reduce stress concentration at the weld toes.
RE: Weld Terminology
regards
RE: Weld Terminology