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Discussion Forums - The Hendrix Group
HomeHomeDiscussionsDiscussionsOil Refinery Co...Oil Refinery Co...weld crack during hot tappingweld crack during hot tapping
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9/7/2009 10:00 AM
 
I need the expert opinion regarding the following issue.After we weld 2"-Sch160# weldolet with connected flange(1500#)on existing 8" seamless pipe(1/2" WT-CS)while in service for hot tapping operation, we observed the crack running across the pipe surface between two weldolet connection. What is the reason for getting the cracks on the pipe surface between these two weldolet areas? We suspect that due to shorter distance between these two weldolet joints(20 cms between edges of two weldolet welds)the solidification/shrinkage cracks were generated due to overlapping of HAZ of two weld joints. Is it true? Is there any standard mentioning the interdistance between two hot tapping connection close to each other?What is the suggested distance if two connections are to be made close to each other?Will excess heat input generate surface crack after weld cooling?The line was not leaking after welding the weldolet(before hot tapping)and it is understood that cracks are not penetrated up to pipe inner wall. Thanks in advance
 
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9/7/2009 10:00 AM
 
normaly the minimum distance to weld adjacent seams is 50mm I think that yous 200mm distance gives you a safety margin to have HAZ sobreposition. I think that your crack is due to bad welding practices related with cleaning, welder or filler metal. luis
 
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9/8/2009 10:00 AM
 
Any code reference for interdistance between two hot tap connection. We had a crack on the pipeline and not the weld.Weld is in sound condition.
 
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HomeHomeDiscussionsDiscussionsOil Refinery Co...Oil Refinery Co...weld crack during hot tappingweld crack during hot tapping


  

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