Repair of Weld Crack on SA 516 Gr.70 lifting Lug Welding 1

[ak1965]

I wish to repair a crack in Fillet weld of a support plate on one of the 02 lifting lugs on a vessel. The material is A 516 Gr.70.

Thickness of plate of Lug is approx. 25 mm. What can be the best welding procedure for repair ?

Do we require a local Srtress relieving or the whole vessel needs SR ?

Which can be the best welding electrode for this reapair ?

 

[metengr]

For a support plate fillet weld crack, I would suggest the following;

1. Remove the crack using a burr grinder and grind until the defect is removed or you reached the parting line of the weld joint.

2. Clean the repair area and verify defect removal using WFMT (wet fluorescent magnetic particle) or LPT (liquid penetrant test).

3. Apply a local preheat of 200 deg F, and hold for 15 minutes before welding.


4. Use the SMAW process and E7018 H4 (low hydrogen) weld rod.

5. After the completion of welding, perform a local post weld heat treatment of the repair area at 1100-1150 deg F for 1 hour at temperature. I would suggest using electric resistance heaters with TC's to monitor post weld heat treatment temperature.

The entire vessel does not need to be post weld heat treated. The size of the band for post weld heat treatment should be based on the requirements in the National Board Inspection Code (see RD-1100) or I would suggest using a circular band that encompasses the entire weld repair region with a temperature gradient at or less than 250 deg F/ft away from the weld region.

 

[ak1965]

Dear metengr

thanks for a good advice. i shall be doing the activities , but apprehensive about the post repair NDT as the temp. wd be high . wd MPT be right choice ?

 

[metengr]

ak1965;
Yes, I did not address post repair NDT, which must be performed as part of this repair. I would suggest wet fluorescent MT after the weld cools to ambient temperature.

 

[ak1965]

yes i understand your reference. However i was referring to the post repair PT ot MPT either of them as RT may not be possible with the weld profile .

 

[metengr]

ak1965;
Use WFMT after the weld repair is completed. My suggestion for MT or LPT in step 1 was to assure the defect was completely removed before welding. There is no requirement for RT.

 

[JoeTank]

I think the weld repair issues have been well addressed thus far, but shouldn't the reason for the cracking be investigated first? Maybe there is a design problem that needs fixing too.

Joe Tank

 

[metengr]

Joe;
Good point. In some cases it can be difficult to determine the root cause because with fillet welds, I have seen root cracks propagate to the weld face because of IP or a large notch (workmanship problem), lack of fusion, etc. If this is a one time defect in a saddle plate fillet weld, I would repair it and let it go. If this happens again or more develop over time, you have a definite problem related to design.

 

[vesselguy]

metengr,

This is just a fillet weld on a lifting lug. I don't understand why the PWHT? Just wanna know.

 

[JeffLester]

Joe -- I have to agree with you. Without knowing the history of this support plate and the associated fillet weld, I would be hesitant to repair and put in service. If the support plate has not been loaded before (i.e. new vessel), then a repair of a faulty weld might make sense. Having seen cracked weldments "function" for a period of time, only to fail unexpectedly with fatal consequences, I would do more investigating before repairing. Just my two cents... Jeff Lester

 

[metengr]

vesselguy;
The saddle plate thickness is reported to be 25mm, and I would presume the shell thickness is at least 25mm, maybe less. Considering the base metal thicknesses and the presumed size of the fillet weld throat and intended application, I felt PWHT would be a conservative approach.