Curvature of reinf pad of lifting lug 2

[dungun]

Dear All.
My fabricator installed 4 lifting lug on the 4m OD vessel with weight about 40MT. However the End User question (rejected) about curvature of the reinf pad for lifting lug, the curvature seem "bulged" due to the manual pressing forming. The "bulge" curvature height by 4.1mm from the outer shell curvature of the vessel.

My questions

1) How to determine the safety of the lug if bulge in question?
2) Where to get the "acceptance criteria" of the curvature
3) How to do NDE to determined the strength of reinf pad

We aware the curvature of the structure increased strength.

Any help please

Thanks

 

[r6155]

Which is the reasonably tolerance required by the end user?… ”UG-82…….formed and fitted to conform reasonably to the
curvature of the shell or surface to which they are attached".

Regards
r6155

 

[dungun]

Dear r6155

Thanks for the response, actually the Tolerance by End user is absent. This is make the problem started. My argument using UG80 (UG 82 .... I will check)

TQ
Dungun

 

[r6155]

If the tolerance by end user is absent the problem is not technical, it is commercial.

Regards
r6155

 

[dungun]

Dear r6155



TQ

 

[dhengr]

Dungun:
I don’t have copies of the codes you might be working with, and you didn’t bother to provide a sketch with sizes, thicknesses and dimensions, but here’s my two cents worth on the subject. In either case, a flat or curved re-pad, you have to get the load (moments, shears, etc.) from the lifting eye pl. to the re-pad and then from the re-pad to the tank shell, paying some attention to the geometry and shape of the parts. And, the fit-up btwn. the re-pad and the tank shell at the edges must be tight enough so that you can make a good sound weld. That means that the gaps btwn. the two parts have to be tight enough so that the root pass is a good sound weld. A large gap at the root pass leads to a poor root pass, lack of good fusion, susceptibility to cracking starting at the root, and it also reduces the throat of the weld. 4mm is a pretty large root gap, I would try to make the root gap (re-pad edges) fit the tank shell better than that.

 

[r6155]

Can you omit the reinf. pad?

Regards
r6155

 

[dungun]

Dear dhengr

Sorry no sketch.

We provide calc using WRC 107 - SATISFACTORY on the part as you mentioned.
4.1mm is the "bulge" at the middle... the welding ok.
So many theory such as welding HAZ, expansion etc
But i have only one - bulge!

TQ

Dear r6155

If omit .. mess to remove it.

I think finite element is the best simulation....

TQ

 

[r6155]

My proposal
1) Cut lifting lug, left in place reinf. pad rejected
2) Near rejeted pad, in the same vertical centerline, install a new lifting lug without reinf. pad

Regards
r6155

 

[dhengr]

Dungun:
“Sorry no sketch.”.... That just doesn’t do the trick, doesn’t help solve your problem. Your description of your problem is really poor, if you really want help. What’s a bulge, in what direction, in, out, up, down, where, and what orientation with respect to the lifting lug pl. and the tank shell? We just can’t see it from here. If you know that the welds are good, and the bulge means that the curved shape of the re-pad changes a little over its width or height, I suspect that won’t make too much difference in your analysis, btwn. a flat pl. and a shaped pl. with a cylindrical form, with a shape radius of 50 or 60". You will get some distortion of the re-pad when you weld the lug pl. on, and more so as that weld gets larger. For example; if you lay a 24" sq. by .75" thk. pl. (a re-pad) flat on a table; then weld a large lifting lug pl., in ‘Tee’ fashion, perpendicular to the flat pl.; I would expect the edges of the flat pl. to start to lift up off the table. Thus, the flat pl. will become somewhat concave (dished), with the concave up as it sits on the table. The HAZ doesn’t really have anything to do with it. It has to do with the nature of material distortion when you weld. And, you really haven’t done a good job of explaining what the customer’s questions or objections are, so that we could respond to them.

You want our help, but can’t waste the time to do a sketch or properly describe your problem and the actual conditions. Sounds like you don’t really want help if it involves much effort on your part. And, if that be the case, why should we waste our time trying to guess at your problem or its solution?

 

[r6155]

I agree 100% with dhengr

r6155

 

[Christine74]

I don't understand what's unclear about the OP's description. The middle portion of the reinforcing pad ID bulges 4.1 mm above the OD of the cylinder. In other words the reinforcing pad has a slightly smaller radius than it's supposed to have, leaving a slight gap.

-Christine

 

[dhengr]

Christine74:
Then, the real question is, does he really know that the welds are o.k. with a 4mm gap at the roots of the welds, or do they just look purtty on the surface. At least one of those roots will very likely have a fairly significant tensile stress field running perpendicular to and right across that root pass. Not a good design detail or stress condition. But still, the analysis of the re-pad pl. itself would not likely be affected, because the radius has changed so little, or it’s still almost flat. 4mm (4.1mm?, really?) out of radius or out of flat is not a big deal, while 4mm gap at the root might be. That’s one of the things I said (meant to imply), btwn. the lines, above. You have to know the orientation and shape of this bulge?, because two of the four side welds on the re-pad pl., all likely fillets, will be much more critical w.r.t. the lifting loads and moments than the other two welds. The latter two welds see primarily shear stress over the middle 2/3rds. of their length, so they are somewhat less critical w.r.t. this weld problem. And, some grand FEA of the problem won’t help much either, because if you don’t have a fundamental understanding of the problem, I can’t imagine how you would know how to model it, or if the output was really meaningful. Furthermore, please show us your FEA model in the area of those welds, along with the output in that area, and explain the results to us. I defy you to make any sense out of the FEA output around welds in most FEA models.

 

[dungun]

Dear All.
Thank for your response.
I will comeback to you.im outstation now.

Cheers
Dungun

 

[KevinNZ]

Assuming the problem is as described. With correct even edges around the pad, so the welds are OK. The vessel is large so the pads would be large too and the gap/bulge of 4mm is small compared to the pad. Now close contact or 4mm gap does not make any difference on how the loads from the lifting lug are transferred to the pad welds. This lifting load pulls away from vessel wall. A small gap just become a larger gap under load.

I agree with R6155 problem is not technical, it is commercial