Do I have to R-stamp if I modify platform clips? 1

[rikywere]

I have a U-stamped pressure vessel on field with wrong platform clips. There is also a repad inbetween vessel and clip. The thing is that clips and platform mismatch and I can solve the problem cutting the top of the clips and doing minor modifications on the platform to acomodate it to current clip locations. Can I cut and weld on the clips without R-stamping? the clips are 500 mm long and I would need to cut arround 200mm and weld at the farest place from the vessel. It is 300mm from vessel (from the pad in fact). Can I just do it on field and that is all or does it have any other implication?
Thanks in advance

 

[metengr]

No R-Certificate is required as long as welding is not done to the vessel pressure boundary. You can weld to the repad but not the vessel base material.

 

[rikywere]

Hello,
Nice, but this modified platform will create different loads that should be checked on the vessel wall, right? Additionally, I will also use lifting lugs to weld some bracings. I can make the calculations, but vendor is giving a waranty for the equipment bassed on their calcs and they do not have to trust mine. I can ask them to redo the calcs, I do not know if they will be willing to... I thing they should because in the end, they are who put the clips in the wrong place... Any opinion?
Thanks,

 

[metengr]

Yes, by all means the loads should be checked to ensure you don't over stress the attachment or the vessel wall. You can do whatever modification you want to components outside of the attachment weld to the vessel wall. The rest of your problem is between you and the vendor.

 

[racookpe1978]

Figure it this way: The original pressure boundary (the original pressure-resisting or "strength" steel) is not going to be modified by the welding and cutting on the slips, right?

If you welded NEW clips on to the pressure boundary, then you would be affecting the pressure-resisting steel of course.

So, to the original question of the r stamp: No.

To the effect of the implied question: Do you have to "re-analyze" the stresses on the entire original steel assembly and clips and "live load" as it is is lifted and twisted into the erected position? OF COURSE! (Because the change in the clips DOES affect those specific (and now undetermined!) rigging point loads of the original clip welds onto the original PV walls and footing and clips.)

Now, they might still be good. Might even be a bit less, might be a bit more but within realistic safety margins. Murphy Law says "no" but what does he know about unknown problems? 8<)

Does the vender have to pay for the re-analysis? Of course they do.
Does the vender want to pay for the new analysis? Of course not.