Welding of SS Internal Head with CS Plates

[massad]

I have a situation here . Can anyone suggest that if we have to weld a SA-51670 plates with a SS316 backing strip then which electrode is best . Well I think root should be of 309 and then caping would be of 7018 OR complete 309 .. Can any one with welding knowledge suggest. I am also attaching a sketch of the weld detail.

Thank you and Best Regards
Assad

 

[metengr]

Use 309 stainless steel to butter the entire side of the carbon steel weld joint, first. You can switch to 316L filler metal to complete the rest of the weld joint - 309 to 316L.

 

[2468jjcr]

Ues E-309Mo or ER-309MO,See detail for ASME Section-II part-C, SFA-5.4 and SFA-5.9 and Section-II part-D, NONMANDATORY APPENDIX A METALLURGICAL PHENOMENA.
Regards.

 

[stanweld]

Why would you use a 316 SS backing strip to join A-516 to A-516?

 

[SnTMan]

massad, I don't know what's going on on the convex side of the head, but if you are stripping the cladding under the lap, you've got a crevice you probably can't backclad due to access.

Regards

Mike

 

[vesselfab]

Gentlemen, I think what he is doing is an internal head as shown in fig. uw-13.1 picture (f)

if this is the case then metengr is correct about buttering all the carbon steel with 309 then filling with a 316 filler.

I am not sure of the reasoning behind using the 316 intermediate head, but there must be a reason

 

[vesselguy]

massad,
Disimilar welds for pressure boundary is not a good idea and most company spec don't allow it. SnTMan is exactly correct.
You might want to weld the cs shells together normally then weld overlay to restore your cladding (I assume you are using clad). Over your cladding, you can weld your S.S. head to S.S. clad or weld overlay. I would prefer a butt weld of the head to a support nub made from build up weld overlay. For this nub, you should 100% UT per SA578 and PT.

 

[vesselfab]

i did not see the picture of the joint ealier showing the joint. sorry for the redundant comment

i for one don't remember ever seeing in a spec that a disimialr seld is not allowed for pressure containing boundary. ASME has a joint design specified for an intermediate head that separates two chambers uw-13.1 (f)

if this is the case, you can not weld the shells together and then just slap the head in there. the outside butt weld is to bond the head to the two shells using a wide root gap.

this is a difficult joint considering the cladding.
sealing on the convex side of head to the shell is the problem. And the cladding will most likely not withstand the shear

perhaps the clad can be left in place at the outside butt weld, but stripped back at the fillet weld to shell joint which would be welded with 309/316 and then clad restored after that joint was made using 309/316

the outside joint would also have to be made 309/316 as metengr described earlier.

see the picture attached

this would all have to be run by the AI i am sure since it is an unusual joint.