Question about weld metal strength for a lower material strength nozzle in a high strength shell

[solinar]

A client is welding a small solid alloy (nickel 200 N02200) nozzle with an allowable stress of 18.6 ksi into a SA516-70 (allowable stress 20ksi) shell. The nozzle is being inserted into to the shell with a full penetration weld and fillet, such as UW-16.1 (c) (d) or (e). The filler metal being used is Nickel ErNi-1 (97% nickel) which has a lower tensile strength than the 516-70.

This means that there is a small portion of shell that has been beveled back of 70 ksi material, and rewelded with 66ksi filler metal. If it was a stab-on type connection, I wouldn't be as concerned, as the area around the nozzle would still be SA-516-70, but in this case, some portion of the shell that has been beveled back for welding, is being replaced with low strength material.

Normally, I would think the proof is in the PQR used to prove the weldment, but in that case, the tensile stress specimen broke in nickel base metal at 68 ksi, which proves the weld metal was stronger than the nickel base metal, but it didn't prove it was stronger than 70 ksi.

My main question is, is there a section of code regarding this case? Something I am missing in UW-16 or elsewhere that addresses using a low strength filler metal for this joint? Admittedly, I am no Section IX expert

 

[SnTMan]

solinar, inferring Sec VIII, Div 1. How small a nozzle? Small sizes can possibly be exempted from reinforcement per UG-36. Otherwise UG-37 rules should account for the lower nozzle and weld metal allowables.

Hopefully, your client has performed the calculation properly. Aside from this if the weld procedure is qualified, I don't see as issue.

Regards,

Mike



The problem with sloppy work is that the supply FAR EXCEEDS the demand