Welding on work hardened austenitic s/s 1

[Bartholomew69]

Goodday all;

I have a spherical presure vessel, about 8m in diameter, 5 bar design presure, 75 deg C design temperature, manufactured in 1980 to the Swedih Pressure Vessel Code, and the Swedish Cold Stretch Code. This code was basically used prior to the advent of duplex materials, by using thinner austenitic (316L) steel and 'stretching' it by overpressure to over its yield, thereby work hardening it and increaing its strength.

My problem is, we have a defect (stress corrosion crack under a compad) that needs repair. The original code calls for the cold stretch procedure to be repeated after any major repairs (roughly defined as greater than 100 mm diameter insert, or major welding).

We do not want to go this route and propose to cut out the defective area and insert a circular section from 316L (thicker (16mm) section calculated to ASME and tapered 1:3 to 6mm original shell).

What procedures do I need to take when welding onto work hardened austenitic s/s??

 

[metengr]

This type of repair can become a serious issue related to safety of the vessel. This can be construed as an illegal alteration to an existing pressure vessel because it violates the original code of construction!

In my view, it is not simply installing a "window patch" as in the original post. In addition to what you stated, I would expect some level of stress analysis because you have introduced a zone of inherent weakness in the pressure boundary of the shell that could effect membrane stresses and ultimately the fatigue life of the vessel.

 

[chicopee]

That's the problem w/ vessels made to other then non-asme codes. Such vessels can be made thinner and probably cheaper but when major repair is needed you have to scrap'em.