Different weld electrode allowable stress effect

[PMCap]

Gentlemen - perhaps one of you has some experience or can provide me some definitive direction or recommendations regarding the following:

Thanks in advance.

I am designing a Pressure Vessel shell.

ASME Section VIII, Div.1 Pressure Vessel
Shell - SA516GR70 2" thick
Liner - 1/8" SA240TP304L
Weld E309L
Backing Bar - SA240TP 304L
Design -Temperature 500 F
Pressure - 550 PSIG
PWHT per Code

Weld E309L electrode was selected because it is compatible with the liner and base materials and the L grade is more suitable (I believe) where PWHT is to be performed.

Questions: In designing the required shell thickness,does the ASME Code have a criteria pertaining to any affect on material allowable stress due to the Weld electrode choice when designing for required shell thickness? Per UCL-32, the weld metal is supposed to have better mechanical properties than the base metal "in the opinion of the manufacturer".

I've seen electrode manufacturer's published Tensile values of 82 ksi for E309L electrodes (at room temperature) which is better than SA516GR70 (Tensile = 70 ksi). However, I have no information to make comparisons at the design temperature of 500 F.

I would expect that perhaps at higher temperature the E309L electrode may have lower mechanical properties than the SA516GR70.

Of course I could always use 304L properties at 500F or use Inconel 625 electrode which definitely has better mechanical properties.

However, I am interested in your experience and opinions. Is any one aware of an ASME Interpretation, or other Code published criteria on this issue.

 

[metengr]

PMCap;
If I understand you correctly, what you have is a vessel with a clad surface over a substrate for corrosion protection. The clad and associated weld for this design would not be part of the pressure boundary thickness calcs. Part UCL is for a different design vessel, where the clading is given credit for the pressure boundary thickness.

 

[PMCap]

metengr

Yes I have a clad surface - however,I am welding into the clad non-pressure boundary type 304L material from one side only (no access to the back of the weld). As the root pass of the weld would be into the 304L backing, the entire weld would need to be as a minimum a P8 electrode to avoid cracking.

Thus the question pertaining to ASME Code criteria on use of this electrode and its affect on the design required shell thickness.

Paul