SA-517 Grades B and E

[jclsws]

Hello all,

We are in the planning stages to build an ASME Section VIII, Div. 1/MC-331 pressure vessel cargo tank. The vessels in our application are typically built from SA-517 material. I have seen two grades used for construction. Most are made from Grade E, but I have seen a couple that are made from Grade B. I know the basic differences in chemistry between the two, but not being a metallurgist I'm not sure how these differences affect my application. I would think that the Grade E with the higher Chromium content would give improved corrosion properties. I am concerned about Vanadium content in the Grade B due to the ASME Code specifying a maximum Vanadium content of 0.04% in the weld filler metal. My question is why would some use Grade B while most use Grade E, and which is the best for my application? The lading is noncorrosive.

 

[Guest102023]

The differences in alloy content are not intended for corrosion resistance. The amounts in Grade E won't buy you much anyway.

The alloying is done for hardenability reasons. The difference between B and E composition is considerable in that respect. That said, I don't understand why Table 2 shows common tensile requirements for all six grades.

"If you don't have time to do the job right the first time, when are you going to find time to repair it?"

 

[metengr]

First, this is a pressure vessel under Section VIII, Div 1 which would require review of ASME Section II, Part D for permitted material for pressure retaining service (Grades A, B and E) and allowable stresses. With that said, the selection should be based on allowable stress value (to minimize wall thickness) and weldability (PWHT concerns). Look at Table 1A in Section II and compare between listed Grades of SA 517 material, in lieu of the mechanical properties in SA 517 directly.

 

[jclsws]

Section II shows identical values for both grades in the temperature range I am concerned with (-20°F - 125°F). Section VIII Part UHT has the same PWHT and essential variable requirements for both grades. In essence the ASME Code makes no distinction in how the two grades are treated. The only difference is that Grade E is a P-No. 11B Gr. 2 material and Grade B is a P-No. 11B Gr. 4 material. My processes will likely be warm or hot forming of the head sections by a third party, cold working of the shell, tear-off pads, etc., flame and mechanical removal of material, FCAW and SAW, and PWHT. With these processes in mind, is there one of these grades that will give my welders and fabricators fewer headaches?

 

[metengr]

I would use SA 517 Grade B.

 

[jclsws]

Thank you for the help. I'm going to see what the availability is like for the Grade B.