B31.3 Unlisted Matieral 303SS

[kcme2005]

We are trying to get a level control product a CRN (canadian registration number) through TSSA. The unit is made from a slug of SS, 2in in diameter by 5in length. It has NPT threads on the outside to engage in the process, and a 1 in hole bored half way in down the center axis for a float and magnet system.
We were able to perform design calculations (at 400°F) based from equations in B31.3 for the 316SS unit from allowable stress data in the code book. However, we also make an identical part out of 303SS, which isn't a recognized material in the code book. TSSA will not list the 303SS without the calculations.

Does anyone know where we can get an allowable stress value for 303SS at 400°F (without having to have a test lab do it for us)? Or does anyone know the code well enough to know another way we could get the 303SS listed?

We already have the 316SS listed, and we need to have the 303SS listed as well.

 

[metengr]

ASME Section II, Part D, Table 3 lists the allowable stress values for ASME SA 320 Grade B8F, which is AISI Type 303 SS. At 400 deg F, the allowable stress is 12.6 Ksi. This material is permitted for use at 400 deg F for ASME Section III (nuclear) applications. For ASME Section VIII Div 1 and 2, the maximum permitted service temperature is only 100 deg F.

ASME B31.3, paragraph 323.1.2 does permit the use of unlisted materials provided they are manufactured to a published specification. Allowable stresses can be calculated using the method in B31.3 or a more conservative approach.

Make sure that you have evaluated all service conditions for using this material.

 

[ApC2Kp]

kcme2005,

There may be reasons the 303 SS is not listed as an accepted material. The resulfurized stainless material gives it good chip forming qualities in Swiss automatic barstock machines and other turning/threading operations. Sulfur content of 0.18% to 0.40% is much higher than the 0.03% of more typical corrosion resistant 304 or 316 SS. Welding is more of a problem - that might be the reason B31.3 didn't include the 303 SS. Your product might not have any welding in its design, so it might not be a concern.
An old Carpenter Stainless Steel applications handbook had a sentence advising their 303 SS Project 70 material not be used for pressure vessels or piping. This was likely due to weld quality issues. Yield, tensile, ductility, and creep qualities appeared to be OK. There was not data for brittle transition temperature, so that might be one thing to check out in regards to possible low end temperatures of your application.