Allowable stress for ductile iron

[fluffyflow]

Hi, I am currently attempting to design a ductile iron pump casing using Sec. VIII div 2 and have found that ductile iron maximum allowable stresses are not found under Table 5A in Sec. II-D and only under Table 2A for Design Stress Intensity which I understand should only be used when designing to Section III Classes 1, Tc, and SC. I understand the values of stresses in each table are based on different theories of failure and design margins, and are not interchangeable.

So, I suppose my question is, does this mean it is not suitable to design a ductile iron pressure vessel to Sec VIII div 2, and if so (which I'm guessing is the case) why is that? Just because of the failure theory associated with that section of code? Any insight and further detail is much appreciated. Thanks.

 

[TGS4]

That is likely a question that should be asked of the Code Committee itself.

 

[EdStainless]

Why would a pump casing be designed to SVIIId2?
Send a letter to the committee, but first check old code case lists, see if it has been asked before.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[metengr]

The code committee is not going to answer any questions unless you are requesting an interpretation, revision or code case. Otherwise, this would be considered consulting. If the material is not listed that is because either it is not permitted, or requested for use.

 

[fluffyflow]

Thank you for the responses. I will look into old code case lists to see if the question has been raised before.
I know the BPV code isn't directly applicable for use on a pump, however sometimes customers request we do so, and so we do.

Can you shed some more light as to why raising this question would be considered consulting? I understand why gray cast iron would provide concern for use in a pressure containing device, however ductile iron should alleviate most of those or maybe I am just missing something obvious...

 

[EdStainless]

If it were listed you could ask about suitable stress, but since they have chosen to leave it out then they are not obliged to comment at all.
"The specifications speak for themselves".......

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube