Help understanding Section 2 Part D
Help understanding Section 2 Part D
(OP)
We are designing a part and trying to clarify for our suppliers and vendors what parts are allowable under Section 2 Part D. I have read the intro, and don't see any explanation about when the temper and thickness given in the charts apply. Is this the temper and thickness of the raw material or the finished part? If we are machining a vessel roughly a 7" cube with 1" thick walls out of a single piece of material and then welding a flange on, is the thickness based on the wall thickness of the part (1") or the thickness of the material used to make it (~8")? And does it have to be one of the allowable tempers before any processing, after machining or after welding? Thanks.





RE: Help understanding Section 2 Part D
Thermal treatments after welding are followed by construction rules in the applicable code book section.
RE: Help understanding Section 2 Part D
RE: Help understanding Section 2 Part D
Second, after final fabrication is completed and welding was performed OR you decide to subject the finished component to final heat treatment after welding to achieve actual strength properties makes no sense either because of distortion to the component.
This is why material should be procured with final heat treatment or at least formed and heat treated before final fabrication.
RE: Help understanding Section 2 Part D
As to thickness, I think that would be the thickness of the raw material. It's the original forming processes that impact material properties the most. For example, SA-240 S31254 1/4" thick has lower strength than 1/8" thick, but you can't improve the material strength just by machining it down; it's the rolling that matters.
Now that's just for the materials. Post-weld heat treatments are a different beast altogether, controlled by testing coupons that are exposed to the same thermal history as the real part.
RE: Help understanding Section 2 Part D
RE: Help understanding Section 2 Part D
Of course, a final N+T is required with this alloy, as the anneal at 1650 F for 3 hrs is an example of overtempering for this alloy. But their response now raises a concern regarding every F91 piece form that foundry and every F91 valve from that valve company.
RE: Help understanding Section 2 Part D
The mill is absolutely correct in their interpretation, SA 387 is a plate specification and what you do with the plate after it is supplied from the mill or foundry in accordance with the heat treatment requirement below is the Purchaser's problem.
Grade 91 plates shall be normalized at 1900
to 1975°F [1040 to 1080°C] and shall be tempered at 1350
to 1470°F [730 to 800°C].
Seems straightforward to me....
RE: Help understanding Section 2 Part D
Well, almost. The purchase specification had included the requirement for a final N+T following all F91 hot work, but such a requirement either was not forwarded by the valve vendor to the foundry that supplied the outlet diffuser ( dished plate), or it was not read by the foundry. Of greater concern is that the valve mfr believes the part does not require a final N+T, regardless of the material breach of contract and regardless of the metallurgical neccesity, as it is not a "pressure part" subject to ASME code.
We are aware that several bypass valve outlet diffusers had failed afer a few years service at some Florida CC plants ( valves by another vendor ), and now we have a clue as to why such a short life can be expected.
RE: Help understanding Section 2 Part D
We normalize ourselves and save substantial money.
what we do is buy the plate as rolled, but have the MTR done on coupons that are normalized at mill, then normalize ourselves to the same procedure as mill.
Just like head manufacturers do. Normalize in conjunction with hot forming.
RE: Help understanding Section 2 Part D
But the valve manufacturer might have a case when they say the ASME code doesn't apply. There is nothing wrong with building a valve that doesn't meet code, and many don't. It's local regulations and system design that determines which things have to meet code or not, which code, and what section. Does this valve have a code stamp on it? Did the purchaser ask for a valve that meets code?