Forging pressurized parts
Forging pressurized parts
(OP)
I want to fabricate a metallic polar boss, which I would classify as a nozzle (large diameter) for a Section 8, Division 3, high pressure, FRP tank. I want to make sure that I have the proper material cert for my inspector. I want to make the part out of 316 stainless round bar (probably SA-479 annealed, while applying CODE CASE 2156 for hollow parts with large diameter), which appear to be approved materials per Section 2 and 8.
My questions:
1. Am I permitted to FORGE the SA-479 annealed stainless to near-net shape, then post-machine?
2. Or should I have it certified to SA-965 (316 Stainless forgings) as a near-net shape part, then post-machine??
3. Does that mean I have to extract coupons from the near-net shape parts for tensile testing/ultrasound NDE testing? I believe SA-965 is the only way to buy the material, correct? This path would require that I find a forging shop that can supply to SA-965, and also provide the extra testing.
Thanks.
My questions:
1. Am I permitted to FORGE the SA-479 annealed stainless to near-net shape, then post-machine?
2. Or should I have it certified to SA-965 (316 Stainless forgings) as a near-net shape part, then post-machine??
3. Does that mean I have to extract coupons from the near-net shape parts for tensile testing/ultrasound NDE testing? I believe SA-965 is the only way to buy the material, correct? This path would require that I find a forging shop that can supply to SA-965, and also provide the extra testing.
Thanks.





RE: Forging pressurized parts
I believe the correct path is to buy the rough shaped part to SA-965 as a forged part based on my interactions with a forging shop. It looks like they can outsource testing that is required.
Does it appear like I'm on the right track? I'm a bit new to ASME code requirements.
Thanks.
RE: Forging pressurized parts
RE: Forging pressurized parts
Sure.... FRP and 700 bar....that is what he said....!
and Im willing to bet that this is the first FRP vessel that he has designed....
I don't see a problem here.....Uuuummm .....do you ?
RE: Forging pressurized parts
RE: Forging pressurized parts
RE: Forging pressurized parts
Not familiar with Sec X, so if you say 15ksi can be done .... but that didnt answer my question.
RE: Forging pressurized parts
The OP was about a metallic polar boss. According to ASME Section X, for a Class III FRP vessel, metallic pressure parts must comply with the applicable requirements of ASME Section VIII, Division 3.
Didn't you ask if you are right in saying that FRP = Fiber Reinforced Plastic? And my answer was "Right."
RE: Forging pressurized parts
RE: Forging pressurized parts
To answer my original question about forgings... I am almost certain that if I buy a forging to SA-965 (forgings) for a metallic part and have it certified by the forge shop, then I post machine, then I will have all the necessary paperwork for the AI. I also discovered that my part does NOT exceed the NPS 4 size, which means CODE CASE 2156 (for parts made of bar) is irrelevant. In fact, the CODE CASE might be irrelevant from the fact that I am using a forging, not bar stock (even though the forging is originally pressed from bar). (Feel free to concur or clarify).
The Division 3 tanks can be designed to any pressure, and from my understanding it will yield optimal usage of material. In other words, it won't be as beefy or over-designed, which should save on material costs.
Followup question:
Section VIII-Division 3 requires materials be in accordance with Section II. The strange thing is that Section II-Part D does not have strength allowables for VIII-div 3 except for TABLE U-2, which is only for wire material. Where are all the strength allowables for other materials like SA-965 (forgings)? Does Section II-Part D omit most allowables to VIII-div 3 because the design is validated from qualification testing to Section X or Section VIII-div 3??
At this point, all I have to rely on is Section II-part D-Table 1A's strength allowables (and unfortunately the the allowables seem extra conservative). Since Table 1A doesn't reference division 3, I suspect that shouldn't be using it. Any clarification is based on specific references to the ASME code would be greatly appreciated.
Thanks.
RE: Forging pressurized parts
Material and NDE requirements in ASME Section VIII, Div. 3 are more restrictive than ASME Section VIII, Div. 2. It also requires more complex analyses than ASME Section VIII, Div. 2. Your followup question suggests that you are not capable of performing the analyses required in ASME Section VIII, Division 3. I strongly recommend that you leave this type of work to a Professional Engineer that meets the requirements of KG-324.1.
RE: Forging pressurized parts
Part 5 of ASME VIII Div 2 and Div 3 require a mentor that is close by all the time.
RE: Forging pressurized parts
RE: Forging pressurized parts
I will take a closer look at the specific material requirements for the division 1 and 3 to do a thorough comparison. I hope it will help me understand why there aren't strength allowables in division 3, except for wire materials. I suspect that it is encompassed in the more stringent requirements of div 3. I will also try to get a hold of gstrcomp.
Thanks!