ASME Section VIII - Thick Cylinder

[MrGezus]

Good morning, all. I am designing a pressure vessel per ASME VIII Div. 1 and have come to a snag. Page 19 UG-27(c)(1) states that when the thickness does not exceed one-half the inside radius, or P does not exceed 0.385SE use this formula.

My shell will be seamless in nature. The pressure will be 10,000 psi using a 20,000 max. stress material.
ID = 16 so R =8
t=(10,000*8)/(20,000*1-0.6*10,000) -> t = 5.71429 minimum wall thickness. This exceeds one half the inside radius, (8/2 = 4) and also exceeds 0.385*20,000SE.

UG-27(c)(2) is for the longitudinal stresses which has an endnote (20) "20 These formulas will govern only when the circumferential joint efficiency is less than one‐half the longitudinal joint
efficiency, or when the effect of supplementary loadings (UG-22) causing longitudinal bending or tension in conjunction
with internal pressure is being investigated." (Correct me if I am wrong, but without the endnote in play, my welds would be considered circumferential joints and have to use this formula.)

So because UG-27(c)(1) does not apply to my case (wall thickness of 5.71429 > 0.5*inside radius), I then go to Mandatory Appendix 1(1-2)

This is the part that gets me. The welds I have to make would be girth welds being that the material is seamless to attach the end caps. Would these fall under Appendix 1 1-2(a)(2) because of the lack of the endnote? It makes sense to me that these welds are circumferential joints to attach the caps. It confuses me because in UG-27(c)(1) you would think to use the circumferential joints (longitudinal stress) but you don't because of that end note (20).

I do see that Appendix 1 1-2(a)(2) has the extra part of "or when P exceeds 1.25SE". It does not (10000<1.25*20,000*1). It looks like I could technically use either. Am I missing something here?

 

[TGS4]

I seems that you have overlooked U-1(d), which states

The rules of this Division have been formulated on the basis of design principles and construction practices applicable to vessels designed for pressures not exceeding 3,000 psi (20 MPa). For pressures above 3,000 psi (20 MPa), deviations from and additions to these rules usually are necessary to meet the requirements of design principles and construction practices for these higher pressures. Only in the event that after having applied these additional design principles and construction practices the vessel still complies with all of the requirements of this Division may it be stamped with the applicable Certification Mark with the Designator.

If someone suggests ASME Section VIII, Division 2, I would remind them of 1.2.2.2

As an alternative to this Division, Section VIII, Division 3 should be considered for the construction of vessels intended for operating pressures exceeding 68.95 MPa (10,000 psi).

May I recommend ASME Section VIII, Division 3.

 

[MrGezus]

I seems that you have overlooked U-1(d), which states
Quote (ASME Section VIII, Division 1, U-1(d))
The rules of this Division have been formulated on the basis of design principles and construction practices applicable to vessels designed for pressures not exceeding 3,000 psi (20 MPa). For pressures above 3,000 psi (20 MPa), deviations from and additions to these rules usually are necessary to meet the requirements of design principles and construction practices for these higher pressures. Only in the event that after having applied these additional design principles and construction practices the vessel still complies with all of the requirements of this Division may it be stamped with the applicable Certification Mark with the Designator.

I agree with you on this that you can't design by rule for higher pressure items. We have done some 5,000/10,000 vessels in the past with the addition of finite element analysis from a third party engineering firm for each. This satisfied the AI.

If someone suggests ASME Section VIII, Division 2, I would remind them of 1.2.2.2
Quote (ASME Section VIII, Division 2, 1.2.2.2)
As an alternative to this Division, Section VIII, Division 3 should be considered for the construction of vessels intended for operating pressures exceeding 68.95 MPa (10,000 psi).

May I recommend ASME Section VIII, Division 3.

Our customer has already rejected the idea of going another route such as API, but assuming the AI does reject our 15k psi vessel proposal, I don't guess we could design it per Div. 3 and build it without the U3 license?

See attachment for code case.

 

[TGS4]

An elastic-plastic FEA in accordance with VIII-2 or -3 would likely suffice. Weld details and other fabrication concerns would need to be negotiated with your AI.

Yup, building to VIII-3 without a U3 stamp is problematic

 

[MrGezus]

So, just an update for anyone interested. I spoke with our AI and he had a chat with the head office. They said noooooope, build it to Div. 3 with a stamp or tell your customer to consider a pressure drop from 15k or use a different code.

 

[TGS4]

MrGezus - Thanks for the update. As you might expect, I agree with the AI.

 

[XL83NL]

Yup, building to VIII-3 without a U3 stamp is problematic

Why's that? Because there are very little U3 stampholders?

 

[TGS4]

I was being facetious. Just like building and stamping to Division 1 would be problematic without a U1 stamp, and building and stamping to Division2 would be problematic without a U2 stamp.