Material strength for calcs

[dmkd1]

Is it permissable to use a suppliers material strength values rather than the ASME section II material strength values when doing pressure vessel thickness calcs. The suppliers material strength values are higher!

 

[gr2vessels]

No, you have to use the cookbook, errr..oops, the ASME II. However, I would do it anyway, if I have the certified UT and yield values. I would calculate my own allowable stress values, as per code. Obviously, I would explain the Client that it is for his benefit (saving). I might have something to explain the third party design verifier, but that's part of the fun.
Cheers,
gr2vessels

 

[roca]

gr2vessels is correct.
I have been involved with situation and it comes in handy sometimes when the vessel is built and the client decides to changes design conditions at the eleventh hour...

 

[doct9960]

If the vessel is ASME stamped, only the AI has the authority to permit using higher allowable stress values.

For Div. 1 vessels, UG-23(a) is pretty straightforward. You can only use the max. allowable stress values listed in ASME Section II, Part D. Strength values in Material Test Reports cannot be used in vessel thickness calcs.

 

[doct9960]

ASME Interpretation VIII-1-01-106...

Question: May the tensile strength recorded on a Material Test Report be used to calculate the wall thickness of a pressure vessel?

Reply: No.

 

[gr2vessels]

Absolutely correct doki, that is the letter of the code. I like the little gap in the rule, where the AI can overturn at whim any code.
I am talking about Australia, where the U-stamp doesn't have much significance, since a recognised authority has to confirm independently that the design is safe and in accordance with the basic safety requirements outlined in AS 1210 and the local fguvernment eregulations. In my opinion, that is the real engineering of a pressure vessel, rather than follow blindly the code, including the mistakes, misprint or other errors of the code.
dmkd1 (the OP) is yet to confess where is he located, inside or outside USA and where is his loyalty, with the code or with the Client.
Cheers,
gr2vessels

 

[dmkd1]

I'm outside the US! And my loyalty is with neither code nor client I'm simply trying to find ways to save money!

Thanks

 

[gr2vessels]

Good on you mate!

 

[doct9960]

gr2vessels,

I am talking about Australia, where the U-stamp doesn't have much significance, since a recognised authority has to confirm independently that the design is safe and in accordance with the basic safety requirements outlined in AS 1210 and the local fguvernment eregulations. In my opinion, that is the real engineering of a pressure vessel, rather than follow blindly the code, including the mistakes, misprint or other errors of the code.

The original question was about ASME and you replied with an AS 1210 point of view. ASME and AS are two different standards. You can't compare apples to kiwis. : ))

And what do you mean with your opinion about "real engineering of pressure vessel"? Are you implying that an ASME stamped vessel is not properly engineered & designed for safety and that authorized inspectors & jurisdictions in North America are incompetent?

 

[gr2vessels]

I didn't mean offence, I was merely saying that the U-stamp has no meaning outside USA, unless the Client is using an American Insurance for his equipment. As for a stamped pressure vessel, one needs to know well the code and has only to apply the relevant clauses.
However, one can contribute some additional engineering if is not bound by the U-stamp obligations. Using an approved method for calculating your own allowable stresses and use them in your design, I think that requires judgement and ultimately the chance of optimizing the design, beyond of the confines of the code.
I am not implying anything of your interpretation, anyone knows a vessel built to ASME is a safe one. This was about stepping out of the code confines and still building a safe vessel, that's all. If you must stamp your vessel in US, that's OK. However, outside US the same safe built vessel doesn't have to be stamped. That gives you the flexibility of designing and building a safe vessel lighter, cheaper, easier to manufacture, faster.
Out of all that doki, you took personal offence, that's all you understood. Australia is one example of places with wider possibilities, along the ASME code and AS 1210.
Once again, I have respect for those who put together the ASME, but I take exception in accepting that ASME code must be followed to the letter if you want to design a safe vessel.
Cheers,
gr2vessels

 

[doct9960]

Of course, I took it personally. Your statement was addressed to me and it's like you are saying that I don't understand the Code and that I blindly follow it, including all its errors, misprints and mistakes.

And if you have respect for those who put together the ASME, please refrain from referring to the Code as a cookbook. The ASME Code is not intended to be used as a cookbook or handbook.

Lastly, if you want to respect forum members, please refer to them by their profile names. My name is doct9960, not doki.

Cheers,
doct9960

 

[roca]

gr2vessels: As far as I am aware for Western Australia which allows ASME VIII vessels all ASME vessels must have the U stamp for registration by either Mines dept of Worksafe.