UB-16(b) Interpretation
UB-16(b) Interpretation
(OP)
Colleagues:
A hypothetical question:
Construction Code ASME Section VIII, Division I, latest edition/addenda. A TEMA type BEM shell & tube, with single course construction of the shell. Shell size 6" IPS, out of SB-619 UNS N10276 Alloy C276 pipe. Design MAWP 75 PSIG + FV @ 325F, with a .0625" inside corrosion allowance. No RT.
What is the minimum required wall thickness (in decimals, not wall schedule) of the shell? How did you arrive at your answer? I have an engineer that I believe is mixing and matching code sections in a design he's submitted for quotation.
A hypothetical question:
Construction Code ASME Section VIII, Division I, latest edition/addenda. A TEMA type BEM shell & tube, with single course construction of the shell. Shell size 6" IPS, out of SB-619 UNS N10276 Alloy C276 pipe. Design MAWP 75 PSIG + FV @ 325F, with a .0625" inside corrosion allowance. No RT.
What is the minimum required wall thickness (in decimals, not wall schedule) of the shell? How did you arrive at your answer? I have an engineer that I believe is mixing and matching code sections in a design he's submitted for quotation.
-TJ Orlowski





RE: UB-16(b) Interpretation
I guess your problem comes from ASME II, Table D, note G14 (division with 0.85 for long stress calcs). The rest is a formula, paper and pen, nothing fancy.
PS. Give me the design pressure and I'll run the calc for you.
RE: UB-16(b) Interpretation
Sorry, my question was not clear. Design pressure is 75 PSIG + FV @ 325F. Relief devices will be set at < 75 PSIG, so MAWP is moot. I agree that this calculation should be pretty straight forward.
-TJ Orlowski
RE: UB-16(b) Interpretation
-TJ Orlowski
RE: UB-16(b) Interpretation
RE: UB-16(b) Interpretation
Applying UG-16(c), I get Duwe6's 0.015 + 1/16" CA + pipe wall tolerance, 12 1/2% of 0.0775, total 0.087
UG-16(b) governs.
Regards,
Mike
RE: UB-16(b) Interpretation
I'm in total agreement. I have an engineer (and also a programmer at TWO well-known pressure vessel software outfits that we license) that I believe is (are) combining UG-16(b) and UG-16(c): asserting that pipe wall tolerance needs to be added to he UG-16(b) minimum of .125".
I had to go back to make sure I hadn't missed something in the new addenda. Our AI and his supervisor are also both in agreement that the UG-16(b) minimum is .125". I just wanted to see what some other fabricators thought.
-TJ Orlowski
RE: UB-16(b) Interpretation
Of course, UG-16(b) will govern eventually.
RE: UB-16(b) Interpretation
-TJ Orlowski
RE: UB-16(b) Interpretation
RE: UB-16(b) Interpretation
UG-16(b) says "regardless of product form", leading you to disregard product form tolerances, UG-16(c) says "after the minimum wall thickness is determined" with no reference to how it is determined, i.e. possibly per UG-16(b).
Regarding software, it seems to me that the program I use most often gets more buggy with each new release. What can you do?
Regards,
Mike
RE: UB-16(b) Interpretation
I cannot interpret "regardless of product form" with as-delivered wall thickness. 'Form' means Pipe, Tube, Plate, Formed Head, etc.
RE: UB-16(b) Interpretation
So for the UG-16(b) example above, nominal wall selected would be 1/8" or greater, tolerance disregarded.
(Would normally say Regards here, but not this time:)
Mike
RE: UB-16(b) Interpretation
I understand it to be: take the GREATER OF your applicable calculation, or 1/16 + CAi + CAo. Our AI, AIA, and it appears that those in this thread agree.
As to software - my view is that they save time on "cookie-cutter" designs. But as soon as you get a project where your specifications are a little wide of your scope (like a small diameter C276 HX built to TEMA B with a 1/16" CA, where 9 out of 10 like this would have no CA), they actually end up costing time.
I spent less than 60 seconds determining that a Sch.10 shell would be OK for this unit originally. Then when one of our engineers said that we'd have to use Sch.40 - it has cost the both of us hours upon hours.
-TJ Orlowski
RE: UB-16(b) Interpretation
Just had it flag a CS exchanger at 650 F as being in the creep range, and use 3S allowables. WRONG. Couldn't override it.
More that half the output is stuff for which I have no interest and no trust.
<End of rant>
Regards,
Mike
RE: UB-16(b) Interpretation
RE: UB-16(b) Interpretation
I understand what you're saying, but I don't interpret the language in the Code that way. The words "regardless of product form" in UG-16(b) tell me that I should DISREGARD whether I'm using pipe or rolled and welded plate, and use a minimum of 1/16" + CA.
Applying your interpretation: my customer would be better suited, and the Code satisfied, if I bought a piece of 10 GA C276 plate, and made a rolled and welded shell (I wouldn't even have to perform RT on the shell, my required thickness would be < .125" even with a .60 efficiency on the long joint, so UG-16(b) would still govern). I don't have a roll with both top roll small enough and enough length to make the cylinder in a single course, so there's going to be at least one circ seam in the shell (still satisfies Code though). Call me naive, but I don't believe that to be the intent of the Code.
I suppose I could just have the C276 stockist perform an eddy current on the the piece of pipe. If it's >= .125" throughout, we're good to go.
-TJ Orlowski
RE: UB-16(b) Interpretation
If you roll a 0.125" sheet, you will be OK from the Code's view. Also full RT or no RT has no impact on external pressure rating.
If the MTR shows a sch 10 pipe, even your thickness measurement is 0.125" throughout, it does not count per Code. There was a code interpretation very clear about this issue.
Of course, if the HX is not stamped, it will be another story.
RE: UB-16(b) Interpretation
Again I have to respectfully disagree. Paper documents do not take precedence over actual values.
If you're telling me that empirical data has no value in the construction and certification of Section VIII, Div.1 vessels and heat exchangers, the other side of that coin is that I would be able to use an MTR showing passing physical properties as a defense for putting inferior material (material that didn't pass my verification of the MTR) into a Code unit.
Paper documents support the actual product being built, not the other way around.
-TJ Orlowski
RE: UB-16(b) Interpretation
Here is Code interpretation VIII-1-86-11:
Question (1): Does UG-16(d) allow the selection of nominal pipe size material which has an actual minimum thickness which is equal to or greater than the calculated minimum wall thickness, regardless of the fact that the undertolerances provide material which is less than that required?
Reply (1): No.
Question (2): Does UG-16(d) require that the nominal thickness less the manufacturing undertolerance be equal to or greater than the minimum thickness required?
Reply (2): Yes.
RE: UB-16(b) Interpretation
*however*, I cannot understand the Committee's rational for disregarding "Actual" measured thickness. "Actual" is real. Why would any design want to ignore reality ?!!?
RE: UB-16(b) Interpretation
Regards,
Mike