UW-12, Appendix L joint efficiencies
UW-12, Appendix L joint efficiencies
(OP)
Background: We're evaluating the ASME VIII, Div.1 mechanical software from a very well known company. We have the full version of the program they currently have on the market, but for a limited time.
Yesterday I was rating some old jobs, comparing our calculations ('07 edition), to the program's (using the same edition). I plucked a TEMA type BEM job, where the shell was 24" OD, attached to tubesheets on both ends [Fig. UW-13.2 - sketch (i)]. The shell had only one(1) course - tube length was ~120. Material was SA-53 Gr. B carbon steel ERW pipe. No radiography on the job.
After running, I was looking at the UG-27 and Appendix 1-1(a) calcs for the main shell cylinder. The report showed joint efficiencies for the circ stress AND long stress of 1.0, With stress values of 14,600 for long and circ. The stress value already incorporates a .85 efficiency factor from Section II (note G3), but can 1.0 be right for the UG-27 and Appendix 1-1(a) efficiencies? I questioned them on it and they are standing behind it - their reasoning being that there are no butt welds in the shell, so E=1.
After scouring UW-12 and Appendix L, I can't reconcile it. They're also using much more aggressive stresses and efficiencies on the same material when used as a front or rear head cylinder, welded to an Appendix 2 flange, and a 2:1 elliptical head.
What am I missing?
Yesterday I was rating some old jobs, comparing our calculations ('07 edition), to the program's (using the same edition). I plucked a TEMA type BEM job, where the shell was 24" OD, attached to tubesheets on both ends [Fig. UW-13.2 - sketch (i)]. The shell had only one(1) course - tube length was ~120. Material was SA-53 Gr. B carbon steel ERW pipe. No radiography on the job.
After running, I was looking at the UG-27 and Appendix 1-1(a) calcs for the main shell cylinder. The report showed joint efficiencies for the circ stress AND long stress of 1.0, With stress values of 14,600 for long and circ. The stress value already incorporates a .85 efficiency factor from Section II (note G3), but can 1.0 be right for the UG-27 and Appendix 1-1(a) efficiencies? I questioned them on it and they are standing behind it - their reasoning being that there are no butt welds in the shell, so E=1.
After scouring UW-12 and Appendix L, I can't reconcile it. They're also using much more aggressive stresses and efficiencies on the same material when used as a front or rear head cylinder, welded to an Appendix 2 flange, and a 2:1 elliptical head.
What am I missing?
-TJ Orlowski





RE: UW-12, Appendix L joint efficiencies
Not sure what is meant by "more aggressive stresses", but for butt weld circ seams (in this context) E is only equal to 1 if each seam is spotted. The dreaded UW-11(a)(5)(b).
Regards,
Mike
RE: UW-12, Appendix L joint efficiencies
This is where I'm getting hung up. No radiography. Suppose we have a 20" OD SA-53 Gr.B ERW pipe, using it as a channel in a TEMA Type A front head, where both ends of the channel have appendix 2 ring flanges, attached with double fillet welds. So for my Cat C&D calculations, table UW-12, type(7), note(5), I can use E=1.0
But for the Appendix 1-1(a) circ (Cat A) calculation, the argument would be that because the material stress has a .85 efficiency built in, I can use E=1.0 for my t=(PRo)/(SE+.4P) calculation, even though I haven't satisfied the requirements of UW-11(a)(5)(b)?? (we don't regularly RT long seams on pipe that comes from the mill)
-TJ Orlowski
RE: UW-12, Appendix L joint efficiencies
On the other hand it doesn't seem right to me to have to apply what amounts to a joint efficiency twice to the same component.
Any help out there?
Regards,
Mike
RE: UW-12, Appendix L joint efficiencies
It is true E=1 if the corner joints are fillet welds.
RE: UW-12, Appendix L joint efficiencies
Previous posts cover the paragraphs, etc, and this is summarized in the flowcharts of Appendix L.
See Figure L-1.4-1. Follow the "No" path from "Full RT Mandatory" to the "Seamless Section", follow the "Yes" branch (because we are to treat the welded pipe as a seamless pipe per UW-12(e)). Follow the first branch that drops down and extends to far right to "Category C Corner Joint". The flow chart indicates that the Category A 'seam' obtains E = 1.0 and the Category C joint also obtains E = 1.0.
Thus a welded pipe welded to flat covers each end with corner joints would use the tabulated allowable tensile stress, with joint efficiency of 1.0, when calculating required thickness for circumferential stress. And would use the tabulated allowable stress divided by 0.85, with joint efficiency of 1.0, when calculating required thickness for longitudinal stress.
RE: UW-12, Appendix L joint efficiencies
RE: UW-12, Appendix L joint efficiencies
the program should indicate in its formula calculation.
RE: UW-12, Appendix L joint efficiencies
Regards,
Mike
RE: UW-12, Appendix L joint efficiencies
So now we're in UW-12(d), where:
So ERW pipe is equivalent to seamless pipe, but UW-12(d), and therefore UW-11(a)(5)(b), must be satisfied. Seamless pipe has no CatA butt weld, so UW-11(a)(5)(b) doesn't apply. ERW pipe does have a CatA butt weld, so UW-11(a)(5)(b) is applicable, and we'd have to spot the long seam in order to use E=1.0.
When I read the L-1.4-1 flowchart, it's in my mind that CatA joints still need to meet the requirements of UW-12(d), so when using ERW pipe, the circ stress (long joint) would be E=0.85 when there is no RT.
Thoughts?
-TJ Orlowski
RE: UW-12, Appendix L joint efficiencies
RE: UW-12, Appendix L joint efficiencies
.85% per UW12 penalty is inevitable.the program should indicate in its formula calculation.
not for the shell long seam but for the efficiency and degree of examination according to UW-12(d)
RE: UW-12, Appendix L joint efficiencies
other, you do not have to re-test pipe as ''spot'' because the pipe is already cert. (A53E/B) longseam. 15% already taken from stress, see stress tables deductions from seamless.
test spot is for the circ. weld only when attached and buttwelded.
RE: UW-12, Appendix L joint efficiencies
Example:
Take a 10 foot piece of 16" OD SA-53 Gr. E/B pipe, weld appendix 2 loose ring flanges to both ends. In this case, I can use E=1.0 or less when examining the circ stress in the middle of the piece.
Now take a 10 foot piece of 16" OD SA-53 Gr. E/B pipe, weld a LWNF to one end, and a 16" OD 2:1 elliptical the other end. In this case, I need to use E=0.85 or less when examining the circ stress in the middle of the same piece.
As far as the middle of the piece is concerned, what has changed?
-TJ Orlowski
RE: UW-12, Appendix L joint efficiencies
For example, take a piece of plate, roll it into a cylinder and weld it. No x-ray. So the joint efficiency is 0.7 (with a type 1 joint). The required thickness is based on the allowable tensile stress and the joint efficiency. But now consider the material "in the middle" at 180° back from the weld seam. This material is affected the same whether the weld seam is full RT or spot or none. Anyway, I think you have a handle on the general principles.
RE: UW-12, Appendix L joint efficiencies
Not middle but at the joint,
Code says E=1 if you examine it or .85 if yo don't.
End plates has stress at the end fully so no joint is penalized there.
circ. stress at girt is different.