UG-39
UG-39
(OP)
We fall into UG-39(b)(2) as far as spacing and hole size, but since we fill the holes with heater rods and weld the rods to the flat head, is it really an opening?
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RE: UG-39
RE: UG-39
genb
RE: UG-39
things have not changed in the Code since your last posting!
genb
RE: UG-39
RE: UG-39
Concerning your first question, well of course it is an opening, as some material is cut from pressure boundary and is not replaced with something of equivalent strength (heater rods do not normally count as structural material).
And sorry, you have no (practical) alternative.
prex
http://www.xcalcs.com
Online tools for structural design
RE: UG-39
since they are small holes, you may get away with
just running ligament efficiency calculations.
genb
RE: UG-39
How do you calculate the following UG-39(b)(2):
"...the required reinforcement for each opening in the pair...shall be summed together and then distributed such that 50% of the sum is located between the two openings."
RE: UG-39
c to center.
genb
RE: UG-39
Have you consider UHx-12 design?
if you heaters have u bends, may qualify for UHX design,
there is where the FEA takes consideration as the TEMA style tubesheets.
'hope this helps, let us know please.
GenB
RE: UG-39
My question to you is, are you intending to detail out a manufacturer's data for the pressure vessel that you are fabricating?
RE: UG-39
data report to be intended for unfired steam or HWB boilers or process heaters
therefore require calculations to comply with the Code.
genb
1 find the required and use the reminder t on the flange for your reinforcing, if more reinforcing is required,
use add-on metal, weld metal,
perhaps a stiffening ring will suffice.(do not ask me I do not know how to calc the stiffener)
genb
RE: UG-39
to me that sentence sounds simply as:
- take d=half the centerline distance of the two openings (but of course not more than UG-37 limitations).
Another way to interpret that sentence, telling exactly the same, is that reinforcement material can never be used twice an that 50% of it must be located on each side of the penetration.
prex
http://www.xcalcs.com
Online tools for structural design
RE: UG-39
prex
http://www.xcalcs.com
Online tools for structural design
RE: UG-39
If your FEA dude has done everything right, and I have found that it takes several iterations for them to get everything right, then you should be able to go with the FEA results. However, be aware that if there is a problem and your FEA results turn out to be incorrect, whereas The Code would have given you the correct results, you will be hosed.
My personal experience is to go with The Code if it has the application. Why would you want to take the risk associated with deviating from The Code? Steel is a lot cheaper than litigation.
Last but not least, if you have one, talk this over with your A.I. Most of those guys know their stuff and are happy to help.
chili
RE: UG-39
I have to disagree with your assessment that FEA can trump Code rules. Referring to U-2(g), you can apply alternate rules IF there are no rules provided in the Code. Unfortunately for heaterguy, the consensus seems to be that there are rules that apply in his instance.
RE: UG-39
tr=A/(p-dh), where A=0.5*dh*t
Or how about this?
tr=(dh/2)^2/(dh^2-(dh/2)^2)*t
tr is the reinforcement thickness
dh is the hole diameter
p is the distance between holes
t is the thickness required without holes
RE: UG-39
Perhaps I did not state my opinion correctly. I have used FEA many times, but never if there was a clear example in The Code. Unfortunately, in custom equipment design, there has been many applications where I could not find a relative application in The Code. The bottom line is Sound Engineering Practice. Using Code rules that are applicable would be considered as Sound Engineering Practice.
As noted..."My personal experience is to go with The Code if it has the application. Why would you want to take the risk associated with deviating from The Code? Steel is a lot cheaper than litigation."
chili
RE: UG-39
I belive he uses roar's design analysis
genb
RE: UG-39
I see you point - and we appear to agree. Good to see.
I also don't see a problem using a tubesheet analysis for heaterguy's problem.
RE: UG-39
your first formula appears to me as the correct one, don't understand the second one that BTW reduces to 4/3*t (?)
prex
http://www.xcalcs.com
Online tools for structural design
RE: UG-39
Is the first one in Section VIII? What makes it correct?
The second one reduces to 1/3*t (I didn't realize that, thank you). It takes the volume of the hole and moves it above the hole in a cylindrical shape with a 2*dh outder diameter and a dh inner diameter.
RE: UG-39
genb
RE: UG-39
reinforcement calculations are based upon reconstitution of metal cut by the opening in all sections through vessel wall made with planes containing the opening centerline. This procedure conceptually works only with areas, not volumes (of course because stresses act on surfaces), so your second formula has no meaning.
The first one is the application of UG-39 rules, as:
-make a section with a plane containing the centerlines of both openings
-area available between the two openings is tr(p-dh) (with your symbols)
-only 50% of it may be used for each opening
-the same 50% area is accounted for each opening on the other side
-the available area for each opening is again tr(p-dh)
This is the rule. Of course, as discussed above, this procedure doesn't account for the orientation and position of the holes: two holes aligned along a radius are very different from the same two along a circumference, as the first case deals with tangential stresses, the second one with radial stresses, and the two are quite different.
However that's it, at least for the moment...
prex
http://www.xcalcs.com
Online tools for structural design