Opening without pressure thrust 1

[IngR]

We have an heat exchanger (dia 60") type fixed Tubesheet, integral both sides. There is no shell around the tubes, the whole exchanger is embedded in a bigger vessel (150").
Both channels are sticking out through the heads of the large vessel.(similar in design to a "kettle type")

The tubes support the tubesheets, so there is no pressure thrust on the "openings" in the heads.
Now our customer respectively UG-37 says, we have to reinforce the Heads!
I'm desperately searchin gfor a text passage or an Interpretation that writes what common sense says:
Reinforcement for openings is only required, if there are pressure loads on the adjacent nozzle.

Far from it, I'm sure this would degrade fatigue limit due to increased rigidity!

 

[prex]

Your customer is correct.
You have pressure on the head and the head is cut, so you need to check the reinforcement, as a cut head is not guaranteed to sustain its own pressure load.
The fact that there is no pressure thrust on nozzle walls could be used in a special calculation accounting for this, but the code does not provide it, so you would need to go with U-(2)g.

prex

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[jte]

prex is right. Since the code does not provide direct equations, you can use U-2(g). Most often this leads to an FEA which can take credit for the tubes in a quantitative manner. You are already doing this in your head qualitatively, so you're half way there. One possible issue here would be that presumably the tubes are hotter than the main vessel shell and thus will exert a thrust due to thermal expansion. This will either be translated into the heads - providing a loading similar to a pressure thrust, or will cause the tubes to buckle. Either way, its worth checking out with calc's, either manual or FEA or...

jt