hydraulic expansion of tubes - tubesheet yield strenght

[Matrix_93]

Hello,
I am studying tube - tubesheet connection during hydraulic expansion.
I used Podohrsky book and I understood how to calculate the limiting pressure and adesion pressure but I don't understand how to calculate the pressure when tubesheet starts with plastic deformation.
My idea is to use equation 5.8 for tubes and use UP instead of ur with yield strenght of tubesheet, is that okay?

 

[EdStainless]

Or just go to Roark and use the formula for a hole in a solid plate and the strain vs pressure in that case.
In reality you need to stay under the engineering yield of the tubesheet by some margin.
This gets tough when the tube yield is much higher than the TS yield.
If you expand a series of test pieces and measure the pushout force required you will see this effect.
You also have to watch using hydraulic expansion with low ductility tubes. Many alloys do not like being put into triaxial strain.

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P.E. Metallurgy, consulting work welcomed

 

[r6155]

Forget this calculation, not practical. See the following:
1) TEMA

2) Heat Exchanger Equipment
Field Manual
Common Operating Problems
and Practical Solutions
Maurice Stewart
Oran T. Lewis
(477 pags in PDF)

3) Chemical Engineering Magazine march 2007
Heat Exchangers: Tube-to-
Tubesheet Joint Tightness
Stanley Yokell

Regards

 

[Matrix_93]

Hello, I solved the problem and I calculated adhesion pressure and contact pressure but what happens if the pressure used during expansion of the tubes is higher than the pressure where plastic deformation starts in the tubesheet?

 

[EdStainless]

Then the tube will be loose and leak.

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P.E. Metallurgy, consulting work welcomed

 

[r6155]

Did you consider the tube hole grooving?

Regards

 

[EdStainless]

deep grooves really only work if the tube is softer than the tubesheet.
Very shallow grooves (like a rough surface) can help a lot. But these must be circular and not a spiral.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed