Tubesheets:ASME Section III, App. A-8000 interpretation.

[GHCooke]

Hello,

Under the ASME code Section A-8142.1 (a) the membrane stress intensity is calculated from the larger of two equations listed.

In both equations first term under the radical appears to be through thickness shear stress (twice for SI), the second term under the radical is the average through thickness radial in-plane normal stress. However in the second equation two terms appear outside the radical.

The first of the two terms outside the radical is the average through thickness radial in-plane normal stress. Why is it added again?

The second term is 2*p(inside tubes)*h/P. What does this represent? It appears to be some sort of in-plane stress in the ligament due to pressure in the tubesheet hole, but isn't this covered by the average radial in-plane stress which is the sum of the radial stresses calculated in A-8132.2-A-8132.4 where A-8132.4 is in-plane stress due to pressure in the tubes?!

If anyone can help me that would be great, or if anyone has information on the derivation of the two equations in A-8142.1 (a) I would greatly appreciate it.

Thanks for your time,

Graeme Cooke

 

[GHCooke]

To add:

If I am interpreting it correctly the two terms outside the radical are for calculating the SI between the normal stress in the ligament due to pressure and the normal in plane radial stress averaged in the ligament.

If that's the case why are they ignoring the normal stress due to pressure on both sides of the tubesheet?

 

[vpl]

Hey Graeme! Did you post this question on the ASME forum or one of the structural forums? This one doesn't get a lot of interest from the structural type people. Questions on what gets something red-flagged? See FAQ faq731-376

Patricia Lougheed