Hi All,

We have reviewed the new Division 2 and have made some intersting observations in this area. If you have a hemispherical head and the required thickness is equal to the actual thickness, then there will be a problem when you plug into the combined stress intensity equations on pages 4-54 and 4-55 of Division 2 2007 edition 08 addenda.

I created a simple model and the stress in the sphere due to internal pressure was 23200 psi and the design pressure was 500 psig, the operating allowable was 23200 psi and E = 1.

This means sigma1 = sigma2 = 23200 psi. Sigma3 = -0.5*500 = -250 psi

From equation 4.3.44 the stress intensity is:

1/sqrt(2)[(sigma1-sigma2)^2 + (sigma2-sigma3)^2 + (sigma3-sigma1)^2)]^0.5

= 0.7071[0^2 + (23450)^2 + (-23450)^2]^0.5
= 23450 psi

Since 23450 > 23200, it would appear the for combined loads the sphere is overstressed even when the only load is pressure.