stresses on clips by COMPRESS according to WRC 107

thread1259-190836

My name is Antonio, I have a doubt concerning to the stress due to internal pressure:

The report mentions the stress at lug edge due to pressure:

Circunferential: P*Ri/t and longitudinal: P*Ri/2t.

In this case: P= 10,02 Kgf/cm²; Ri=1550mm; t(shell)=(16-3,0)=13mm; t(pad)=9,5mm; t=13+9,5=22,5mm

My question is: Why the results for the equations above don´t match with the result shown by COMPRESS. Manually we get the value of 690,26 Kgf/cm² against 1.197,256 by COMPRESS, for circunferential stress for example.

Following partial text from COMPRESS report:

Thanks in advance.

Applied Loads

Internal pressure: P = 10,02 kgf/cm2
Mean shell radius: Rm = 1.559,5mm
Shell yield stress: Sy = 1.866,08 kgf/cm2


Maximum stresses due to the applied loads at the lug edge (includes pressure)
Rm / t = 1.559,5 / 22,5 = 69,3103
C1 = 15,25, C2 = 61 mm
Note: Actual lug C1 / C2 < 1 / 4, C1 / C2 = 1 / 4 used as this is the minimum ratio covered by WRC 107.
Local circumferential pressure stress = P*Ri/t =1.197,256 kgf/cm2
Local longitudinal pressure stress = P*Ri / (2*t) =598,593 kgf/cm2