Dear all,
can anyone tell me reagarding sustain stress calculation through CEASAR. in CEASAR if u go to configure setup/sif/.. and there is a option called PD/4t. by default it is inactive but when u activate this ur sustained stress will be changed upto 40%. after activation ur stress value will be more. can anyone tell me the reason of this variation

Most piping codes provide two equations for the "longitudinal pressure stress" component. The code prints "PD/4t" in the "code equation, but unfortunately this is a "thin wall approximation", and as you found, can be in error by a large amount.

The alternate equation, which is the CAESAR II default is: "P * Di^2 / (Do^2 - Di^2)".

When you check the checkbox in the configuration, you instruct CAESAR II to use PD/4t instead of the more exact form of the equation. This may be necessary to benchmark an existing system or a previous analysis made with older software.