Dear all

CAESARII 5.2 is not adressing negative pressure input and it gives an error 215E. i faced this problem while analysing a line involving untied ME bellows in Condendate Suction Piping.
kindly help

regards

Caesar does not do negative pressure. You will have to apply an axial force to your bellows.

Moverz

i have analysed the same line before also, using CAESAR II 4.5 and it worked well with pressure (operating gauge pressure) = -8 N/cm2 (ie. vaccum)

i have few more questions-

1. why CAESAR 5.2 is not addressing it?

2. How to determine pressure thrust forces on nozzle and anchor with operating pressure below atmosphere in CAESAR 5.2. Do i need to calculate thrust forces manually now in such a situation.

thanks for replying

regards

1) Because the piping codes don't addess negative pressure. What everyone seems to have missed is that pressure (in the piping codes) only comes into play at the very end, when the "code stress" is computed for primary loads. Pressure is accounted for in the PD/4t term of the longitudinal stress equation: Sl = PD/4t + iM/z

Now, if you did input a negative pressure, we just took the absolute value when computing PD/4t. However, so many people questioned why the program never warned them about "buckling" (or how do you design stiffening rings), we made negative pressure an error, in Version 5.20

Since then many users have complained, so in 5.30 we're going to allow negative pressure, but the program will warn you that: (a) the Sl equation will use the absolute value of the pressure, and (b) buckling is not addressed.

2) The only time CAESAR II determines a thrust force is if you have an expansion joint (with an effective ID defined) in the model.

Richard

I am analysing a model of condensate suction piping that involves untied ME bellows and the operating gauge pressure
= -8N/Cm2.
1.if i analyse this model (with pressure = -8N/Cm2 as input) in CAESARII 4.5, CAESAR applies the absolute value to the code equations,i agree ,but it calculates Pressure Thrust Forces at expansion Joint ends that are COMPRESSIVE in nature.

2.Now if i analyse the same model (with pressure = -8N/Cm2 as input) in CAESARII 5.2, it gives an error and i am not able to determine the compressive Pressure Thrust Forces at expansion Joint ends.
please help
thank you for replying

regards

Manually apply the thrust force on the bellows elements.