Modal analysis modelling of branch connections in CII

[nipra03]

Hi.
I want to know if anyone has done a modal analysis of small bore bramch connections (<=2") on larger pipe(> 20") in CII ?
Are the results comaprable to say a FEA analysis ?
And can one run a fatigue analysis on such a cnnection due to say a harmonic forcing function i.e. vibration of the small connection ?

 

[C2it]

Modal analysis reults are as good as the input.

So far as small branches are concerned there are poits to be aware of. For example, clearly length must be from the pipe wall, notthe header centre-line. Also, the relative flexibility of the header wall might be significant. If the wall is heavy then there should be no local issues, but if thin wall then the smlall bore connection will actiually behave like a beam on an elastic foundation. It would thus have a much lower resonant ferquency than calcs might predict.