VIII Appendix 26 Bellows Calculations

[reesh]

I was wondering if anyone has used the external pressure calculation for unreinforced bellows in Section VIII, Appendix 26, 26-6.5?

There is a disagreement about whether when the Code asks to use the absolute value of the pressure in the internal pressure equations whether it means psia or the absolute value of the negative pressure. So if you had a pressure of -5 psi, would you use 10 psia or |-5 psi| in the equation?

The conservative way would be to use the psia value, but if this is the case, what is done when there is a full vacuum?

Any help would be apprecited. Thanks.

 

[doct9960]

I interpret the "absolute value" in Appendix 26-6.5.1 as the mathematical absolute value (i.e. the positive value of a number).

That "psia" thing you were talking about is the "absolute pressure" which is a completely different term.

 

[reesh]

Thanks, that's what I think too. Someone raised the question and nobody was sure of the answer. The fact that an absolute vacuum would result in a zero value using psia for pressure also makes no sense to me.

Just wanted to get a second opinion from someone who has used this clause more often.