Re: Tank Datasheet Appendix LFrom: Schoe 
Date: Thursday, May 19, 2011
Time: 10:29:52 PM
Remote Name: 18.104.22.168
Thanks for your reply.
Im confused about this vapor pressure. From the previous edition of API650, the unit of this vapor pressure is in inH2O. However it was change to PSIA in the new editions.
Since I have a vapor pressure of 12inH2O, this is equivalent to 300mmH2O, which I think is a normal design pressure for some atmospheric tanks.
Does this vapor pressure will not be added to the design pressure? If it will be added, the design pressure is already 2.5psi ~1762 mmH2O. Thus, this pressure will be over with API650 boundary.