The software calculates the Maximum Allowable Working Pressure (MAWP) for each of the three stress types. The computation of the MAWP is performed by setting the stress equations equal to the allowables and solving for P. The minimum computed P value is considered to be the maximum allowable working pressure for the particular stress type.
When analyzing vessels A7-B or A8-B (Figures G and H stayed by bars), an additional pressure rating is computed. If the long-side height is greater than the pitch of the stay bars, then a pressure rating is computed per Eq. (2) of UG-47 with the long-side height substituted for the pitch. If this value of pressure is less than the previously calculated MAWPs, then this becomes the vessel pressure rating. Similarly for vessel B3-B (Figure K stayed by bars), if (L2 + R/2) is greater than the pitch, then an additional pressure rating is computed per Eq. (2) of UG-47 with (L2 + R/2) substituted for the pitch.