(LONG) case in occasional loads.

B31.1 equ (16) uses operating pressure for the occasional stress calculation. But AutoPipe code combinations is using the (LONG) case. (LONG)  is defined as the Maximum longitudinal pressure stress considering all operating cases, not the the concurrent pressure and other loads during the occasional  event.

Please advise how to use the operating pressure (Po) and the occasional longitudinal  force (Fb) the code combination in B31.1 equ (16)?