External Pipe Pressure Calc

i know similar questions have been posted before and i haveread the threads, but could not find the answer to my specific question.

please find my query below

During Hot/ Cold tapping we are using paragraph UG-28 of Section VIII Division 1 method to calculate the maximum allowable external pressure for hydrotest purposes. As the branch connection, weldolet or split tee is welded on to the existing pipe, and the pipe is hydrotested for the new weld. I was wondering whether this method is appropriate to calculate the maximum allowable external pressure. and one more query i have is during hot tapping when the line is hot and pressurized does that have any effect on the calculation, as i dont see the method taking that into account. lets say the internal pressure of the existing pipe is already at 100barg during hot tapping. Will this pressure not have a nullfying effect on the applied external(hydrotest) pressure, is there any allowa