Q: during, a class calculation in your PCC software I am getting some errors in the weldolets section. It seems that some dimensions (tn) are missing and the program cannot make the simple-pressure rating calculations.

However, when I tick the option “use without specific ratings in ASME 31.8”, the calculation runs without problem (in this case I assume that the program calculates all the individual parameters). Please note that this problem occurs only in calculation with ASME 31.8 (it is ok with EN1594) for pipe sizes 26”-30” with the specific option “unticked”.

A: the reason looks like the 26" schedule 160 pipe is not existing in ASME B36.10M. The only thing you can do is to make a custom pipe with material A105 and calculate the pipe to simulate your calculation.

The dimensions of the Generic weldolets are given to us by a customer many years ago. The large weldolets are probably fabricated upon request. Most of the European customers use the detail calculation to verify the suitability of the larger weldolets for the design conditions.

To summarize, if 'ASME B31.1, ..., use without specific ratings' is not ticked PCC does:

  • find the pipe with the same size and schedule, and execute the calculation with the same material of the weldolet to assess the selected schedule. If the pipe size and schedule can not be found and error is shown in the calculation.

if ticked:

  • use the pipe with weldolet to execute the 'area replacement' calculation as per the code relevant paragraph, in ASME B31.3 this is the 304.3.3 'Reinforcement of welded branch connections' paragraph.

Also look at this article: Changing dimension of fittings does not affect ASME B31.3 calculation