Dear All,

I did a fatigue analysis calculation a while ago in which the decisive case was the pressure cycles (10^6 times). I used the ASME VIII D2 graphs to figure out the corresponding stress limits for the calculation.(I know that the graphs have been replaced by some formulas in the recent revisions)
our client has recently demanded a fatigue evaluation based on B31.3 and not ASME since the design code is B31.3 and by that, they mean using the "right" f factor in the formula f(1.25Sc+0.25Sh). I might be way off but I thought that the aformentioned formula is applicable for thermal cycles only. could anyone clarify?

This is my own interpretation of the given situation... Any refinement or corrections in my statements are welcome since I haven't encountered this before...

In the usual B31.3 Code Evaluation, since most of the applications are low pressure cycles the stress produced due to pressure is considered a primary or sustained load..But for a million cycles of pressurizing and depressurizing, I think FEA software such as FE Pipe or Nozzle Pro can be used to perform detail fatigue evaluation of the pressure components such as pipe, tees, other fittings, etc...

B31.3 I think can still be used because pressurizing and depressurizing is also correlated to temperature cycles...Once you pressurized the line temperature will start to climb up also, and depressurizing the line will cause the temperature to go down.. So the f factor for a million cycles can also be used.

You can do more reading on FE-Pipe, because they have this capability to evaluate pressure cycles that are very high..Just curious what type of plant or process is this with a very high pressure cycles..

Cheers!!!