Number of cycles deffined in ASME B31.1 1

[energeng]

Hello everybody,

I have a question concerning the term "N"--> total number of equivalent reference displacement stress range, that it used to calculate the factor "f" that affect the ecuation 1A Sa=f(1.25Sc+0.25Sh) showed in para 102.3.2 of ASME B31.1
I don´t know exactly how interpretate 1 cycle.
1 cycle is the range from cold temperature to hot temperature or 1 cycle is the range from cold temperature to hot temperature and again comeback to the cold temperature ??Can anyone to explain what kind of cycle is concerning in "N" term?

Thanks in advance.

 

[energeng]

please, help

 

[trottiey]

I'm just learning these piping codes, so I was hoping someone else might help you better. I'll give it a shot:

N is the number of temperature cycles that your piping will see over its lifetime. I would assume that one temperature cycle would mean a full trip, e.g. from cold to hot and back again.

Just from first principles, if you go from cold to hot to hotter to hottest, and back down, that doesn't cause any more fatigue damage than if you just went straight from cold to hottest and back. If you have complex temperature cycles, take a look at rainflow counting.

Does that help?

 

[energeng]

Trottiey, thank you very much. It´s very useful.