Cyclic Fatigue Stress Analysis

[Sawsan311]

Dear All,

For a liquid process system (highly subcooled such as water), is there any general guideline when the system is identified to require cyclic fatigue stress analysis. I am aware that ASME B31.3 and ASME SEC VIII Div.2 part 5 both discuss the relation of number of cycles against the allowable stress at each cycle. However, what is the criteria to be considered to assess that the system requires such analysis or not?

Thanks

 

[mk3223]

As you mentioned, the number of cyclic condition as stated in the Codes is the basic rule of the requirement for conducting the fatigue analysis for a given operation.
Is there any specific conditions in your system in question?

 

[XL83NL]

If a B31.3 piping system is considered High Pressure Fluid Service, fatigue analysis is always required. See K304.8.

For Normal Fluid Service, refer to 302.3.5. Note it’s for displacement stress range, which doesn’t cover cycling stresses due to sustained loads.

Para 302.3.5 refers to appendix W which may provide further guidance.

Huub
- You never get what you expect, you only get what you inspect.

 

[Sawsan311]

Thank you all for the feedback,

I am interested to know if there is any specific criteria for identifying the system of a cyclic process, can we consider a liquid pumping system prone to cyclic conditions due to possible infrequent overpressure by surge. can a cycle be categorized over a time duration or a frequency so we can assess the system being of a cyclic process nature.

thanks