Ratcheting clarification

[Sam K]

Hi Guys,

need some clarifications about ratcheting issue.

From Paragraph 5.5.1.5, Combinations of steady state and cyclic loadings may result in ratcheting or incremental cyclic growth of a component.
now I wonder if we want to study a Nozzle which is over loaded by piping loads, based on ASME section VIII div 2 part 5 we have to consider different protections for the Nozzle which includes:
1-protection against General/plastic Collapse
2-protection against local Failure
3-Protection about Ratcheting
4-Protection against Fatigue
5-Buckling

now my question is if we don't have any cyclic loading in the Pressure vessel shall we still consider the Ratcheting term?
just imagine the Nozzle is over loaded by Occaional loads such as Blast or seismic which are not cyclic.still we have to consider the Ratcheting term when we want to do a FEA analysis on the Nozzle?

 

[TGS4]

Yes, ratcheting is mandatory. An interpretation was issued on this just a few months ago. The interpretations tool is down right now, so I can't give you the exact number.

 

[XL83NL]

Search engine is up again;

https://cstools.asme.org/Interpretation/SearchInterpretation.cfm

 

[TGS4]

Interpretation BPV VIII-2-18-08 should adequately answer your question.

 

[Sam K]

then as I understand if we have any occasional load from piping which affect the Nozzle load, based on Div2 Part 5 it should be classified as D in table 5.3/5.4/5.5?
so it will be considered for the Ratcheting case.right?

 

[TGS4]

That sounds about right.