Annular Plate Requirements in Apx. X

[rab1944]

Has anyone noticed that the stress thresholds requiring the use of an annular plate in Apx. X.3.2 are the same as when using carbon steel? That seems odd when the duplex allowables are higher.

 

[JoeTank]

It's based on corner joint rotation only. Higher hoop stresses lead to more radial growth and more rotation.

Joe Tank

 

[rab1944]

Joe,
Thanks for the responce.

I understand the hoop stress issue but my question was dealing with a must higher strength material subjected to the same hoop stress as carbon steel. Would not the threshold for a reaction as you describe be higher for duplex than for carbon steel?

 

[JoeTank]

The bending stresses in the critical zone are well above yield stress for both carbon and duplex materials. There are fatigue aspects to the code requirements also. It is conservative, but the carbon steel rules have been adopted the duplex materials.

Joe Tank