Hoop stress design factor for offshore flanges?

[PipelineEgr]

Hi everyone,

I was wondering if flanges follows the same hoop stress design factors for offshore pipeline used in, say ASME B31.8? For example location class 2 uses 0.5 factor whereas 0.72 applies along the location class 1. But what if, the demarcation point between location class 1 and 2 are define at the tie-in point of the pipeline. so, do the flange hoop stress design factor at the zone 1 side uses 0.72 whereas the flange at the zone 2 side uses 0.5? Is this specified in any codes?

 

[LittleInch]

Errr, what is a "flange hoop stress design factor"??

Never seen this in any flange spec I've ever come across.

Flanges come in Working pressure and temperature ranges and need to be the same strength material and thickness as the connecting pipe at the weld end.

Pipelines tend to use MSS-SP 44 as it allows use of higher grade forgings to match the pipeline material strength.



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Also: If you get a response it's polite to respond to it.

 

[GBTorpenhow]

No, the flange only cares about the pressure/temperature class curve given in ASME B16.5 or MSS SP-44, or whatever specification the flange is designed to.

The connecting pipe design is driven by the code design factors, and as LittleInch states if using a weld neck flange it will need to match the connecting pipe wall thickness and grade. This could possibly dictate different flange requirements for bore and/or material grade on either side of the connection in your example if using weld neck flanges. If the connection is made with slip on or threaded flanges that do not depend on connecting pipe wall thickness/grade, the flanges would be identical on either side of the demarcation.

 

[PipelineEgr]

My thoughts exactly guys. I've looked into all the relevant codes and there is no mentioned on hoop stress for a flange design. As what you all have said, they're designed based on the pressure-temperature ratings. Thank you both LittleInch and GBTorpenhow for confirming and the extra knowledge shared by you both.