B31.3 Stress Analisys
B31.3 Stress Analisys
(OP)
Dear colleagues,
I'm new in piping matters, so i ask for your understanding if my doubts are too simple.
I'm cheking a Stress Analisys Procedure for a cryogenic application in accordance with B31.3, and i'm not sure about the load combination cases to be considered and the acceptance criteria:
- When considering Sustained loads + Occasional loads < 1.33Sh, should the Displacement Stress be added taking into account that in operation we'll have all these stress togheter?.
- In what cases should the "bowing effect" be considered?, during start-up activities or in operation?. Our Contractor has specified 39ºC thermal gradient in section for "bowing" effect, is this figure correct (our operation temp. is -160ºC)?.
Thank you for your help.
Cyrus
I'm new in piping matters, so i ask for your understanding if my doubts are too simple.
I'm cheking a Stress Analisys Procedure for a cryogenic application in accordance with B31.3, and i'm not sure about the load combination cases to be considered and the acceptance criteria:
- When considering Sustained loads + Occasional loads < 1.33Sh, should the Displacement Stress be added taking into account that in operation we'll have all these stress togheter?.
- In what cases should the "bowing effect" be considered?, during start-up activities or in operation?. Our Contractor has specified 39ºC thermal gradient in section for "bowing" effect, is this figure correct (our operation temp. is -160ºC)?.
Thank you for your help.
Cyrus





RE: B31.3 Stress Analisys
Thermal expansion stresses should be verified coupled to sustained loads (not occasional loads) per 302.3.5.
The bowing effect is also a thermal effect and should be coupled to expansion stresses in determining the displacement stress range.
Don't know if a gradient of 39°C (from top line to bottom line of pipe I suppose) is a consistent value (though it doesn't seem unrealistic): this effect depends primarily on process conditions (two phase flow perhaps?).
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RE: B31.3 Stress Analisys
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