frd03
Structural
- Feb 11, 2007
- 22
Hello John Breen,
Thanks for your traditional attention!
If possible, I would like to continue a quite more this discussion and I really would apreciate your comments.
1) I did a plastic simulation with Abaqus FEA (including cyclic hardening) using a small pipe ( 11/2" sch40) including a 90 degree RL curve ( the lenghts and temperature were choosed to create a yelding on specific points-similar to SA range ), in steel. I applied 15 sucessives loading cycles from 21 up to 300 oC.
I noticed, near the anchors/ends and also in the middle of internal radius of the curve, the similar stress values since the first and the last cycle ( around 27 kgf/mm2 >= Sy=25 kgf/mm2, so plasticity, ok ) when I take out the loading I can see the residual stresses but in a a new cycle the final value under temperature loading was similar to the previous cycle and I did not notice a stress reduction after some cycles as self-springing effect !
2) Concerning vibrations on pipings I am worried because, for example a hot oil line or a steam line can pulse to 10 or 30 Hz (fluid)due to the propellers and the alternate pressure following this frequency so the S x N curve can present a low life for the material pipe ( ex.100.000 hours)while the temperature of line keep it very regular ( f=1 !? ). How should be the safety procedure for this design ? ( and the Asme orientation ? ).
3) There are many cases where I could apply smaller thickness of carbon steel pipes if they were avaliables, keeping the safety design, but generally I do not have this option.
You know the amount of piping in middle petrochemical plant, and for ex. 20 % of reduction on weight materials could represent some hundreds of toneladas.
In the steel structural building market we have a large range of W-profiles (wide beams)so we can develop a design very adjusted for our needs. Why we are not a similar situation with pipes and components ?
Thanks Again !!
Francisco Dominguez
Thanks for your traditional attention!
If possible, I would like to continue a quite more this discussion and I really would apreciate your comments.
1) I did a plastic simulation with Abaqus FEA (including cyclic hardening) using a small pipe ( 11/2" sch40) including a 90 degree RL curve ( the lenghts and temperature were choosed to create a yelding on specific points-similar to SA range ), in steel. I applied 15 sucessives loading cycles from 21 up to 300 oC.
I noticed, near the anchors/ends and also in the middle of internal radius of the curve, the similar stress values since the first and the last cycle ( around 27 kgf/mm2 >= Sy=25 kgf/mm2, so plasticity, ok ) when I take out the loading I can see the residual stresses but in a a new cycle the final value under temperature loading was similar to the previous cycle and I did not notice a stress reduction after some cycles as self-springing effect !
2) Concerning vibrations on pipings I am worried because, for example a hot oil line or a steam line can pulse to 10 or 30 Hz (fluid)due to the propellers and the alternate pressure following this frequency so the S x N curve can present a low life for the material pipe ( ex.100.000 hours)while the temperature of line keep it very regular ( f=1 !? ). How should be the safety procedure for this design ? ( and the Asme orientation ? ).
3) There are many cases where I could apply smaller thickness of carbon steel pipes if they were avaliables, keeping the safety design, but generally I do not have this option.
You know the amount of piping in middle petrochemical plant, and for ex. 20 % of reduction on weight materials could represent some hundreds of toneladas.
In the steel structural building market we have a large range of W-profiles (wide beams)so we can develop a design very adjusted for our needs. Why we are not a similar situation with pipes and components ?
Thanks Again !!
Francisco Dominguez