Best practice for modelling refractory lined pipes for stress analsis?
Best practice for modelling refractory lined pipes for stress analsis?
(OP)
What is the best practice for this, or should I say, most efficient practice? Modelling the steel and refractory as either a composite shell or as a solid seems tricky to me due to getting the properties of the refractory right and how it should interact with the steel shell. I have read that you can modify the elastic modulus to combine the stiffness of the steel and concrete and then just model the steel. Is that a bona fide method? The equation they gave for an empirical calculation of the elastic modulus of the lining refered to some concrete standard and I was unble to find the parameters they used, but assuming you could find the property from a table would this be an ok method when you are only interested in the stress in the pipe? Is this appicable to an FE approach in any case?





RE: Best practice for modelling refractory lined pipes for stress analsis?
RE: Best practice for modelling refractory lined pipes for stress analsis?
Depending on probles size, etc. and other things we don't know it might be more efficient to use overlaid elements...but this also may have some pitfalls....
Ed.R.
RE: Best practice for modelling refractory lined pipes for stress analsis?
RE: Best practice for modelling refractory lined pipes for stress analsis?
The composite material causes a shift in the neutral axis which in turn changes the stress and strain distribution...Just taking the results of the composite run (displacements) and applying them to another model the same size made of steel will not give the correct results.....To show this take a simple composite beam and compare the results of a hand calc. with those for a similar beam amde of one material......
Of course I am assuming that the lining has a significant effect on the actual situation....
Ed.R.
RE: Best practice for modelling refractory lined pipes for stress analsis?
I have encountered instances of refractory which developed significant cracks (due to a combination of tension and thermal effects), which allowed the hot fluid to reach to the steel pipe wall at the root of the cracks, significantly increasing the local steel temperature near the roots of the cracks, well above the theoretical temperature that is calculated for the uncracked refractory. This also ensured that the steel wall was effectively carrying all of the hoop tension, because a full-depth crack in the refractory means that it has no effective tensile strength. (Probably more of an issue for fluid filled pipes than gas filled ducts, because of the higher heat transfer coefficients for typical liquids.)
RE: Best practice for modelling refractory lined pipes for stress analsis?
corus
RE: Best practice for modelling refractory lined pipes for stress analsis?
Don't ignore those with hands on operating experience. Trying to model the affects of expansion gaps and what is effectively civil engineering in precise way stands a good chance of coming unstuck if you pardon the pun.
I've seen a couple of failures where the promises of detailed analyis failed. Then you'll get you get the "told you so". One such calc I remember cost the equivalent of a years salary and still went severely pear shaped (literally) costing several times more to fix.
RE: Best practice for modelling refractory lined pipes for stress analsis?