UNSYMMETRICAL SADDLES
UNSYMMETRICAL SADDLES
(OP)
I have a 15 foot long, 6 foot ID vessel. Initially the saddles were symmetrically placed at D/4 from right and left tangent lines. Latter due to nozzle interference issue, I moved right saddle in by 1 foot thus reducing saddle to saddle separation by 1 foot. The left saddle was not moved. Is this ok? Compress calculations are showing all the stresses way below the allowables. I want to know if this is done often? Is unsymmetrical saddle placement ok? Please comment and tell this newbie if the decision he made was a wise one?





RE: UNSYMMETRICAL SADDLES
Steve Braune
Tank Industry Consultants
www.tankindustry.com
RE: UNSYMMETRICAL SADDLES
RE: UNSYMMETRICAL SADDLES
It appears that Zick method which is very conservative is still used in the industry. Compress also used Zick method. I keep hearing that FEM has proved that Zick method is too conservative, but is any one using FEM for saddle design? Are people using minimum saddle dimensions based on FEM analysis? I guess saddle dimensions suggested by FEM must be way lower than those given by Zick. Please direct me to some reading about this topic.
RE: UNSYMMETRICAL SADDLES
where is the guideline of 0.2L ?
RE: UNSYMMETRICAL SADDLES
RE: Reference check after CODEWARE COMPRESS analysis use SADDLE PRO by Paulin Reseach Group http://www.paulin.com
Leonard Thill
www.thill.biz
RE: UNSYMMETRICAL SADDLES
The 0.2L max guideline comes from our company standard. Its also mentioned in PV Design Manual by Moss. Compress should take into account the boot weight on the saddle. I use Zick for most designs and FEA when justified. Skimping on saddle design is generally not worth the extra effort.
RE: UNSYMMETRICAL SADDLES
RE: UNSYMMETRICAL SADDLES
Zick provided a solution to this problem many years ago and it takes a lot to move folks away from a solution that is proven to work. FEM just adds a lot of technical activity to an already solved problem. I find it difficult to justify the expense of an FEM solution that ends up with esentially the same result. Also, using advanced analytical technics usually ends up with reducing materials and details to the point that the robustness of the final design is gone... no margin for the practical problems of owning the vessel... corrosion, unanticpated settlement, piping loads, etc. Bottom line... put the owner's money in the vessel, not the analysis.
Steve Braune
Tank Industry Consultants
www.tankindustry.com
RE: UNSYMMETRICAL SADDLES
Brian
RE: UNSYMMETRICAL SADDLES