Concrete saddle
Concrete saddle
(OP)
Guys,
Could you provide reference to design concrete saddles in lieu of steel saddles for horizontal vessel.Can we use Zick method?
Thanks!
Could you provide reference to design concrete saddles in lieu of steel saddles for horizontal vessel.Can we use Zick method?
Thanks!





RE: Concrete saddle
Start with my answers in thread378-133164 (self supporting steel pipe) in the 'piping & fluid mechanics' forum.
Books are: -
Bednar - pressure vessels. Good with lots if info, but a lot of work to find your specific case.
AWWA M11(American Water Works Assn manual M11) steel pipe design & installation. Good, but use the latest edition (2004 I think). There are still some errors even in this latest edition (see my thread answer above).
ASCE 79. Good publication but expensive for a 'one off' design. AWWA M11 will be better even though a little conservative.
Troitsky steel tube design. Good sections on both above & below ground pipes.
BarryEng
RE: Concrete saddle
The saddle dimension (parallel to the axis of the pipe - or pressure vessel) does not influence the saddle tip stresses (see Roark & Young - formulae for stress & strain), so saddle lengths of 300 mm are OK even for large pipes. Make sure that you adequately reinforce the horns of the saddle (see ASCE 79 for more info). They act like small cantilevers subject to loads from the pipe pressurisation.
BarryEng
RE: Concrete saddle
Another means would be necessary for the saddles themselves.
Mike
RE: Concrete saddle
Mr. L.P. Zick, Director of Engineering, CB&I in 1940's
The L P Zick paper see the following link:
http://www.codeware.com/papers.html
The L P Zick paper for horizontal vessels on saddles
RE: Concrete saddle
RE: Concrete saddle
I guess this begs the question of whether there *should* be a difference in the equations. The load transfer to the saddle will be different for a vessel that is welded to the shell than if the vessel is loosely sitting in the saddle.
RE: Concrete saddle
Of course! At least for evaluating the stresses in the shell. The question I've been asking for a while (with no satisfactory answer yet...) is, as alluded by Tom Barsh, "Can the Zick method be used for steel saddles welded to the shells?" After all, Zick based his study on steel vessels on concrete saddles! Why do you think those plates are called "wear plates" and not "reinforcing pads"? I've yet to see a solid justification for using Zick for welded on steel saddles. The only reasons I can come up with are 1) We (industry) have not had significant failures whith this approach; and 2) There is no alternate method short of FEA. (Yes, Leonard, I know Paulin can handle this, but I don't use his software...)
jt
RE: Concrete saddle
Roark & Young (formula for stress & strain) has a method but it does not include the stiffening effect of the steel shell when pressurised.
ASCE79 (power penstocks) uses an approach based on ASME. The formular is the same as in Bednar (pressure vessels).
AWWA M11 (steel pipe design & installation) uses a simpler approach with essentially the same result (calculations are simpler). This is based on work by Stokes of South Australia & published in the Transactions of the Institution of Engineers Australia in 1965. Stokes developed a method of analysis & verified the work with models. I do not know if the ASME method has been verified with model tests.
BarryEng
RE: Concrete saddle
I do not know why you would ever prefer conrete saddles ove welded steel saddles for new construction. I would imagine that they would be more expensive and potentially troublesome.
Using the Zick methodology for the evaluation of existing concrete saddles in one thing.
Concrete saddles have the potential for concentration of the load on the inside edge of the saddle, as the vesssel is filled (the inside edge is the one closest to the vertical vessel centerline). Welded steel saddles deflect and distribute the load to the shell of the vessel.
Weleded steel saddles are inspected in the shop..... conrete saddles ....who knows
Anyone out there have any bad stories to share ?
RE: Concrete saddle
An interesting discussion on this topic...
http:
What do all of you tink ?
RE: Concrete saddle
An interesting discussion on this topic...
http:
What do all of you tink ?