Dear Steve,
We are now into a deeper topic. What should be the stifness at the point where we connect our support with steel or concrete. We can of course calculate individual stifness. The range will vary (very flexible if we have a cantilever steel supporting arrangement to very stiff if we connect to a concrete column, for example). The point here is to what depth we should perform an analysis.
I know that people with nuclear background calculate stifness for all these points. But they have the time and money to do so. And the risk involved in case we end up in a failure is also too high.
So to sum up the story, I advise all to follow conventional solutions for simple problems to save time and money. In case you have critical problems, do all that is necessary.
By the way, axial stop with a gap was a new idea for me. I never used the same in any projects. Could work since guide with gaps are used extensively. But please remember that in that case we will deal with gaps correct to last decimal in mm (not the case for guides). Again time and money involved in erection.
One last recommendation for horizontal spring installations. Please remember that we are deling with siesmic forces also at least in most sites. In that case we will have tension force compomemt in the spring (Spring is never designed for tension). This is the specific reason why we normally never use horizontal spring installations.
Pankaj Mandal.
-----Ursprüngliche Nachricht-----
Von: Steve McKenzie [mailto:Mechproj@xtra.co.nz]
Gesendet am: 19 April 2002 14:56
An: PipingDesign@yahoogroups.com
Betreff: Re: [PipingDesign] Limit stop in Piping stress analysis
Dear Kaustubh
We think the same. However nothing is perfectly rigid. If a bit of
flexibiity will overcome the problem, why not use it? A "stop" is never a
stop; it always moves. The problem, as I see it, is to constrain the
movement of a long, straight pipe to within limits. If springs on the
"stops" will do it then why not? The calulations will show. However I
totally agree that the use of three hard stops on a single straight run is a
recipe for fracture. So build in some flexibility by springs or cables and
counterweights.
By the way, there has been a lot of talk about coefficients of friction on
flat shoes, using teflon and the like. If I have a pipe that simply has to
move, I always use rollers. Do the sums and you will find the resistance is
very small. And they cannot tip and jam.
I repeat I am not an expert on this subject, but I do like a debate, and thats what I bvelieve is part of the purpose of discussion groups.
Cheers
Steve McK
> Dear Steve,
>
> I did not get you exactly.
>
> What I think, it can not be possible with rigid restraints. In case of
rigid restraints the line would be overstressed due to not allowing thermal
expansion. In case of multiple restrictions in a straight line, The supports
can be sheared off or it can damage the pipe as well.
>
> With rigid supports, we can achieve the distribution of load
theoretically, as suggested by Tushar, but this system will be very very
difficult to be implemented at site. And more over, the performance of the
system could not be evaluated exactly due to deviations at site.
>
> I case of springs, being the low stiffness, supports absorb the thermal
expansion of the line and reduce the thermal stresses. But this certainly
can not work with conventional rigid limit stops.
>
> Regards,
> Kaustubh
>
>
>
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Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/ Received on Fri Apr 19 10:40:00 2002
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