>
>
>
> Hi Pankaj,
>
> As u said, it is always correct that no one can put more than
one axial
> stop in a straight pipe run. If any one wishes to put more than
one axial
> stop, then they must go for expansion loop to absorb the thermal
expansion
> and also to avoid overstressing of pipe line due to axial
thermal stresses.
> However, the idea of limit stop with some gap is not new in
stress analysis
> field, this is only a tool to avoid partial axial displacements
and also
> limiting loads to the maximum possible allowable limits.
>
> It is a common practice to use actual stiffness values near the
equipment
> nozzle to avoid over rigidity fixing conditions in flexibility
analysis.
> However, flexible limit stops are not common in the practical
industrial
> stress analysis field, but if one is having time and money then
they can do
> this kind research on this subject.
>
> Cheers
> Phani
>
>
>
>
> Mandal Pankaj <Pankaj.Mandal@siemens.com> on 19/04/2002 09:10:28
PM
>
> Please respond to <a href="/group/PipingDesign/post?postID=eCnwvFSEOIAg7kTAVK-vXyayom1w8waXTMU8xL6XS2TmlHpaTcnIPWtKBu7YogbEbvQ2g6_UQkfe7t-McWqgiK_yhg">PipingDesign@yahoogroups.com</a>
>
> To: "'PipingDesign@yahoogroups.com'"
<PipingDesign@yahoogroups.com>
> cc: (bcc: S V S PHANIKUMAR/L&T-CHIYODA)
> Subject: AW: [PipingDesign] Limit stop in Piping stress
analysis
>
>
>
>
> 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.
>
>
>
> -----Urspr
> ----------
>
>
> üngliche Nachricht-----
> Von: Steve McKenzie [mailto:Mechproj@xtra.co.nz]
> Gesendet am: 19 April 2002 14:56
> An: <a href="/group/PipingDesign/post?postID=eCnwvFSEOIAg7kTAVK-vXyayom1w8waXTMU8xL6XS2TmlHpaTcnIPWtKBu7YogbEbvQ2g6_UQkfe7t-McWqgiK_yhg">PipingDesign@yahoogroups.com</a>
> 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
>
> ----- Original Message -----
> From: "KAUSTUBH JOSHI" <kvj@epc.ltindia.com>
> To: <PipingDesign@yahoogroups.com>
> Sent: Saturday, April 20, 2002 12:19 AM
> Subject: Re: [PipingDesign] Limit stop in Piping stress analysis
>
>
> > 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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>
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