Dear ones,
In cases like this, is the aspect of COMPOSITE
ANALYSIS coming to the scene. I do not think there is
any satisfactory solution to carry out a detailed
analysis, taking into account all the elastic
participants (could be the equipment itself, the
nozzles, the flexing of the structure, the six degrees
of freedom at any node) in the system. Can any expert
throw more light in this direction?
Cheers!
My name is C. V. GANGADHARAN, currently located in Abu
Dhabi.
--- Steve McKenzie <mechproj@xtra.co.nz> wrote:
> Hi Pankaj
>
> as a non expert I will take this opportunity to get
> some information.
>
> When piping stress guys give their information to
> the structural guys, I
> have typically seen only force and moment data
> given. Do you give the
> corresponding deflection/rotation "spring rate" data
> as well? If you do,
> do they design to provide a suitably compliant
> structure? Or do they/you
> treat their structures as inelastic?
> If sometimes yes and sometimes no, how do you decide
> when to require an
> elastic structure?
> These questions arise from often observing many
> support structures which
> are more elastic than the pipes they support, while
> still being
> sufficiently strong to resist the nominated
> loadings. This can result in
> understressed pipes (or spring supports) and
> unnecessary capital cost.
>
>
> Cheers
>
> Steve
>
>
>
> -----Original Message-----
> From: <a href="/group/PipingDesign/post?postID=61n8qVdSQdMrQ2rfJMMX2OBFV4GEnvN9ANWofot3nTnOl7q48-seLH5vPAgfWeaypyQKJArcGMd5xPM7wTDWcuB-">Pankaj.Mandal@fluor.com</a>
> [mailto:Pankaj.Mandal@fluor.com]
> Sent: Tuesday, February 15, 2005 8:53 PM
> To: <a href="/group/PipingDesign/post?postID=po5-MyZfSF9pQEdQXp7txtluqb5CkmG1jMvPqEss4F6Mo-b3M5FCDxHLrXgTAp4zGVqN9KToQxiZBTyvqzRf3DIA">PipingDesign@yahoogroups.com</a>
> Subject: Re: [PipingDesign] Pipe supports
>
>
>
> Shreedhar,
>
> I didn't get your point: "............if it not
> welded, it will tend to
> relax."
>
> In general, some amount of erection tolerance exists
> for a pipe support.
>
> For example, a "guide" is in most cases "guide with
> a gap" and hence
> some
> degree of rotation is always let free. However what
> I was trying to
> prove
> that wherever we have large rotation across a guide,
> erection tolerance
> does play a governing role and as a stress analyst
> one needs to take
> care
> of that too.
>
> Pankaj.
>
>
>
>
>
>
> "shreedhar" <shivapuji@mis.co.ae>
> 02/15/05 12:20 PM
> Please respond to PipingDesign
>
>
> To: <PipingDesign@yahoogroups.com>
> cc:
> Subject: Re: [PipingDesign] Pipe
> supports
> .
>
>
>
> Dear Pankaj,
>
> Below listed are my views of the subject ...
>
> Best wishes,
> Shreedhar Shivapuji.
>
> ----- Original Message -----
> From: <Pankaj.Mandal@fluor.com>
> To: <PipingDesign@yahoogroups.com>
> Sent: Tuesday, February 15, 2005 9:49 AM
> Subject: [PipingDesign] Pipe supports
>
>
> >
> > As a common practice, pipe supports such as guides
> and axial stops are
>
> > modeled in stress analysis software as point
> contact supports i.e. it
> > restricts movements only and allows free rotation.
>
> [Another thing to be noticed ... physically, shoes
> are guided which is
> somewhere below the centreline of the pipe. But in
> the analysis we guide
> them along the centreline.]
> >
> > It we really go into construction of these
> supports, in most cases, it
>
> > locks one or more additional degree of freedom,
> not accounted for in
> > our analysis.
>
> [No. There won't restriction on rotation unless the
> support is welded.]
> >
> > Let's take an example of a simple pipe guide on
> shoe, locking movement
> in
> > say X-axis (let X be north, Z be east and Y - up).
> If we consider no
> > gap in the pipe support, rotation about Y-axis is
> also locked. Now my
> question
> > to all is whether this locked rotation is
> considered in your analysis.
>
> [Again, if it not welded, it will tend to relax.
> Hence, there won't be
> restriction on rotation.]
> >
> > I did a similar test case for a pipe support near
> equipment. The
> > result was quite disturbing. Introducing a
> rotational stop at support
> > point resulted in a huge moment, which surely
> would not make our
> > structural colleagues happy. On the other hand, if
> we introduced some
> > gap in the support (which is the most probable
> case), rotational
> > effect was nullified, but loads on equipment
> nozzle were increased
> > considerably.
>
> [Rotational restraint can be used if the equipment
> can be protected (by
> keeping within the nozzle allowables). But
> construction of such a
> support can be quite intricate.]
> >
> > Expert opinion solicited.
> >
> > Regards,
>
>
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