RE: Pipe supports

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: Pankaj.Mandal@fluor.com [mailto:Pankaj.Mandal@fluor.com] Sent: Tuesday, February 15, 2005 8:53 PM To: PipingDesign@yahoogroups.com
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,
Received on Tue Feb 15 03:32:00 2005