Sajit,
dennis' commetns excellent.
a couple of things piqued my interest and some thoughts came to mind.
your comment.
"GRE system scope for the vendor was ambient temperature 16" water injection
pump".
so while the stress should be done (16" warrants this) it shouldnt be a
serious problem.
what you have to pay attention to is the things that Caesar does not do such
as
the local support design (ie local ring rushing at point of support) . When
"stress analysis is requested it doesnt just stop at Caesar input/output.
is there really a need to do dynamic analysis. it is a good idea to do it , but as you discovered, collecting the data to do it properly is a big exercise. Mostly people dont want to pay to do this until a problem is already identified, because of the effort required. Usually it is left in a wait and see scenario. The blame falls after this "wait and see option is chosen" , but later a dynamic problem rears its ugly head.
An experienced engineer will be able to design a system that is inherently "protected" or at least minimises such risk. (hence all my comments). By knowing where to look and what to do that will minimise such risk.
the trend these days is too pass everything off to the vendor/supplier. This is ridiculous as they do not have the tools or knowledge to do this. They then scrounge around looking for the cheapest solution with no clue as to the information required ....as you discovered to be the case.
As has been said many times on this site, cheapman pays more than twice, get
someone who knows what they are doing. It saves time and money.
There are good software packages out there now to do this, and experience
with them, even caesar , helps in knowing what to do right.
The most sensible and practical things can be done in advance to avoid the
need to do the full blown surge and dynamic analysis. It is my exp that this
is usually the course taken.
cheers
Al
> Sajit,
>
> I have been involved in extensive analysis of above ground GRE pipeline
> systems recently and can advise the following points:
> a.. GRE is an anisotropic material so behaves quite differently to
steel.
> Its axial strength is around 50% of its hoop strength. I would advise
> against analysing it as steel with the properties adjusted.
> b.. Caesar II currently included the UKOOA rules for GRE design rather
> that the more recent ISO 14692 rules.
> c.. In my experience the vendors and manufacturers are usually not
> competent to carry out stress or dynamic analysis of the GRE piping.
> d.. Centron do have the tools do do an ISO 14692 analysis for design
> purposes but this does not replace the need for a Caesar II type analysis.
> e.. Be wary of the many older "design guide" rules for GRE which include
> suggestions that the loads between anchors might be low. My own
calculations
> clearly confirm that this is not the case. Many of the design guides
include
> some very poor advice.
> f.. ISO 14692 includes design for cyclic service such as vibration and
> short term loads such as surge.
> g.. I would not take the manufacturers rating of the pipe at face value.
> Do some calculations yourself using ISO 14692 so you better understand the
> behaviour of the GRE material.
>
>
>
> Regards
> Dennis Kirk-Burnnand B.E. (Mech)
> DENNIS KIRK ENGINEERING
> denniskb@ozemail.com.au www.ozemail.com.au/~denniskb
> -----Original Message-----
> From: <a href="/group/PipingDesign/post?postID=BDIURBQc8DyIoO7cjuOT8nL96021SK1H_VseVVacfmffVpnb--2p0urGm2pptB1BwT9ssgJQBD__7e4giXgtzGRmnw">PipingDesign@yahoogroups.com</a>
[mailto:PipingDesign@yahoogroups.com]On
> Behalf Of Sajit Viswan
> Sent: Friday, 29 July 2005 4:06 PM
> To: <a href="/group/PipingDesign/post?postID=BDIURBQc8DyIoO7cjuOT8nL96021SK1H_VseVVacfmffVpnb--2p0urGm2pptB1BwT9ssgJQBD__7e4giXgtzGRmnw">PipingDesign@yahoogroups.com</a>
> Subject: [PipingDesign] GRE Stress Analysis by Vendor
>
>
> Based on the wisdom of having the stress analysis
> performed by the GRE vendor.
>
> On a certain job, it was specified that the vendor
> perform not only the thermal analysis, but also the
>
> Surge and the dynamic analysis.
>
> The GRE system scope for the vendor was an ambient
> temperature 16" water injection pump
>
> suction header and manifolds. There is a spool of CS
> between the GRE piping and the pump suction.
>
> In order to perform the surge analysis, the vendor
> needed a lot of data.
>
> It turned out that it would take a comparable amount
> of effort to have all that data compiled, as much as
> it
>
> would probably take to do the analysis itself.
>
> It was later decided to remove the requirements of the
> surge and the dynamic analysis from
>
> the scope. The likely surge pressures that the system
> will experience was concluded to be
>
> less than the rating of the GRE piping being
> requisitioned. There was no vibration data
>
> available for the pump. Besides the GRE piping was not
> directly connected to the pump.
>
> Eventually the vendor was to do only the thermal
> analysis.
>
> The vendor did the analysis using the CAESAR software.
> The modelling was the same as the CS
>
> pipe analysis except that the property values for the
> GRE piping were used.
>
> Overall, It occured to me that it may take only less
> effort to do this in-house.
>
>
> The thermal expansion coeffecient of GRE is about 1.8
> times that of CS and the Modulus of
>
> elasticity is about 1/15 times that of CS. This
> attribute of GRE allows 2 anchors in a
>
> straight line with only marginal restraint load
> increase, in comparison to loads that would
>
> have resulted, were it a CS line.
>
> There was a note about the GRE stress analysis being
> different from a CS some time back.
>
> Could not trace that email by subject.
>
> Sajit
>
>
>
>
> ___________________________________________________________
> How much free photo storage do you get? Store your holiday
> snaps for FREE with Yahoo! Photos <a href="http://uk.photos.yahoo.com">http://uk.photos.yahoo.com</a>
>
>
> =========================================
> PipingOffice - Excel Spreadsheets for Piping Calculations
> <a href="http://www.pipingoffice.us/">http://www.pipingoffice.us/</a>
> =========================================
> Main site: <a href="http://www.pipingdesign.com">http://www.pipingdesign.com</a>
>
>
>
>
> SPONSORED LINKS Mechanical engineering Mechanical engineering jobs Cad
> drafter
> Process piping Mechanical
>
>
> --------------------------------------------------------------------------
--Received on Fri Jul 29 13:15:00 2005
> --
> YAHOO! GROUPS LINKS
>
> a.. Visit your group "PipingDesign" on the web.
>
> b.. To unsubscribe from this group, send an email to:
> <a href="/group/PipingDesign/post?postID=sipJ6b5Yl4IoQYZjDn5eKIeveG71z6G5U4JDScOflaYkdmnoE00A-30VbS_-Gr49tJr_TIWbRLgOgdlmzq7mZ2WFG1tA1LJCwZFe1O9NIaB35Q">PipingDesign-unsubscribe@yahoogroups.com</a>
>
> c.. Your use of Yahoo! Groups is subject to the Yahoo! Terms of
> Service.
>
>
> --------------------------------------------------------------------------
--
> --
>
>
>
> [Non-text portions of this message have been removed]
>
>
>
>
>
> =========================================
> PipingOffice - Excel Spreadsheets for Piping Calculations
> <a href="http://www.pipingoffice.us/">http://www.pipingoffice.us/</a>
> =========================================
> Main site: <a href="http://www.pipingdesign.com">http://www.pipingdesign.com</a>
>
> Yahoo! Groups Links
>
>
>
>
>
>
>
>
This archive was generated by hypermail 2.1.8 : Tue Mar 04 2008 - 11:40:43 EST