Hi Sajit
It has been interesting to see where this thread was going. If you request that the pipe vendor carry out the stress analysis, then you may be restricting your choice of vendors. There are many excellent GRP fabricators who can build a world class pipe to the nominated standards and codes, but do not have the engineering support to conduct surge/stress analysis. If you insist on this requirement then you may wind up paying higher material prices. The advantage is that you don't need to spend the time and money doing the initial analysis yourself; your activity is restricted to one of validation.
For small fixed scope jobs I would take advantage of a vendors design capability and specify on a performance basis. For larger jobs, the Engineer should assume this responsibility, and limit the vendors scope to that of supply to a standard, in order to obtain the most competitive prices.
Cheers
Steve
-----Original Message-----
From: <a href="/group/PipingDesign/post?postID=17ZfGWHegUjQER8WTYRdph7KQQi00mCEr2M5T5B_heiirzz6lwxjb5GNI1WWKwr5BiP0NocQOzzCH2-zfMn1zaNjgA">PipingDesign@yahoogroups.com</a> [mailto:<a href="/group/PipingDesign/post?postID=17ZfGWHegUjQER8WTYRdph7KQQi00mCEr2M5T5B_heiirzz6lwxjb5GNI1WWKwr5BiP0NocQOzzCH2-zfMn1zaNjgA">PipingDesign@yahoogroups.com</a>]
On Behalf Of Sadath Khan
Sent: Monday, August 01, 2005 9:52 PM
To: <a href="/group/PipingDesign/post?postID=17ZfGWHegUjQER8WTYRdph7KQQi00mCEr2M5T5B_heiirzz6lwxjb5GNI1WWKwr5BiP0NocQOzzCH2-zfMn1zaNjgA">PipingDesign@yahoogroups.com</a>
Subject: RE: [PipingDesign] GRE Stress Analysis by Reputable Vendor- can
be more relaible
Dear All
We need to be carefull about telling the manufacturers that they may not
have the experince in stress and surge analysis the tendency is that
each reputable manufacturer has his engineeirng team doing stress and
surge analyusis coupled with FEM analsysis,
GRE or composite piping neeeds to be selcted based on the manufacturer
experience unlike steel looking at prices only
In genral all reputable manufacturers of GRE has teams or companines who
does detailed engineering and provide solutions
at the end of the day it is the manufacturer who suffers and hence he
take lot of pain to see that his product is sucessfull
above is my opinion just for your informaiton.
Sajit Viswan <sxviswan@yahoo.co.uk> wrote: Denis,
Thank you for info.
I see that Shell standards are now based on the ISO standards which were based on the UKOOA before.
Have you used the ASME B31.3 2004 (Chapter VII) rules? Is the industry using this?
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
<a href="/group/PipingDesign/post?postID=VpddUnruM-1mNy4l9nbMGEThECzmXKFf5Z50yVbqyfOENYmPH1pFAW3ZY9srUL4myBVnCrX7DTb9vUtpmvZf8QQ">denniskb@ozemail.com.au</a>
www.ozemail.com.au/~denniskb
-----Original Message-----
From: <a href="/group/PipingDesign/post?postID=17ZfGWHegUjQER8WTYRdph7KQQi00mCEr2M5T5B_heiirzz6lwxjb5GNI1WWKwr5BiP0NocQOzzCH2-zfMn1zaNjgA">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=17ZfGWHegUjQER8WTYRdph7KQQi00mCEr2M5T5B_heiirzz6lwxjb5GNI1WWKwr5BiP0NocQOzzCH2-zfMn1zaNjgA">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
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Received on Mon Aug 01 06:08:00 2005
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