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
denniskb@ozemail.com.au
www.ozemail.com.au/~denniskb
-----Original Message-----
From: PipingDesign@yahoogroups.com
[mailto:PipingDesign@yahoogroups.com]On
Behalf Of Sajit Viswan
Sent: Friday, 29 July 2005 4:06 PM
To: PipingDesign@yahoogroups.com
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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