Well said Christopher.
As I said in my original reply it is my direct experience that the manufacturer may know how to make the pipes but sometimes do not know how to go about designing the installation.
Aluser2's comment about local support stress is a case in point where there does not appear to be a satisfactory solution available at present. We have tried ring bending calculations but they generate deflections much larger than seen in the field. FEA seems the only answer and is giving much better results.
One of the worlds major GRE manufacturers was running Caeser II on a 16" above ground pipeline recently and tried to tell me that I had to provide anchors every 40 metres. It was only my own knowledge of the material that made me query this. I pointed out to the Caeser II operator that the anchor loads during hydrotest could be as high as 47 Tonnes. Not only was I not willing to design anchors for this load but the pipe manufacturer did not have a way to attach the pipe to an anchor that would safely transfer this load. I further pointed out that without the anchors this very high load simply disappeared and that the pressure and thermal movement could easily be accommodated at a 45? change in direction in the middle of the 400m long pipeline. The Caeser II operator eventually agreed with both the anchor loads I had calculated and the deletion of the anchors. When asked why they had insisted on anchors every 40 m I was told that it was the company's standard practice!!!!
Be careful, be very careful. Understand the material you are working with to the point where you can check the work of the designer. Query anything you think does not seem right. Do not trust the solutions provided by the "Design Guides" even when they come from the pipe manufacturer. Do your own basic engineering and use something like ISO 14692 to guide you. Alternatively find a competent consultant independent of the supplier/manufacturer to do this work for you.
Regards
Dennis Kirk-Burnnand B.E. (Mech)
DENNIS KIRK ENGINEERING
<a href="/group/PipingDesign/post?postID=lJMZmuT3CxZKp64rU-DKZwgZFC90UDeWxS8QXxYcClDmUgKE3P--YTb2vSPL-G_5fRrFjm14cVpsgDTuhLDSzIO7">denniskb@ozemail.com.au</a> www.ozemail.com.au/~denniskb
-----Original Message-----
From: <a href="/group/PipingDesign/post?postID=da7qoexkOLHnAhocUMpYhwQh_3i4-7-oYGxWut8VJfB_PerRfF2W3EN2f8JhkDKRd6uFmnkBHK6cDDPUTRKp3if78n2WVg">PipingDesign@yahoogroups.com</a> [mailto:<a href="/group/PipingDesign/post?postID=da7qoexkOLHnAhocUMpYhwQh_3i4-7-oYGxWut8VJfB_PerRfF2W3EN2f8JhkDKRd6uFmnkBHK6cDDPUTRKp3if78n2WVg">PipingDesign@yahoogroups.com</a>]On
Behalf Of Christopher Wright
Sent: Monday, 1 August 2005 10:56 PM
To: <a href="/group/PipingDesign/post?postID=da7qoexkOLHnAhocUMpYhwQh_3i4-7-oYGxWut8VJfB_PerRfF2W3EN2f8JhkDKRd6uFmnkBHK6cDDPUTRKp3if78n2WVg">PipingDesign@yahoogroups.com</a>
Subject: Re: [PipingDesign] GRE Stress Analysis by Reputable Vendor- can
be more relaible
On Aug 1, 2005, at 4:51 AM, Sadath Khan wrote:
> 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,
You want to keep in mind that you're the one who's responsible for your
design. When you're facing a multimillion dollar liability judgment,
you're not going to be able to say, 'Not my fault, I was only following
the recommendation of someone who wanted to sell me something.'
Christopher Wright P.E. |"They couldn't hit an elephant at
chrisw@skypoint.com | this distance" (last words of Gen.
.......................................| John Sedgwick, Spotsylvania
1864)
<a href="http://www.skypoint.com/~chrisw/">http://www.skypoint.com/~chrisw/</a>
--Received on Mon Aug 01 22:41:00 2005
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