Re: Specs- re use of FRP pipe

From: <Geoff>
Date: Tue Sep 13 2005 - 18:29:00 EDT

Yes I know that with pressing the client would have relented in the end. But time was against us and there were a raft of other issues on site that needed resolution. It wasnt a happy job. Under priced and a hard nosed Superintendent who would not move from the Specification.

The reason for using thermoplastics is that I do work in the water and wastewater industry. ABS and PE are good for corrosion resistance, inside and out. Cost advantage over painted steel or stainless. No need to wrap, coat or fusion epoxy bond coat in buried installations. This industry has low temperatures and pressures and thus no need for ferrous products although ductile iron cement lined is used often.

In the building industry ABS is available as a co extruded insulated product. Easily joined using chemical welding. No corrosion on the inside or out. No need to paint so it saves time and money. Less anti corrosion chemical usage, only have to protect the chillers and evaporative coolers.

I think that thermoplastics pipe would be used more in the petrochem industry if the Codes were more specific. I find ASME B31.3 to be rather backward when it comes to thermoplastics. They are more complex to design than steel and I dont think the committees are on top of it yet. Interestingly in a modern mineral process plant (more like a chemical plant with solvent extraction etc) thermoplastics and FRP is more prevalent.

There are some good FRP products such as those manufactured to ISO 14692. But I have dislike of the pipe reinforced with chopped fibres and sand filled epoxy. Another problem experienced in the 1970's was where the reinforcement strands appeared through the gel coat. Because of capilliary action water would get between the inner gel coat and the FRP body. When a negative pressure wave resulted from a waterhammer excursion the the gel coat would delaminate and tear off the wall.

There were many failures of this material in the Middle East in the 1970's. The manufacturers are still a mixed bag of bad to good. You have to know the standard and ask the right questions of manufacturers. But sometimes you are removed from this exercise in a supply and install contract. No amount of specification will stop the "canary" project manager (They are the ones that go "Cheap"," Cheap","'Cheap" all the time) from taking the lowest price. So to save them from themselves I avoid designs in FRP.

The devil is in the detail such as jointing, repairs, local buckling at supports and how to design to prevent failure.

Geoff

aluser2 <alwynk@shaw.ca> wrote:
Geoff,'interesting post.
I'm surprised you couldnt press the issue on cutting out the bad segments and seam welding in a new one. (or flange if its flanged) The lengths are often random and all lengths have to be welded/joined together regardless. To complete a run you need a shorter piece somewhere. I dont see the difference.

If the spec called for welded segments he wouldnt have a case to argue. I suspect you could have pressed the issue.

Its good for a spec to addressed repair in advance.. which is needed for any kind of work not just FRP.
I gathered from posts you often used Thermoplastics. Whats your deciding factor . just try to stay away from it. Thats pretty hard in your line of business. I would have regarded that case as an aberration. Interesting Any other thoughts.

Hi,

I once had a DN900 FRP pipe buried 8m deep. The trench was benched in steps of 1m wide by 1.5m deep.The line was being backfilled when a "galah" dropped a piece of equipment into the trench. It hit the FRP and it crazed like mad. The client Sydney Water wouldnt accept any repair procedure. He said he paid for new pipe so thats what he wanted. We had to excavate the trench to pull sufficient pipe out to get the defective length out.

From then I have avoided FRP like the plague. Never put something in the ground you cant fix to the satisfaction of the customer!!!!!!! tomcruz55 <tomcruz55@yahoo.com> wrote:
And when you got a leak/break on the main header (aboveground or underground), you can forget about using Belzona or TDW.


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Main site: http://www.pipingdesign.com

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Design Detail and Development (a division of Blenray Pty Ltd)

Mail Address PO Box 1351 Castle Hill NSW 1765 Australia Tel Mob 0402 35 2313 Office 02 8850 2313 AH 02 8850 2324
We specialise in pipe network and waterhammer analysis, pipe stress analysis, the design of buried pipelines and thermoplastic pipe systems.

[Non-text portions of this message have been removed] Received on Tue Sep 13 18:29:00 2005

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