By structural loads I meant dead and live loads applied at the surface that
affect the deflection, stress,strain, combined loading and buckling resistance
of the pipe. Other loads include external pressure from the water table and
soil, and internal pressure from the fluid . Internal pressure and external live
loads have dynamic components.
I did mean celerity. The term celerity means wave speed. In terms of thermoplastic pipe the celerity is affected by the design of a combined soil/plastic pipe structure. If grouted in position in a microtunnel the wave speed is something near that of steel whereas in loose fill is nearer aboveground plastic pipe.There has been little research to determine the effect of various compactions of backfilll on wave speed.
aluser2 <alwynk@shaw.ca> wrote: Good comments and a really excellent discussion
.re:
"When the structural loads are applied either as static or time hisory
effects on a modal analysis the effects are inconsistent."
I am interested in what Geoff was saying. Not sure what he means by applying
structural loads. These are
different loads and would only appear as part of LOAD CASE combinations when
combined with transient analysis.
I agree the results from dynamic analysis can be inconsistent but this
usually occurs when the MAnagers /clients have no concept of the essential
and detail level reliable data usually required to model and get reliable
answers. Not knowing the material properties and restaints and or fluids
and even operating conditions all lead to unrelaibility in the analysis and
doing it properly takes information +communication and a lot of effort. The
trend is to quick dirty answers for eveything and then wanting perfect
outcomes. (usually with the expectation of pushbutton simplicity). I have
found that when the communication and information is good the software
(brand names) can be really good and highly informative and predictive. But
it is needle and haystack work as variability from detail accuracy is very
high. The slightest misinformation can really bite you.
But as geoff and others have said, purchasers rarely want to spend the time and effort and jump to the blame game when transients rear their ugly head. I have even had complaints for specifically excluding transients in proposals when I know (as is so often the case) they dont want to spend the time and money and are not forthcoming with information.
with the greatest courtesy I think geoff meant "efficacy" not "celerity"
"jury is till out on the celerity of buried thermoplastic pipelines"
- celerity as used often by steve means
fleetness, gait, haste, hurry, hustle, legerity, promptness, quickness,
rapidity, speed, speediness, swiftness, velocity
Actually i think the fitness for purpose of these materials is reasonably
well understood. Occasionally you see vendors trying to push thermoplastic
pipes into petrochem service though, and in some cases it has
foolishly happened... although I am always open to new ideas and the
envelope is constantly being pushed in materials and their applications
Anyway its great to discuss these issues as that is how knowledge spreads and everybody becomes better informed. Its not such an uphill battle then.
> Geoff,
>
> Thanks for your comments. While I sometimes wonder about plastic pipe
marketing claims (at least as they relate to water or sewer pipes etc. above
service line size, let me just say that even if they were correct for any
specific locale/application I'm not sure what that should mean to an
engineer. Further to what I mentioned in my long post (for Paul's "hurt
brain" condition I plead guilty), and then your specific mention of plastic
pipe work in the UK, I did happen to see recently (I suspect as a possible
result of at least some level of same) some folks there are apparently now
grappling with some issues apparently related to the use of plastic pipes as
mentioned at <a href="http://www.bhrgroup.co.uk/bhrsoln/stratech/pipepermeation.htm">http://www.bhrgroup.co.uk/bhrsoln/stratech/pipepermeation.htm</a>
that leads off,
>
> "...New information on the performance of polyethylene (PE) and polyvinyl
chloride (PVC) water pipes and gaskets in hydrocarbon contaminated soils is
urgently needed to help Utilities determine when the integrity of these
assets may be compromised. The UK government wants to see 30% of future
building projects on brownfield sites - but such sites frequently bring
exposure to contaminates. There is a growing need for better information on
the long-term behaviour of PE and PVC pipes when exposed to such
contaminates..."
>
> I wonder if the "30%" of construction to be in "brownfield sites" figure
stated here is a factor (perhaps along with some unintended problems?) in
the "urgency" expressed? In this regard, I have noticed that some
regulatory agencies at least in the USA are even now taking it appears some
pro-active, educating stances concerning these sorts of issues (e.g. see
<a href="http://deq.mt.gov/LUST/TechGuidDocs/Techguid16.pdf">http://deq.mt.gov/LUST/TechGuidDocs/Techguid16.pdf</a> etc.)
>
> Perhaps not unlike other sort of legacy issues mentioned in my post
(third-party damage etc.), it thus appears at least some of our friends in
the UK are apparently trying to deal somehow with this possibly very
difficult issue that is also the result of increasing
development/by-products of the Industrial/Hydrocarbon Age etc. (and also the
"urgency" perhaps indicative in general of the type of issues I mentioned in
some cases that at least in the past have not always been considered
upfront?).
>
> I am not familiar with "hot dip galvanized" in the context of ductile iron
piping, but I am aware that some European manufacturers have promoted for
many years zinc coating systems (in accordance with ISO 8179) as well as
other specialty coating systems. My company furnishes pipes per ISO 2531
and with external coating per ISO 8179 on international projects when same
is specified.
>
> Randy Conner - ACIPCO
>
>
> "Some powerful forces in the history of the world have been fueled by
combined effects of ignorance and inertia."
>
> -----Original Message-----
> From: <a href="/group/PipingDesign/post?postID=lWssvs0xYXk65LcvwRLryYcqQjafSmDgZ74QUp-fZxn0cb9RAXHCGq32Ohorm0lJ8UIRbAeluYFnuaNGuLXyOch6J0Q">PipingDesign@yahoogroups.com</a>
> [mailto:PipingDesign@yahoogroups.com]On Behalf Of Geoff Stone DD&D
> Australia
> Sent: Tuesday, January 17, 2006 7:26 PM
> To: <a href="/group/PipingDesign/post?postID=lWssvs0xYXk65LcvwRLryYcqQjafSmDgZ74QUp-fZxn0cb9RAXHCGq32Ohorm0lJ8UIRbAeluYFnuaNGuLXyOch6J0Q">PipingDesign@yahoogroups.com</a>
> Subject: RE: [PipingDesign]( Large Chilled) Water Network Design
>
>
> Randy,
>
> I always enjoy reading your commonsense factual commnets from the other
side of an argument. I agree plastic pipe materials are not the answer to
every application neither are they to be dismissed.
>
> The problems associated with buried pipelines in the WAE, I have been
associated with, are that they are 3m below ground, in reclaimed land, that
are subjected to sea water influx. GRP has had some mixed success there but
beciuse of its low strain tolerance requires more intensive design and
construction procedures. I attribute failures to the letting of design and
construct contracts where the bottom line rules the so called engineering.
Standards such as ISO 14692 and BS7199 are not enforced. Rather
manufacturers own standards are employed. Once buried and the contractor has
pulled off shore, who cares. There have been some spectacular failures over
the years.
>
> In the UK the water and wastewater market is dominated (90%) by
thermoplastics. DICL is used for high pressure rising mains only and then I
am told it is hot dip galvanised. Larger mains are in steel. I am sure that
this is an economic choice where the lower pressure applications can use
thermoplastics.
>
> In Australia Tyco manufacture DICL to DN750 in Class 20 and 35 (20bar
and 35 bar ratings). This is aimed at competing with thermoplastics. Our
economics are different. The cost of transport from one manufacturing
facility to the customer varies enormously.
>
> DICL is still used. Mild Steel Cement Lined (MSCL) is about 10% more
expensive than DICL. Thermoplastics & GRP are price targetted depending upon
factory loading, transport & customer history long before pressures are
considered.
>
> The jury is till out on the celerity of buried thermoplastic pipelines.
End constraints also modify the actual numbers. The effect of embedment and
native soil has not been researched. If there is column separation and
rejoining it hardly matters what material you use the extreme pressures will
exceed Joukowsky predictions.
>
> All material properties are strain rate dependent. The normal stress
strain graphs we learnt at college and university are generalisations. If
the theory of explosions, impact loads and fracture machanics are studied
impacts from waterhammer loads need to be considered in more depth.
Materials are able to withstand higher stress levels than predicted by
static analysis provided that they do not have faults such as weld defects,
notches, cavities, delaminations etc.
>
> Even the attempts to link waterhammer pressure loads to structural
(pipe) behaviour are fraught with danger. It is nighe impossible to
replicate a physical model for waterhammer analysis in the same way as a
structural pipe model. When the structural loads are applied either as
static or time hisory effects on a modal analysis the effects are
inconsistent. Pressures are applied at curved surfaces whereas structural
loads are applied differently.
>
> The codes and standards are presented as compromises with conservative
approaches to the design of systems. They must be tempered with field
experience. The design is but one part of an installation. The code such as
B31.3 covers, design, fabrication, examination, installation and testing.
The code is also backed up with material standards and requirements for
qualification. They are an intricate web of documents that cannot be grasped
overnight or by reading a few emails. It takes decades to get abreast of
them and keep up with the changes.
>
> Geoff
>
>
>
>
>
> 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.
>
>
>
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Design Detail and Development (a division of Blenray Pty Ltd)
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[Non-text portions of this message have been removed] Received on Sun Jan 29 21:21:00 2006
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