I noticed that a couple responses to this and other threads have apparently sort of tried to promote/talk the original inquirer of this thread out of an apparent initial choice of steel piping to instead types of plastic or polymeric pipes. I believe the general capabilities/long-term properties, as well as limitations, of contemporary lined steel and ductile iron pipes are now very well-known by many experienced designers, installers, and maintenance people in a great many utilities and industries, including various hydronics and geo-applications etc. While perhaps contrary to perception, at least many traditional plastics and composites (some call "modern") have likewise been around for quite a while and are fairly well-known. I am thus not attempting to diminish the importance of attention to any of the responses that have been so far provided, nor is it my intent to deny the utility of any type of piping for any prospective application. However, I just thought it might be good to add (for any less experienced folks that might read the referenced posts here or in archive, and maybe even as a reminder to others) a little more information. While virtually all piping materials are now covered by some sort of standards, and the installed costs of various pipes are often not far apart, the pipes produced from comparative manufacturers' literature and even consensus standards are sometimes far from "equal" in many respects. While the standards, as well as allowable stresses and various forms of safety factors etc. expressed in standards and textbooks, are helpful, I believe sometimes it takes direct side-by-side practical testing and/or experience to recognize the real differences in the actual supplied strengths as well as many other features of comparative pipes. In this regard some might be interested in several such differences, e.g. as a result of some direct side-by-side comparisons/tests of actual commercial pipes and wall materials therefrom, with much testing either independent or witnessed by third-parties, of say ductile iron pipes compared to various types of contemporary common plastics such as available at http://www.dipra.org/pdf/DIPvsPVC.pdf, http://www.dipra.org/pdf/DIPvsHDPE.pdf, and http://www.dipra.org/pdf/dipVsPVCO.pdf etc.
I am familiar with basic "celerity theory" upon which I guess some claims that plastic pipelines will produce low surge is based, but I think there is reason to suggest the results of some approaches are perhaps over-simplified as they relate to the real world of how pipelines are connected and operated; also, some evidence indicates low or no surge allowance suggestions may eventually be inadequate with regard to what level of surge may be actually present in practical pipeline application. I likewise believe one needs to be particularly cautious with a claim/perception that generally low-moduli, weaker plastic pipes are the answer to problems caused e.g. by unanticipated high pressures, whether that be from surge or maybe even from other future demand unanticipated by the original "designer". Over the years I have personally witnessed common smaller sized, minimum classes of ductile iron and steel piping, as well as some joints and even some restrained joints of same, handle even many thousands of psi pressure in our laboratories. On the other hand, I have seen quite heavy schedules/classes of various plastic pipes in the same laboratories handle only small fractions of such pressure levels. I've additionally heard and seen from engineering lists and elsewhere of a good many, in some cases quite calamitous field failures of many other types of pipes that have for whatever reason been blamed on surge or surge/pressure-related fatigue. This is not surprising to me(e.g. as shown in the tables of results in the documents at the above links I've provided), when the actual bursting pressure in the laboratories of say 6" (~150mm) ductile iron pipes are compared to various plastic pipes of the same size, and I see for example that the minimum available class ductile iron pipe withstood on the order of four thousand or so psi (275 bars), whereas the various quite heavy (chosen for most conservative comparison) schedule plastics typically withstood only a few hundred psi! With regard to larger pipes, my company actually hydrostatically tests every piece of for example 1000 mm Class K9 ductile iron pipe and its joining ends (with actual push-on gaskets, in a proprietary very high pressure proof-test procedure) to a level of 839 psi (58 bars) before they leave the works. Most steel pipes are high-pressure hydrostatically tested at the factory in similar fashion. Metal pipes can also withstand the effects of negative pressures/vacuum, and buckling as a result of even high external pressures in accordance with analyses per AWWA Manual M11, DIPRA, and other references. While not promoting the happenings, if/when? unintentionally high pressure is put on a pipeline due to surge or frequent pumps starting and stopping, future demand, or simply a pipeline "filler" or test pump operator falling asleep in an overnight filling/testing operation etc., which piping materials are most likely to survive to provide some dependable service to the Owner? It should also be revealed that low moduli pipes only relieve surge compressions at the expense of increased expansions and Poisson movements of the pipe wall, as well as sometimes substantial thermal variations/movements. There have been some who have written that the long-term effects of such movements, and I guess also of the relatively soft pipe walls relative to whatever is in the bedding or encasement that is initially placed by the contractor or later migrates into contact with the pipe wall, are also uncertain. Plastic pipes also prolong the "critical time" for such operations as valve closure time so as to create a maximum surge event when compared to that of metallic, perhaps making the knowledge/skill level of field operators even more critical. While I think we are all in basic agreement on the issue that corrosion must be appropriately considered and addressed where it is or will be a problem (as should I believe should such issues as environmental cracking/embrittling/ageing agents, exposure to hydrocarbons/solvation, and permeation of volatile environmental contaminants etc. in various plastic pipes), I believe neither corrosion nor "celerity" should disqualify substantially proven, traditional materials from appropriate consideration in many applications.
While the original inquirer may not need any defense in his choice, perhaps to some others all benefits of traditionally chosen systems may not be fully appreciated until they are gone (maybe not unlike the old pop song, "you don't know what you've got 'til its gone - they've paved paradise and put in a parking lot"?) I believe one other perhaps notable aspect not traditionally given great shrift in some standards, but that is getting more exposure in the contemporary media and regulatory agencies is "third-party damage". In an increasingly populated world, with increasingly congested infrastructure, accidental damages due to initial or subsequent construction in the area and other substantial loadings/impacts are an increasing and perhaps even now the greatest threat in many areas. An ability to locate pipes and leaks in a real world (of imperfection), and to readily repair same with simple tools, available devices/materials, and labor are also helpful (or even critical). As perhaps immortalized in the movie "Forrest Gump" and many others, perhaps near inevitably "s$%+ (stuff) happens"!
I've also noticed some entities are now even suggesting or requiring folks to
consider various "vulnerabilities", up to including intentional sabotage and
terrorism, in their decisions regarding aspects of infrastructure. In similar
regard, I happened to notice not long ago an interesting, quite detailed account
of an unfortunate incident that eventually involved the quite substantial
"Alaska or Alyeska Pipeline" (I think a mostly 48"/~1200 mm 1/2"/~12.5 mm thick
steel pipeline about 800 miles long, exposed over some extant, and also
supported by "vertical support members" composed of some smaller steel pipe I
remember my company furnished 30 or so years ago) at
http://www.planetark.org/dailynewsstory.cfm/newsid/12691/newsDate/8-Oct-2001/sto\
ry.htm. While I heard of this incident some time ago, this article appears to
provide more detail regarding this particular incident than what I had
previously heard -- it indicates the weapons of choice to accomplish this only
rifle piercing of this pipeline may have been a .338 Winchester Magnum, and
apparently a good bit of what used to be called in the American Wild West,
firewater. With such weapons, this fellow was clearly capable of doing some
damage to something!! While this one bullet penetration in a quarter century
reportedly caused quite a mess (due to extremely high pressures etc.), I believe
I read elsewhere that more than two thirds of the oil that leaked in this
incident was reportedly recovered and somehow reinjected back into the system.
I think this pipeline has otherwise pretty well endured several other trying
incidents over a very long time, including I think crossing a fault where an
~150 year in North America earthquake event (with several meters of relative
ground movement) that actually occurred not far removed in time from this
"shooting". Perhaps worth noting also, I think I saw elsewhere that this
pipeline had delivered 13 billion barrels of oil prior to these two incidents!
What is perhaps less noticed in the above article is that this steel pipeline
"...has been hit by bullets in the past." I suspect there thus could well have
been more, even messier incidents had any weaker material been employed. We
live in an increasingly interesting world where virtually anything can and does
happen -- two weeks ago and a couple miles from where I'm sitting I know a lady
woke up looking at a bullet lying on the bed next to her. This was on New Years
Day, and the slug had apparently been fired into the sky by a New Years reveler
, came down crashing through/penetrating her roof, attic, and plaster ceiling
etc., until it apparently came to rest by then fairly harmlessly onto the bed
beside her!!
It may very well be true that there are at least a few engineers around now that understand some substantial possible intricacies involving surge and water hammer issues with all types of pipes, and promotion/sharing of measured knowledge should certainly be encouraged. We must all also continually look for/at improvements, advances and alleged advances in materials and processes. Some may eventually know enough about everything to very closely tailor designs and products etc. to everything that they will be called upon to handle in the field (without worrying about "conservatism"/unknowns). However, in the mean time maybe there are huge numbers of pipeline projects out there that must be built to work reasonably well in a very big and increasingly complicated world, and I just wanted to make sure all are aware there may be other points of view (it sometimes helps to have very strong, tough pipe).
Sorry for the long post. While these views are my own, I should note I have worked for many years for a company that is now in its second century of providing increasing quantities of metal pipes for the world's needs.
Randy Conner - ACIPCO
"In ancient times, warriors traveled to the ends of the earth. They sought out
those regions which produced metal with strength, agility, and endurance. We
did not have to go far to find the precious steel that gives our ship the same
qualities. We found our mettle in New York." [Acting Secretary of the United
States Navy, Hansford Johnson speaking during the recent ceremony commemorating
the melting of steel salvaged from the World Trade Center into the bow stem
casting for the new U.S. Navy vessel, the USS New York].
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