Integrity Testing of a PE Sewer Main across a River
Integrity Testing of a PE Sewer Main across a River
(OP)
A concern has be raised by an authority about the installation of a PE main across a river. The pipeline is to be installed by horizontal direction drilling. It is a DN560 PN16 pipe operating at <4bar. The pipeline will be installed in the aquifer that supplies the towns water.
Council have rejected notions of metering either side of the river because of the need for calibration.
Hydrotesting every three months is only good for the day the test is carried out.
My experience is to do nothing and rely upon testing of the water source for pathogens as would be done in any event.
Any other thoughts?
Council have rejected notions of metering either side of the river because of the need for calibration.
Hydrotesting every three months is only good for the day the test is carried out.
My experience is to do nothing and rely upon testing of the water source for pathogens as would be done in any event.
Any other thoughts?





RE: Integrity Testing of a PE Sewer Main across a River
"If everything seems under control, you're just not moving fast enough."
- Mario Andretti
- when asked about transient hydraulic analysis
http://virtualpipeline.spaces.msn.com
RE: Integrity Testing of a PE Sewer Main across a River
I already suggested that but the Council baulked at the $500,000 price tag. I also suggested re routing across an existing bridge but that would cost more.
I have now suggested a risk workshop with Council, authority and contractor present to determine the risk, likelihood and consequences. Perhaps they will then resolve the issue.
It is all about money. Council do not have any but are facing an authority who is risk averse.
Cheers
Geoff
RE: Integrity Testing of a PE Sewer Main across a River
"If everything seems under control, you're just not moving fast enough."
- Mario Andretti- When asked about transient hydraulics
http://virtualpipeline.spaces.msn.com
RE: Integrity Testing of a PE Sewer Main across a River
"If everything seems under control, you're just not moving fast enough."
- Mario Andretti- When asked about transient hydraulics
http://virtualpipeline.spaces.msn.com
RE: Integrity Testing of a PE Sewer Main across a River
(I guess the followup question if the first one is somehow answered might be, "What will one do if (when?) the underwater hdpe pipeline leaks, is damaged or is separated under the crossing?" -- Perhaps very limited options could exist for that kind of pipe, again perhaps a reason for "concern". I guess at least with a steel casing as suggested by BigInch, it might be possible to somehow extract the pipe, or pieces thereof, from accessible points on the bank etc.
RE: Integrity Testing of a PE Sewer Main across a River
"If everything seems under control, you're just not moving fast enough."
- Mario Andretti- When asked about transient hydraulics
http://virtualpipeline.spaces.msn.com
RE: Integrity Testing of a PE Sewer Main across a River
With DICL I would be really concerned with leakage from the rubber ring gaskets. Again construction costs would be way over that for HDD PE pipeline. Building coffer dams to install DICL in trench is not something to be considered. There is a high flood plain that is common in Australia.
We have asked the authority to advise where else they have demanded such measures and what were the acceptable solutions? Even Sydney Water do not do anything and there are many HDD pipelines in PE. In Europe & Asia 90% of new water and sewage lines are in a thermoplastic. DICL is reserved for higher pressure mains. Even then DICL lines are being displaced by GRP.
The environmentalists have jumped on the bandwagon with the high energy costs of making metal products. With the carbon trading schemes in vogue the DICL will not be with us much longer.
RE: Integrity Testing of a PE Sewer Main across a River
If the truth be known, I think they're being a bit unreasonable, but authorities of all kinds are well known for that.
"If everything seems under control, you're just not moving fast enough."
- Mario Andretti- When asked about transient hydraulics
http://virtualpipeline.spaces.msn.com
RE: Integrity Testing of a PE Sewer Main across a River
1.Actually, while problems can occur with any pipe there should be no more concern of leakage through a ductile iron pipe (DIP) system. In fact, as shown on page 3 of the document at http://www.dipra.org/pdf/DIPvsHDPE.pdf, (per AWWA C151) for DIP, "Each pipe tested to a minimum of 500 psi for at least 10 seconds at full pressure..." whereas for hdpe pipe (per AWWA C906), "Only one pipe size from three size ranges (4- to 12-, 14- to 20-, and ≥ 24-inch) are subjected to an elevated temperature sustained pressure test semiannually. Also, only one pipe per production run may be subject to a quick burst test. A ring tensile test or a five-second pressure test can be substituted for this test." (thus, it appears there is no hydrostatic testing requirement for each hdpe pipe). Furthermore, when it comes to required testing of a completed, buried pipeline in the field, I know that the make-up water allowance for testing hdpe pipelines can be quite large. At one time I know one of the major hdpe pipe manufacturers in the USA advocated e.g. for 12" piping field tested at 150 psi a testing allowance roughly about ten times more make-up volume than allowed for 12" ductile iron pipe per ANSI/AWWA C600! I guess the plastic industry claim of "jointless" and "leak-free" piping is based on the assumption that all of that make-up water unquestionably goes into elasto-plastic expansion of the pipe (in spite of varying surrounds that might even include e.g. concrete encasements), and not a drop whatsoever can possibly go out of an imperfectly fused joint or (inevitable at some point) lateral service or other connection, not to mention manufacturing defects or physical damages/punctures during or after installation! At least after a contractor showed me a reportedly leaking, fused hdpe pipe joint cut out and in the back of his pick-up truck in Mississippi roughly a quarter century ago, I have known that in reality (and contrary to some plastic pipe manufacturers and fusers et al disingenuous or outright deceptive claim) hdpe piping does in fact have joints, and it is not in fact (at least always) leak free! In fact, over the last few years I have seen claims that dependable QA of hdpe welded or fused joints has been quite difficult, and some authorities now claim that there are now large numbers of variously imperfectly fused joints and other connections out there in existing hdpe systems (I believe you would see this as well with even a quick Google search). Additionally, DIP has been/is being successfully installed in the USA by HDD and other direct trenchless methods for now going on at least 12-14 years, and the practice is incidentally now spreading worldwide.
2. Going into this 21st century, I believe the demand e.g. for ductile iron pipe at least in the USA (and perhaps due to the many advantages it offers even also worldwide) is greater than it has ever been. While this is no doubt due in part to the pressing need in general for good water/wastewater conveyance, I have also seen that in at least the most comprehensive/objective studies of bad things that happen to pipelines (i.e. those that do not exclude incidence of breaks or failures such as third-party damages), it appears the greatest frequency of significant problems to working pipelines are caused by application of force, either internal pressure or external forces/impacts etc. In this regard, and while certainly not denying some utility of any other pipes, metal vs plastic pipes are "apples and oranges. E.g. metal pipes can generally/overall be more easily located, can obviously withstand higher pressures and incursions/impacts, and have a very good performance record in all respects than even the thickest class plastic pipes.
3. I understand "engineered" plastic pipes must in general be derived largely from "virgin materials" for most dependable performance. The plastic advocate site at http://www.ppfahome.org/pe/faqpe.html contains the quote, "All polyethylenes are made from petroleum feedstocks also known as hydrocarbons." Also, in the case of even pvc pipes, the vinyl advocate's site at http://www.azom.com/details.asp?ArticleID=987 (vinyl" in this site is synonymous:with "polyvinyl chloride) furthermore contains the quotes:
"Vinyl is composed of two simple building blocks: chlorine, based on common salt, and ethylene, from crude oil.
The resulting compound, ethylene dichloride, is converted at very high temperatures to vinyl chloride monomer (VCM) gas."
"Only 43 percent of vinyl comes from nonrenewable petroleum feedstocks. The balance (57 percent) comes from salt."
" More than 14 billion pounds of vinyl are produced annually in North America. " Of course, however, there is no little and apparently escalating concern in some sectors for the perhaps non-obvious consumption avenues of oil!! (e.g. see the site at h
On the other hand e.g. ductile iron pipe is derived most largely from recycled (obviously renewable, to large extent) automobile and appliance etc. scrap iron and steel.
4. While I believe also estimates of "energy" etc. involved with manufacture etc. of various pipe materials have bounced some around the map over the years (based on assumptions etc. made), I noticed e.g. as explained in the article, "Ductile Iron vs Polyvinyl Chloride Pressure Pipe", by Energetics and published in the June 1991 issue of Water of the Australian Water and Wastewater Association, that no little amount of energy and greenhouse gas emissions have reportedly been involved with the manufacture of e.g. pvc pipe. I saw that report made the statements in its Executive Summary, ""It is evident from Table 1.1 that the manufacture of DN 100 uPVC pressure pipe (class 20) requires 80% more energy per metre length (see Table 5.2) compared to ductile iron. A DN 150 pipe of the same class consumes 150% more. In terms of greenhouse emissions, the manufacture of one metre of DN 100 uPVC pipe of the same class i.e. class 20, emits 20% more carbon dioxide compared to ductile iron, while a DN 150 releases about 70% more. " That report didn't even get into another perhaps even more significant energy aspect of pipelines, that being the energy that will be consumed in service to deliver the required volume of water throughout a pumped pipeline's life (in the form generally of electrical power to the pumps). In spite again of very lofty assumptions of favorable "frictional coefficients" by the plastic pipe industry (it appears as I've read in inquiries from some engineers, backed up by little if any published results of field testing of actual pipelines) and maybe even the perceptions of those convinced by those claims of the plastics industry, at least with modern inch-sized pipes in the USA much less energy will be consumed to deliver a given quantity of water by a larger inside diameter (modern lined) ductile iron system. Again, much stronger material means lesser wall thickness required for the same outside diameter or even smaller outside diameter plastic pipes (and understandably concomitant greater flow diameter/capacity/lesser head loss) even while the metal pipes are providing even much greater structural/strength. A downloadable computer program tool, "Hydraulic Analysis of Ductile Iron Pipe" is available from http://www.dipra.org/ (for interested readers to look at/compare such effects, for themselves and at their leisure).
5. Finally, with regard to eventual total life-cycle including "end of life" issues (a major need for replacement e.g. is after all simply increased demand and "too small", old mains), it is known that iron pipe is tough enough to be dug up and re-used elsewhere, most common metals are readily recyclable, and furthermore it appears iron actually significantly escalates in value over time (in that arguably not much unlike other "precious metals, to the point where it is now obviously even some prized by thieves, though maybe to a little lesser extent than e.g. copper!) On the other hand, I don't think many shards of plastic waste are likely to be stolen at any time in the near future! Thus, much plastic is apparently now being landfilled and/or burned, reportedly further to produce concomitant greenhouse gases, dioxins, hydrochloric acid/phosgene gas or whatever fumes etc.
Please be advised it is not the intent of this post to disparage the plastics, as they have been around long enough for at least some very experienced Engineers to learn most of what they can and cannot do, and they apparently have some utility in areas (and frankly, I don't even begrudge at least reasonably honest pipe salespeople trying to sell); however, I felt it was necessary to respond to the comments made about ductile iron. Based on some citable references, perception and assumption are not always reality.