Ductile iron pipe 1

[sokos]

What is the C (Hazen William coefficient factor) for:
1) New Ductile iron pipe=
2) Old Ductile iron pipe(10 years old)=

 

[dicksewerrat]

Look in your hydraulics book

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[rconner]

The value that has traditionally been recommended by the Ductile Iron Pipe Research Association (DIPRA) for cement lined ductile iron pipe is C=140. Values for "C" actually obtained in the field for actual pipelines can vary above and below this number, e.g. as illustrated by many field measurements of many pipelines over many decades by DIPRA, available in Tables 1 and 2 at

http://www.dipra.org/pdf/cementMortarLinings.pdf

(I think the minor losses of any fittings that may have been in test reaches have typically been conservatively ignored by DIPRA).
Some other parties, including the Haestad/Bentley folks (who appear to have some experience in this field) explain in a table “C-factors for various pipe materials” in their new book, “Advanced Water Distribution Modeling and Management,” that “C” for actual pipelines can also vary due to other variables. I believe this Table is available for view at the link “C. Tables” at

http://www.haestad.com/library/books/awdm/online/wwhelp/wwhimpl/java/html/wwhelp.htm.

Of course, I guess it should probably also be noted “C” factors in older piping for all materials can be affected over time by partially closed valves, sedimentation or other obstructions, and also other modifications to the piping over many years (that may not necessarily have anything to do with flow surface -- (see also another interesting take on some of these issues/behaviors, such as mentioned in the thread at

http://www.haestad.com/hmicom/listserv/archive/default.asp~action/mess/messid/6074/searchid/69247

).

 

[nackra]

Also, check your regulatory agency requirements, Illinois has some limitations for "old" sewer forcemain design.

http://www.ilga.gov/commission/jcar/admincode/035/035003700D04700R.html

 

[cvg]

this information was published by Hazen and Williams in their book "Hydraulic Tables" originally copyrighted 1905. While DIPRA recommends 140 for new pipe, I have never used that value and generally hesitate to use anything over 120 for new pipe for a more conservative approach. As you might expect, the agency which promotes the use of ductile iron pipe states a very high value of the coefficient...

 

[rconner]

From reading the DIPRA cement lined pipe publication at the first link I provided it would appear that DIPRA is basically "recommending" what the voluminous actual water pipeline flow test data (I suspect gathered predominantly by professionals and with perhaps even no little attention and interest of the many of the notable utilities involved for many decades) indicates. As far as I know cement linings for cast iron piping did not exist in the Western hemisphere when the first Hazen-Williams work was published; however, I believe they have a very well established world wide record in achieving and maintaining quite high Hazen-Williams flow coefficients, that has been reported by authorities including DIPRA since they were first used in the USA shortly thereafter (in 1922). It is perhaps worthwhile to note that that very first cementlined 8” cast iron pipeline installed in 1922 in Charleston, SC is still in successful service, has reportedly carried some quite aggressive water in the past, has been flow tested many times over the last 84 years, and I believe the pipeline installed with this very first production effort at cementlining pipe has rather consistently demonstrated C factors in the range of 130 or more. Frankly, had the original designer assumed a C = 140 for even this very early lining effort, I suspect there would have been little if any practical hydraulic problems over now more than eight decades as a result of that assumption (I believe e.g. that at a flow velocity of say 3 ft/sec velocity there would be only about a half a psi or 0.04 bar head loss difference between a C=130 and C=140 assumption in an 8” cementlined pipeline 1,000 feet/305 m long). I am generally an advocate of conservatism and don’t disagree with reasonable/equitable practice of same by responsible engineers; however, in this regard I would be much more worried say about some alternate material competition to DIPRA, who appear to be promoting C factors in the C=150-160 range (the latter value I’ve seen appears to be alleged better than the “smooth (straight) pipe” curve!), in some cases also with actual internal diameters of pipe less than DIP, or even less than “nominal”, and with it appears far less if any published research on working pipelines.

 

[cvg]

I would agree that a factor of 140 may be appropriate for a new, CML pipe, properly installed. In fact, Hazen's book recommends a value of 130 for new iron pipe. It documents cast iron pipes with coefficients as high as 147. It documents mortar lined pipes with values up to 145 - 150. However, it also states that this extreme smoothness is not durable and that subsequent experiments on the same pipes generally have given lower coefficients. The Hazen Williams published values for 11 to 12 years old are approximately 110.

Hazens book documents numerous factors including quality of installation, quality of lining, size, water quality, age, growth of tubercles etc. All of these will reduce the capacity of the pipe and reduce the roughness coefficient. He published a table which shows the decrease in the value of C over many years, assuming unfiltered river water. The table assumes all iron pipe starting at C=130 and after 100-years the C is reduced to a value between 29 and 59 (varying based on size). This table takes into account the fact that tuberculation will accumulate on the pipes (at a rate of about 3% per year) and reduce the effective inside diameter and reduce the amount of flow through the pipe.

As a result, most designers use a reduced value for C to account for these and provide a reasonable safety factor.

 

[rconner]

Thanks for the information/reference, and scanning this book (that I happened to have) was an interesting historical read. It appears Mr. Allen Hazen passed away some time prior to 1933, when the third edition of the “Hydraulic Tables” book that carried his name was published. I noticed this book contained the quote, “For masonry conduits of concrete or plastered, with very smooth surfaces, when clean, values of c=140 may be observed. Generally such surfaces become slime-covered, reducing the value of c to 130 or less in a moderate length of time; and if the surfaces are only a little less smooth, say in such shape as is represented by ordinary good work, the value of c is reduced to 120.” I did also see the reference in this book to some tests indicating some initially very high “smoothness” was “not durable” (it appears specifically referencing to some tests of “Cement pipe, poured in steel molds” with apparently very high c coefficients >144, but in one case also of some sort of “tunnel”/the Catskill Aqueduct” c=136). However, I did not happen to see a claim that even these coefficients dropped say all the way down to 110; nor am I sure if it would be fair (seeing what was actually described/tested, in even referring to these few cases that did not appear to be factory cement lined iron pipes ) to apply whatever this experience was to values for factory cement lined iron water distribution pipes that perhaps had not caught on too much in all areas at that time and most of which of course have been produced in more recent decades. It appears on the other hand that the bulk of the DIPRA work I mentioned before showing high and substantially sustained flow coefficients has however been confirmed on cementlined pipe since that time.

It is well-known that tuberculation over much of exposed barrel areas, with in many cases subsequent dramatic reduction effects on “C” (as explained by Hazen et al) has occurred as described when unlined steel or iron pipes, or pipes and/or fittings etc. that were provided with only extremely thin (very few mils) tar-dipped or asphaltic etc. linings and were subsequently exposed to some aggressive waters over time. It is my understanding the thicker cement linings were developed specifically to eliminate or minimize the aforementioned gross tuberculation, and thus do all practical to maintain high flow coefficients. While I mentioned some cement lined iron pipe has been in service since 1922, perhaps unfortunately I believe they were not necessarily universally adopted/specified for water service in all areas until the 1960’s or 70’s, and maybe even later for some fittings. I suspect the presence of much non-cementlined pipe for some decades in some systems has provided some opportunity for confusion with regard to iron piping flow capabilities and expectations, and probably even some deliberate misinformation by iron pipe competitors. Nevertheless, I believe that now major utilities, consultants, and manufacturers have in most recent decades been near universally recommending/specifying cement lined pipes and fittings for water service.

Of course all linings and for that matter all pipe materials are subject to formation of “slimes” in some raw water and sewer applications (see e.g.

http://www.canclay.com/htdocs/Sliming Graph of Pipes Large.pdf

and as discussed concerning actual sewer system studies after a few years in these forums at

http://www.eng-tips.com/viewthread.cfm?qid=73633&page=19,

or in some very hard water cases even substantial build-ups of calcium carbonate, struvite, and other “scales” etc. that undeniably can result in some deleterious effects on flow (as well as sedimentation and partially closed valves or other occlusions etc. mentioned above that also can markedly affect coefficients); however, I suspect much of the water at least in most of the modern world (at least in distribution mains that are the topic of this thread) is treated by disinfection and often also for appropriate water balance by various other processes to produce essentially “clean” water for consumers that also does not clog distribution piping.

I believe the first standard for Cement-Mortar Lining for Cast Iron Pipe and Fittings (ASA A21.4) was not published until 1939, of course six years after the 3rd edition Hazen book was published, and the forward to the current ANSI/AWWA standard C104/A21.4 is also good reading/explains much of this history, if anyone is further interested in same. My 31 years of admittedly some limited experience, and the preponderance of applicable evidence and documentation I have seen (as well as a few cement lined pipes I have personally looked at myself after carrying aggressive water for up to 60 years), indicates such linings have in general been quite successful in achieving these objectives (and of course this lining is now standardized by the consensus ANSI/AWWA A21 committees and standards, I suspect indicating some confidence of these much more notable folks/entities as well).