Ductile iron pipe
Ductile iron pipe
(OP)
What is the C (Hazen William coefficient factor) for:
1) New Ductile iron pipe=
2) Old Ductile iron pipe(10 years old)=
1) New Ductile iron pipe=
2) Old Ductile iron pipe(10 years old)=
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RE: Ductile iron pipe
Richard A. Cornelius, P.E.
WWW.amlinereast.com
RE: Ductile iron pipe
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
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://
RE: Ductile iron pipe
h
RE: Ductile iron pipe
RE: Ductile iron pipe
RE: Ductile iron pipe
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.
RE: Ductile iron pipe
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
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).