Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe (2009) / Chapter Skim
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3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data
3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data
Pages 43-98
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From page 43... ...
The Bureau of Reclamation's pipelines are long, cross many different types of terrain and environments, and are required to provide uninterrupted, reliable service. Reclamation's corrosion control decisions have been made to limit the risk of premature corrosion failures while accommodating different types of pipe and environmental conditions.
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From page 44... ...
Data Type 1 -- Documented failures of operating pipelines due to external cor rosion for pipelines of a given pipeline type, including pipe thickness, pipeline age, and soil condition. Such information can be converted into a linearized maximum pitting or corrosion rate for that specific failure (assuming that pitting begins upon pipe installation)
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From page 45... ...
Such information can be converted into linearized maximum pitting rates and, for measurements from a set of pipe segments, into a distribution of corrosion rates and a distribution of estimated failure times for a pipeline of a given thickness.
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From page 46... ...
As summarized in Chapter 1 of this report, the first presentation to the com mittee was made by representatives of the Bureau of Reclamation on its history, its concerns with the use of DIP with PE and CP, and the development of its Technical Memorandum 8140-CC-2004-1. A presentation was then made by L Gregg Horn and his colleagues from the Ductile Iron Pipe Research Association (DIPRA)
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From page 47... ...
Regarding question 1 -- whether PE with CP works on DIP installed in highly corrosive soils -- Horn stated that based on DIPRA's research and extensive data sets, "polyethylene encasement works in highly corrosive soils without cathodic protection." In response to question 2 -- whether PE and CP reliably provide a minimum service life of 50 years -- DIPRA's answer was "yes." Its consultant for statistical analysis presented information and graphs of corrosion rates to support these positions. Horn and colleagues stated that DIPRA has always recommended against bonded coatings for DIP and that they are not aware of any North American DIP company which is a member of DIPRA that would provide DIP with bonded dielectric coatings. A presentation was given by Graham E.C.
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From page 48... ...
, which allowed water to enter the probe body; they concluded that these data could not be used because of faulty probe configurations. Bell also discussed development of a new ductile iron probe that theoretically should more closely represent corrosion rates on DIP.11 Another presentation was provided by Mike Woodcock on his experience as a metallurgist with corrosion and corrosion control methods for iron pipe.12 He dis cussed the DIP microstructure, showed scanning electron microscope micrographs, and presented his experience with respect to widely varying corrosion rates seen for different DIP over the years.
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From page 49... ...
DATA COMPARISONS OF INTEREST The primary pipeline type of interest is DIP with PE and CP in highly corrosive soils -- defined as soils having a resistivity below 2,000 ohm-cm. The uncertainty about the use of DIP with PE and CP under these conditions arises from various concerns: that CP may fail to be effective due to CP malfunction or electrical shield 13 Michael Szeliga, Russell Corrosion Consultants, Inc., "An Independent Evaluation of the Effective ness of Polyethylene Encasement as a Corrosion Control Measure for Ductile Iron Pipe," presentation to the committee, Washington, D.C., July 29, 2008.
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From page 50... ...
In addition, the terminology for pitting corrosion rates has been standardized to "maximum observed pitting rate" for Data Types 1 and 2, "mean maximum pitting rate" and "standard devia tion of the mean maximum pitting rate" for data fitting a normal distribution, or 15 Bonds et al., "Corrosion and Corrosion Control of Iron Pipe: 75 Years of Research."
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From page 51... ...
Different soils, however, alter the corrosion rates for both materials." 17 Based on the DIPRA data, Bonds et al. also concluded, "Overall results indicated that the corrosion pitting rates of ductile versus grayiron pipe were soil specific to an extent but were essentially the same statistically (t-tests, 95% confidence)
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From page 52... ...
In order to evaluate the effectiveness of the different corrosion control meth ods, the committee sought field data and supportive information from a variety of sources and compared the input received to determine answers to the following questions: • What is the corrosion rate of bare ductile iron or cast iron compared to iron pipe with PE? • Has corrosion occurred and at what rate under intact PE on ductile iron or cast iron as a comparison for locations where electrical shielding may occur?
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From page 53... ...
, and vinyl-encased iron pipelines under a range of conditions.21 Exposure or burial times for the DIPRA ductile iron specimens ranged from 1 to 35 years and for gray iron from 1 to 103 years. This DIPRA study information presented to the committee in terms of "mean maximum pitting rates" is shown in Table 3-1, Rows 1 through 6.22 The mean maximum pitting rates (referred to by DIPRA as "mean deepest pitting rates")
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From page 54... ...
pipe examples, Average: 12.3 mpy Maximum observed Szeligac maximum observed pitting rates between 3.2 mpy and 22.5 pitting rates reported mpy, with 17 penetrations for 45 samples Data Types 1 and 2 NOTE: DIPRA, Ductile Iron Pipe Research Association; mpy, mils per year aRichard Bonds, L.M. Barnard, A.M.
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From page 55... ...
. Additional information provided by the Woolley analysis of the DIPRA data histograms24 for the bare and as-manufactured DIP showed that the underlying data sets of maximum observed pitting rates for the calculated mean values in Table 3-1, Rows 1 and 2, did not fit normal distributions; therefore the mean values have little physical significance, and these values are Data Type 4.
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From page 56... ...
These maximum observed pitting rates for bare and as-manufactured pipe samples as shown in Table 3-2 were obtained by the committee from the Woolley graphs, which presented the normal distribution curves from which the means and standard deviations were calculated and the histograms of the raw data were given. 25 Bonds et al., "Corrosion and Corrosion Control of Iron Pipe: 75 Years of Research." 26 Michael Szeliga, "Analysis of Ductile Iron Corrosion Data from Operating Mains and Its Sig nificance," ASCE Pipelines, Advances and Experiences with Trenchless Pipeline Projects Conference, Boston, Mass., 2007.
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From page 57... ...
However, as the graphs contained histograms of the raw data along with the normal distribution curves, the graphs of the fitted normal distributions, the reported means, and the reported standard deviations, this information could be used to set a scale to the histograms and thus to determine the maximum observed pitting rates for all five situations in soil conditions ≥10 points. The maximum observed pitting rate is approximately 26 mpy for bare DIP and approximately 34 mpy for as-manufactured (asphaltic-coated)
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From page 58... ...
pipe examples, of which 22 displayed complete wall penetrations, had a maximum observed pitting rate of 22.5 mpy.28 POLYETHYLENE-ENCASED DUCTILE IRON PIPE WITHOUT CATHODIC PROTECTION Mean Maximum Pitting Rates for Damaged Polyethylene Encasement The DIPRA study also compared as-manufactured (asphaltic shop-coated) pipe with pipe with intentionally damaged PE.29 The "combined" mean maximum pitting rate for a total of 62 pipe samples with intentionally damaged PE from five locations was reported as 11.2 mpy, with the individual mean maximum pitting rates from the five sites being: 0 mpy (Aurora, Colorado -- 8 pipe samples)
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From page 59... ...
Maximum Observed Pitting Rates for DIP with Damaged PE Fountain Valley Project Reclamation observed corrosion and two leaks on a 24- to 25-year-old, 16-inch (400 mm) DIP with PE on the Fountain Valley Project section of the FryingpanArkansas31 Project in 2007.32 This Reclamation project is located in Colorado, south of Colorado Springs.
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From page 60... ...
on an 18,000-foot-long DIP force main at damaged PE locations after 13 years.34 The pipeline was installed in 1973 and experienced its first corrosion leak in 1986, with a maximum observed pitting rate of 31.6 mpy (Data Type 1, Row 2a in Table 3-4)
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From page 61... ...
Deepest Maximum Observed Notes Row Reference or Data Source Size Thickness Pipe Age Soil Resistivity Pit Pitting Rate (All Data Types 1 and 2) 1 Bureau Fountain Valley 16-inch Class 50 24 to 25 520 ohm-cm 340 mils 13.6 mpy 2 leaks and 1 complete Project, Colo.
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From page 62... ...
Spickelmire, "Corrosion Control Considerations for Ductile Iron Pipe -- A Consultant's Per spective," Materials Performance 41(7)
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From page 63... ...
DIPRA reported that the mean maximum pitting rate of 151 samples with undamaged PE was 0.453 mpy in soils with corrosivity values equal to or greater than 10 points in accordance with the ANSI/AWWA C105 Standard, Appendix A, 38 Bonds et al., "Corrosion and Corrosion Control of Iron Pipe: 75 Years of Research"; Richard Bonds et al., "Corrosion Control Statistical Analysis of Iron Pipe," NACE Materials Performance (January 2005)
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From page 64... ...
Maximum Observed Pitting Rates A limited amount of additional information on the DIPRA study data sets was provided by DIPRA to Reclamation allowing the distributions of maximum observed pitting rates to be found for DIP with PE, as shown in Table 3-5, Row 1.40 As noted, the data histogram and the probability plot for DIP with PE indicate a bimodal distribution, with 137 samples showing no pitting corrosion and 14 show ing pitting corrosion with a mean maximum pitting rate of 4.9 mpy (for the 14 samples)
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From page 65... ...
TABLE 3-6 Maximum Observed Pitting Rate Under Polyethylene Encasement Without Cathodic Protection Project Location, Maximum Data Source or Observed Reference Soil Conditions Description Pitting Rate Notes and Data Type DIPRA study Case 2 with soil Corrosion rate Approx. 8 Distribution of observed pitting dataa and condition values based on DIPRA mpy rates for individual pipe segments Woolley ≥10 points, per Table 8 for 151 obtained from committee analysis analysisb report ANSI/AWWA samples with of DIPRA data.
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From page 66... ...
or on the age of the pipe and the measured deepest pit, and it assumes uniform linear pitting rates. If the actual pipe wall thickness is greater than the assumed wall thickness, then the maximum observed pitting rate will be correspondingly larger than the tabulated value.
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From page 67... ...
Soil Observed Notes (All Data Row Reference Data Source Pipe Size Thickness Pipe Age Resistivity Deepest Pit Pitting Rate Types 1 and 2) 1a DIPRA, Marston Lake, 6-inch Est.
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From page 68... ...
CIP December 2,800 mpy noted as being site joint 1959 to ohm-cm damaged testing August 1969 4 Bureau of Fountain 16-inch Class 50, 24 to 25 520 130 mils 5.2 mpy Pit under Reclamation Valley Project, 340 mils years ohm-cm undamaged PE Colo. 5 Others Vancouver, Section Class 52, 16 years 590 310 mils 19.0 mpy 3 complete wall B.C., Canada A-B: 100 310 mils ohm-cm penetrations to 1 of 3 feet, 6 cement lining, sections inches with 1 leak dug up in 1986-1987 6 Others Vancouver, Section Class 52, 14 years 500 134 mils 9.0 mpy B.C., Canada C-D: 100 310 mils ohm-cm 1 of 3 feet, 6 sections inches dug up in 1986-1987 7 Others Vancouver, Section Class 52, 16 years 280 118 mils 7.0 mpy B.C., Canada E-F: 175 310 mils ohm-cm 1 of 3 feet, 6 sections inches dug up in 1986-1987 8 Others Sheridan, 16-inch Class 50, 14 years 1,350 180 mils 12.0 mpy Wyo., Marshal 340 mils ohm-cm Field
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From page 69... ...
9 Others San Diego, 16-inch Est. 800 25 years 348 800 mils 32.0 mpy In 1999 Calif.
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From page 70... ...
14 Others Michael 16-inch 367.3 21 years No data 187.3 mils 8.9 mpy Over-the-line Szeligac mils on ohm- potential survey cm but did not indicate reported as active corrosion extremely under intact PE corrosive soil NOTE: mpy, mils per year; DIP, ductile iron pipe; DIPRA, Ductile Iron Pipe Research Association; "Others" refers to data sources other than the Bureau of Reclamation or DIPRA; CIP, cast iron pipe; CIPRA, Cast Iron Pipe Research Association; PE, polyethylene encasement; NACE, National Association of Corrosion Engineers; MIC, microbiologically influenced corrosion.
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From page 71... ...
Therefore, the committee has assumed that the maximum pitting rate indicated by one or more of the probes under the PE was likely between 5 and 6 mpy. The average corrosion rates for all probes inside the PE at the bottom of the pipe (6 o'clock position)
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From page 72... ...
MERL-08-15. 45 Spickelmire, "Corrosion Control Considerations for Ductile Iron Pipe -- A Consultant's Perspective." 46 Jerry Duppong, CH2M HILL.
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From page 73... ...
47 Spickelmire, "Corrosion Control Considerations for Ductile Iron Pipe -- A Consultant's Perspective."
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From page 74... ...
51 Cast Iron Pipe Research Association, A Report on Observation of Corrosion Protection of Cast Iron Pipe by Loose Polyethylene Wrap (San Diego, California, December 1968) ; DIPRA, A Report on Inspec tion of Cast Iron Pipe and Ductile Iron Pipe Protected by Loose Polyethylene Encasement.
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From page 75... ...
Location: Former DIPRA test site, Sorrento Valley, San Diego, Calif. FIGURE 3-3 San Diego, California, 8-year-old, 24-inch ductile iron pipe with polyethylene encasement at former test site of the Ductile Iron Pipe Research Association.
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From page 76... ...
54 Mark Corsentino, Anchorage Water and Wastewater Utility, communication with the commit tee, 2008. 55 Spickelmire, "Corrosion Control Considerations for Ductile Iron Pipe -- A Consultant's Perspective."
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From page 77... ...
Reasons for Variance in Reported Pitting Rates There seems to be a wide variation in the pitting rates reported in the DIPRA study summary and between DIPRA's random digs and what is actually being seen in some of the field cases cited. One reason may be the difficulty in accurately locating corrosion activity on DIP with PE during random digs.
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From page 78... ...
. 60 Szeliga, "An Independent Evaluation of the Effectiveness of Polyethylene Encasement as a Cor rosion Control Measure for Ductile Iron Pipe." 61 Szeliga, "An Independent Evaluation of the Effectiveness of Polyethylene Encasement as a Cor rosion Control Measure for Ductile Iron Pipe."
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From page 79... ...
The 6.8 mpy mean for undamaged PE in uniquely severe soil conditions is 15 times higher than the reported 0.453 mpy mean rate for undamaged PE in soils of ≥10 points. Likewise, the maximum observed pitting rate for undamaged PE in uniquely severe soil conditions may be much higher than the calculated 8 mpy maximum observed pitting rate for undamaged PE in soils of ≥10 points.
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From page 80... ...
Kroon, "Cathodic Protection of Pipe Encapsulated in Polyethylene Film," NACE Corrosion 2007 Paper 07040, Houston, Tex.; D Lindemuth, "Polyethylene Encasement and Cathodic Protection Proven Synergistic Corrosion Control for Ductile Iron Pipe," presentation to the committee, Washington, D.C., July 28, 2008.
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From page 81... ...
The soil resistivities for the fifth site, in Vacaville, were 1,200 ohm-cm to 48,000 ohm-cm as-received and 1,000 ohm-cm to 25,000 ohm-cm when saturated. Individual soil resistivity values for these pipelines are summarized in Table 3-8 in the following major section, "Summary of Known Cathodically Protected Polyethylene-Encased Pipelines." Southwest Pipeline One of the earliest-referenced studies of DIP with PE and CP is a large transmission pipeline project in North Dakota, where an impressed current CP system 67 Lindemuthand Kroon, "Cathodic Protection of Pipe Encapsulated in Polyethylene Film." 68 Lindemuthand Kroon, "Cathodic Protection of Pipe Encapsulated in Polyethylene Film." 69 Lindemuth, "Polyethylene Encasement and Cathodic Protection Proven Synergistic Corrosion Control for Ductile Iron Pipe."
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From page 82... ...
1984 24-inch 3 miles DIPRA Others Akron, Ohio 2001 16-inch 0.25 miles Trinidad, Trinidad and 1979-1982 24- to 60-inch Approximately 10 miles of the 30-mile Tobago Heavy-duty total were cathodically protected with polyethylene, 16 impressed current distributed anode to 20 mils thick ground beds California City 1975 14- and 16-inch Est. 1 to 2 miles Others pipeline Vernal, Utah 1984 Varies: 4- or 6-inch Sewer line 0.02 mile (100 to 200 feet)
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From page 83... ...
No external corrosion leaks reported through 2008; installation date assumed based on excavation date of 2007 and 21 year pipe age reference. 2,200 ohm-cm as received and One DIPRA excavation; pulse type, impressed current CP.
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From page 84... ...
Paul, 2007-2008 Dual 18-inch sewer 2.3 miles of dual force mains equaling Minn. force mains 4.6 miles total Others Totals: Pipeline distance, 369.57 miles; of that, pipelines in soils <2,000 ohm-cm, 352.65 miles NOTE: WEB, Walworth, Edmunds, and Brown; DIPRA, Ductile Iron Pipe Research Association; DIP, ductile influenced corrosion.
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From page 85... ...
iron pipe; CP, cathodic protection; est., estimated; PE, polyethylene encasement; MIC, microbiologically Denver, Colorado Two 4.5-mile-long parallel force mains with PE in Denver, Colorado, were cathodically protected in 1984.71 The two parallel force mains (14- and 18-inch diameter) were provided with an impressed-current CP system.
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From page 86... ...
Pipeline abandoned and replaced after only 12 years of service. NOTE: CP, cathodic protection; PE, polyethylene encasement; DIP, ductile iron pipe; mpy, mils per year; MIC, microbiologically influenced corrosion; "Others" refers to data sources other than the Bureau of Reclamation or the Ductile Iron Pipe Research Association.
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From page 87... ...
Additional testing and time are needed to explain fully the degree and severity of electrical shielding and the influences on both actual protection levels provided and on potential measurements made inside and outside the PE. 73 Spickelmire, "Corrosion Control Considerations for Ductile Iron Pipe -- A Consultant's Perspective."
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From page 88... ...
. 77 American Cast Iron Pipe Company, Investigation of the Fracture of a 16" DIP from SWPP Station 283+.
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From page 89... ...
Akron, Ohio The committee received information about a corrosion leak that occurred on a 16-inch DIP with PE and CP in Ohio in a less-than 6-year burial time.79 Historically, a 7-mile section of CIP had experienced corrosion breaks in the same area. After a third leak occurred in the same area on the cast iron pipeline, a short, 1,300-foot section was replaced with Class 56 (520 mil thick)
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From page 90... ...
were installed at a power plant in Vernal, Utah, in 1984, and CP was installed and operating by 1985.80 The raw-water and fire-water pipelines were excavated 80 William Spickelmire, discussions and correspondence with Jeff Mattson, Corrosion Control Technologies, Sandy, Utah, 1997 through 2008.
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From page 91... ...
The sewer line case is included here for completeness but is not included in the failure analysis to be presented in Chapter 4. However, the maximum observed pitting rate for this line was 11.3 mpy, which is very similar to the 12.5 mpy maximum observed pitting rates on one of the water lines; the latter is known to be entirely from external corrosion.
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From page 92... ...
Stroud from DIPRA stated, "The number of documented failures of polyethyl ene encased pipelines -- the vast majority of which are the result of improper instal lation -- is insignificant compared to the miles of Cast and Ductile Iron pipe that are afforded excellent protection with this method of corrosion prevention."87 85 CH2M HILL, California City Corrosion Control Study; California City Engineering Department, communication with the committee, September 2008. 86 Szeliga, "An Independent Evaluation of the Effectiveness of Polyethylene Encasement as a Cor rosion Control Measure for Ductile Iron Pipe"; Spickelmire, "Corrosion Control Considerations for Ductile Iron Pipe -- A Consultant's Perspective." 87 Troy Stroud, "Polyethylene Encasement Versus Cathodic Protection: A View on Corrosion Protec tion," Ductile Iron Pipe News (Spring/Summer 1998)
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From page 93... ...
Department of the Interior, "Corrosion Considerations for Buried Ductile Iron Pipe," presentation to the committee, Washington, D.C., July 28, 2008. 89 Joseph Pikas, "Case Histories of External Microbiologically Influenced Corrosion Underneath Disbonded Coatings," NACE International Corrosion 1996, Paper No.
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From page 94... ...
. Pitting Rates When looking at the pitting rate, it is of particular relevance to the committee's work that if the rate is above 5 mpy for a pipe with a 250-mil wall thickness, then 90 A.W.
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From page 95... ...
The DIPRA data used in conjunction with the Woolley report96 allowed the distributions of maximum observed pitting rates to be determined for the five pipe conditions reported in Bonds et al.97 For the other mean maximum pitting rates reported by DIPRA, the data distributions were not available to the committee, so the maximum observed pitting rates could not be determined. It should be noted, however, that the DIPRA study mean maximum pitting rate for the uniquely severe soils with undamaged PE was 6.8 mpy, which is 15 times the comparable mean maximum pitting rate of 0.453 mpy for soils ≥10 points as defined by ANSI/AWWA Standard C105, Appendix A.98 Therefore, the maximum observed pitting rate of DIP with damaged PE should be much higher than the 8 mpy maximum observed pitting rate for undamaged PE in ≥10 corrosive soils.
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From page 96... ...
Maximum observed pitting 2b Table 3-1, soils uniquely See Note 1 rates ranged from 3.182 severe, 70 samples with mean mpy to 22.5 mpy for of 28.7 mpy 45 pipe examples with 2c Table 3-1, varied soils, 89 See Note 1 measured pitting rates No data sought samples in five testbed sites including 17 penetrations with "combined mean" of 24.7 mpy for all five, all sites and the means for the individual sites ranging from 0 to 32 mpy depending on individual site 3 Damaged PE Table 3-3, varied soils, 69 See Note 1 Tables 3-3 and 3-4, varied Table 3-4, varied soils, maximum samples in five testbed sites, soils, 11 examples with observed pitting rate of 68 mpy with "combined mean" of 11.2 maximum observed pitting for Szeliga site and 50 mpy for mpy for all five sites, with the rate of 68 mpy. Corrosion Cape May, N.J., location.
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From page 97... ...
DIPRA, Ductile Iron Pipe Research Association; PE, polyethylene encasement; CP cathodic protection; DIP, ductile iron pipe; mpy, mils per year. NOTE 1: Insufficient data provided to convert uniquely severe soil mean rates or individual test site mean rate data to maximum observed pitting rates.
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From page 98... ...
, DIP with PE and CP in pipeline installations can be found to exhibit the maximum observed pitting rates characteristic of bare and as-manufactured DIP and DIP with damaged PE. These data indicate that DIP with PE and CP will not meet the target 50-year pipeline lifetime when installed in highly corrosive soils.
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