Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe (2009) / Chapter Skim
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5 Evaluation of Other Corrosion Control Alternatives
5 Evaluation of Other Corrosion Control Alternatives
Pages 116-130
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From page 116... ...
The results of this evaluation are summarized in this chapter. BONDED DIELECTRIC COATINGS ON STEEL PIPELINES WITH CATHODIC PROTECTION Although the majority of dielectrically bonded steel pipes with CP are reported not to have a history of leaks, in a few instances corrosion resulted in leaks.
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From page 117... ...
Technical Memorandum 8140-CC-2004-1a Southwest 1983-1992 Varies; 43 Severely No external corrosion leaks reported Pipeline Project, Tape assume miles corrosive through 2008. N.Dak.; Bureau 24- to below 36-inch 2,000 ohm-cm Mid-Dakota Rural 1996 to 2002 Varies; 25.4 Severely No external corrosion leaks reported Water System, assume miles corrosive through 2008.
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From page 118... ...
The external corrosion leaks reported by OPS can be categorized as being caused by one or more of the following: • Disbonded coating, • Interference or stray currents, • Improper levels of CP at or near the leak area, and/or • CP system failure. To reduce the number of leaks, the regulations and PHMSA require liquid and gas pipeline operators to implement an Integrity Management Program (IMP)
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From page 119... ...
A chart of cumulative leaks versus time for almost 70 years of service clearly shows the benefit of CP in extending the service life of this water transmission pipeline. In the paper containing the chart of leaks versus time, the author discusses the positive experience that Canadian cities have had with hot-spot protection of existing ductile iron and cast iron mains in reducing the number of leaks and presents corresponding cumulative leak charts versus time of CP installation. Similarly, a paper on "Protecting Ductile Iron Water Mains" describes a number of examples of the effectiveness of CP in minimizing corrosion leaks on corroding or new pipelines. Another example of how CP can reduce corrosion is demonstrated by the city of Cheyenne, Wyoming, which had a high-pressure 1964 steel water line in which some sections had inadequate CP levels.
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From page 120... ...
BONDED DIELECTRIC-COATED DUCTILE IRON PIPELINES WITH CATHODIC PROTECTION Bonded dielectric coatings for use on DIP have been provided since the mid 1970s. According to Horton, external coatings for DIP that historically have been used "include, but are not limited to: polyurethane, coal tar epoxy, coal tar enamel, tapewrap, extruded polyethylene, metallic zinc, zinc/epoxy/polyurethane, and fusion bonded epoxy." Information provided by the Ductile Iron Pipe Research Association (DIPRA) for a 5-year period indicates that less than 1 percent of DIP produced has been provided with bonded, dielectric coatings. Most of the dielectric bonded coatings require some type of surface prepara tion of the DIP prior to application of the coating; this may include abrasive blast ing and removal of the epidermal layer or simply cleaning the pipe and applying the coating directly to the epidermal layer, depending on the type of coating.
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From page 121... ...
; Madison Chemical Industries, Inc., Long Form Specification Polyurethane Coatings for the Internal Lining and External Coating of Ductile Iron Pipe and Fittings, Specification No. SP-LF 1997-03, Milton, Ontario, Canada; Berry Plastics Corporation Corrosion Protection Group, Polyken YGIII System for Ductile Iron Pipe Application Specifications, Franklin, Mass.; Tek-Rap Inc., DI-4 Ductile Iron Coating System Specification, Houston, Tex.; Polyken Bonded Tape Coating Proce dures for Small Diameter Bare Steel or Ductile Pipe (when plant applied application is not possible)
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From page 122... ...
. 17 British Standards Institute, BS EN 545, "Ductile Iron Pipes, Fittings, Accessories and Their Joints for Water Pipelines.
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From page 123... ...
The other countries in Europe have reportedly used bonded dielectric polymeric-barrier-type coatings since the 1980s.23 Zinc coatings have been used in France since the early 1950s. Although the majority of North American DIP is covered with PE, there are examples of bonded, dielectric coated ductile iron pipelines with CP.
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From page 124... ...
The city verified in 2008 that it has had no corrosion leaks in its coated DIP and was beginning a program to replace the CP galvanic anodes on the YDI pipelines.27 25 Technical Memorandum 8140-CC-2004-1, "Corrosion Considerations for Buried Metallic Water Pipe." 26 Roy Brander, "Water Pipe Materials in Calgary, 1970-2000," 2001 Infrastructure Conference, Orlando, Fla. 27 Jim Buker, The City of Calgary Project, communication with the committee, 2008.
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From page 125... ...
epoxy, tape, extruded polyethylene Seattle, Wash. Varies; tape and Varies 31 miles Varies, very No external thermoplastic corrosive corrosion leaks reported through 2008.
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From page 126... ...
aCorrprofax on List of Ductile Iron Pipe with Bonded Coatings, June 1998. bApproximately46 miles polyurethane and 4 miles coal tar epoxy.
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From page 127... ...
Since the corrosion control project managers at WSSC at present cannot obtain DIP with bonded dielectric coating, they have installed several thousand feet of bare DIP with CP; they do not use DIP with PE and CP for fear of electri cal shielding.28 San Diego, California Based on its historical problems with pipelines with PE, the city of San Diego now requires bonded dielectric coatings (polyurethane) and CP on its DIP lines.29 The city also reported good success with the use of petrolatum wax tape for wrap ping valves and fittings since beginning its use in 1989.30 San Diego reports that it has had good success with bonded dielectric coatings on pipelines and has done a number of bonded dielectric coatings on DIP with polyurethane and on one pipeline with coal tar epoxy.
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From page 128... ...
The tape applicator also added that there had been few problems with tape coating of the bells and that the adhesion values were very good on the entire project.34 The corrosion engineer confirmed that they were pleased, that there was little problem with the coated DIP, and that a second phase with coated DIP had been planned, but the DIP manufacturers would not provide pipe to be coated so the second phase of the project used plastic pipe instead.35 Cairo, Egypt Another approach to applying a dielectric bonded coating to DIP is to tape coat the pipe without abrasive blasting of the DIP surfaces. On a large-diameter DIP pipeline installed in Cairo, Egypt, the U.S.-made DIP was primed with the standard asphaltic primer before being shipped.
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From page 129... ...
Because of the advantages of thermoplastic coating -- including but not limited to the ability to coat the entire bell-and-spigot assembly including the bell face, and the physical properties and characteristics of the coating -- it was selected as the standard DIP coating system.40 However, since Seattle can no longer obtain DIP on which to apply this type of dielectric coating and because of its concerns with electrical shielding with PE, it has installed approximately 40,000 feet of bare DIP with CP. The city is still investigating other types of coatings that may be applied over unblasted ductile iron.41 OTHER CORROSION MITIGATION METHODS The committee considered other corrosion mitigation methods that might have potential for providing the needed level of reliability for DIP (some of these are discussed in greater detail in Appendix D)
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From page 130... ...
Galvanized zinc coatings with various top coats have been used for DIP in Europe. There are ISO (International Organization for Standardization)
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