Making "Baggies" Work for Ductile Iron Pipe

Coating of Ductile Iron Pipe (DIP) for buried water mains has been and continues to be a contentious subject. A considerable number of corrosion engineers and civil engineers take exception to the claim that effective protection of DIP can be achieved economically by wrapping the pipe in loose polyethylene. There seem to be as many reports of failure as success. The authors recently completed a three-year study of external corrosion of water mains, under the auspices of the American Water Works Association (AWWA) Research Foundation. One of the conclusions in the study is that polyethylene encasement (more familiarly "baggies") can be an effective system for protection of DIP water mains in many environments. However, there needs to be additional attention to design and installation beyond that described in the relevant national standards. Polyethylene encasement is discussed in AWWA Manual M41 "Ductile Iron Pipe and Fittings." AWWA Standards C105-99 "Polyethylene Encasement for Ductile-Iron Pipe Systems" and C600-99 "Installation of Ductile-Iron Water Mains and Their Appurtenances" reflect the current DIP industry understanding about what should be used for corrosion protection for their product. Unfortunately, should additional protection from what may be afforded by such installation be needed by the use of other protection systems (coatings), the DIP manufacturers will refuse to bid your project. DIP has many characteristics that make it desirable for waterworks use, but it will corrode if buried unprotected. So if you use it, wrap the DIP in baggies, and take the additional steps that allow you to effectively monitor it and preserve your corrosion control options in the future. These steps are detailed in this paper and include electrical isolation from attachments and appurtenances, intentional electrical continuity at joints, corrosion monitoring stations and, if necessary, cathodic protection.

Language

  • English

Media Info

  • Media Type: CD-ROM
  • Features: Figures; Photos; References; Tables;
  • Pagination: 13p
  • Monograph Title: Pipeline Engineering and Construction: What's on the Horizon? Proceedings of the Pipelines 2004 International Conference, August 1-4, 2004, San Diego, California

Subject/Index Terms

Filing Info

  • Accession Number: 01003257
  • Record Type: Publication
  • ISBN: 0784407452
  • Files: TRIS
  • Created Date: Aug 17 2005 1:20PM