Electrical Discontinuity in Ductile Iron Pipe
Several factors suggest the on-going need to continually study the effect of corrosion on electrical discontinuity in ductile iron pipes (DIP). For instance, according to a 2002 congressional study, corrosion costs U.S. water and wastewater systems over $50.7 billion annually. The American Society of Civil Engineers’ (ASCE) 2013 “Report Card for America’s Infrastructure” graded U.S. potable water and wastewater infrastructure a “D.” American Water Works Association’s “2014 State of the Water Industry” report cited the top two water industry issues as: 1) state of water and sewer infrastructure, and 2) long-term water supply availability.

What is corrosion?
“Corrosion is an electrochemical process involving both a chemical reaction and the flow of electrical current. In order for corrosion to occur, there must be an anode and a cathode, electrically connected by a metallic path, with the anode and cathode immersed in an electrically conductive electrolyte that is ionized. There must also be an electrical potential between the anode and the cathode. If any of these components are eliminated, corrosion cannot occur.

“Since corrosion involves the flow of electrical current, it is obvious that any resistance introduced into the circuit will greatly affect the rate of corrosion.” (Troy F. Stroud, P.E, Corrosion Control Measures for Ductile Iron Pipe, Ductile Iron Pipe Research Association, Birmingham, Alabama)

“To cause corrosion, stray currents must flow onto the pipeline in one area, travel along the pipeline to some other area or areas where they then leave the pipe (with resulting corrosion) to reenter the earth and complete the circuit to their ultimate destination. The amount of metal lost from corrosion is directly proportional to the amount of current discharged from the affected pipeline.“…the Ductile Iron pipe most probably will collect stray current. This area needs to be electrically isolated from adjacent piping that will not be collecting stray current. One method of achieving this is installing insulating couplings.”(Richard W. Bonds, P.E., Stray Current Effects on Ductile Iron Pipe, Ductile Iron Pipe Research Association, Birmingham, Alabama)

Controlling Corrosion
“When encountered, however, there are two main techniques for controlling stray current electrolysis on underground pipelines. One technique involves insulating or shielding the pipeline from the stray current source; the other involves draining the collected current by either electrically bonding the pipeline to the negative side of the stray current source or installing grounding cell(s).” (Richard W. Bonds, P.E., Stray Current Effects on Ductile Iron Pipe, Ductile Iron Pipe Research Association, Birmingham, Alabama)

  • “Insulated joints are used to break the metallic electrical connection between two pipelines, pipeline components or structures, thereby preventing the flow of electrical current between them.”(AWWA Manual M41, “Ductile-Iron Pipe and Fittings”, American Water Works Association)
  • “Polyethylene’s excellent dielectric properties enable it to effectively shield the pipe from low-level stray direct current.” (Polyethylene Encasement: Effective, Economical Protection for Ductile Iron Pipe in Corrosive Environments, Ductile Iron Pipe Research Association, Birmingham, Alabama)
  • “Another approach to stray current mitigation involves making modifications to the pipeline to reduce its susceptibility to stray currents and to provide a safe means of stray current discharge. The modification of the pipeline to reduce stray current activity maintains all control for the stray current measures directly in the hands of the pipeline operator.” (A.W. Peabody, Peabody’s Control of Pipeline Corrosion, 2nd Edition, p. 232)

The Bevel-Sert is a beveled radius used in conjunction with buried Ductile Iron Pipe and push on fittings. The Bevel-Sert is made out of 3608/4710 NSF-61 Certified High Density Polyethylene (HDPE) material and accommodates the outside diameter of the spigot end of the ductile iron pipe. The integral flange acts as a bendable wrap around the spigot end and becomes a barrier between the spigot and the bell ends. When used in Ductile Iron Pipe applications, the Bevel-Sert acts as an insulator and a barrier to electrical current at each joint, promoting the existence of an electrically discontinuous pipe joint segment when the joint segment is bottomed out in the bell.

Test results show that use of the Bevel-Sert in Ductile Iron Pipe joints increases the resistivity and thus helps to reduce the potential for corrosion. Click on the links below to see the test results:

Omni Engineering Report – December 2012
Resistance Measurements of Ductile Iron Pipe Using the Bevel-Sert

Omni Engineering Report – December 2002
Resistance Measurements of Ductile Iron Pipe