In these systems, A.C. voltages are transmitted to the pipeline by conductive or inductive interference. Magnetic induction acts along the pipeline or pipeline segment that is approximately parallel to the power line and can cause significant pipeline potentials even at relatively large separation distances.
Consideration must be given to safety of personnel and the public who may come into contact with above ground portions of the pipeline such as valves and test stations. These exposed structures can be a potential shock hazard when touched while the soil is at a significantly different potential.
Advances in interference control have resulted in the gradient control wire method. This method consists of one or more bare zinc conductors buried parallel to and near the pipeline and regularly connected to it. Plattline™ zinc ribbon anode used in this way is very effective in mitigating excessive pipeline potentials due to both inductive and conductive interference.
Plattline I – is an alloyed zinc product and is generally used in seawater or brackish water systems. It meets the chemical requirement of MIL-A-18001K and ASTM B418-95a Type I.
Plattline II – is a high purity product and generally used in underground and fresh water systems. It meets the chemical requirements of ASTM B418-95a Type II.