Zinc ribbon anode for grounding buried pipelines

Paul Boughton

One of the largest uses for zinc ribbon anodes in the past 20 years is for grounding of buried pipelines running parallel to an overhead power line. This is normally called AC mitigation.

The zinc ribbon anodes are buried parallel and connected to the pipeline to dissipate the large induced potentials from the power lines. This is called the gradient control wire method of interference control.

Zinc ribbon is very effective in mitigating excessive pipeline potentials due to both induced and conductive interference. It evens out pipeline and soil potential differences. No cathodic isolation device is needed in these systems when zinc ribbon is used.

Zinc ribbon has historically been used for grounding mats at above ground appurtenances along a pipeline as well. This use provides safety for the people working on the pipeline in the area. Additionally, zinc ribbon can provide cathodic protection to the pipeline if necessary.

Cathodic protection usage of zinc ribbon has focused on above ground storage tank bottoms. This application is easy and very efficient with no continuous monitoring required. The zinc ribbon anode is positioned underneath the tank in the sand layer with about a 3-inch offset.

Another large use for zinc ribbon anodes is to cathodically protect the reinforcing steel in PCCP water pipe. The zinc ribbon anode is used to protect the high strength steel wire that provides the strength for these concrete-coated water pipes. If this wire fails, the pipes could burst, causing serious problems. Water projects using this type of pipe are located in many countries.

The Platt Brothers is based in Waterbury, CT, USA. www.Plattbros.com

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