Gradient Control Mat Decoupling

There are many sources of potentially dangerous voltage that can appear on your pipeline: voltage from induced AC at the power frequency (50-60 Hz), and voltages from AC fault current or lightning strikes. In order to protect workers from exposure to these voltage sources, you may already have a gradient control mat installed around your pipeline in key maintenance areas. However, no known manufacturers provide data on the effectiveness of their product in controlling step and touch potentials, both indicators of how much voltage protection the mat offers.

Other mats on the market are only designed to meet IEEE Standard 80, which only allows for potentials due to power frequencies. This does not control for lightning or high AC fault voltage protection, leaving your workers potentially exposed. Also, the common “spiral configuration” mat and other single conductor mats have been found completely ineffective in limiting step and touch potentials from lightning to safe levels.

Dairyland’s Gradient Control Mat (GCM) is designed in a grid-type configuration, limiting step and touch potentials for a safer work environment around your pipeline. Our 3” by 3” grid was compared against a typical spiral-type mat for potential voltage control, where Dairyland’s GCM limited potentials to orders of magnitude lower than a 12” spiral design. By safely limiting lightning voltage levels, the GCM is also inherently able to limit potentials due to power frequencies from induced AC.

Gradient control mats can affect cathodic protection levels, due to the need to connect it directly to the pipeline. We recommend installing a Solid-State Decoupler along with your GCM to help mitigate any CP interaction issues. By decoupling the mat from your pipeline, you will eliminate interaction with the CP system, and CP readings can be taken near the mat without incorrect results. The galvanic potential of the mat becomes irrelevant and the life of the anodes is greatly increased.