Introduction to Decouplers

In this webinar, Dairyland Senior Business Development Leader, Jay Warner, will examine the basic function of decouplers and over-voltage protection devices and explain how they should be used in conjunction with cathodic protection systems to obtain optimal corrosion and safety protection. He will answer common questions like why a decoupler is needed, where they are commonly applied, and how to test them once they’ve been installed. He will also explain how using these devices ensures that the cathodically protected structure is properly earthed to protect personnel and assets from AC interference and lightning strikes.

Cathodic Protection (CP), when properly applied, is an effective technique to minimise the natural corrosion process that occurs on pipelines, tanks, and other buried steel structures. To maintain effective CP coverage with minimal current demand, the structure must be well-isolated from earth for DC current flow.

However, these structures require electrical earthing for both personnel safety and protection of the structure from damage due to over-voltage conditions. These earthing bonds require the CP system to protect significantly more material surface area for which it was not designed. As a result, it is often difficult to maintain adequate CP potentials on the structure that is to be protected.

A practical and widely accepted solution is to install DC decoupling devices in series with the bonding connections between the cathodically-protected structure and the earthing systems. Decouplers are designed to block CP current while allowing steady state AC, AC faults and lightning to pass freely. This prevents CP current from passing through the earthing systems and so minimises the amount of CP current required to protect the pipeline.