Technical Article

What if Decouplers Didn’t Exist?

Imagine a world where solid-state decouplers never existed. What would be the effects on pipelines and the workers who maintain them? To better understand the critical roles decouplers play on modern pipelines, let’s take a closer look at the impacts of this imaginary scenario.

Cathodic protection

The role of decouplers in cathodic protection (CP): A CP system provides corrosion protection by applying a low voltage negative DC bias to the structure. However, required safety grounding systems connected to the structure short this CP current to ground and can compromise the efficiency of the CP system.

Under normal circumstances, the decoupler functions to isolate or block the flow of DC current (cathodic protection) to other equipment or grounding material. Decoupling eliminates any negative influence on your CP system caused by neighboring equipment or grounding materials. Therefore, it improves the performance of your CP system.

If decouplers didn’t exist: Without decouplers, pipeline owners would face complex and costly challenges to achieving adequate levels of CP on their pipelines due to direct bonded grounding material and proximity to other nearby structures and equipment. Inadequate CP increases the chance of defects, leaks and other problems caused by corrosion on your asset. The cost of corrosion is extremely high and is well documented by the National Association of Corrosion Engineers (NACE).

Solid-state decouplers are an essential component of any cathodic protection system. They allow simultaneous DC isolation and AC grounding. That allows pipeline operators to improve the performance of their CP system while remaining grounded for safety.

Performance Characteristics

In addition to improving the performance of CP systems, decouplers are carefully designed to handle critical site conditions to ensure proper performance of the device and maintain worker safety. These important performance features include:

  1. AC fault current generated by a failure of nearby equipment represents a safety hazard. This fault current can be transmitted via the pipeline, endangering nearby workers or causing damage to the pipeline. When an AC fault occurs, the decoupler instantly conducts fault current to ground, carrying AC current away from the pipeline and providing instant protection. Products must be properly and adequately rated for fault current to ensure proper product performance.
  2. Lightning protection: When a lightning strike occurs, it can be a safety hazard to personnel and can pose a risk to the pipeline. Dairyland decouplers feature high lightning current ratings so that they can safely channel the lightning current to ground, protecting nearby workers and the structure itself from high voltage. As soon as this event has ended, the decoupler automatically switches back to its DC isolation/cathodic protection role. Lightning current ratings should be properly tested and certified by third-party laboratories to ensure product performance under these brief but extreme conditions.
  3. Mitigation of induced AC current: Many pipelines are buried along a shared right-of-way with high-voltage power lines, which induce AC current in the pipeline. This is not only a safety hazard to workers but can also cause significant damage from AC corrosion. Decouplers are designed to continuously conduct induced AC current to ground, mitigating this risk while simultaneously isolating the pipeline’s CP system. Proper product selection is critical when induced AC is a concern, as some industry products are not capable of adequately handling steady-state AC current.
  4. Fail-safe design: While the failure rate of Dairyland decouplers is extremely low (small fractions of a percent), they are designed as “fail-safe.” This ensures that in the unlikely event of a product failure, the product always fails short circuit, thereby ensuring continuity of your safety grounding. Other products that fail open-circuit can create dangerous safety hazards, in addition to requiring regular maintenance and replacement.

In conclusion, thank goodness solid-state decouplers DO exist. Solid-state decouplers allow for simultaneous optimization of a CP system through DC isolation, as well as providing a continuous path to ground for safety. While other products can perform elements of these functions, Dairyland decouplers have the performance history, third-party certifications and design features required to ensure reliability for the duration of their use.

To learn more about decouplers and the critical roles they play on modern pipelines, please read this article on the Dairyland Knowledge Base: What Are Solid-State Decouplers and How Are They Used?

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