The Energy Pipelines Cooperative Research Centre and Deakin University of Australia are working on an innovative sensor able to monitor corrosion-related pipeline damage.
The degradation of materials' properties based on environmental interaction is inevitable as metals attempt to return to their native low-energy oxide state. The best that can be done is not avoidance, but only control. Several industry studies over the past several decades place the direct cost of corrosion in the US at approximately $275 billion annually.
Accidents and explosions are the norm as a result of corrosion. In 2014 alone, they include:
- On January 10, a 12-inch PSNC gas transmission pipeline exploded in Asheville, N.C. Property damage was approximately $825,000.
- In February, gas pipelines exploded in North Dakota and Kentucky. While the North Dakota explosion caused no injuries, in Kentucky two people were hospitalized and homes were destroyed.
- Three accidents in March due to oil and or gas pipeline leaks spilled substantial amounts of oil and caused gas explosions in Texas, New York, and Ohio. In Ohio, the oil spill affected animals in a nature preserve.
Pipeline corrosion falls under the uniform or general corrosion category. This uniform corrosion also is seen in bridge rust, tarnished silver, and color changes of bronze statues. Some metals, including stainless steel, titanium, and even aluminum, form oxide film naturally, but the film can break down and cause cracking, pitting, and other forms of corrosion. Uniform corrosion can be accurately predicted, and the solution is to protect the metal by adding coatings or creating more resistant alloys. Organic coatings are often used to slow the process, inhibitors can be added, and with steel, adding chromium staves off corrosion.
In underground situations, the challenges are obvious. It’s difficult to see the level of corrosion, impossible to add surface solutions on an ongoing basis, and inhibitors are often the solution of choice.
Typically, coatings inside the pipes are used to prevent corrosion. However, over time the coatings cease to be effective, resulting in leaks or failure. Many major gas explosions are attributable to such corrosion and leaks. The current means of finding corrosion problems are only effective after damage is greater than 30% of the pipe’s wall thickness. Corrosion monitoring is also very expensive now, requiring manual ultrasonic measurements and often digging up pipe, removing coatings, etc.
The new sensor technology is based on continuous monitoring of the protection used on the pipes. The sensor monitors and identifies corrosion well before it becomes a catastrophic event.
So far, tests are lab-based, but they are expected to move into the field in a real underground pipeline yet this year. While the sensor is being designed specifically for oil and gas pipeline applications, it’s easy to imagine a broad range of industrial applications where corrosion occurs and testing is cumbersome or close to impossible, as with underground pipes.
— Carolyn Mathas is a freelance blogger and editor for EE Times's Industrial Control Designline.