Millions of miles of metallic pipelines are buried underground around the world, providing essential transportation corridors to collect, convey and distribute many types of fluid assets, including petroleum products, natural gas, water, wastewater and more.
This important infrastructure, however, is constantly threatened by corrosion. From the surrounding soil, and from electrical interactions with nearby infrastructure, such as power transmission lines, electric trains and impressed currents that are used to protect other buried pipelines. These same forces can also attack the underside of storage tanks where they contact the soil.
While specialized coatings, membranes and vapor corrosion inhibitors are most commonly used to protect pipelines and storage tanks from corrosion, many asset managers are increasingly turning to cathodic protection (CP) systems as a secondary measure.
Electrochemical corrosion protection for critical infrastructure
There are currently two widespread methods of cathodic protection: passive galvanic cathodic protection and impressed current cathodic protection. These technologies can be used individually or in tandem to address specific pipeline corrosion protection needs.
Galvanic cathodic protection utilizes a sacrificial anode, which is a metal that has a stronger electrochemical potential than the steel that makes up the pipeline. This anode material is buried next to the pipeline and is connected to the pipeline through a bonding wire, forming an electrochemical cell. The anode releases electrons to the pipe through the wire connection. The pipe, which acts as the cathode, is polarized in the process. This polarization minimizes pipeline corrosion by making the pipeline more electrochemically passive. However, in the process of “sacrificing” those electrons, the anode experiences corrosion. Over time, the sacrificial anode deteriorates and must be replaced to ensure consistent pipeline protection.
Impressed current cathodic protection system uses anode electrodes that are meant to last without replacement. Typically, the anode material is composed of graphite, titanium, platinum, or other inert material that is buried next to the pipeline. The anode is energized to a positive potential, usually by a rectifier that converts AC power to DC, so that it releases electrons to the cathode pipeline through the rectifier path. The cathode pipeline becomes negatively polarized because of the potential being impressed by the rectifier, rather than relying on the electrochemical potential of the anode. As with galvanic protection, the polarization of the cathode minimizes the corrosion of the pipeline.
One of the most important aspects of operating CP systems is ensuring proper functionality and providing optimal protection to pipelines and storage tanks. Wireless cathodic protection monitoring will help extend the life of pipeline assets, minimize downtime, reduce maintenance costs and protect the environment from line breaks and spills. Collecting and reporting CP operational data is also a regulatory requirement for many industries.
Mobiltex devices are used by hundreds of companies worldwide, providing reliable CP monitoring under the toughest conditions.
Wireless remote monitoring and control of CP systems
Oil and gas companies have used CP systems for decades, but only recently have begun automating performance monitoring, data collection and control of these systems with wireless devices. Without such technology, field technicians must physically visit each rectifier and CP test station to inspect rectifiers, validate CP system operation, and test the performance of each CP system. They must also manually install specialized control devices that provide synchronized interruption of CP systems while technicians perform close interval surveys—measurements of pipe-to-soil electrical potential along the length of the pipeline.
Given that many oil and gas companies are responsible for hundreds or thousands of kilometres of pipelines, this inspection process can only be done once or twice per year, leaving many gaps in performance data. It also means that if a CP system fails, or is not performing properly, the problem won’t be detected until a technician visits, leaving it vulnerable to corrosion.
Not only are inspection visits costly and time-consuming, they expose crews to potential risks from weather, travel to remote locations, and electrical hazards. Crews must also refocus their attention from highly-skilled, proactive pipeline maintenance and optimization, to laborious, lengthy survey activities.
Mobiltex devices, such as the compact RMU2, can be quickly and easily installed to provide wireless monitoring of cathodic protection performance and alert technicians of operational issues.
CP monitoring enhances system reliability and increases efficiency
Mobiltex corTalk devices are changing this, with powerful, compact devices that provide continuous performance monitoring and current interruption control of CP systems. These devices transmit information by cellular or satellite networks and provide technicians with near-real-time performance data, remote-controlled synchronized interruption of rectifiers, and alert notifications when a CP system fails or experiences unusual operating conditions.
CorTalk remote cathodic protection monitoring systems have been designed to fit inside existing enclosures, such as test stations and rectifiers, and can be quickly and easily installed into new or existing set-ups. Once active, technicians can use any web-enabled device to access the corView database to download performance data, generate reports, and see where CP systems are operating normally, performing current interruption activities or experiencing distressing conditions.
Technicians can also use the corView web interface to remotely modify device configurations, virtually eliminating the need to travel to remote locations, except when repairs are needed or to perform inspections at set intervals.
In recent years, municipal water and wastewater utilities have begun implementing CP systems and Mobiltex corTalk monitoring to extend the service life and better manage underground infrastructure.