Real-time corrosion monitoring reduces costs

Oil and natural gas pipelines carry toxic and often volatile hydrocarbons to refineries and markets. Recent high-profile pipeline failures have brought an increased emphasis on preventing corrosion, the chief culprit in these failures, which can result in lost production, equipment replacement and regulatory fines. Traditional corrosion monitoring methods often identify problems when it is too late to deploy preventive measures, resulting in widespread energy disruption across the supply chain. As a result, pipeline operators are looking for ways to improve their systems for detecting and preventing corrosion. The good news is that today's corrosion monitoring systems are capable of detecting corrosion in real time without interrupting the process, and provide an effective predictive solution to reduce corrosion-related costs.

Corrosion can be costly to manage. It is estimated that corrosion costs the process industries roughly $300 billion each year in lost production, equipment failure and fines for environmental and safety violations. BP, the poster child for the perils of pipeline corrosion, was fined $12 million for the pipeline leak on the North Slope in Alaska in 2006. The company must also replace 16 miles of pipeline at a cost of nearly $150 million. Clearly, corrosion poses significant risks, and the costs for poor corrosion management can be catastrophic.

While pipelines have gotten most of the press recently, refineries are also quite susceptible to corrosion. They have miles of metal pipe, vessels and tanks, and are governed by strict regulations on emissions and safety. Unfortunately, corrosion problems will only increase as the world begins to rely more heavily on heavy oil, which has a higher acid content. Replacing plant components with more corrosion-resistant metals is not feasible, given the recent explosive increase in the prices of nickel, chromium, zinc and many other constituents used in manufacturing these metals. Plant operators must become more vigilant by adopting robust corrosion monitoring methods. Run-to-failure is not an option with the worlds increasing appetite for energy. If corrosion can be measured in real or near real time in an automated way, the operators can take operational steps to minimize acceleration of corrosion and extend equipment life.

Traditional monitoring methods no longer suffice.

ARC Advisory Group's Plant Asset Management (PAM) Systems Worldwide Outlook estimates that manufacturers spend over $50 million on corrosion monitoring annually, and that this amount will nearly double over the next five years. Corrosion monitoring predicts the health of all metal equipment, virtually every piece of equipment in a process plant. Major suppliers of corrosion monitoring solutions include Cormon, CorrOcean, Honeywell, Pepperl+Fuchs and Rohrback Cosasco.

The traditional method for monitoring corrosion in pipelines is by using metal coupons. The coupons are weighed, inserted into the process stream, then periodically removed and weighed

to determine if corrosion has occurred. Pipeline operators also use ultrasonic testing modules on smart pigs to measure the pipe thickness. Because they are periodic, these measurement methods, while accurate in detecting corrosion, merely confirm that corrosion has taken place. Damage is documented, but it is difficult to take a proactive approach to prevent it.

¡Real-time corrosion monitoring. Newer corrosion monitoring methods such as electrical resistance and linear polarization resistance probes provide more timely corrosion data. These devices measure resistance across wires that are exposed to the process stream; if the level of resistance increases, corrosive conditions are present. While this is an improvement over the coupon method, the probes do not detect localized corrosion, or pitting, the cause of most pipeline failures. Solutions such as Honeywell's SmartCET and Pepperl+Fuchs' CorrTran MV devices get around this problem by adding harmonic distortion analysis to calculate more accurate corrosion rates and electrochemical noise measurements to detect localized corrosion. Emerson and Rohrback Cosasco systems added wireless corrosion monitoring to the mix with the Mircocor wireless transmitter.

With these new technologies, refinery and pipeline operators can measure and pinpoint corrosion in real time, and in essence can treat corrosion as another process variable as they do with more familiar field instruments such as pressure transmitters, temperature sensors, flowmeters and level devices. It will be possible to install corrosion instrumentation on plant assets such as pipes, vessels and heat exchangers, giving operators a way to check for corrosion without manual inspections. Wireless technology will enable measurements in remote or hard-to-reach plant areas.

Real-time corrosion monitoring helps to extend the life of key plant assets and pipelines. Operators can use it to manage corrosion more effectively, optimizing the effectiveness of corrosion prevention measures. Production losses are minimized, and maintenance costs go down with fewer manual inspections and a reduction in the amount of corrosion inhibitors used. Plant operators can shift from unnecessary preventive or reactive maintenance strategies to a proactive, reliability-centered approach. More importantly, real-time corrosion monitoring reduces their exposure to the risk of catastrophic failures and the associated environmental and safety repercussions.