Ultrasonic Technology for Pipeline InspectionWed, 01/25/2012 - 13:09
Pemex has been very proactive in utilizing pipeline inspection services for a number of years. “In the pipeline segment, Pemex is actually very up-to-date in terms of technology, and has been for the last 25-30 years. Pemex is one of the most active companies in the world regarding pipeline inspection services,” says Oscar Luís González Arias, Director for Latin American operations at NDT Systems & Services, a pipeline inspection company. “Rather than the challenge being caused by unwillingness to adopt new technology, it has come from trying to adapt to the growing demands of Pemex’s dierent divisions in the pipeline segment.”
González Arias explains that Pemex first started regular pipeline inspections around 1982, and that the only company able to carry out such inspections at the time eventually became a part of the now NDT group. “The system put in place by Pemex at that time was very similar to what is found in other markets around the world today,” he explains. “The company conducting the inspection is only responsible for delivering the data to the client, with no extra services involved. This is still the extent of the work US pipeline inspection companies carry out today.”
NDT Systems & Services was created as an ultrasonics company, but around three years ago the company acquired Tuboscope Pipeline Services – a company focused on magnetic flux leakage (MFL) technology. “Now we bring both technologies to the market,” says González Arias. “In Mexico the greatest experience comes from the Tuboscope side, which has been present in the market for over 20 years. Worldwide, NDT Systems & Services is the leader in ultrasonic technology. In magnetic flux leakage we are competitive and have some advantages over our competition. Having had continuous work with Pemex since 1982, we have the best knowledge of Mexican pipelines and their requirements. The fact that we have a support centre in Mexico that assists NDT teams around the world testifies to this.”
González Arias goes on to explain how NDT’s inspection business with Pemex continues to increase: “Because Pemex is a public sector company, it is always looking for ways to bring more value into its contracts. One way Pemex found to do this was to increase the amount of work required by inspection companies in their contractual arrangements. This started with Pemex Gas and Pemex Refining, but has now spread to all subsidiaries of the company. As a result, we now do much more work for Pemex than a traditional pipeline inspection company. NDT Mexico is in charge of preparing the pipeline for the inspection, cleaning, suitability, and geometry inspection, all before the actual inspection. Mexico is also one of the few places in the world where pipeline inspection companies process the data gathered from the inspection and present possible solutions to the client such as a detailed repair plan, a fitness for purpose assessment, or integrity plan; in some cases we have even been involved in the repair of the pipeline, and scheduling of the next maintenance programmes.”
NDT employs two methods for pipeline inspection: magnetic flux leakage and ultrasonic technology. Although the two methods are not mutually exclusive, there are specific applications for each. There are many scenarios in which one is better suited than the other. Ultrasonics is a more advanced technology because it uses direct measurement; however, it still cannot be used in gas pipelines, where MFL technology is applicable. The operator usually chooses which technology to utilize depending on the inspection requirements. This choice is linked to the diculties the operator has in the pipeline, the type of problem being looked for, and the conditions of the pipeline’s operation.
NDT’s inspection systems are based on minimizing downtime. In most pipelines, downtime is no longer a factor because NDT’s systems function within operating pipelines. The company’s equipment and tools are inserted into the line and propelled through by the hydrocarbon flow. Ultrasonics technology can be used in pipes for a regular inspection where the flow ranges from 1m/s to 3-4m/s, and MFL can be used at speeds as high as 5-6 m/s. Although the ultrasonics range is lower, the technology only works in liquid pipe flows, and there are very few pipelines transporting liquids that can flow much faster than the speeds it demands. However, some oshore gas pipelines flow at speeds of over 13m/s, which means that pipeline inspection companies such as NDT need to reduce the flow. González Arias explains that “there are some cases, especially oshore in natural gas pipelines, where productivity is aected because the high pressure in the pipelines causes very high speeds, which the tools cannot handle. We never require the pipeline to be shut down, but in some cases they have to reduce the throughput to give us the correct speed for the duration of the inspection.”