For decades, pipeline integrity managers have used a set of evolving tools to help improve the solutions available for difficult integrity challenges. One of the key challenges has been the ability to inspect and gather data on unpiggable and challenging pipelines. While great progress has been made on mainline piping systems that are conventionally piggable, the greatest integrity challenges that remain in pipeline networks worldwide are with the difficult-to-navigate pipelines. Not only must an inspection tool navigate these lines, but it must also accurately measure the size and specific location of all flaws.
This article will highlight the next series of technological advances required by the industry to overcome unpiggable or difficult-to-inspect pipeline integrity verification. The next generation of in-line inspection technology needs to move beyond navigation to additionally focus on the accuracy of detection, measurement and location of flaws. The benefits, such as finding a pit-within-a-pit, detecting and sizing very small anomalies, and reducing false digs, are clear. But how do we get there? Accuracy and the ability of the next generation technology will clearly rely on one major leap forward - Resolution.
Recent high-profile pipeline failures have focused increased regulatory scrutiny on the integrity assessment and management of pipeline assets throughout the world. While many piping systems have historically been deemed “unpiggable,” advances in smart pigging and other inspection technology now allow for inspection of these lines. The high consequence of potential failures does not allow operators to selectively manage different parts of their pipeline systems with variable attention. While regulatory compliance may be achieved by hydrotesting some lines, this testing does not provide a complete picture of the condition of a pipeline to assist in predictive maintenance as part of the operator’s integrity management program. In-line inspection now allows operators to gather a large amount of inspection data about systems on which they previously were able to obtain very little or incomplete information.
In addition to collecting information about more pipeline systems, the quality and resolution of the available data is also increasing. Many modern high resolution inspection technologies may accurately size the length and depth of a flaw, but it is now possible to go beyond the basic flaw dimensions. High resolution wall thickness data allows for Level 2 (Effective Area) assessments on areas of metal loss, while high resolution geometry data allows engineers to calculate stress concentration factors or build finite element models of individual dents in order to demonstrate fitness-for-service.
Competing inspection technologies can be evaluated not only by comparing the cost of inspection, site preparation and mechanical set-up, but also by examining what can be done with the data after the inspection. Discussions of in-line inspections often focus on the details of the data quality, precision of measurement and statistics about flaws of a variety of depths. These are important and easily quantifiable data, but for a pipeline operator, the most crucial decisions come down to the ability to safely operate the pipeline and to spend maintenance budgets efficiently. Gathering a high quality data set from an inspection allows for better planning and overall management of a pipeline system.
The growing challenge
With these types of significant strides being made in navigating the “unpiggable” over the past decade; successfully inspecting hundreds of lines previously termed “unpiggable”, a new challenge has arisen and is now in the forefront. Across the pipeline industry, there is continued focus and attention paid to the ability to not just locate, but to accurately identify and size small diameter defects which are classified as pitting or pinhole corrosion. It is not enough to be able to navigate extreme pipeline geometries, but operators require the ability to identify and size anomalies with the greatest level of precision as is available from the conventional ILI tools. Operators are challenging ILI service providers to not only navigate the impossible, but also to acquire data that is as detailed and accurate as any in the industry.
A look ahead to the future
For all intents and purposes, an ILI tool is very much like a camera taking pictures along the inside of the pipeline. So for illustrative purposes, let us use a digital camera analogy. ILI tools are following a similar path as digital cameras in terms of increased resolution. When cameras first became commercially available, their resolution was subpar to the film media common in the day. But as digital technology progressed, pixel resolutions increased to rival, and eventually surpass that of standard film. The increased resolution brought crisper, more resolute and detailed images.
This Quest Integrity test loop illustrates the evolution of digital imaging.
The ILI tool of yesterday struggled to collect data on the bottom 30% of a pipe’s surface, struggled in broad area corrosion, struggled in navigation. Today’s ILI tools are following a similar path as that of the digital camera, moving forward in resolution, accuracy and repeatability - today’s concerns. The higher resolution ILI tools becoming commercially available are offering these better quantifiable images and measurements. For the main-line conventionally piggable pipelines, there are ILI tools that offer sizing of anomalies just 0.40” inches across and identification of anomalies with diameters as small as 0.25”. To achieve this type of resolution, however, requires multiple sensor carriers on long heavy tools. On such an ILI tool design, trade-offs are required, sacrificing tool ease-of-use and navigability. What would be most desirable would be a short one or two module tool containing hundreds of MFL or UT sensors, that was still light weight and flexible enough to be hand carried in the field and able to navigate tight bends, multiple pipe radii, taps, tees, valves and other restrictions that are the characteristic of unpiggable and challenging pipelines.
Extending our analogy, our next generation pipe-camera should be easy to use. Digital images are taken constantly, because today’s cameras are light weight and easy to use – just point and click. For a pipe camera, we would want a tool that is light weight, requires minimal on-site setup time and is easy to launch and receive. Flow conditions in these challenging pipelines can be hard to control and a next generation tool would want to be able to navigate and gather a complete dataset and a wide range of flow velocities – often during the same inspection run. As well as providing operation security and confidence, a bidirectional pipeline-camera would allow for inspection of lines that end in a tee or pipe vault.
However, all of these ease-of-use or navigation considerations still require our camera to take high-resolution pictures of the pipeline. It was not until small digital cameras began to take pictures on par with bulkier film cameras that they became truly ubiquitous. Inspection data from an ILI run is of key importance to a pipeline operator. This data helps to effectively enhance operator confidence, drive repair plans, and prevent a loss of containment. In lines where small diameter pitting and pinhole-type defects are a concern, quality and resolution of the ILI inspection data is key.
Now that we have ILI tools that can navigate the most difficult of pipelines, we need to ensure that they return as high a quality of picture of the condition of those pipelines as possible. Not only must an ILI tool be able to navigate past back-to-back mitre bends and buckles, but it must also be able to detect and size the small diameter pitting that lies in between the mitres. As designers of ILI tools that go into some of the most difficult pipelines in the world, solving this challenge is what the pipeline operators require and demand. In today’s environment of increasing regulatory scrutiny, we must all strive towards obtaining the best pipeline pictures in the most challenging environments. This demand of ever improving data and ever improving ease of use and navigational ability is the challenge made by the formerly unpiggable pipelines.
Written by Quest Integrity
Read the article online at: https://www.worldpipelines.com/special-reports/10032017/its-about-accuracy-next-generation-ili-technology-moves-beyond-navigation/