Getting smarter: PII Solutions’ Magnescan uses high-resolution magnetic flux leakage technology to detect pipe corrosion
Certain lengths of pipeline can be hard to reach, so industry has long used special devices to clean them and remove blockages. These inspection gauges, commonly referred to as ‘pigs’, travel through such stretches of pipeline, driven by the flow of liquid or gas inside.
These utility pigs perform a valuable function but, with the advance of magnetic and ultrasonic technologies, manufacturers have been working to make the devices smarter. Improvement in the devices allows companies to gain greater insight into the condition of their pipelines, detecting potentially hazardous issues such as minuscule cracks or rusting walls.
However, while these smart pigs have become a linchpin in industries such as oil and gas or water, there are still limits to this developing technology – particularly in being able to traverse complex or ‘unpiggable’ pipelines – and manufacturers and oil firms are working hard to improve them.
Baker Hughes, one of the world’s largest oilfield services companies, has become a leader in the field of smart inspection services, driven by the need to maintain vast pipeline networks around the world. For industries such as oil and gas that use subsea or below-ground pipelines, smart pigs need to deliver the most accurate inspection data possible with the least disruption to the pipeline flow. Spending time digging up pipes or stopping the flow of liquid would cost valuable time and money. Proactively inspecting pipelines should also allow potential accidents and leakages to be spotted before they occur.
Paul Whitwell, strategic marketing manager at Baker Hughes’ process and pipeline services, says that there have been important developments with in-line inspection (ILI) technology because of continuous improvements in mechanical design, allowing the tools to be used in pipelines previously considered ‘unpiggable’. “Examples of improvement have been the ability to now inspect pipelines with thicker walls; multi-diameters, including lower minimal internal diameterd; pipes located offshore in deep water; bi-directional inspection configurations and multi-purpose pipeline inspections,” he says.
The firm has developed a family of inspection devices called Vectra ILI that use high-resolution magnetic flux leakage (MFL) and triaxial sensor spacing technologies. They provide a detailed and accurate look at complex anomalies within pipelines, and are capable of finding, identifying and sizing axial flaws.
Another of the firm’s devices, the Geopig high-resolution calliper in-line inspection tool, measures dents, wrinkles, buckles and flattening of the pipewall, as well as strain-in-dent analysis. Its accuracy is better than ±3.3ft (1m). In addition, Geopig’s onboard inertial measurement unit collects the data to calculate a GPS coordinate for every anomaly and feature contained in the final report. This accurate data allows operators to pinpoint problems and reduce need for costly, unecessary digs. It also provides information on bending strain, to let companies know about potential pipeline movement caused by slope instability, frost heave, subsidence, temperature/pressure variations, flooding, upheaval, or new construction impact.
Another organisation pushing forward pig technology is PII Pipeline Solutions, a joint venture between General Electric and Al Shaheen, the investment group of Qatar Petroleum. As with Baker Hughes, it develops smart pigs using the magnetic and ultrasonic technologies that have become the primary techniques in the industry. Jeff Sutherland, innovations leader at PII, says: “Within the design, our primary objective is to ensure that quality data will be collected for the entire length of the pipeline, to provide the most accurate assessment of its integrity.”
PII itself evolved and was privatised in the 1990s out of British Gas, which developed the benchmark for high-resolution MFL inspection tools in the 1970s that targeted corrosion loss of the pipe wall. The current generation of tools uses a combination of magnetic and electromagnetic technologies, calliper measurements and military-grade inertial measurement technologies. “Not only does this assess metal loss, but it inspects for dents and excessive strain,” says Sutherland.
Mitigating risk: Using devices such as the PII UltraScan Duo helps companies detect metal loss and cracks to prevent accidents
In the 1990s, PII had also developed ultrasonic tools for wall measurement and crack detection. However, as it has been part of GE since 2002, PII now has access to the latest innovations being developed for the group’s global markets, including technology for industrial use, healthcare and aviation, says Sutherland.
This access has helped the firm to develop pipeline inspection tools such as the UltraScan Duo. This device uses the most advanced ultrasonics method available, phased-array ultrasonics, which GE developed before it acquired PII.
“Our latest technology platform is known as EMAT, which stands for electromagnetic acoustic transduction and targets crack flaws in natural gas pipelines through interrelated electromagnetics – such as radio waves – and ultrasonic waves,” says Sutherland.
Challenges do arise during the design of smart pigs, including those due to the varying size of pipelines that firms use. Sutherland says that designing a smart pig for a 10in (25.4cm) onshore pipe is very different from designing for a 36in (91.4cm) offshore pipe. In fact, one-third of the world’s pipelines are unpiggable because of multi-diameter designs, access and valve restrictions and impassable fittings, as well as a myriad other configuration problems.
“The constructed geometries of some older pipe – pre-1980s – had not considered the needs for inspection, as pigs didn’t really exist. Standards and practices have now taken account of the need and requirements for smart pig inspections but some customised vehicle design was still needed for inspections of older infrastructures,” he says.
To overcome these problems, PII has developed a device called the SmartScan which can traverse both very tight bends in the pipeline and significant changes in diameter. The flexible, multi-diameter tool – measuring just over 4m long and weighing almost 1,000kg – travels through the pipeline, using a combination of GPS data, magnetic sensors and other proprietary technology to collect information that is then analysed to assess the condition of the pipe.
On occasion, for pipeline networks that are generally shorter and have limited accessibility, lower operating pressures or underlying geometries that hinder the use of broadly available inline inspection tools, the use of robotic pigs should be considered, says Sutherland. “Robotic tools are best applied when the system must control its own motion and potentially move against the natural flow direction of the pipeline,” he adds.
Making waves: The EMAT device targets cracks using radio and ultrasonic waves
As smart pigs move with the product inside the pipe at full operational pressures, they do little to disrupt usual operations and are best suited to long-distance transmission pipelines.
“Our MFL and crack detection tools have successfully completed more than 700km in one project, while still accurately identifying flaw type, size and location. They detected and predicted features the size of the tip of a pen or the lines on your hand, to within a location accuracy of metres, over an inspection distance from London to Edinburgh,” says Sutherland.
This kind of accuracy and level of data is essential when inspecting pipelines, but smart pigs are not an infallible means of ensuring pipeline integrity. Smart pigs merely provide operators with meaningful data, and when travelling through pipelines that can run to hundreds of kilometres in length, that information can prove overwhelming. It is up to the pipeline operator to interpret and act upon the technical data that has been provided. Sifting through it all can take months, by which time an accident could occur. Fortunately pipeline ruptures are rare, but smart pigs have to be used as part of a wider maintenance strategy to prevent accidents from happening.
Smart pig devices can detect corrosion and crack features to less than 0.5mm deep, but Sutherland admits the process can often be akin to finding a “needle in a haystack”. This is because the data analysis and processing are carried out not really to detect features but to accurately discern the type, location and size of the flaw, which an operator can then use to ensure the integrity of the pipeline.
“Inspection performance generally exceeds specifications and requirements,” he says. “However, pipeline integrity programmes also need to manage the ‘outliers’, which are odd, atypical flaws, or one-off combinations of flaws.”
For an operator, the priority is to know of near-critical features that pose an imminent threat to the integrity of the pipeline, he adds. Hence, a measure of the inspection system is detection of the smallest crack, but the true motivation and requirement for inspection is confident and accurate identification of near-critical flaws. “Such features are larger than the smallest detectable feature size, but also may exist as interactive combinations of smaller features,” says Sutherland.
Another desirable development would be for the smart pig to send back live data. However, the pipeline acts as an effective shield, or Faraday cage, against communication with the tools while they are within it. This is an area that PII is now focusing on, looking at ways to enhance instrumentation by improving signal to noise, and at general reduction of ambiguous results through smarter sensor design and data analytics.
While firms continue to look at ways to improve the technology, it appears that more and more complex pipelines will eventually become ‘piggable’, making it an industry that is set not just to fly but
to soar.
Whitwell says: “There has yet to be any rival technology developed that truly competes with ILI – smart pigs. This is the only technology that can reliably inspect the entire length, circumference and pipe wall extent of a pipeline. Nothing compares to ILI for the identification of time-dependent pipeline threats.”
Maintenance and health and safety engineers to meet in Birmingham
Engineers will gather later this month to attend the nation’s leading show covering maintenance, plant and asset management.
Maintec, held from 24 to 26 March at the NEC in Birmingham, is now in its 40th year. It has attracted more than 300 exhibitors this time around, including well-known names such as Atlas Copco, SKF, Gill Sensors, Borger UK and Michell Instruments. Professional bodies and trade organisations also in attendance include the Institution of Diagnostic Engineers and the British Fluid Power Association.
A specialist hazardous area, Hazex, has also been created to display the latest advances in monitoring and detection equipment, controls and containment solutions.
The show has a three-day seminar attached to it, with case studies and technical presentations. Maintec is co-located with several other exhibitions and conferences, including the Health and Safety Event, established to promote best practice in safe industrial working.
Tickets to both events are free, and can be booked at the following websites: www.easyfairs.com and www.healthandsafetyevents.co.uk