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9/4/2018 Examining Data Quality of Robotic Pipeline Inspection Methods | Pipeline & Gas Journal

https://pgjonline.com/magazine/2018/june-2018-vol-245-no-6/features/examining-data-quality-of-robotic-pipeline-inspection-methods 1/6

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Figure 1: Explorer crawls through the yellow spool pieces mounted.

June 2018, Vol. 245, No. 6 (/magazine/2018/june-2018-vol-245-no-6)

FEATURES (/MAGAZINE/2018/JUNE-2018-VOL-245-NO-6#FEATURES)

Examining Data Quality of Robotic PipelineInspection MethodsBy Paul Monsour, Senior Pipeline Integrity Engineer, Sempra Energy; Francis Gracias, Manager of Data Analysis, PipetelTechnologies; Rod Lee, General Manager, Pipetel Technologies

The robotic pipeline inspection method has been more widely used for integrity assessment of natural gas and liquid product pipelines overthe past seven years. While the operational advantages o�ered by this method may be better known and documented, there is a relativelyscarce amount of literature on the quality of data and results acquired by a pipeline inspection robot and the speci�c threats that can beaddressed.

This article examines the ability of robotic pipeline inspection methods to address speci�c pipeline threats, including surface corrosion,internal and external anomalies, deformations, construction features, and other useful pipeline features and characteristics. Results andspeci�c examples of pipeline anomalies and features found by the Pipetel Explorer robotic pipeline inspection method (that weresubsequently excavated and validated) will be discussed. Finally, this article will qualitatively compare the quality of data acquired byconventional free-swimming inline inspection tools with robotic inline inspection tools.

Robotics Inspection

Pipetel Technologies has been inspecting pipelines that cannot be inspected by traditional inline inspection (ILI) tools using the Explorerrobotic pipeline inspection systems since 2010. Currently, Pipetel operates a �eet of Explorer robots from 8-inch to 36-inch diameter.

Explorers are tetherless, remotely controlled, self-powered robots capable of inspecting gas pipelines under live pipeline conditions up to750 psig. Explorers are bidirectional and can travel upstream or downstream under �ow or with no �ow.

They enter and exit pipes without pre-built traps and receivers through pipe spools mounted on top of industry standard hot tap �ttings(Figure 1). Explorers have also entered and exited pipes through conventional pig traps. Since Explorers are wirelessly controlled, they canbe stopped to re-inspect any segments or features of interest.

Over the past seven years, Pipetel has inspected pipes with bore reduction up to 75% of outer diameter, vertical segments, mitered-joints,

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Figure 2: A specialist observing the MFL sensor on an Explorer

back-to-back elbows, short and long radius elbows, barred or unbarred tees, and valves of various kinds including plug valves.

Every Explorer is equipped with high resolution cameras on both ends, a high resolution magnetic �ux leakage (MFL) sensor (Figure 2),and a laser deformation sensor. All three datasets are acquired wirelessly and also stored onboard, analyzed and the results included aspart of the deliverables.

Unlike conventional ILI tools which travel at the speed of the product �ow with some speed control, Explorers travel at a controlled andsteady speed of about 4 inches per second (1,200 ft per hour) ensuring the resulting MFL and deformation data is free from any speedexcursion and speed related degradation.

For inspections where the point of entry and exit are the same, pipes can be inspected once when travelling away from the point ofentry/exit and a second time when traveling back to the point of entry/exit. This results in a redundant set of video, MFL and deformationdata for comparison, further analysis and assurance.

Early Adopter

Since the early 2000s, Sempra Energy has been funding the development of Pipetel’s robotic pipeline inspection method throughNYSEARCH/Northeast Gas Association. And beginning in 2011, Sempra successfully used the Pipetel Explorer robotic inspection methodin a number of its pipelines. The diameter of these pipelines includes 8-, 10-, 12-, 14-, 16-, 20-, 22-, and 24-inch sizes. The length of thesepipelines ranges from a few hundred feet to over 2.5 miles.

There are several bene�ts in using robotic pipeline inspection methods instead of ECDA or hydrotest. First, the cost of assessing a pipelinewith an Explorer inspection is more economical. Secondly, many of the pipelines are located in urban and congested areas, environmentallysensitive areas, or other areas such as railways, highways, bridges and river crossings where permitting for ECDA or hydrotesting isdi�cult.

In some cases, it was simply impossible to gain access to these pipes. For example, a pipeline with a segment under a freeway that Explorer16/18 successfully inspected, despite the fact that it was deployed from a location far from the highway. The pipeline, built in the 1950s,remained in service at an operating pressure of 375 psi during the inspection.

Finally, an Explorer inspection provides comprehensive data and information about the integrity conditions of the pipeline that allowsengineers at Sempra to develop e�ective maintenance plans.

Pipeline Threats

An Explorer inspection provides data from MFL sensors, a laser deformation sensor (geometry) and videos. The quality of data forinterpretation and measurements is similar to that provided by conventional free-swimming ILI inspection data. Similar to MFL sensors onconventional ILI tools, the MFL sensor on an Explorer also measure 360 degrees of the pipe circumference every 0.08 to 0.1 inch axially.The data is correlated with �eld results. As shown in the examples below, a �eld picture of external corrosion is shown with thecorresponding MFL data.

Seam Weld Corrosion

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Figure 3: Long seam welds as seen in the video and MFL data, on either side of a girth weld

An example of the long seam welds (Figure 3) as seen by the cameras on Explorer and the corresponding MFL data. In this example, thelong seam weld on each pipe segment is circumferentially o�set from each other across a girth weld. When corrosion threats are presentalong the long seam weld, they are detected and measured by the MFL sensors.


Figure 4: A 12% dent found during an Explorer inspection

Dents and other third-party damages are often found during an Explorer inspection. Dents can be detected in the MFL, deformation andvideo data. The dent was about 1% as measured by the MFL and deformation sensor and seen by the cameras on Explorer. In comparison,the dent in (Figure 4) was a 12% dent. Furthermore, metal loss interacting or near a dent is detected in the MFL data. These anomalies arereported such that appropriate remediation can be applied.

Pipeline Characteristics

Seamless pipes: The MFL data depicts a change in pipe type across a girth weld. The pipe segment on the right on side of the girth weld isa seamless pipe whereas the pipe segment on the left is a seam welded pipe.







Figure 5: The start and end of a casing as located by the MFL sensor

Cased pipes: Similar to a change in wall thickness, the presence of a casing along a pipe segment can also be detected by the MFL sensoron Explorer. As shown in (Figure 5), Explorer located the start and end of a casing. The end of the casing is in contact or closer proximitywith the pipe.

Construction Features


Figure 6: A chill ring in a pipeline. (Top) recorded by Explorer cameras, (middle and bottom) corresponding MFL and deformation data, respectively

Chill rings: The construction feature in (Figure 6) is a chill ring at a girth weld as seen by the cameras on Explorer. Since Explorer is arobotic ILI system controlled by a Pipetel operator at all times, the Pipetel operator can maneuver Explorer through a chill ring preventingExplorer from getting caught by the chill ring.

Couplings: When a coupling is detected in a pipeline by Explorer, Pipetel uses the MFL, deformation, and video data to measure the gap, ifany, across the two pipes.

This saves the operator from excavating to perform direct measurement (likely using X-ray) on the separation across the two pipes. Acoupling across two pipes as seen by the cameras on Explorer. The corresponding MFL and deformation data are used to predict the gapacross the two pipes.


Figure 7: A coupling in a pipeline. Top �gure was recorded by the cameras on Explorer. The middle and bottom �gures were the corresponding MFL and deformation data respectively





Repair patches and sleeves: Explorers have proven to be very e�ective in �nding and locating repair sleeves. Not only do these addedmetals (typically referred to as metal gains) appear in the MFL data, they can be visualized by the cameras on Explorers (Figure 7).

Heat marks from the welding associated with the repairs are usually visible. Localized patches on a pipe and full-circumferential repairsleeve can be found along a pipe. The added metal from the repair sleeves appears as “metal gain” in the MFL data.

Hot-tap �ttings: Unbarred tees and other full bored �ttings are regularly encountered by Explorers. An unbarred tee at the 3 or 9 o’clockcircumferential location. Tees do not need to be barred for an Explorer inspection.

Pool of liquid of other debris: The video data of a pool of liquid collecting at a low spot along a pipe. An Explorer inspection oftenuncovers other debris inside a pipe. Liquid collecting at an unexpected location may lead to internal corrosion threats if not remediated.This is yet another piece of information for operators to act upon in safeguarding the operations of pipelines.

Elbows: When Explorers go through an elbow the angle of the elbow was measured and reported allowing the operators to correlate andupdate their construction records. All Explorers are capable of traversing elbows including short-radius, long radius, and mitered elbows.

Qualitative Comparison

The MFL and deformation sensors on a robotic pipeline inspection system, more speci�cally an Explorer in this case, are competitive oreven better than those found on conventional ILI tools. The MFL sensors are capable of fully saturating or magnetizing the pipe materials upto the maximum wall thickness capability of the sensors.

They o�er similar or even better axial sampling frequency and circumferential sensor spacing as conventional ILI tools. The resulting MFLdata from an Explorer inspection o�ers the distinct advantage of being free from any speed related degradation which commonly exists inconventional ILI. This is because Explorers travel at a relatively slow speed of 4 inches per second and the speed remains constant despitethe �ow and pressure conditions inside the pipes.

In conventional ILI, degradation of data often takes place in gas pipelines due to speed. During launch, after an elbow or a change in wallthickness, due to the compressibility of gas, pressure behind the ILI tools must build up for propulsion resulting in high acceleration of theILI tools and subsequently degradation of data. Explorers are free from these compromises and will almost always provide excellent speedpro�les well below 1 meter per second.

The deformation sensor on Explorers also o�ers superior circumferential resolution compared to conventional ILI tools. While the resolutionof the deformation sensor on any conventional ILI tools is limited by the sensor spacing of each mechanical sensor, the resolution of thedeformation sensor on Explorer is continuous since a laser is used without any discrete spacing.

The circumferential resolution of the laser ring is not limited by any physical sensor spacing. Not only does this allow Pipetel to accuratelymeasure dents and other deformations, it allows for higher resolution and accuracy of subsequent dent strain analysis should the operatorchoose to perform such analysis.

Finally, as seen throughout this paper, the MFL and deformation data are always supported by visual evidence captured by cameras. Thisevidence provides added certainties and reveals new information about a pipe.

Conclusions

An Explorer robotic inspection provides a comprehensive data set from a pipeline. This article provided many examples of threats, featuresand other information commonly found in an Explorer inspection.

More importantly, the amount of information and knowledge returned from an Explorer inspection provides a holistic view on the status andconditions of a pipeline for operators to develop actionable plans to maintain the safe operations of their pipelines.

The MFL and deformation sensors are at least comparable, if not superior, to those found on conventional ILI tools. Robotic inline inspectionmethod is conducted at a controlled, steady and relatively slow speed, and is therefore completely exempted from any degradation of dataquality due to speed related compromises. Together with the ability to see inside each pipe, robotic pipeline inspection method is setting anew and elevated standard in inline inspection of pipelines. P&GJ

Editor’s notes: The sample data and �gures related to the Pipeline Threats section are not from Sempra projects. Content is partiallyreproduced from a version published at the Clarion Unpiggable Pipeline Solutions Forum 2017.

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