In a Nutshell:
Girth weld misalignments, usually dating back to the construction of a pipeline, are a serious threat to the integrity of a pipeline. This is especially the case if the topology of the pipeline route might lead to pipeline movement. To assess such girth weld anomalies with high accuracy and confidence in the results, it is highly beneficial to conduct a series of pull-through tests prior to inspection, using pipe spools with girth weld defect characteristics that are similar to the ones expected in the pipeline to be assessed. In those cases, preparation is key. With our testing capabilities and experiences, we offer a valuable service to our customers by delivering the right solution to guarantee the integrity of their assets. ROSEN experts from our Asia Pacific region recently carried out a solution-specific pull test in preparation for the in-line inspection of a 40" onshore pipeline in a mountainous area in Myanmar/China. Due to both the asset’s construction history and trajectory, the client was concerned about pipe misalignments, subsequent girth weld anomalies and metal loss features. Therefore, they were looking for a reliable solution to carry out the in-line inspection of said pipeline. Our solution included the unique combination of internal eddy current (IEC), high-resolution XYZ mapping and an enhanced digital extended density (DXD3) sensor, a new integrated sensor tailored at assessing girth weld anomalies that makes the sizing of girth weld anomalies more accurate, thus minimizing both integrity risk and effort related to in-field verifications.
In this particular case, local ROSEN experts in our Asia Pacific region were contracted to carry out a 40" pull test for a client in Chengdu, Southwestern China, in order to determine whether a specific Magnetic Flux Leakage (MFL) metal loss in-line inspection (ILI) tool was the right solution for the asset in question. Therefore, a large diameter pull test was carried out at the customers premises located in a mountainous area more than 3,000 meters above sea level, tailored to the individual requirements of the client and based on our regional offerings. This was done in preparation of the inspection of a 700-kilometer-long onshore pipeline running from Myanmar to Yunnan, China, scheduled for later this year. The asset in question had never been inspected before, meaning no data on the pipeline was available. The client was concerned about pipe misalignments, subsequent girth weld anomalies as well as severe metal loss features being present in the pipeline. In order to identify possible threats to the asset, they contacted our local experts to find a suitable inspection solution.
After receiving the ‘go’ for the project and with only one week of preparation time, our local experts were working with our client in their pull test yard to set up and complete the pull test with pipe spools in similar girth weld configurations expected to be present during the inspection and in two different velocities – 1 and 1.5 m/s – to validate the influence of inspection velocity on the data quality of our ILI tool. Our main objective was to find a solution for identifying all the artificial features created by the client during the pull test.
UNIQUE SOLUTION FOR IN-LINE INSPECTION OF GIRTH WELDS
The challenging conditions of the following inspection of the pipeline, which is located in a mountainous area, include a very low flow rate. Additionally, the low quality of the girth welds, dating back to the construction of the pipeline, can lead to a degradation of the quality of the inspection data resulting from the poor velocity profile during inspection. Poor data quality can make it challenging to correctly identify and size defects at the girth weld – which in turn can result in unnecessary cost and efforts related to in-field verifications.
Therefore, our experts proposed the following tool configuration to inspect the 700-kilometer asset and to provide ultimate customer value given the integrity threats at hand:
- Internal eddy current (IEC) (RoCorr IEC)
- A corrosion detection tool with gyroscope (RoCorr MFL-A with XYZ mapping)
- A digital extended density (DXD3) sensor, a brand-new integrated sensor that makes the sizing of girth weld anomalies more accurate
Figure 2 – With our advanced technology, we are able to identify girth weld misalignment between pipe joints, a common threat to pipelines exposed to the forces of nature
Our experts suggested this configuration because it is the most advanced solution for this specific challenge when it comes to sensor and detection capabilities. With the unique internal eddy current technology, we are able to reliably determine the misalignment of the pipe. In combination with the corrosion detection tool and the new DXD3 sensor, our experts are able to size the metal loss features present in the pipeline even better.
NEW DXD3 SENSOR
To improve the accuracy of assessing girth weld anomalies, we have enhanced the performance of our inspection solution thanks to the new digital extended density (DXD3) integrated sensor. The sensor surface is coated with ceramic, which is highly resistant against wear and abrasion. The sensor allows for a more accurate sizing of girth weld anomalies, thus resulting in improved integrity assessments – minimizing both integrity risk and effort related to in-field verifications. Besides a temperature sensor, it includes a variety of coil modules that discriminate between internal and non-internal features, as well as determine sensor lift-off. Also, an increased number of hall sensor elements results in better specification due to improved channel spacing compared to other sensor models.
Figure 3 – Overall review of the collected data picked up by the new DXD3 sensor, with remarks on the joint spool number and related girth weld defects
A CLOSER LOOK AT TECHNOLOGY
Corrosion plays a crucial role in pipeline integrity; it is a time-dependent deterioration process. For reliable and safe operation, monitoring internal corrosion is inevitable. Our RoCombo IEC/XT service offers simultaneous detection of shallow internal corrosion and ID anomalies.
RoCombo IEC/XT is a market-unique service based on the eddy current principle, a well-established, reliable inspection method with high sensitivity and accuracy. Eddy currents are generated when a conductor is exposed to a changing primary magnetic field due to the motion of the field source (IEC sensor with coil system) relative to the conductor (pipe wall) or due to variations of the field over time. This can cause a distribution of circular currents in the pipe body, which are concentrated near the pipe wall surface, adjacent to the exciting coil. These circulating eddies induce secondary magnetic fields that oppose the change of the original magnetic field in accordance with Lenz’s law of electromagnetic induction. The mutual inductance between the coil system and the conductor then results in a characteristic signal. The presence of metal loss disturbs the EC field, causing a change in the signal, which is used to determine feature dimensions and severity.
Figure 4 – Eddy current technology
In addition, the eddy current measurement component is combined with a deflection sensor that allows for simultaneous measurement of the inner pipeline contour. Thus, not only corrosion but also deformations can be captured in one run.
WISE INVESTEMENT – MINIMIZING BOTH RISK AND FIELD VALIDATION COST
After the successful completion of several 60-meter-long pull tests, our ILI tool was in excellent condition, and the data gathered during the test was of high quality.
The velocity was very stable throughout the entire pull test. We were able to correctly detect all artificial features (170 features in total, ranging from 1% to 90% metal loss) created by the client for the purpose of this test. Doing so, we were able to convince the client of our tools’ capabilities and our ability to successfully address girth weld misalignments with our inspection solution prior to the actual inspection.
Our unique combination of internal eddy current (IEC), high-resolution XYZ mapping and the enhanced digital extended density (DXD3) sensor, tailored to assessing girth weld anomalies, delivers ultimate customer value by minimizing both integrity risk and effort related to in-field verifications.
This underlines the importance of preparation and the return of investment when it comes to the early detection of pipeline defects as well as extensive testing prior to the inspection. The data gathered during the inspection of the asset will then serve as a proactive basis for a successful and effective pipeline integrity management. The ROSEN Group has access to an extensive global network of in-house engineering and consultancy experts who work closely with operators of oil and gas facilities and in associated and supporting industries. Find out more about our testing capabilities: testing.rosen-group.com.