Although unpiggable pipelines present a set of unique challenges, they are able to benefit from high resolution direct measurement as much as, if not more than, lines that are conventionally piggable. Difficulty in access puts a premium on ease of inspection as well as on accurate, actionable data and assessment. It is the underlying assessment of the data that can be of greatest benefit to the operator of an unpiggable pipeline.

The dilemma

A pipeline operator needs to inspect a pipeline running through a major metropolitan area. The pipeline has been constructed in various phases over time and contains numerous transitions from 150–200 mm and back again. Several previous inspection attempts have failed and the only option left for regulatory compliance is hydrotesting.

While a hydrotest may achieve regulatory compliance for a pipeline, such compliance alone is not a guarantee of safe or cost-effective operation. It is common knowledge that hydrotests only provide a snapshot of the condition of a pipeline and are not useful in finding dents or small corrosion areas that do not impact the pressure carrying capacity of the line. Even areas of nearly through-wall corrosion can pass a hydrotest only to fail in service a few months later. Accuracy of inspection data is important because of the high cost of prove-up digs at many of the locations along the length of the line.

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The solution

Quest Integrity was approached by a pipeline operator with this exact dilemma. The company’s dual diameter 150–200mm InVista tool navigated the small radius bends in the line while collecting radius and wall thickness data on both the 150 mm and 200 mm sections of pipe in a single inspection. By working collaboratively with the pipeline operator throughout the inspection process, Quest Integrity determined that the tool would be able to navigate the line. Testing was completed using the available pump information. To facilitate this effort, Quest Integrity made multiple mobilisations on the project running both a sizing and inspection tool. As a result, the inspection was successful on the first run of the InVista tool. More than 51.5 km of ultrasonic data was collected.

By performing a high-resolution inspection, the pipeline operator gained a more complete picture of its pipeline. Not only was previously unknown third-party damage discovered, but information about the original construction of the pipeline could also be seen in the data. Previously unknown schedule and weld type changes were observed and all features were mapped to known above ground locations.

A full fitness-for-service engineering assessment was delivered for the entire 51.5 km length of inspected pipeline and hundreds of individual anomalies were sized and identified. A prove-up program was undertaken to repair critical anomalies and to develop statistical confidence in the inspection data for this individual run. The pipeline operator and Quest Integrity worked together in locating and investigating anomalies in the most cost-effective and time-efficient manner.

With the data from this successful inspection, the pipeline operator is able to proactively address issues with this pipeline before they become significant problems. In addition, the resources that would have otherwise been used for subsequent hydrotests can be more efficiently redirected to other integrity management projects.

Accurate inspection with InVista

By overcoming challenges associated with traditionally difficult and unpiggable pipelines, the InVista technology provides operators with an inspection solution for many pipelines where none previously existed. The technology locates, identifies and quantifies circumferential, longitudinal and internal/external defects, enhanced with inertial measurement data. During inspection, the tool collects highly accurate wall thickness and geometry data sets with 100 per cent overlapping axial and circumferential pipeline coverage in a single run. The accuracy and coverage of the data collected enabled Quest Integrity to perform an automated API 579-1/ASME FFS-1 compliant Level 2 fitness-for-service assessment calculating the rerated maximum allowable operating pressure section by section over the entire length of the pipeline.