The operational performance of a pipeline strongly depends on its internal and external geometry. Consequently, reliable information on the position of features in a pipeline, the position of the pipeline and changes in position is of great importance to all pipeline operators. During its lifetime, the design shape of a pipeline may change through external interference, such as upheaval, landslides, anchor drop or machinery approaching the right of way.
This results in flow restrictions or prevents the passage of cleaning and inspection tools. But – lo and behold – this is an aspect an operator can control. In order to do so, reliable means for identifying, locating, quantifying and assessing these changes in diameter are critical. In this case, our ROSEN Asia Pacific team faced an unknown restriction within the pipeline and had to develop a solution to inspect the asset at maximum flow rate.
In early 2020, ROSEN was contracted to inspect a 2.7-kilometer-long 16-inch gas pipeline in Borneo. The main objective of the In-Line Inspection (ILI) of the eleven-year-old pipeline was to identify possible internal diameter restrictions prior to the Magnetic Flux Leakage (MFL) run. The first step was the pre-inspection cleaning, a standard practice. During this process, we ran a gauge plate and found a restriction within the pipeline. We assumed the denting was caused during the initial installation of the pipeline.
This indicated that a standard MFL run would not be possible given the current internal condition of the pipeline.
Our experts advised our client to consider identifying and profile the location of the internal restriction. In order to do so, we utilized our advanced high-resolution geometry inspection to provide an accurate determination of the dent size and other geometric properties.
Our geometry tool combines a traditional mechanical caliper arm with an electronic distance measurement system (which optimizes measurement accuracy). The arms of each set of sensors can be depressed enough to have a minimum passage of 80 percent.
KEEPING THE SPEED UNDER CONTROL
Pipeline integrity management strongly depends on the quality of the in-line inspection data. Many gas pipelines are operated at high flow rates for maximum throughput. In the past, these flow rates had to be substantially reduced when operating in-line inspection tools.
Figure 1 – Schematic illustration of the Speed Control Unit (SCU) with control valve
In this case, the customer was concerned about avoiding loss of production due to the low flow rate during the inspection. Therefore, ROSEN equipped the geometry tool with an additional technology, called a Speed Control Unit (SCU). It reconciles the conflicting goals – the required moderate inspection velocity versus high throughput rates – by creating a controlled bypass of the product through the inspection vehicle. The product bypass is most efficiently controlled by an active valve system. To achieve smooth run conditions, the target tool velocity can be preset inside the tool electronics. Each individual speed control unit for different pipeline sizes is designed using 3D finite element modeling to minimize unwanted turbulences, resulting in the maximum difference between the tool speed and the gas flow.
During the inspection for our customer in Borneo, the SCU was utilized during the inspection at a high flow rate (product speed 5 m/s) to avoid any loss of production while maintaining the necessary data quality.
BUT THAT IS NOT ALL
Additionally, our regional experts had to configure a new design and set of tools with a size of 16 inches, including an SCU-capable unit. Our off-the-shelf SCU designs typically cover a tool size of 20 inches or more. Therefore, this was an unconventional and unprecedented approach, as 16 inches is not an ordinary size for an SCU geometry inspection, and smaller tools do not have ample openings for greater speed reduction.
Figure 2 – The geometry tool was equipped with an SCU
THE COMPLETE PICTURE
Based on the gauge plate run, we already suspected that there was a potential high sharp edge (misalignment) somewhere in the pipeline, which could harm the MFL tool with its existing configuration. However, after running our geometry inspection with the SCU, ROSEN was able to successfully identify and provide the complete profiling of the internal diameter restrictions and geometry defects within the pipeline. The geometry inspection with the SCU was completed without any loss of production on the customer’s end. Based on the data from the geometry inspection, we concluded that it was safe to run the MFL inspection and were then able to modify the axial MFL tool according to the restrictions present in the pipeline. After the modifications, the MFL run was completed successfully.