Pipeliners Dictionary

Inline Inspection (ILI)

Inline Inspection (ILI) is a non-destructive method of examining the internal conditions of pipelines without having to physically open or remove sections of the pipeline. It is a crucial component of pipeline maintenance and management, and helps ensure the safe and efficient operation of pipelines over their lifespan.

The primary objective of ILI is to detect and quantify internal anomalies in pipelines, such as corrosion, cracks, dents, deformations, and other forms of structural damage. These anomalies can pose significant risks to the safety and reliability of pipelines, and must be identified and addressed as soon as possible to avoid costly failures and unscheduled downtime.

Inline inspection is performed using specialized tools called pigs or smart pigs. Pigs are cylindrical devices that are designed to traverse the interior of a pipeline, inspecting the pipeline's walls and detecting any anomalies as they move along. Pigs can be equipped with a variety of sensors and inspection tools, including ultrasonic transducers, magnetic field sensors, and eddy current probes, that allow them to detect a wide range of anomalies in pipelines.

There are several types of pigs that can be used for inline inspection, including:

• Ultrasonic Pigs: Ultrasonic pigs are equipped with ultrasonic transducers that emit high-frequency sound waves into the pipeline's walls. The sound waves bounce back from the pipeline's internal surface and are detected by the pig's sensors, which generate an image of the pipeline's internal structure. Ultrasonic pigs are used to detect and quantify corrosion, wall thinning, cracks, and other types of structural damage in pipelines.

• Magnetic Flux Leakage Pigs: Magnetic flux leakage pigs use magnetic fields to inspect pipelines for anomalies. The pig's sensors detect changes in the magnetic field that are caused by anomalies in the pipeline's walls, such as corrosion, cracks, and dents. This type of pig is especially useful for inspecting pipelines that are coated with metal or other magnetic materials.

• Caliper Pigs: Caliper pigs are equipped with sensors that measure the diameter of the pipeline as the pig moves along. Caliper pigs can detect deformations, dents, and other anomalies in the pipeline's walls that cause changes in the pipeline's diameter.

• Combined Pigs: Combined pigs are equipped with multiple inspection tools, such as ultrasonic transducers and magnetic field sensors, that allow them to detect a wide range of anomalies in pipelines. Combined pigs provide the most comprehensive inspection of pipelines and are often used when a detailed assessment of pipeline conditions is required.

Inline inspection is typically performed on pipelines that are in service and under pressure, meaning that the pipeline does not need to be shut down or drained for the inspection to take place. This is an important advantage of inline inspection, as it allows pipeline operators to assess the condition of their pipelines without having to incur the cost and downtime associated with shutting down the pipeline for maintenance or repairs.

In conclusion, inline inspection (ILI) is a non-destructive method of examining the internal conditions of pipelines that helps ensure the safe and efficient operation of pipelines over their lifespan. ILI is performed using specialized tools called pigs or smart pigs, which are equipped with a variety of sensors and inspection tools that allow them to detect a wide range of anomalies in pipelines. There are several types of pigs that can be used for inline inspection, including ultrasonic pigs, magnetic flux leakage pigs, caliper pigs, and combined pigs. ILI is typically performed on pipelines that are in service and under pressure, allowing pipeline operators to assess the condition of their pipelines without having to incur the cost and downtime associated with shutting down the pipeline for maintenance or repairs.

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