Pipeliners Dictionary

Alternating current (AC) techniques

In pipeline surveying, alternating current (AC) techniques are used to detect and locate faults, corrosion, and other anomalies in pipelines. The main advantage of AC techniques is that they can be used on pipelines that are in service and pressurized, unlike many other pipeline inspection methods that require the pipeline to be drained and depressurized. This means that AC techniques can be performed while the pipeline continues to operate, reducing downtime and minimizing the risk of leaks or other incidents.

1. AC Interference Testing: This method uses low-frequency AC current to detect changes in electrical resistance caused by corrosion or other anomalies along the pipeline. The current is transmitted into the pipeline and its resistance is measured at regular intervals. Any changes in resistance can indicate the presence of corrosion, cracks, or other anomalies.

2. AC Voltage Gradient (ACVG) Surveys: This method involves applying an AC voltage to the pipeline and measuring the resulting electrical field. The electrical field is measured along the length of the pipeline and any changes in the electrical field can indicate the presence of corrosion, cracks, or other anomalies. ACVG surveys can provide a highly detailed and accurate assessment of the pipeline's condition, making it a useful tool for pinpointing specific areas that require repair or replacement.

3. AC Corrosion Mapping: This technique involves using AC current to detect and map corrosion on the pipeline surface. The current is transmitted into the pipeline and its electrical resistance is measured along the length of the pipeline. Any changes in resistance can indicate the presence and location of corrosion. AC corrosion mapping can provide a comprehensive overview of the pipeline's condition and can be used to prioritize areas for further inspection and maintenance.

4. AC Magnetic Flux Leakage (MFL) Surveys: This method uses AC magnetic fields to detect corrosion and other anomalies in pipelines. The magnetic field is applied to the pipeline and its response is measured along the length of the pipeline. Any changes in the magnetic field response can indicate the presence of corrosion, cracks, or other anomalies. MFL surveys are a highly effective method for detecting and locating pipeline anomalies and can provide valuable information for pipeline maintenance and repair.

These AC techniques are often used in combination with other pipeline inspection methods, such as ultrasonic testing and radiographic inspection, to provide a comprehensive evaluation of the pipeline's condition. By using a combination of methods, pipeline operators can ensure that all potential pipeline anomalies are detected and addressed, reducing the risk of pipeline failures and ensuring the safe and reliable operation of their pipelines.

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