How do you choose the best RFT probe for different pipeline materials and diameters?

1 Probe frequency

The frequency of the RFT probe affects the penetration depth, resolution, and sensitivity of the inspection. Higher frequencies can detect smaller defects and provide better resolution, but they also attenuate faster and have lower penetration depth. Lower frequencies can penetrate deeper and cover larger areas, but they also have lower resolution and sensitivity. Therefore, you need to balance these trade-offs according to the thickness, condition, and material of the pipeline. Generally, lower frequencies are recommended for thicker, rougher, or more corroded pipes, while higher frequencies are suitable for thinner, smoother, or less corroded pipes.

2 Probe diameter

The diameter of the RFT probe affects the signal strength, coupling, and coverage of the inspection. Larger probes can generate stronger signals and improve the coupling with the pipe wall, but they also have lower coverage and may not fit into smaller pipes. Smaller probes can cover more area and fit into narrower pipes, but they also have weaker signals and may lose coupling with the pipe wall. Therefore, you need to match the probe diameter with the pipe diameter as closely as possible to ensure optimal performance. Generally, the probe diameter should be between 50% and 80% of the pipe diameter.

3 Probe design

The design of the RFT probe affects the signal quality, directionality, and versatility of the inspection. There are different types of RFT probes, such as single-coil, dual-coil, bobbin, driver-pickup, and array probes. Each type has its own advantages and disadvantages, depending on the shape, orientation, and location of the defects. For example, single-coil probes are simple and robust, but they have low signal-to-noise ratio and poor defect characterization. Dual-coil probes are more sensitive and directional, but they have complex electronics and calibration. Bobbin probes are easy to use and provide full coverage, but they have low resolution and may miss axial defects. Driver-pickup probes are more flexible and adaptable, but they require more setup and maintenance. Array probes are more advanced and versatile, but they are also more expensive and complex. Therefore, you need to consider the type of defects you expect to find and the level of detail you require to choose the best RFT probe design for your application.

4 Probe calibration

The calibration of the RFT probe affects the accuracy, repeatability, and comparability of the inspection. Calibration is the process of adjusting the probe settings and parameters to match the characteristics of the pipeline and the inspection standards. Calibration is essential for ensuring that the RFT signals are correctly interpreted and measured, and that the inspection results are consistent and valid. Therefore, you need to calibrate the RFT probe before each inspection, using reference standards that simulate the pipeline material, diameter, thickness, and defects. You also need to verify the calibration periodically during the inspection, using calibration checks or verification standards.

5 Probe maintenance

The maintenance of the RFT probe affects the reliability, durability, and safety of the inspection. Maintenance is the process of cleaning, inspecting, repairing, and replacing the probe components and accessories to ensure that they function properly and safely. Maintenance is important for preventing damage, wear, and contamination that may affect the performance of the RFT probe and cause errors or hazards. Therefore, you need to follow the manufacturer's instructions and recommendations for maintaining the RFT probe, such as storing it in a protective case, avoiding impacts or abrasions, cleaning it with appropriate solvents, inspecting it for cracks or defects, repairing or replacing it if necessary, and documenting its history and condition.