Which type of coils are generally used for tubing inspection?

For tubing inspection in the context of electromagnetic testing, encircling coils are typically preferred due to their design and effectiveness. These coils encompass the entire circumference of the tube, allowing for a comprehensive scan of the material. This design is particularly beneficial as it can detect flaws that could be present around the entire surface of the tubing, such as cracks or corrosion, which may not be fully captured by other types of coils.

Encircling coils produce a magnetic field that is sensitive to changes in the material's properties, making them suitable for identifying manufacturing defects or damage that could compromise the integrity of the tubing. Their ability to uniformly inspect the entire surface area of the tube enhances detection capability, ensuring that any issues are not overlooked.

In contrast, other types of coils—like U-shaped coils or gap coils—serve different inspection needs or applications that may not involve the thoroughness required for tubing inspection, which is why they may not be suitable choices for this specific task.