Ndt Testing By X-Ray Crawler

Automated X–ray systems for testing of weld joints use x–ray tubes or gamma–heads mounted on crawlers, which move through the pipe.

Crawlers allow the positioning of the radiation source precisely in the center of the pipe and can panoramically expose the weld to radiation .In this way, the image of the weld is displayed on the x–ray film in one exposure.

Panoramic radiographs, produced with x–ray tubes ,can easily be interpreted with the help of a weld defect catalogue.

Inspection through two walls is an alternative method for radiographic inspection of weld joints.

In this case it is not possible to have a panoramic shot of the pipe wall so the inspection has to be made in sections.

The x–ray film is placed on the external surface of the pipe section to be inspected and the x–ray source is placed against the pipe wall on the opposite side. This way, the section of the weld joint is radiographed through two walls.

The wall closest to the x–ray source is out of focus, but even then its shadow in the image can make the interpretation of the radiograph more difficult.

The productivity of this method is lower than when using an automated inspection system. Moreover this method requires a higher level of qualification from the personnel both to carry out the work and to interpret the results.

Results received from semi–automatic and annual measurements (ultrasonic, eddy current, dye penetrants, magnetic particle) are slightly more difficult to read and interpret and therefore require a more experienced operator.