Fully Automated Inspection of Welded Seams with a New High Resolution Durable X-ray Camera System

Fully automatic x-ray inspection systems are widely used in light alloy foundries. Now this kind of ADR-system is applied to the X-ray inspection of welded seams. This paper presents a new system for the automatic evaluation of im- ages in combination with a new high resolution X-ray camera with high grey value dynamics. A new handling concept made short inspection times possible. Instead of conveying the pipe along its axis, a lateral movement was utilised instead. Com- pared to standard systems, the movement during inspection was shifted to the X-ray source and detector, which led to a 30% reduction in inspection time. The newly developed X-ray camera features an active area of 200mm by 50mm with a total number of 4.2 million pixels. As neither the electronics nor the sensor is exposed to the X-ray beam, the camera is not damaged by X-ray photons with energy of up to 250 keV. Multiple tests with the PT duplex wire (EN 13068) and the wire IQIs (EN 462-1) have provided an image quality that is superior to the requirements of the X-ray film norm (EN 584) for the X-ray inspection of welded seams. The images acquired by the camera are used as input for the automatic evaluation. Due to the high grey level dynamics of these images, all processing is performed with 16-bit image operations so that there is no loss of information caused by grey-level downscaling. In the first image processing step, the grey levels of an image are converted to wall thicknesses. This allows the extent of a defect in the direction of the beam to be measured. In the next step, the detection of the limits of the seam (borders and mid-line) is performed to enable an adaptive filtering. The results of this detection are transferred to the manipulation control to guarantee an optimum positioning of the weld in front of the camera. The adaptive filtering is able to detect faults such as pores, foreign materials and cracks. Finally a quality rule is applied. The image data of a pipe combined with the results of the evaluation is stored in an archive and automatically transferred to a DVD.