With the development of material technology, non-metallic materials are applied to pressure pipes in petrochemical plant. Fiber reinforced plastic (FRP) is widely used because high mechanical strength and corrosion resistance. The non-metallic pipeline has been running for more than 20 years in petrochemical plant of China. Due to the fiber material anisotropy, it is difficult to measure thickness and detect defect by conventional ultrasonic method in FRP inspection. According to Chinese pressure pipeline inspection laws and regulations, the main inspection methods are macroscopic examination and hydraulic pressure test. The inspection of non-metallic pipelines has not been specified in detail. Compared with traditional radiographic detection, digital radiographic detection has better contrast and image processing technology, so digital radiographic detection has more advantages in thickness measurement and corrosion detection.
Elbows are most prone to corrosion defects due to fluid erosion. In this paper, fiber reinforced plastic pipe is detected by digital radiographic technology. In digital radiographic detection, appropriate parameters and accurate measurement are proposed. The accurate wall thickness of the pipe is obtained and the internal defects are detected. By comparing the measurement results with the actual wall thickness, the measurement accuracy of digital radiographic detection could meet the requirement of ultrasonic thickness gauge in NB/T47013.3. Digital radiographic technology is strongly recommended for FRP pipeline periodic inspection.