Application of Digital Radiography (DR) in Pipeline Corrosion Inspection

Release Date:

2021/06/06

In the petrochemical industry, certain pipelines operate for extended periods under high-temperature or ultra-low-temperature conditions and are subjected to chemical and electrochemical interactions from both the internal process fluids and external environmental media. As a result, these pipelines are prone to corrosion and wall-thickness reduction, which can create safety hazards and, in severe cases, lead to leaks or explosions. To ensure the safe operation of pipelines throughout their inspection intervals, there is an urgent need for online detection of pipeline defects and potential hazards; however, conventional inspection methods are difficult to apply to insulated pipelines. The primary challenge lies in the fact that such inspections typically require extensive removal of the insulation layer, and the elevated surface temperature of the exposed pipe after insulation removal can adversely affect inspection results. Moreover, reapplying the insulation following inspection may give rise to secondary corrosion. Therefore, selecting a reliable inspection technology for insulated pipelines is of paramount importance.

Currently, the commonly used nondestructive testing techniques for insulated pipelines include pulsed eddy current testing, magnetic flux leakage testing, and radiographic film inspection; however, each of these methods has its own limitations. In pulsed eddy current testing of insulated pipelines, ferromagnetic materials in the surrounding pipe wall and within the insulation layer can interfere with the extraction of characteristic signals, and variations in insulation thickness can also distort the test results, while the technique exhibits relatively low sensitivity to localized corrosion. Radiographic film inspection suffers from low inspection efficiency, limited dynamic range, difficulties in long-term film storage, and challenges in digital archiving. Magnetic flux leakage testing is capable of detecting only large corrosion pits and produces images that are not easily interpretable.

Digital radiography (DR) enables the detection of pipeline corrosion and defects without the need to remove insulation. During inspection, X-rays that penetrate the pipe under examination are captured by a digital detector array (DDA), which directly converts them into digital images for immediate display—eliminating the need for darkroom processing. DR offers wide dynamic range, high inspection efficiency, and the capability to automatically measure wall thickness, corrosion pits, pipe diameter, and other parameters. Digital radiographic images can be viewed on computers, tablets, smartphones, and other devices, and are easy to store, retrieve, transmit, and share, thereby greatly facilitating pipeline integrity assessment and monitoring across industries such as oil and gas, chemicals, power, machinery, metallurgy, pharmaceuticals, and food processing.

1. Basic Principles of DR

DR technology utilizes X-rays or gamma rays to penetrate the pipeline under inspection. Due to attenuation characteristics, the intensity of the transmitted radiation varies across regions of different thicknesses relative to the incident intensity. The radiation that passes through the workpiece is detected by a flat-panel digital detector and converted into a digital signal, which is then sent to a computer for processing to generate a digital image.

DR technology is one of the fastest and most efficient radiographic imaging techniques, capable of acquiring digital images in just a few seconds. Portable DR inspection systems typically consist of an X-ray generator, a digital detector array, a computer, software, cables, power cords, network cables, and other components.

2. Test Diagram

3. Application Legend

4. Summary

(1) DR technology can be applied to the inspection of in-service high-temperature (and ultra-low-temperature) pipelines with insulation layers, enabling efficient detection and identification of pipeline corrosion and deposits, wall-thickness measurement, and weld defects. This facilitates the assessment of the safe operation of in-service or over-service-life pipelines and the timely identification of potential hazards.

(2) DR technology addresses the operational disruptions and economic losses associated with conventional inspection methods for insulated pipelines—namely, production shutdowns and the need to remove insulation—and also provides an indirect basis for evaluating the condition of the insulation layer.

(3) The application of DR technology is in line with the national policy of energy conservation and environmental protection. It offers high detection sensitivity, rapid and efficient operation, reduces radiation dose, minimizes radiation risks to employees and the public, and alleviates the burden of radiation protection. By eliminating the use of film and the associated darkroom processing steps, it also eliminates the environmental and health impacts of chemical reagents.

(4) Due to the constraints imposed by the insulation layer and the inability of digital flat-panel detectors to bend, defect images on both the detector side and the X-ray source side exhibit varying degrees of magnification. Therefore, defect evaluation must be adjusted based on the characteristics of digital images and reference test blocks.

(5) In fact, DR technology is not only applicable to the detection of pipeline corrosion and weld defects; it can also be used for the inspection of castings made from metals, alloys, and non-metallic materials, as well as for assessing the assembly accuracy and structural integrity of plastics, rubbers, ceramics, composite materials, electronic components, and critical equipment. Additionally, it is employed in mineral sorting and in the authentication of cultural relics and archaeological artifacts.

Source: SGS Industrial Services

Ultrasonic Phased Array Technology

Twenty national standards and six industry standards for nondestructive testing have been approved and released!

Ultrasonic Phased Array Technology

Twenty national standards and six industry standards for nondestructive testing have been approved and released!

To further carry forward the spirit of Lei Feng and promote the volunteer ethos of “dedication, friendship, mutual assistance, and progress,” in accordance with the spirit of the Henan Provincial Association for Science and Technology’s “Notice on Launching a Centralized ‘i-Science Popularization’ Science and Technology Volunteer Service Campaign in the Spirit of Lei Feng,” Luoyang Weicheng Engineering Testing Co., Ltd. responded enthusiastically to the call and organized a science popularization event on the safe operation of forklifts. On March 4, our company meticulously planned and conducted an emergency response drill for special equipment—forklift accidents—and invited several nearby companies that use forklifts to observe the exercise. The purpose of this drill was to simulate real-world working conditions, specifically the sudden occurrence of an accident during the process of using a forklift to handle goods.

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The 10th Anniversary Gratitude Celebration of Luoyang Weicheng Engineering Testing Co., Ltd. Concludes Successfully

On the afternoon of December 29, 2023, Weicheng Testing Co., Ltd. held a grand gratitude celebration—“Our Ten Years”—inviting distinguished guests, including Mr. Jia Hong, Director and Vice Chairman of the Titanium-Zirconium Industry Development and Application Center of the China Equipment Management Association, as well as Mr. Lu Fusheng, Executive Deputy Director, Vice Chairman, and Secretary-General, along with clients and partners, to jointly witness this milestone occasion. The first segment of the event: A Decade of Development The event officially commenced at 2:00 p.m., with the company welcoming all attendees

2024-01-11

In 2023, Luoyang Weicheng Engineering Testing Co., Ltd. Successfully Held the “Intensive Training and Competition” — Gamma-Ray Radiographic Inspection Emergency Drill

On October 11, Luoyang Weicheng Engineering Testing Co., Ltd. held a large-scale training and competition—specifically, a γ-ray radiographic inspection radiation emergency response drill—under the theme “Everyone Talks About Safety, Everyone Knows How to Respond to Emergencies.” The event invited leaders from the provincial, municipal, and district levels to attend and observe. Prior to the start of the emergency response drill, Cui Songbiao, General Manager of Luoyang Weicheng Engineering Testing Co., Ltd., and Gong Aifeng, Deputy General Manager, extended a warm welcome to the visiting provincial, municipal, and district leaders and pledged that Weicheng Testing would consistently focus on enhancing its professional technical expertise and emergency response capabilities as key drivers for corporate safety management.

2023-10-19

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