All of these advantages make magnetic flux leakage inspection the most popular method. The requirements for the detection environment is not high, and they are unaffected by the transportation medium. It can not only examine the internal surface for defects, but also external surfaces. For example, surface defects, stomata, scars, shrinkage cavities, corrosion pitting and so on. Besides, it can detect many types of defects. Online detection can be easily carried out and a high degree of automation can be implemented. Magnetic flux leakage inspection does not need pre-processing and the signals are easy to detect. Figure 1 shows a MFL tool.Ī MFL tool, comprising three main sections: a drive section at the front of the tool, a central magnetizer section and a data logger situated towards the rear of the tool. With the development of the semiconductor electronics industry, magnetic sensors have made great progress, which has removed the limitation of measuring tools to magnetic powder. This method is intuitive, simple, has high sensitivity, and has been widely used in industry. In the initial stage, the sensors widely used magnetic powder, which displayed the results by piling up. As noted, magnetic flux leakage (MFL) techniques have evolved in the pipeline inspection industry since the 1960s. Magnetic flux leakage is the most widely used method which can detect cracks in both the axial and circumferential directions, although it is susceptible to the pipe wall and other factors. However, due to various factors and impact of the constraints, both of their results are uncertain, and the results need to be quantified and evaluated. Magnetic flux leakage and the ultrasonic inspection technique are the most frequently used for evaluating the integrity of pipelines. The ultrasonic inspection, eddy current inspection and magnetic flux leakage inspection techniques are common methods. Because of the special feature of the long nature of oil pipeline inspections, these are carried out from the interior of the pipe. Each method has its advantages and limitations. Common methods include ultrasonic inspection techniques, eddy current inspection techniques, ray inspection techniques, penetration inspection techniques and magnetic flux leakage inspection techniques. Nondestructive testing techniques have been widely used for evaluating the condition of pipelines. All this puts more pressing requirements on pipeline detection. Restricted by detection technology and means, pipeline detection is blind, which leads to a waste of manpower, materials and financial resources. Every year the cost of pipeline maintenance of China is as much as several hundreds of millions Yuan, and there is an increasing trend. These defects are formed due to a lack of penetration and fusion during pipe manufacturing. Some spiral weld defects exist on certain old and long pipelines of PetroChina (Beijing, China).

The safety of deepwater risers is essential for sustainable operation of offshore platforms, which need to increase the accuracy of damage detection and fatigue estimation. The Baltic Sea pipeline will be an important contribution to the long-term security of supply and the energy partnership between the European Union and Russia, but lots of work is needed to protect the pipelines. The cost for repairs or replacement of subsea pipelines is much higher than for onshore pipelines. To ensure safe operation is paramount, and there are considerable maintenance methods that can be adopted. Oil and gas companies have a vast amounts of facilities and equipment. After more than 40 years, the gap between China and the world’s developed countries has gradually shrunk, especially in the areas of pipeline engineering design technology, construction level, operation management and maintenance, but China’s pipeline industry started relatively late and has developed slowly, and there are many considerable gaps in the pipeline coverage, service range, technical equipment and so on.

The pipeline industry in China has developed along with the oil industry. Any metal losses or small defects in pipelines could cause serious accidents. However, most pipelines are buried underground, where they are easily affected by humidity or pressure and are prone to deformation and corrosion. It is well known that most safest and effective way to transport oil-gas is to employ a pipeline system. Nowadays, petroleum and natural gas are key energy and chemical raw materials, which have a pivotal function in the life of people, industrial and agricultural production and national defense. The Significance of Pipeline Defect Detection