Research On Pipeline Corrosion Monitoring Based On FBG Sensing Technology

As one of the most important modern transportation,pipeline is developing toward large-scale and complicated pipe network system,and it is important to ensure its safe operation which influences the national economy and human life.The pipeline accident and failure are mostly caused by corrosion accumulation and are usually shown as the inner-wall reduction or the crack propagation,which are gradual processes from variable to qualitative,with hidden and slow characteristics.However,the current monitoring technology of pipeline corrosion present many defects,such as sole function,poor detection and positioning accuracy,and mostly off-line monitoring.It is still lack of long-term and real-time online monitoring technology for pipeline corrosion.Invisible and intangible pipeline corrosion has always been the big concern for many companies,therefore,it has become the key point and difficulty to achieve long-term monitoring technology of pipeline corrosion.Due to its high precision,strong anti-interference and long-term stability,fiber grating sensing(FBG)technology has been successfully applied to the safety monitoring of large-scale engineering structures and major equipment.Herein,based on the fiber grating sensing technology,this paper presents a long-term real-time online monitoring method for pipeline corrosion,and a pipe-specific fiber grating composite sensor is fabricated and demonstrated.Through monitoring the axial and circumferential strain of the pipe outer wall,it can achieve the long-term on-line monitoring of pipeline corrosion,and further estimate its corrosion trends and service life.The main work of this paper is as follows:(1)The effects of the length and depth of the inner surface corrosion(crack)on the surface strain of the corrosion(crack)were studied by means of finite element analysis,which demonstrate the trends of depth and strain.The corrosion of the pressure pipe(crack)model helps provide theoretical basis and technical support for pipeline corrosion(crack)monitoring.(2)Based on the characteristics of pipeline corrosion(crack)model and fiber grating sensing technology,the measurement method of pipeline corrosion(crack)is systematically studied,and the design requirements of fiber grating sensor array are put forward.This paper studies the method of implanting composite materials to fiber grating sensor array based on material,structure and sensing performance.A special type of fiber grating composite sensor is developed by using special equipment.The sensitivity,linearity and stability of the material sensor array are tested to verify its effectiveness and long-term reliability in pipeline monitoring.(3)Aiming at the characteristics of piping structure and working environment,the layout technology and installation technology of linear fiber grating composite sensor array are studied.In particular,the characteristics of composite material of sensor array and the consistency of pre-stretching on pipe deformation and sensor deformation are studied.The method of reducing the measurement error is proposed.This paper analyzes the requirements of the monitoring network of the corrosion distribution of the pipeline,and puts forward the architecture and integration method of the monitoring system,which provides the theoretical basis for the sensor layout.(4)The optical fiber grating composite sensor array are utilized to monitoring the uniform corrosion,local corrosion,circumferential crack,axial crack and oblique crack.The results show that the experimental data are basically consistent with the theoretical calculation value.This kind of multi-point monitoring technology based on fiber grating sensing can distinguish different types of pipe corrosion and realize the long-term real-time online monitoring of pipeline corrosion.