An on-line monitoring device and method for pipeline leakage and corrosion based on fiber Bragg grating sensing

Abstract

The invention relates to a pipeline leakage and corrosion online monitoring device and method based on optical fiber grating sensing. The device comprises a beam splitting system, a demodulating system, a control system and optical fiber grating sensors which are fixed on the outer wall of a long straight pipeline and the outer wall of a bent pipe. The optical fiber grating sensors fixed on the outer wall of the long straight pipeline only have one optical fiber grating and are arranged axially at equal intervals, and judge whether the long straight pipeline leaks or not according to a change condition of detected hoop strain of the pipeline, find out the leak position and acquire uniform corrosion condition; and the optical fiber grating sensors fixed on the outer wall of the long straight pipeline are provided with a plurality of optical fiber gratings and the optical fiber gratings on the same optical fiber grating sensor are uniformly arranged along the circumference, and the optical fiber grating sensors judge non-uniform corrosion condition at the bent pipe according to a change condition of detected local hoop strain. The device is simple in structure, low in cost, convenient to mount and high in monitoring precision.

Description

technical field [0001] The invention belongs to the technical field of pipeline monitoring, in particular to an on-line monitoring device and method for pipeline leakage and corrosion based on fiber grating sensing. Background technique [0002] Pipelines are widely used in the transportation of oil, gas, water, etc. and the laying of power cables. The health status of pipelines determines the service life and failure rate of pipelines. In order to reduce the failure rate, pipelines need to be monitored. The existing pipeline monitoring methods (magnetic flux leakage testing, eddy current testing and ultrasonic testing, etc.) mainly place the intelligent detector in the pipeline, and under the impetus of the conveying medium, complete the detection of corrosion defects inside and outside the pipeline. The principle is to measure the change of wall thickness to obtain the corrosion development status of the pipeline. Existing pipeline monitoring methods regularly detect (bur...

AI Technical Summary

Problems solved by technology

The traditional pressure sensor-based negative pressure wave detection method has certain limitations, that is, the propagation speed of the negative pressure wave must be known

However, the negative pressure wave velocity is affected by many parameters such as fluid density, pipe material, and pipe wall thickness, which makes it impossible to obtain an accurate value of the negative pressure wave velocity in actual engineering.

[0004] In the article "Fiber Bragg Grating Temperature and Strain Sensing System Applied in Oil and Gas Pipeline" published in "Laser Technology" Volume 31 Issue 1 in February 2007, a fiber grating temperature sensor is installed at the entrance and exit respectively. Install a pressure sensor in the station to obtain the variation of crude oil pressure and temperature in the oil and gas pipeline, so that according to different strain and temperature values, corresponding measures such as heating, pressurizing or decompression are taken in the station to ensure that the crude oil is in the oil pipeline. However, this kind of system can only detect the situation when a large amount of oil and gas has leaked, and cannot timely predict the leakage in the early stage; in October 2013, the article "Based on In "Study on On-line Corrosion Detection System of Oil and Gas Pipeline with Fiber Bragg Grating Sensor in Short Grid Area", fiber grating strain sensors are arranged along the outer surface of the oil and gas pipeline along the circumferential direction to monitor the circumferential strain of the oil and gas pipeline, thereby monitoring the corrosion of the oil and gas pipeline and preventing oil leakage

However, this system only monitors a single temperature or a single strain for each measurement point, the monitoring data is too single, and the false alarm rate is high

In the Chinese invention patent "A Fiber Bragg Grating Sensing Test System for Oil and Gas Pipeline Detection" with the authorized notification number ZL03137597. In this system, when the fiber grating sensor or transmission fiber fails, it will not be able to complete the replacement, resulting in the problem that the oil and gas pipeline cannot be reused

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