Non-destructive monitoring method for internal pressure intensity of pipeline

Abstract

A non-destructive monitoring method for internal pressure intensity of a pipeline. The method establishes an equation relationship by the fact that the variation of the internal diameter of the pipeline is the same as that measured by FBG sensors, and can effectively obtain the value of the internal pressure intensity of the pipeline by measuring the strain values of the FBG sensors installed on the pipeline so as to monitor the internal pressure intensity of the pipeline. The present invention has the advantages of simple principle, convenient installation, no damage to pipeline structure, long-distance real-time on-line monitoring and the like, and can measure the pressure intensity of various pipelines with different diameters by changing the calibration distance of sensors and the dimension of sensor clamps. This can complete non-destructive, real-time and accurate monitoring on the internal pressure intensity of the pipeline.

Claims

1. A non-destructive monitoring method for internal pressure intensity of a pipeline, comprising: establishing an equation relationship by the fact that a variation of an internal diameter of the pipeline is the same as that measured by fiber bragg grating (FBG) sensors to obtain a relationship between the internal pressure intensity of the pipeline and strain values measured by the FBG sensors; obtaining the internal pressure intensity of the pipeline by measuring the strain values of the FBG sensors installed on the pipeline to conduct non-destructive monitoring on the internal pressure intensity of the pipeline, wherein a stress state of any point of the pipeline is: hoop stress: ${\sigma }_1=\frac{\mathrm{Pd}}{2\delta },$ axial stress: ${\sigma }_2=\frac{\mathrm{Pd}}{4\delta },$ and radial stress: σ.sub.3=−P, wherein P is the internal pressure intensity of the pipeline, d is an outside diameter of the pipeline, and δ is a wall thickness of the pipeline, wherein an increment Δd of the internal diameter of the pipeline is: $\begin{array}{cc}\Delta d=d.Math.{\mathrm{.Math.}}_1=d.Math.\frac{1}{E}.Math.\left({\sigma }_1-{\mathrm{\upsilon \sigma }}_2\right)& \left(1\right)\end{array}$ wherein E is the Young's modulus of a pipeline material, and ν is the Poisson's ratio; obtaining a relationship between the increment of the internal diameter of the pipeline and the internal pressure intensity of the pipeline as defined in formula (2) by substituting σ.sub.1 and σ.sub.2 into formula (1): $\begin{array}{cc}\Delta d=\left(\frac{2d^2-\upsilon d^2}{4E\delta }\right).Math.P& \left(2\right)\end{array}$ measuring the strain values of the FBG sensors to realize the increment of the internal diameter of the pipeline, wherein sensor clamps and an outer wall of the pipeline are in close fitting, and the FBG sensors are installed on the sensor clamps so that the increment of the internal diameter of the pipeline is the same as the variation measured by the FBG sensors, wherein the variation measured by the FBG sensors is defined in formula (3):
Δd=ε.Math.L  (3) wherein ε is the strain value measured by the FBG sensors, and L is a calibration distance of the FBG sensors; obtaining the relationship between the internal pressure intensity of the pipeline and the strain value measured by the FBG sensors as defined in formula (4) by combining formula (2) and formula (3) to eliminate Δd: $\begin{array}{cc}P=\left(\frac{4E\delta L}{2d^2-\upsilon d^2}\right).Math.\mathrm{.Math.}& \left(4\right)\end{array}$ obtaining the internal pressure intensity of the pipeline by monitoring the strain values measured by the FBG sensors; and installing the FBG sensors, comprising: pasting two sensor clamps symmetrically on a surface of the pipeline with epoxy resin glue, wherein a diameter of an arc of a contact surface of the sensor clamps and the pipeline is the same as the outside diameter of the pipeline; forming a groove respectively in both ends of the sensor clamps; installing the both ends of the FBG sensors respectively on groove ends of the two sensor clamps, wherein the both ends of the FBG sensors are in the same level; installing the FBG sensor respectively on upper and lower ends of the sensor clamps, wherein a spacing between the groove ends of the two sensor clamps is the calibration distance of the FBG sensors; and installing sensor clamp cover plates on the groove ends of the sensor clamps and tightening with screws, wherein the FBG sensors are fixed on the sensor clamps.

Description

DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a schematic diagram of installation of a FBG sensor.

(2) FIG. 2 is a schematic diagram of a cross section of a pipeline.

(3) FIG. 3 is a schematic diagram of a sensor clamp.

(4) FIG. 4 is a schematic diagram of a sensor clamp cover plate.

(5) In the figures: 1 sensor clamp; 2 sensor clamp cover plate; and 3 FBG sensor.

DETAILED DESCRIPTION

(6) Specific embodiments of the present invention are described below in detail in combination with the technical solution and accompanying drawings.

(7) The schematic diagrams of a non-destructive monitoring method for internal pressure intensity of the pipeline provided by the present invention are shown in FIG. 1 and FIG. 2. The specific steps of the installation method for the FBG sensors 3 are as follows:

(8) Step 1: Making sensor clamps 1 according to the diameter of the pipeline to be measured. The diameter of arc of the contact surface of the sensor clamps 1 and the pipeline is the same as the outside diameter of the pipeline to ensure a larger contact area between the sensor clamps 1 and the surface of the pipeline so as to prevent the sensor clamps 1 from loosening due to poor pasting. A groove is respectively formed in both ends of the sensor clamps 1 and used for installing the FBG sensors 3.

(9) Step 2: Pasting the sensor clamps 1 on the surface of the pipeline with epoxy resin glue. The two sensor clamps 1 are symmetrically pasted to ensure that both ends of the FBG sensors 3 are respectively installed in the grooves of the two sensor clamps 1, and both ends of the FBG sensors 3 are in the same level, avoiding the measurement error caused by the installation angle of the FBG sensors 3.

(10) Step 3: After the epoxy resin glue is solid, installing a FBG sensor 3 respectively on the upper and lower ends of the sensor clamps 1, and averaging the strain values measured by the upper and lower FBG sensors 3 to make the measurement result more accurate; and respectively installing sensor clamp cover plates 2 on the ends of the sensor clamps 1 and tightening with screws to fix the FBG sensors 3 on the sensor clamps 1.

(11) The structures of the sensor clamps 1 and the sensor clamp cover plates 2 are shown in FIG. 3 and FIG. 4.