Method for measuring density of cable sheath tube

Abstract

The invention discloses a cable sheath tube density measurement method, which comprises the following steps of: 1, firstly, using a probe with an iron wedge block as a pipeline density measurement signal generation tool, and using a normal probe as a pipeline sound velocity measurement signal generation tool; 2, measuring the thickness of the pipeline by using a vernier caliper, and recording the thickness of the pipeline; 3, measuring the sound velocity of the pipeline; 4, performing gain measurement in water; 5, measuring the density of the pipeline; and 6, analyzing the data to obtain the density # imgabs0 # of the pipeline. According to the method, fast Fourier transform is carried out on multiple reflection echo signals of ultrasonic waves in an iron wedge block, the amplitude of the center frequency of each echo signal is extracted, data fitting is carried out under logarithmic coordinates, and the acoustic impedance of the pipeline can be obtained by combining the slope of a fitting curve with the multiple reflection theory, so that the initial calculation density of the pipeline is obtained; and then, combining parameters such as sound velocity and thickness of the pipeline, performing further accurate calculation by utilizing a multivariate quadratic model, and finally obtaining the density of the pipeline.

Description

Technical Field

[0001] The invention relates to a method for measuring the density of a cable sheath pipe, and belongs to the field of pipeline measurement. Background Art

[0002] In modern industry, pipeline systems are widely used in oil, gas, chemical, water supply, heating and other fields. The performance of pipelines directly affects the safety and efficiency of industrial processes. Therefore, accurate detection of the physical properties of pipelines, such as thickness, density, corrosion, etc., is crucial to ensure the reliability and safety of pipelines.

[0003] Cable protection tubes are an important part of infrastructure such as power and communications. Their quality and performance are directly related to the safe and stable operation of the system. The density of cable protection tubes is one of the important indicators for evaluating its material uniformity, strength and corrosion resistance. Its accurate measurement is crucial to ensure the quality of cable protection tubes.

[0004] At present, the density measurement methods of cable protection tubes mainly include the following: Physical weighing method: This is the most direct method. By measuring the mass and volume of the cable protection tube, its density is calculated. However, this method is cumbersome to operate and requires precise measurement of the size of the protection tube. In addition, for large or irregularly shaped cable protection tubes, the measurement difficulty and error will increase significantly. Chemical analysis method: By sampling and analyzing the chemical composition of the cable protection tube, the theoretical density of the material is calculated. Although this method has high accuracy, it is destructive and cannot detect finished or installed cable protection tubes. It is also costly and time-consuming. Radiation detection method: Using the ability of X-rays or gamma rays to penetrate substances, the density is inferred by measuring the attenuation of the rays in the substance. Although this method is non-destructive, the equipment is expensive, the operation is complicated, and there is a certain radiation risk to the operator. It is not suitable for large-scale or routine detection.

[0005] In view of the limitations and shortcomings of the above existing measurement methods, it is particularly important to find an accurate, convenient and non-destructive method for measuring the density of cable protection tubes. As a mature non-contact detection technology, ultrasonic multiple echo reflection method has been widely used in the field of material testing and has shown advantages such as high precision, high efficiency and low cost.

[0006] At present, the existing ultrasonic density measurement method is mainly used in some existing technologies, such as patent CN113932866B, which mainly uses the ray attenuation principle to calculate density and only uses ultrasound to measure flow velocity. The ray attenuation method is easily disturbed by impurities and uneven distribution of particles in the fluid, and it is difficult to measure special fluids. In addition, the intrinsic relationship between ultrasound and density is not fully explored in density measurement, and it relies on ray measurement and calibration data, which increases the complexity and uncertainty of the system.

[0007] Patent CN116558591A measures flow and density by coupling an ultrasonic velocity sensor with a differential pressure gas dynamic density meter. However, in large-diameter pipelines, when the natural gas velocity and density are unevenly distributed, the differential pressure density meter is greatly affected by local changes in the flow field, and the measurement accuracy fluctuates significantly. Although the three-way symmetrical measurement and partition layout it adopts take into account the fluid distribution characteristics, the hardware cost is high, the installation and debugging are difficult, and the installation accuracy requirements are stringent.

[0008] Patent CN118111518A uses the time difference and sum of bidirectional ultrasonic detection at oblique asymmetric positions on both sides of the closed pipeline to calculate the flow rate and density. However, this method is easily affected by factors such as pipeline wall roughness, fluid viscosity changes, and pipeline bending. In complex fluid conditions, such as fluids containing bubbles, particles, or high-speed flow, the bidirectional detection signal has large interference, and simple time calculation methods are difficult to eliminate interference, limiting the improvement of measurement accuracy.

[0009] Patent CN203224418U measures the solid concentration or density of the medium based on the comparison of the intensity and attenuation of the transmitted and received ultrasonic signals. The method is simple and crude. For media with small density changes or complex components, it is difficult to accurately determine the relationship between signal attenuation and density, and the measurement accuracy is low. In addition, there is a lack of in-depth analysis of ultrasonic signals, which cannot meet the needs of complex environments or high-precision measurements.

[0010] In summary, the existing ultrasonic measurement technology has problems in density measurement, such as insufficient accuracy, many interference factors, and limited scope of application. There is an urgent need for a new and more advanced ultrasonic measurement technology to achieve high-precision and high-stability pipeline density measurement to meet the growing needs of industrial production and other fields. Summary of the invention

[0011] Purpose of the invention: In order to overcome the deficiencies in the prior art, the present invention provides a method for measuring the density of a cable sheath pipe. The method performs fast Fourier transform on the multiple reflection echo signals of ultrasonic waves in the iron wedge block, extracts the central frequency amplitude of each echo signal, and performs data fitting in logarithmic coordinates; by fitting the slope of the curve and combining the multiple reflection theory, the preliminary calculated density of the pipeline is obtained, and then, combined with the sound velocity, thickness and other parameters of the pipeline, a multivariate quadratic model is used for further precise calculation to finally obtain the density of the pipeline.

[0012] Technical solution: To solve the above technical problems, a cable sheath tube density measurement method of the present invention comprises the following steps:

[0013] Step 1: First, use a probe with an iron wedge as a tool for generating pipeline density measurement signals, and use a straight probe as a tool for generating pipeline sound velocity measurement signals;

[0014] Step 2: Measure the thickness of the pipe with a vernier caliper and record the thickness of the pipe;

[0015] Step 3: Measure the sound velocity in the pipeline;

[0016] First, replace the straight probe, squeeze an appropriate amount of ultrasonic coupling agent on the outside of the pipe, press the straight probe tightly against the outside of the pipe, and save the data of the pipe sound velocity measurement;

[0017] Step 4: Perform in-water gain measurements:

[0018] Replace the straight probe with a probe with an iron wedge, immerse the probe surface with the iron wedge into pure water and keep the relative position unchanged, and save the data of the water gain measurement;

[0019] Step 5: Measure the pipeline density:

[0020] Squeeze an appropriate amount of ultrasonic coupling agent on the end face of the pipe, press the probe with the iron wedge against the end face of the pipe, and save the data of the pipe density measurement;

[0021] Step 6: Analyze the above data to obtain the density of the pipeline.

[0022] Preferably, step 6 comprises the following steps:

[0023] Step 61: Analyze the sound velocity of the pipeline:

[0024] Process the echo signal and use the formula to calculate the sound velocity c of the pipeline. Where L represents the pipe thickness, t2 represents the second pulse echo transmission time, and t1 represents the first pulse echo transmission time;

[0025] Step 62: Extract the slope of the fitted line Kw of the gain measurement in water:

[0026] The echo data of the underwater gain measurement experiment was fast Fourier transformed, and the amplitude of each echo signal was taken as the logarithm as the dependent variable and linearly fitted with the echo number to obtain the slope Kw of the fitting line;

[0027] Step 63: Extract the slope of the fitting line for pipeline density measurement Kg:

[0028] The echo data of the pipeline density measurement experiment was fast Fourier transformed, and the amplitude of each echo signal was taken as the logarithm as the dependent variable and linearly fitted with the echo number to obtain the slope of the fitting line Kg;

[0029] Step 64: Calculate the reflection coefficient R of the interface between the iron wedge and pure water w :

[0030]

[0031] Z w =ρ w *c w

[0032] Z l =ρ l *c l

[0033] Among them, Z w is the acoustic impedance of water, Z l is the acoustic impedance of the iron wedge, ρ w is the density of water, c w is the speed of sound in water, ρ l is the density of the iron wedge, c l is the speed of sound of the iron wedge;

[0034] Step 65: Calculate the acoustic reflection coefficient R of the interface between the iron wedge and the pipe:

[0035] R=R w *exp(K g -K w )

[0036] Step 66: Calculate the acoustic impedance Z of the pipe:

[0037] Step 67: Get the preliminary calculated density ρ of the pipeline: Where Z is the acoustic impedance of the pipeline and c is the sound velocity of the pipeline.

[0038] Step 68: Accurate calculation of pipeline density based on multivariate quadratic model

[0039] The density of the pipeline can be obtained by inputting the sound velocity, thickness and other parameters of the pipeline as well as the preliminary calculated density into the multivariate quadratic model. The form of the model is as follows:

[0040]

[0041] Among them, y t is the density of the pipe, y m is the preliminary calculated density of the pipeline, c is the pipeline sound velocity, d is the pipeline thickness, β0, β1,…,β9 are model coefficients.

[0042] The model is built on the following principles:

[0043] Linear term β1y m ,β2c,β3d reflect the influence of each variable on density. mAs a preliminary calculation of density, it is obtained by the ultrasonic echo multiple reflection method, which contains information about ultrasonic echo and reflection process, and can reflect the acoustic characteristics of the pipeline and its correlation with density. c, as the pipeline sound velocity, is a key parameter reflecting the material and internal structure of the pipeline. Pipes of different materials and densities have significant differences in sound velocity, and there is a specific relationship between the sound velocity and density. d is the pipeline thickness, which affects the contact area between the iron wedge and the pipeline, and then affects the reflection intensity of the ultrasonic wave on the contact surface, and finally has an important impact on the reflected signal. The square term β5c 2 ,β6d 2 It can capture the impact of the quadratic relationship of each variable on the true density, and the interaction term β7y m c,β8y m d,β9cd reflects the influence of the interaction between variables on the true density. The coefficients in the multivariate quadratic model are determined by fitting the experimental data of the known pipeline, and the parameters such as the sound velocity and thickness of the pipeline to be tested and the preliminary calculated density y m By inputting it into the model, the density value of the pipeline can be obtained.

[0044] Compared with the prior art, the cable sheath pipe density measurement method of the present invention has the following significant advantages: This method uses ultrasonic echo reflection technology to determine the pipeline density, which is a non-destructive testing method with the characteristics of high efficiency and convenience. However, in actual measurements, due to practical factors such as the difference in the contact area between the probe and the end face of the pipeline and the diversity of pipeline materials, the density data obtained by direct measurement is often only an approximation, not an absolutely accurate true density. To this end, the present invention innovatively integrates multiple parameters such as the speed of sound and thickness of the pipeline, and uses advanced multivariate quadratic mathematical models for in-depth analysis, which effectively improves the accuracy of density measurement. This method can accurately and reliably measure the pipeline density, and has technical effects such as low measurement cost, wide application range, and easy operation. These advantages give this method broad application prospects and important practical value in industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 This is a schematic diagram of the placement of the sound velocity measurement probe;

[0046] Figure 2 This is a schematic diagram of the placement of the underwater gain measurement probe;

[0047] Figure 3 This is a schematic diagram of the placement of pipeline density measurement probes;

[0048] Figure 4 Get a flow chart for the data;

[0049] Figure 5 A flowchart for data analysis;

[0050] 1- Data storage USB flash drive; 2- Special quality detector for cable protection tube; 3- Probe line; 4- Probe with iron wedge; 5- Pipeline; 6- Straight probe; 7- Water interface; 8- Water storage container. DETAILED DESCRIPTION

[0051] The present invention will be further described below in conjunction with the accompanying drawings.

[0052] The device used to implement the present invention comprises a special quality detector for a cable protection tube, a probe line, a probe with an iron wedge, a straight probe, an ultrasonic coupling agent, a vernier caliper, a data storage U disk, and a computer.

[0053] Acquiring echo data

[0054] Step 1: Measure the pipe thickness

[0055] Use a vernier caliper to measure the pipe thickness and record the measured data

[0056] Step 2: Measure the sound velocity in the pipe

[0057] First, insert the data storage USB into the cable protection tube quality tester, connect the device with a straight probe, turn on the instrument, squeeze a proper amount of coupling agent on the side of the pipeline to be tested, press the straight probe tightly on the position of the pipeline with coupling agent, and then set the parameters so that at least two echoes can be displayed on the screen, adjust the gain to a suitable value so that the echo signal can be fully displayed on the screen without waveform distortion, and save the data of pipeline sound velocity measurement.

[0058] Step 3: Perform In-Water Gain Measurements

[0059] Remove the straight probe and replace it with a probe with an iron wedge. Then immerse the surface of the iron wedge in pure water and keep the relative position unchanged. Then set the parameters so that at least five echoes can be displayed on the screen. Adjust the gain to a suitable value so that the echo signal can be fully displayed on the screen without waveform distortion. Save the data of the gain measurement in water and wipe the water on the probe surface with a rag to prepare for density measurement.

[0060] Step 4: Measure the density of the pipe

[0061] Squeeze an appropriate amount of ultrasonic coupling agent on the end face of the pipe, press the probe with the iron wedge onto the end face of the pipe, note that the center of the probe should coincide with the center of the pipe end face, and save the data of the pipeline density measurement.

[0062] Turn off the instrument, unplug the data storage USB drive, insert it into the computer, process and analyze the measured data, and first rename the measured data file to prevent errors when calling the file during subsequent data processing.

[0063] The echo signal is processed and the sound velocity c of the pipeline is calculated using the formula:

[0064]

[0065] Where L represents the pipe thickness, t2 represents the second pulse echo transmission time, and t1 represents the first pulse echo transmission time;

[0066] Step 2: Extract the slope of the fitted line Kw for the gain measurement in water:

[0067] The echo data of the underwater gain measurement experiment was fast Fourier transformed, and the amplitude of each echo signal was taken as the logarithm as the dependent variable and linearly fitted with the echo number to obtain the slope Kw of the fitting line;

[0068] Step 3: Extract the slope of the fitting line for pipeline density measurement Kg:

[0069] The echo data of the pipeline density measurement experiment was fast Fourier transformed, and the amplitude of each echo signal was taken as the logarithm as the dependent variable and linearly fitted with the echo number to obtain the slope of the fitting line Kg;

[0070] Step 4: Calculate the reflection coefficient R of the interface between the iron wedge and pure water w :

[0071]

[0072] Z w =ρ w *c w

[0073] Z l =ρ l *c l

[0074] Among them, Z w is the acoustic impedance of water, Z l is the acoustic impedance of the iron wedge, ρ w is the density of water, c w is the speed of sound in water, ρ l is the density of the iron wedge, c l is the speed of sound of the iron wedge.

[0075] Step 5: Calculate the acoustic reflection coefficient R of the interface between the iron wedge and the pipe:

[0076] R=R w *exp(K g -K w )

[0077] Step 6: Calculate the acoustic impedance Z of the pipe:

[0078]

[0079] Step 7: Get the preliminary calculated density ρ of the pipeline: Where Z is the acoustic impedance of the pipeline and c is the sound velocity of the pipeline.

[0080] Step 8: Accurate calculation of pipeline density based on multivariate quadratic model

[0081] The density of the pipeline can be obtained by inputting the sound velocity, thickness and other parameters of the pipeline and the preliminary calculated density into the multivariate quadratic model. The form of the model is as follows:

[0082]

[0083] Among them, y t is the density of the pipe, y m is the preliminary calculated density of the pipeline, c is the pipeline sound velocity, d is the pipeline thickness, β0, β1,…,β9 are model coefficients.

[0084] The model is built on the following principles:

[0085] Linear term β1y m ,β2c,β3d reflect the influence of each variable on density. m As a preliminary calculation of density, it is obtained by the ultrasonic echo multiple reflection method, which contains information about ultrasonic echo and reflection process, and can reflect the acoustic characteristics of the pipeline and its correlation with density. c, as the pipeline sound velocity, is a key parameter reflecting the material and internal structure of the pipeline. Pipes of different materials and densities have significant differences in sound velocity, and there is a specific relationship between the sound velocity and density. d is the pipeline thickness, which affects the contact area between the iron wedge and the pipeline, and then affects the reflection intensity of the ultrasonic wave on the contact surface, and finally has an important impact on the reflected signal. The square term β5c 2 ,β6d 2 It can capture the impact of the quadratic relationship of each variable on the true density, and the interaction term β7y m c,β8y m d,β9cd reflects the influence of the interaction between variables on the true density. The coefficients in the multivariate quadratic model are determined by fitting the experimental data of the known pipeline, and the parameters such as the sound velocity and thickness of the pipeline to be tested and the preliminary calculated density y m By inputting it into the model, the density value of the pipeline can be obtained.

[0086] After adopting the above technical solution, the ultrasonic multiple echo reflection method is a non-invasive measurement method. It does not require the disassembly or destruction of the pipeline. It only needs to use an ultrasonic probe on the outside of the pipeline for measurement. This non-invasiveness makes the measurement process simpler and faster, and will not affect the normal operation of the pipeline. It can process ultrasonic echo signals in real time and quickly calculate the density of the pipeline. This real-time performance is particularly important for scenarios where real-time monitoring of pipeline status is required, such as pipeline monitoring in industrial production and density monitoring of oil and gas pipelines. Through multiple echo reflections, the acoustic impedance of the pipeline can be determined more accurately, and then the density of the pipeline can be calculated. This method has higher accuracy and reliability than traditional single-point measurement or point-by-point scanning methods. The ultrasonic multiple echo reflection method is not only suitable for solid pipelines, but also can be used to measure the density of liquid-filled pipelines or pipelines with coatings. This makes this method have broad application prospects in industrial production, such as pipeline monitoring in the chemical, petroleum, and natural gas industries. Compared with other non-destructive testing methods, the measurement device of the ultrasonic multiple echo reflection method is relatively simple and low in cost. At the same time, since this method does not require disassembly or destruction of the pipeline, it also reduces the cost and time consumption during the measurement process. The measurement process of the ultrasonic multiple echo reflection method is relatively simple, and the operator only needs to master the basic ultrasonic measurement principles and equipment operation methods to perform the measurement. This makes this method easier to promote and popularize in practical applications.

[0087] In summary, the present invention uses ultrasonic multiple echo reflection method to measure pipeline density, which has the technical effects of non-invasiveness, real-time data processing, high accuracy, wide application range, low cost and easy operation. These advantages make this method have broad application prospects and important practical value in industrial production.

[0088] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for measuring the density of a cable sheath tube, characterized in that: The following steps are involved: Step 1: First, use a probe with an iron wedge as a tool for generating pipeline density measurement signals, and use a straight probe as a tool for generating pipeline sound velocity measurement signals; Step 2: Measure the thickness of the pipe with a vernier caliper and record the thickness of the pipe; Step 3: Measure the sound velocity in the pipeline; First, replace the straight probe, squeeze an appropriate amount of ultrasonic coupling agent on the outside of the pipe, press the straight probe tightly against the outside of the pipe, and save the data of the pipe sound velocity measurement; Step 4: Perform In-Water Gain Measurements Replace the straight probe with a probe with an iron wedge, immerse the probe surface with the iron wedge into pure water and keep the relative position unchanged, and save the data of the water gain measurement; Step 5: Measure the pipe density Squeeze an appropriate amount of ultrasonic coupling agent on the end face of the pipe, press the probe with the iron wedge against the end face of the pipe, and save the data of the pipe density measurement; Step 6: Analyze the above data to obtain the density of the pipeline.

2. The method for measuring the density of a cable sheath tube according to claim 1, characterized in that: The step 6 comprises the following steps: Step 61: Analyze the sound velocity of the pipeline: Process the echo signal and use the formula to calculate the sound velocity c of the pipeline. Where L represents the pipe thickness, t2 represents the second pulse echo transmission time, and t1 represents the first pulse echo transmission time; Step 62: Extract the slope of the fitted line Kw of the gain measurement in water: The echo data of the underwater gain measurement experiment was fast Fourier transformed, and the amplitude of each echo signal was taken as the dependent variable and linearly fitted with the echo number to obtain the slope Kw of the fitting line; Step 63: Extract the slope of the fitting line for pipeline density measurement Kg: The echo data of the pipeline density measurement experiment was fast Fourier transformed, and the amplitude of each echo signal was taken as the logarithm and linearly fitted with the echo number as the dependent variable to obtain the slope of the fitting line Kg; Step 64: Calculate the reflection coefficient R of the interface between the iron wedge and pure water w : Z w =ρ w *c w Z l =ρ l *c l Among them, Z w is the acoustic impedance of water, Z l is the acoustic impedance of the iron wedge, ρ w is the density of water, c w is the speed of sound in water, ρ l is the density of the iron wedge, c l is the speed of sound of the iron wedge; Step 65: Calculate the acoustic reflection coefficient R of the interface between the iron wedge and the pipe: R=R w *exp(K g -K w ) Step 66: Calculate the acoustic impedance Z of the pipe: Step 67: Calculate the preliminary calculated density ρ of the pipeline: Where Z is the acoustic impedance of the pipeline, c is the sound velocity of the pipeline; Step 68: Accurate calculation of pipeline density based on multivariate quadratic model The density of the pipeline can be obtained by inputting the sound velocity, thickness parameters and preliminary calculated density of the pipeline into the multivariate quadratic model. The form of the model is as follows: Among them, y t is the density of the pipe, y m is the preliminary calculated density ρ of the pipeline, c is the pipeline sound velocity, d is the pipeline thickness, β0, β1,…, β9 are model parameters obtained by fitting.

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