CN116735672A - Method for judging dielectric layer defect of polyurethane heat-insulating pipe and application - Google Patents
Method for judging dielectric layer defect of polyurethane heat-insulating pipe and application Download PDFInfo
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- 230000007547 defect Effects 0.000 title claims abstract description 99
- 238000000034 method Methods 0.000 title claims abstract description 58
- 229920002635 polyurethane Polymers 0.000 title claims abstract description 48
- 239000004814 polyurethane Substances 0.000 title claims abstract description 48
- 238000001514 detection method Methods 0.000 claims abstract description 58
- 230000004927 fusion Effects 0.000 claims abstract description 34
- 238000003384 imaging method Methods 0.000 claims abstract description 29
- 239000010410 layer Substances 0.000 claims description 67
- 238000012545 processing Methods 0.000 claims description 24
- 238000001914 filtration Methods 0.000 claims description 16
- 230000002950 deficient Effects 0.000 claims description 12
- 239000011241 protective layer Substances 0.000 claims description 11
- 238000009413 insulation Methods 0.000 claims description 10
- 238000004321 preservation Methods 0.000 claims description 10
- 102000003712 Complement factor B Human genes 0.000 claims description 8
- 108090000056 Complement factor B Proteins 0.000 claims description 8
- 238000005516 engineering process Methods 0.000 claims description 8
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- 238000007499 fusion processing Methods 0.000 claims description 7
- 230000003321 amplification Effects 0.000 claims description 5
- 238000003199 nucleic acid amplification method Methods 0.000 claims description 5
- 238000012360 testing method Methods 0.000 claims description 5
- 230000000694 effects Effects 0.000 claims description 4
- 238000004088 simulation Methods 0.000 claims description 4
- 238000009826 distribution Methods 0.000 abstract description 2
- 230000035945 sensitivity Effects 0.000 abstract description 2
- 238000012850 discrimination method Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 239000011810 insulating material Substances 0.000 description 2
- 238000005272 metallurgy Methods 0.000 description 2
- 239000003208 petroleum Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 229920005830 Polyurethane Foam Polymers 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 229920001903 high density polyethylene Polymers 0.000 description 1
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- 239000011496 polyurethane foam Substances 0.000 description 1
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Abstract
The invention discloses a method for judging defects of a medium layer of a polyurethane insulating pipe and application thereof. According to the capacitive imaging detection principle, each detection result value of the capacitive imaging detection signal is integrated by a three-dimensional effective detection area and corresponding detection sensitivity distribution numerical value, so that the identification information of the defects of three different medium layers is contained in the capacitive imaging detection signal, and the obvious demarcation phenomenon exists in the three medium layer defect fusion values through fusion of the detection signal intensity, the distortion rate, the gradient value, the compensation factor, the unit coefficient and the twice preset threshold value, thereby realizing the identification of the defects of the three medium layers of the polyurethane insulating pipe. The method provided by the invention can utilize a single capacitive sensor to judge three medium layer defects at one time, reduces the judging cost and improves the judging accuracy.
Description
Technical Field
The invention relates to the technical field of nondestructive detection signal processing, in particular to a method for judging dielectric layer defect of a polyurethane thermal insulation pipe and application thereof.
Background
The polyurethane heat-insulating pipe is a high-efficiency heat-insulating material and is widely applied to the fields of petroleum, chemical industry, metallurgy, electric power, heat supply and the like. In the fields of petroleum, chemical industry and metallurgy, the polyurethane heat-insulating pipe can keep the temperature of a conveying medium in a pipeline stable, improve the production efficiency and also can prevent the pipeline from icing, cracking and other problems in a low-temperature environment. In the electric power field, polyurethane insulating tube can reduce the energy loss of electric wire, improves conveying efficiency. In the heat supply field, polyurethane insulating tube can reduce heat energy loss, improves heating efficiency. Working pipe defects, insulation layer defects and protection layer defects in the polyurethane insulation pipe can lead to the reduction of the insulation performance of the pipeline and influence the service life of the pipeline. The defect of the three medium layers is judged, so that a reasonable maintenance scheme is facilitated, and the method has important significance in guaranteeing the safety of the application field of the polyurethane heat-insulating pipe and prolonging the service life of the polyurethane heat-insulating pipe.
The capacitive imaging detection technology is a novel nondestructive detection technology, and can effectively detect defects of insulating materials and defects of metal materials. At present, although three medium layer defects of the polyurethane heat-insulation pipe can be compared and distinguished by utilizing the interval effect or the lift-off effect of the capacitance imaging detection technology, the three medium layer defects can be effectively compared and distinguished only when the three medium layer defects exist by utilizing the method; and the polyurethane insulating pipe needs to be detected for many times, so that the detection cost and the detection time are increased. Therefore, for three medium layer defects such as a protective layer defect, a heat preservation layer defect and a working tube defect in a polyurethane heat preservation pipe, a method for accurately distinguishing a single medium layer defect, two medium layer defects and three medium layer defects at one time by utilizing a capacitance sensor is necessary.
Disclosure of Invention
In order to overcome the problems in the prior art, the invention provides a method for judging the dielectric layer defect of a polyurethane heat-insulating pipe and application thereof.
The technical scheme adopted for solving the technical problems is as follows: a method for judging the defect of a medium layer of a polyurethane heat-insulating pipe based on a lift-off effect comprises the following steps:
step 1, receiving input capacitance imaging detection signals under the same lifting height and working electrode spacing;
step 2, performing low-pass filtering processing on the capacitive imaging detection signal obtained in the step 1 to obtain a low-pass filtering processing signal A n And AS (application server) n ；
Step 3, processing the signal A by the low-pass filtering obtained in the step 2 n And AS (application server) n Distortion factor B n For A n Gradient value C n ＝grad(A n ) For the gradient value C n Solving the vertical height h between gradient peaks n And horizontal length l n The method comprises the steps of carrying out a first treatment on the surface of the Processing signal a by low-pass filtering n Find the peak value D at the center of the defect n ；
Step 4, regarding the vertical height h obtained in step 3 n And teratogenesis rate B n Division operation is carried out to obtain E n ＝h n /B n The method comprises the steps of carrying out a first treatment on the surface of the For the horizontal length l n And peak value D n Division operation is carried out to obtain F n ＝l n /D n ；
Step 5, introducing compensation factor a c For said E n And compensation factor a c Division operation is carried out to obtain G n ＝E n /a c The method comprises the steps of carrying out a first treatment on the surface of the For said F n And compensation factor a c Multiplication is carried out to obtain H n ＝F n ×a c ；
Step 6, introducing unit coefficient b c For the H n And unit coefficient b c Multiplication is carried out to obtain I n ＝H n ×b c ；
Step 7, for the G n And I n Fusion processing is carried out to obtain a fusion value J n ＝G n +I n ；
Step 8, judging the fusion value J n Whether or not it is less than or equal to a preset threshold value P n1 The method comprises the steps of carrying out a first treatment on the surface of the If yes, judging that the protective layer pipe is defective; if not, the next step of judgment is carried out;
step 9, judging the fusion value J n Whether or not it is less than or equal to a preset threshold value P n2 The method comprises the steps of carrying out a first treatment on the surface of the If yes, judging that the heat preservation layer is defective; if not, judging that the working tube is defective.
In the method for judging the dielectric layer defect of the polyurethane insulating pipe, the capacitance imaging detection signals under the same lifting height and working electrode spacing in the step 1 comprise lifting height H m And working electrode spacing D m Detection signal Y for detecting polyurethane heat-insulating pipe containing dielectric layer defect by lower capacitance sensor n Height of lift-off H m And working electrode spacing D m Detection signal YS of defect-free polyurethane heat preservation pipe detected by lower capacitance sensor n 。
The method for judging the defect of the medium layer of the polyurethane heat-insulating pipe comprises the step 3 of determining the distortion ratio BY n ＝(A n -AS n )/AS n 。
The method for judging the medium layer defect of the polyurethane heat-insulating pipe comprises the step 5 of compensating the factor a c Is the square of the charge amplification.
The method for judging the dielectric layer defect of the polyurethane heat-insulating pipe comprises the step of obtaining the unit coefficient b c Related to application scene of capacitive imaging detection technology, unit coefficient b in simulation application c 1pF, unit coefficient b in test application c Is 1mV.
The method for judging the medium layer defect of the polyurethane heat-insulating pipe comprises the step 8 of presetting a threshold value P n1 And a preset threshold P in step 9 n2 According to the lift-off height H m And working electrode spacing D m The lower capacitance sensor effectively detects the maximum bulk defect and the minimum bulk defect of different dielectric layers, and the preset threshold value P n1 Less than a preset threshold value P n2 。
The application of the method for judging the defect of the medium layer of the polyurethane heat-insulating pipe is applied to judging the defect of the polyurethane heat-insulating pipe containing the defect of the medium layer.
The method provided by the invention has the beneficial effects that three medium layer defects can be judged at one time by utilizing a single capacitance sensor, and the purposes of judging the three medium layer defects at one time, reducing the judging cost and improving the judging accuracy are achieved by combining the distortion rate, the gradient value, the compensation factor, the unit coefficient and the twice preset threshold judgment method.
Drawings
The invention will be further described with reference to the drawings and examples.
FIG. 1 is a flow chart of a defect discriminating method according to the present invention;
FIG. 2 is a flow chart of the preset threshold setting of the present invention;
FIG. 3 is a diagram showing the construction of a polyurethane insulating pipe tested piece in example 1 of the present invention;
FIG. 4 is a graph showing the fusion value of the capacitive sensor for detecting the test piece (having 10 different defect widths) according to embodiment 1 of the present invention;
FIG. 5 is a graph showing the fusion values of the capacitive sensor for detecting the test piece (having 10 different defect depths) according to embodiment 1 of the present invention;
fig. 6 is a graph showing the fusion value of the capacitive sensor according to embodiment 1 of the present invention to detect the test piece (having 9 different insulating layer thicknesses).
Detailed Description
The present invention will be described in detail below with reference to the drawings and detailed description to enable those skilled in the art to better understand the technical scheme of the present invention.
As shown in FIG. 1, the invention discloses a method for judging the defects of a medium layer of a polyurethane insulating pipe, which can be applied to judging the defects of the polyurethane insulating pipe containing the defects of the medium layer under a plurality of lifting heights, and according to a capacitance imaging detection principle, each detection result value of a capacitance imaging detection signal is integrated by a three-dimensional effective detection area and corresponding detection sensitivity distribution numerical value, so that judging information of the defects of three different medium layers is contained in the capacitance imaging detection signal, and obvious demarcation phenomenon exists in the three medium layer defect fusion values of the polyurethane insulating pipe through fusion of the detection signal intensity, the distortion rate, the gradient value, the compensation factor, the unit coefficient and the twice preset threshold value, thereby realizing the judgment of the defects of the three medium layers of the polyurethane insulating pipe. The method specifically comprises the following steps:
s101, receiving input capacitance imaging detection signals under the same lifting height and working electrode spacing, wherein the capacitance imaging detection signals under the same lifting height and working electrode spacing comprise lifting height H m And working electrode spacing D m The lower capacitance sensor detects the detection signal (Y 1 、Y 2 、……、Y n-1 、Y n ) Height of lift-off H m And working electrode spacing D m The lower capacitance sensor detects the detection signal (YS) of the defect-free polyurethane insulating pipe 1 、YS 2 、……、YS n-1 、YS n )。
Specifically, the signal and mathematical processing software receives the input capacitance imaging detection signal under the same lift-off height and working electrode spacing, wherein the capacitance imaging detection signal under the same lift-off height and working electrode spacing comprises a lift-off height H m And working electrode spacing D m The lower capacitance sensor detects the detection signal (Y 1 、Y 2 、……、Y n-1 、Y n ) Height of lift-off H m And working electrode spacing D m The lower capacitance sensor detects the detection signal (YS) of the defect-free polyurethane insulating pipe 1 、YS 2 、……、YS n-1 、YS n )。
S102, obtaining a low-pass filter processing signal A after the low-pass filter processing of the capacitive imaging detection signal n And AS (application server) n 。
Specifically, after the signal or mathematical processing software receives the detection signal, the detection signal is processed by using a low-pass filtering function in the software to obtain a filtering processing signal A n And AS (application server) n And filtering out the noise signals doped in the detection signals.
S103, processing the signal A by the low-pass filter n And AS (application server) n Distortion factor B n ＝(A n -AS n )/AS n ；
S104, processing the signal A by the low-pass filter n Gradient value C n ＝grad(A n )；
S105, for the gradient value C n Solving the vertical height h between gradient peaks n And horizontal length l n ；
S106, processing the signal A by the low-pass filter n Find the peak value D at the center of the defect n 。
Specifically, the low-pass filter processing signal A is processed by signal or mathematical processing software n And AS (application server) n Distortion factor B n ＝(A n -AS n )/AS n . Processing the signal A by signal or mathematical processing software n Gradient value C n ＝grad(A n ) And for the gradient value C n Solving the vertical height h between gradient peaks n And horizontal length l n . Processing the signal A by signal or mathematical processing software n Find the peak value D at the center of the defect n 。
Preferably, the low-pass filter is applied to the signal A n And AS (application server) n Distortion factor B n ＝(A n -AS n )/AS n For the low-pass filtered signal A n And AS (application server) n Distortion factor B n ＝(A n -AS n )/AS n Including the distortion rate B by means of excel software n Aberration rate B is calculated by labview software n Distortion factor B is calculated by mathtype software n Teratogenesis B is calculated by matlab software n And Python software to determine teratogenesis B n 。
PreferablyFor the low-pass filtered signal A n Gradient value C n ＝grad(A n ) Characterized in that the low-pass filter processing signal A n Gradient value C n ＝grad(A n ) Involving the determination of gradient values C by means of excel software n Gradient value C is calculated by labview software n Gradient value C is calculated by mathtype software n Gradient value C is calculated by matlab software n And Python software to find gradient value C n 。
S107, regarding the vertical height h n And teratogenesis rate B n Division operation is carried out to obtain E n ＝h n /B n ；
S108, regarding the horizontal length l n And peak value D n Division operation is carried out to obtain F n ＝l n /D n 。
Specifically, the vertical height h is calculated by signal or mathematical processing software n And teratogenesis rate B n Division operation is carried out to obtain E n ＝h n /B n The method comprises the steps of carrying out a first treatment on the surface of the For the horizontal length l by signal or mathematical processing software n And peak value D n Division operation is carried out to obtain F n ＝l n /D n 。
S109, introducing compensation factor a c ；
S110, for the E n And compensation factor a c Division operation is carried out to obtain G n ＝E n /a c ；
S111, for the F n And compensation factor a c Multiplication is carried out to obtain H n ＝F n ×a c 。
Specifically, the compensation factor a is introduced by signal or mathematical processing software c Wherein the compensation factor a c Is the square of the charge amplification. By signal or mathematical processing software, to said E n And compensation factor a c Division operation is carried out to obtain G n ＝E n /a c . By signal or mathematical processing software, to said F n And compensation factor a c Multiplication is carried out to obtain H n ＝F n ×a c 。
S112, introducing unit coefficient b c ；
S113, for the H n And unit coefficient b c Multiplication is carried out to obtain I n ＝H n ×b c 。
Specifically, the unit coefficients b are introduced by signal or mathematical processing software c Wherein the unit coefficient b c Related to application scene of capacitive imaging detection technology, unit coefficient b in simulation application c 1pF, coefficient of unity b in experimental application c Is 1mV. By signal or mathematical processing software, to the H n And unit coefficient b c Multiplication is carried out to obtain I n ＝H n ×b c 。
S114, for the G n And I n Fusion processing is carried out to obtain a fusion value J n ＝G n +I n 。
Specifically, the G is processed by signal or mathematical processing software n And I n Fusion processing is carried out to obtain a fusion value J n ＝G n +I n 。
Preferably, for said G n And I n Fusion processing is carried out to obtain a fusion value J n ＝G n +I n For the G n And I n Fusion processing is carried out to obtain a fusion value J n ＝G n +I n Involving the determination of the fusion value J by means of excel software n Fusion value J is calculated by labview software n Fusion value J is calculated by mathtype software n Fusion value J is calculated by matlab software n And Python software to calculate the fusion value J n 。
S115, judging the fusion value J n Whether or not it is less than or equal to a preset threshold value P n1 ；
S116, if yes, judging that the protective layer is defective; if not, the next judgment is carried out.
S117, judging the fusion value J n Whether or not it is less than or equal to a preset threshold value P n2 ；
S118, if yes, judging that the heat preservation layer is defective;
s119, if not, judging that the working tube is defective.
Specifically, the preset threshold value P n1 And a preset threshold value P n2 According to the lift-off height H m And working electrode spacing D m The lower capacitance sensor effectively detects the maximum bulk defect and the minimum bulk defect of different dielectric layers, and the preset threshold value P n1 Less than a preset threshold value P n2 For example, if the fusion values of the maximum defect of the protective layer, the maximum defect of the heat preservation layer and the maximum defect of the working tube detected by the capacitance sensor are 1, 3.3 and 5.2 respectively, and the fusion values of the minimum defect of the protective layer, the minimum defect of the heat preservation layer and the minimum defect of the working tube detected by the capacitance sensor are-3, 2.7 and 3.8 respectively, the threshold value P is preset n1 A value between 1 and 2.7 can be selected, a threshold value P is preset n2 Values between 3.3 and 3.8 may be selected, as shown in fig. 2, including: a01, obtaining detection results of the capacitive sensor for effectively detecting the maximum bulk defects and the minimum bulk defects of different dielectric layers; a02, setting a preset threshold P according to the fusion value of the detection result n1 And a preset threshold value P n2 And preset threshold value P n1 Less than a preset threshold value P n2 。
The invention provides a method for judging defects of three dielectric layers of a polyurethane insulating pipe based on a capacitance imaging detection technology, which comprises the steps of acquiring capacitance imaging detection signals under the same lifting height and working electrode spacing after receiving input capacitance imaging detection signals under the same lifting height and working electrode spacing, wherein the lifting height H is included in the capacitance imaging detection signals m And working electrode spacing D m The lower capacitance sensor detects the detection signal (Y 1 、Y 2 、……、Y n-1 、Y n ) Height of lift-off H m And working electrode spacing D m The lower capacitance sensor detects the detection signal (YS) of the defect-free polyurethane insulating pipe 1 、YS 2 、……、YS n-1 、YS n ) The method comprises the steps of carrying out a first treatment on the surface of the The capacitive imaging detection signal is subjected to low-pass filtering processing by using signal and mathematical processing software to obtain a low-pass filtering processing signal A n And AS (application server) n Filtering noise signals doped in the detection signals; the low pass filtering is performed by signal and mathematical processing softwareProcessing signal A n And AS (application server) n Distortion factor B n ＝(A n -AS n )/AS n The method comprises the steps of carrying out a first treatment on the surface of the Processing the signal A by signal and mathematical processing software n Gradient value C n ＝grad(A n ) For the gradient value C n Solving the vertical height h between gradient peaks n And horizontal length l n The method comprises the steps of carrying out a first treatment on the surface of the Processing signal a by low-pass filtering n Find the peak value D at the center of the defect n The method comprises the steps of carrying out a first treatment on the surface of the For the vertical height h by signal and mathematical processing software n And teratogenesis rate B n Division operation is carried out to obtain E n ＝h n /B n The method comprises the steps of carrying out a first treatment on the surface of the For the horizontal length l by signal and mathematical processing software n And peak value D n Division operation is carried out to obtain F n ＝l n /D n The method comprises the steps of carrying out a first treatment on the surface of the In order to avoid the influence of different charge amplification factors of different capacitance imaging detection systems on a discrimination method, a compensation factor a is introduced c Wherein the compensation factor a c Is the square of the charge amplification; by signal and mathematical processing software, to said E n And compensation factor a c Division operation is carried out to obtain G n ＝E n /a c The method comprises the steps of carrying out a first treatment on the surface of the By signal and mathematical processing software, to said F n And compensation factor a c Multiplication is carried out to obtain H n ＝F n ×a c The method comprises the steps of carrying out a first treatment on the surface of the In order to adapt the discrimination method to different application scenes, a unit coefficient b is introduced c Wherein the unit coefficient b c Related to application scene of capacitive imaging detection technology, unit coefficient b in simulation application c 1pF, coefficient of unity b in experimental application c 1mV; by signal and mathematical processing software, to the H n And unit coefficient b c Multiplication is carried out to obtain I n ＝H n ×b c The method comprises the steps of carrying out a first treatment on the surface of the By signal and mathematical processing software, to the G n And I n Fusion processing is carried out to obtain a fusion value J n ＝G n +I n The obtained fusion value J n Information such as detection signal intensity, distortion rate, gradient value and the like is fused, so that discrimination information of defects of three medium layers is furthest mined; judging the fusion value J n Whether or not to be less than or equal toPreset threshold P n1 The method comprises the steps of carrying out a first treatment on the surface of the If yes, judging that the protective layer is defective; if not, the next step of judgment is carried out; judging the fusion value J n Whether or not it is less than or equal to a preset threshold value P n2 The method comprises the steps of carrying out a first treatment on the surface of the If yes, judging that the heat preservation layer is defective; if not, judging that the working tube is defective. The method provided by the invention can be used for judging three medium layer defects at one time by utilizing a single capacitance sensor, and the three medium layer defects are judged by combining the distortion rate, the gradient value, the compensation factor, the unit coefficient and the twice preset threshold value, so that the purposes of judging the three medium layer defects at one time, reducing the judging cost and improving the judging accuracy are achieved.
[ example 1 ]
Based on the above discrimination method, the present embodiment provides the lift-off height H m And working electrode spacing D m The experimental implementation method is a specific numerical value to verify the effectiveness of the method. A schematic diagram of a tested piece of the polyurethane heat-insulating pipe is shown in fig. 3, the polyurethane heat-insulating pipe consists of a protective layer, a heat-insulating layer and a working pipe, the three medium layers are respectively formed by three different materials of high-density polyethylene, rigid polyurethane foam plastic and steel, and a defect exists in each medium layer. By means of working-electrode spacing D m A capacitance sensor of 4mm at a lift-off height H m And detecting defects of three medium layers of the polyurethane heat-insulation pipe under the experimental condition of 3 mm. In addition, in order to avoid the influence of the defect width, depth and thickness of the dielectric layer on the invention, 10 different defect widths, 10 different defect depths and 9 different thicknesses of the dielectric layer are detected in the experimental process, and the fusion value graphs obtained by using the invention are respectively shown in fig. 4-6. In FIG. 4, 10 different defect widths are combined to a preset threshold value P n1 =2.5 and preset threshold P n2 The determination is carried out by the method of=3.5, the number I is determined to be a protective layer defect, the number II is determined to be an insulating layer defect, the number III is determined to be a working tube defect, and the three medium layer defect determination results are completely matched with the icon. In FIG. 5, the fusion value of 10 different defect depths is also set to a preset threshold value P n1 =2.5 and preset threshold P n2 Determination is made by =3.5, determination number according to the present inventionI is a protective layer defect, number II is an insulating layer defect, number III is a working tube defect, and three medium layer defect judging results are completely matched with the icon. In FIG. 6, the fusion value of 9 different dielectric thicknesses is also set to a predetermined threshold value P n1 =2.5 and preset threshold P n2 The determination is carried out by the method of=3.5, the number I is determined to be a protective layer defect, the number II is determined to be an insulating layer defect, the number III is determined to be a working tube defect, and the three medium layer defect determination results are completely matched with the icon.
The above embodiments are only exemplary embodiments of the present invention and are not intended to limit the present invention, the scope of which is defined by the claims. Various modifications and equivalent arrangements of this invention will occur to those skilled in the art, and are intended to be within the spirit and scope of the invention.
Claims (7)
1. A method for judging the defect of a medium layer of a polyurethane heat-insulating pipe based on a lift-off effect is characterized by comprising the following steps:
step 1, receiving input capacitance imaging detection signals under the same lifting height and working electrode spacing;
step 2, performing low-pass filtering processing on the capacitive imaging detection signal obtained in the step 1 to obtain a low-pass filtering processing signal A n And AS (application server) n ；
Step 3, processing the signal A by the low-pass filtering obtained in the step 2 n And AS (application server) n Distortion factor B n For A n Gradient value C n ＝grad(A n ) For the gradient value C n Solving the vertical height h between gradient peaks n And horizontal length l n The method comprises the steps of carrying out a first treatment on the surface of the Processing signal a by low-pass filtering n Find the peak value D at the center of the defect n ；
Step 4, regarding the vertical height h obtained in step 3 n And teratogenesis rate B n Division operation is carried out to obtain E n ＝h n /B n The method comprises the steps of carrying out a first treatment on the surface of the For the horizontal length l n And peak value D n Division operation is carried out to obtain F n ＝l n /D n ；
Step 5, introducing compensation factor a c For said E n And compensation factor a c Division operation is carried out to obtain G n ＝E n /a c The method comprises the steps of carrying out a first treatment on the surface of the For said F n And compensation factor a c Multiplication is carried out to obtain H n ＝F n ×a c ；
Step 6, introducing unit coefficient b c For the H n And unit coefficient b c Multiplication is carried out to obtain I n ＝H n ×b c ；
Step 7, for the G n And I n Fusion processing is carried out to obtain a fusion value J n ＝G n +I n ；
Step 8, judging the fusion value J n Whether or not it is less than or equal to a preset threshold value P n1 The method comprises the steps of carrying out a first treatment on the surface of the If yes, judging that the protective layer pipe is defective; if not, the next step of judgment is carried out;
step 9, judging the fusion value J n Whether or not it is less than or equal to a preset threshold value P n2 The method comprises the steps of carrying out a first treatment on the surface of the If yes, judging that the heat preservation layer is defective; if not, judging that the working tube is defective.
2. The method for judging the dielectric layer defect of the polyurethane insulating tube according to claim 1, wherein the capacitive imaging detection signals under the same lifting height and working electrode spacing in the step 1 comprise lifting height H m And working electrode spacing D m Detection signal Y for detecting polyurethane heat-insulating pipe containing dielectric layer defect by lower capacitance sensor n Height of lift-off H m And working electrode spacing D m Detection signal YS of defect-free polyurethane heat preservation pipe detected by lower capacitance sensor n 。
3. The method for determining the defect of the medium layer of the polyurethane insulation pipe according to claim 1, wherein the distortion ratio BY in the step 3 is as follows n ＝(A n -AS n )/AS n 。
4. A polyurethane according to claim 1The method for judging the dielectric layer defect of the thermal insulation pipe is characterized in that the compensation factor a in the step 5 c Is the square of the charge amplification.
5. The method for judging the dielectric layer defect of the polyurethane thermal insulation pipe according to claim 1, wherein the unit coefficient b is as follows c Related to application scene of capacitive imaging detection technology, unit coefficient b in simulation application c 1pF, unit coefficient b in test application c Is 1mV.
6. The method for judging the medium layer defect of the polyurethane insulation pipe according to claim 1, wherein the preset threshold value P in the step 8 is n1 And a preset threshold P in step 9 n2 According to the lift-off height H m And working electrode spacing D m The lower capacitance sensor effectively detects the maximum bulk defect and the minimum bulk defect of different dielectric layers, and the preset threshold value P n1 Less than a preset threshold value P n2 。
7. The application of the method for judging the defect of the medium layer of the polyurethane heat-insulating pipe based on any one of claims 1-6 is characterized in that the method is applied to the defect judgment of the polyurethane heat-insulating pipe containing the defect of the medium layer.
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