SU1536304A1 - Apparatus for acoustic-emissive diagnosis of pipe-lines - Google Patents

Abstract

The invention relates to non-destructive quality control of products by acoustic emission signals (AE) and can be used to monitor and diagnose gas and oil pipelines during their testing and operation. The aim of the invention is to improve the accuracy by determining the difference in arrival times of the harmonic components of the AE signals by measuring the signal at two levels of discrimination and measuring the energy parameters of the signal taking into account the attenuation of AE waves in the material of the product. The difference приход of the arrival times of the two harmonic components of the signal is determined in the device in accordance with the expression Τ = X ₄ + X ₁ - X ₂ , where X ₄ is the difference in arrival times measured at the second level of discrimination

X ₁ and X ₂ are the length of the leading edge of the harmonic components of the signal from its physical origin (first level of discrimination) to the second level of discrimination. 2 Il.

Description

The invention relates to the field of non-destructive quality control of products based on acoustic emission (AE) signals and can be used to monitor and diagnose gas and oil pipelines during their testing and operation.

The aim of the invention is to improve the accuracy by determining the difference in the arrival mode of the harmonic components of the signal A3 by measuring the signal at two discrimination levels and measuring the energy parameters of the signal taking into account the attenuation of AE waves in the material of the product.

Figure 1 shows the structural diagram of the device for acoustic-emission monitoring of pipelines; in fig. 2 shows timing diagrams of the A3 data, which show the operation of the device,

The device for acoustic emission diagnostics of pipelines contains an electro-acoustic transducer I connected in series and an amplifier 2 connected in series by a first filter 3, the input of which is connected to. the output of the amplifier 2, the first detector 4 and the first differentiation unit 5, connected in series the second filter 6, whose input is connected to the output of the amplifier 2 - the second detector 7 and the second differentiation unit 8, the first and

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about

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Agora sources 9, 10 of the reference voltage Genis, connected in series the first subtracting unit 11, the first pass of which is connected to the output of the transient source 9 of the reference voltage, and the second with the output of the second source 10 of the reference voltage, and block 12 dividing, the second the input of which is connected to the output of the first source of the reference voltage, the first

3 and second 14 voltage comparators, the first input of which is connected to the power supply of the first differentiation unit 5, the third and fourth comparator 15.16 voltage, the first input of which is connected to the output of the second differentiation roll 8, connected in series by the first converter 17 time voltage, the first input of which is connected to the output of the first voltage comparator 13, and the second input to the output of the second voltage comparator 14, the first multiplication unit 18, the second input of which is connected to the output of the division unit 12, the first peak detector 19 , The second subtracting tree 20, the summation unit 21, the second multiplication unit 22, the second peak detector 23 and the Information output block 24 connected in series to the second converter 25 are voltage-voltage, the first input of which is connected to the output of the third voltage generator 15, and the second - ct output of the fourth comparator 16 junction, the third multiplication unit 26 The second input of which is connected to the output of dividing unit 12, and the third peak detector 27, the output of which is connected to the second input of the second subtraction unit 20, third time-to-converter The first input is connected to the output of the second voltage comparator 14, the second to the fourth voltage comparator 16 and the output to the second summing input 21 connected in series to the fourth multiplication unit 29, the first input connected to the output of amplifier 2, and the second with the output of the third peak detector 23, the quad 30 and the integration block 31, the output of which is connected to the second input of the Information output block 24, the fourth peak detector 32, the first input of which is connected to the output of the fourth block 29 And an output to the third input

information output unit 24, control unit 33, the first output of which is connected to the second input of multiplication unit 22, and the second output to the second input of the first to the fourth 19, 23, 27, 32 peak detectors. The second input of the first and third comparator 13, 15 voltages is connected to the output of the first source 9 of the reference voltage. The second input of the second and fourth comparators 14,16 voltage is connected to the output of the second source 10 of the reference voltage.

The device for acoustic-emission diagnostics of pipelines works as follows.

The receiving electroacoustic transducer 1 is installed on the controlled pipeline (not shown). Due to the dispersion of sound in the pipeline, the time of propagation of the various harmonic components of the acoustic signal from the source to the AE receiver is unequal. Thus, by the difference in arrival time (Ј) of these harmonics, it is possible to judge the distance (l) of the source to

Customer Service: 1

  - VC-, where

L 4 - (j

C, GЈ - propagation speeds of various harmonic components of the acoustic signal

The AE pulses are controlled by the receiving transducer 1, amplified by the amplifier 2 and fed to filter blocks 3, 6, where harmonic components of different frequencies are extracted, after which these components go to their own detector (first and second detectors 4.7). Detectors 4.7 have a large time constant and provide an increase in the leading edge of the signal according to a law close to linear. The first and second blocks 5 and 3 of differentiation serve to provide a linear law of variation of the leading edge of the envelopes of the harmonic components of the acoustic signal. From the differentiation blocks 5.8, differentiated signals are fed to comparators of 13-16 voltages that form a time interval equal to the difference in arrival times of different harmonics of the acoustic signal to the receiving transducer 1 at level 51

not selected discrimination threshold. Comparators of 13-16 voltages also form a time interval equal to the duration of the signals at the outputs of differentiating blocks 5.8 between two levels of discrimination, established with the help of sources 9.10 of the reference voltage. When the signal (U, r) exceeds the established discrimination threshold (R), the leading edge of the signal (U) is formed, and the leading edge of the signal (Uut) is formed when the signal Uir exceeds the same

level of discrimination; II1G is the leading edge of the signal at the output of differentiation unit 5 (the harmonic component of the acoustic signal that comes first in time to the receiving transducer), and the same at the output of differentiation unit 8 (the harmonic component due to dispersion relative to the signal (Uir) The error in determining the delay time d1U will be determined by the expression bj U4 (l / Sft - 1 / S), where cr is the steepness of the leading edge of the signal. It is possible to eliminate this error when determining the duration Nala (X (, X) of the actual (physical) start to discrimination threshold level, in this case, the arrival time difference of the signals may be recorded (Figure 2):

Ј X4 +

X, - X,

To calculate the value (Ј), two levels of discrimination (U, and U4) are set for the signal and then we can write for the signal U, r and similarly for the signal Пгг:

where Xt, Hy is the duration of the leading edge of the signal from its physical onset to the discrimination level U2, & t, u.t is the duration of the signal from the discrimination level U to U2.

0

The measurement of f is made as follows. From the output of the first differentiation unit 5, the signal of the harmonic component of the acoustic signal, whose propagation velocity is higher, goes to the first input of the first and to the first input of the second comparators 13,14 voltages, and from the output of the second differentiation unit 8 to the first input of the third and to the first input the fourth comparators 15,16 voltage receives a signal from the second harmonic

5 component. The second inputs of the first and third compressors 13, 15 voltage with the help of the first source 9 of the reference voltage sets the threshold of discrimination (them)

0 and at the second input of the second and fourth voltage comparators 14, 16, a discrimination threshold (U4) is established by the second source 10 of the reference voltage, and

5 Ui t. U. These voltage levels are also fed to the inputs of the first subtraction unit 1, where they are subtracted and a constant voltage c is formed at the output of the first subtraction unit 11

0 amplitude A.U Ui - U, „

The first input of dividing unit 12 is the difference of the voltages UU U - U1 and the second voltage U g and its output is the constant voltage UUt);

At. when the signal from the output of the first block 5 differentiates the voltage level at the output of the first source 9 of the reference voltage, the first voltage comparator 13 is triggered. The pulse from its output includes the first time-to-voltage converter 17. When the signal from the output of the first unit 5 differentiates the voltage level equal to the voltage at the output of the second source 10 of the reference voltage, the second voltage comparator 14 is triggered, thereby stopping the operation of the first time-voltage converter 17, and thus A voltage is generated whose amplitude is proportional to the duration (frt,) of the leading edge of the signal at the output of the first differentiation unit 5 from the voltage level (R) to the voltage level (U4). This voltage is applied at first.

five

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five

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the input of the first multiplication unit 18, and its second input is supplied with a voltage (uUt) from the output of the healing unit 12, equal to UU, H4 / (U4 - 1). In the first multiplication unit 18, these voltages are multiplied and a voltage is formed at its output whose amplitude is proportional to the duration (xx) of the leading edge of the signal. This voltage is memorized by the first peak detector 19, in a similar way, using the third and fourth comparators 15.16 voltages, the second time-voltage converter 2.5, and the third multiplication unit 26 multiplying the voltage of the third peak detector 27, the amplitude which is proportional to the duration (X2) of the leading edge of the signal at the output of the second differentiation unit 8 from the voltage level (Uj) to the voltage level (U2), constant voltage levels from the outputs of the first and third peak detectors 19.27 m in the second subtracting unit 20, outputs a signal with an amplitude equal but different | variability of these voltages (X ,, - Xg). The second and fourth comparators 14,16 voltages also control the operation of the third converter 28, a voltage, the output voltage of which with amplitude, the proportional difference of the arrival time of two harmonics of the signal at the level of a higher discrimination threshold, is fed to the second input of block 21 summation, the input of which is connected you

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The time taken by the second peak detector 23.

The signal from the output of amplifier 2 is also fed to the first input of the fourth multiplication unit 29, and its second input receives a signal from the output of the second peak detector 23 ". Thus, the output of the fourth multiplication unit 29 produces an acoustic emission signal with an amplitude adjusted for the duration the path he traveled, i.e. taking into account the attenuation coefficient in the pipeline material. This signal is then fed to the fourth peak detector 32 and to the quadrant 30, where the value of the corrected signal amplitude is squared and fed to the integrator 31, which calculates the energy (E) of the acoustic emission signal according to expression

E, U (t) dt.

Ha the information output unit 24 receives information from the third peak detector 23 about the distance from the source to the acoustic emission signal receiver, from the fourth multiplication unit 29 about the amplitude of the acoustic emission pulses and from the integration unit 31 about the pulse energy

acoustic emission. one

After displaying information from the block

24, the information output by the control unit 33 sets the device to the initial state.

Thus, this device

45

the course of the second block 20 subtract. This allows you to improve the accuracy of diagnosis,

ticks due to the introduction of blocks that increase the accuracy of the space-time selection of AE signals and determine the energy of the AE, taking into account the attenuation of the will of the AE in the material.

Claims (1)

Invention Formula A device for acoustic emission diagnostics of pipelines, containing a series-connected electroacoustic transducer and amplifier, first and second filters whose inputs are connected to the amplifier output, a control unit, an information output unit, characterized in that it is fitted with connected successively by the first detector pattern, at the output of block 21, summing; 1and we get a voltage whose amplitude is proportional to the difference in the arrival time of two harmonics of the signal K, taking into account their physical Skogen arrival time to the receiving transducer 1, The voltage from the output of the summation unit 21 is applied to the first cycle of the second multiplication unit 22, and to its second input comes from the unit 33 packs. This is the voltage that is proportional to the velocity (V). Consequently, at the output of the second multiplication unit 22, a voltage is generated with an amplitude proportional to the distance from the source to the receiver of the acoustic emission signals. Zcho voltage is memorized at 50 55 9I rum and the first differentiation unit connected in series by the second detector and the second differentiation unit connected in series by the first subtraction unit and the division unit connected in series by the first time-voltage converter, the first smart unit, the first peak detector, the second subtraction unit, the summation unit, the second a multiplication unit and a second peak detector connected in series by a second time-voltage converter, a third multiplication unit and a third peak de By a vector connected in series by a fourth multiplication unit, a quad and an integration unit, the first second, third and fourth voltage comparators, the first and second sources of the reference voltage, the third time-voltage converter, the fourth peak detector, the input of the first detector is connected to the output the first filter, the input of the first differentiation unit is connected to the first input of the first and second voltage comparators, the input of the second detector is connected to the output of the second filter, the output of the second differential block phase converter is connected to the first input of the third and fourth voltage comparators, the first input of the first subtraction unit is connected to the output of the first voltage source, and the second to the output of the second voltage source, the second input of the division unit is connected to the output of the first voltage source, the first input of the first time-voltage converter is connected to the output of the first voltage comparator, and the second is connected to 3630410 the output of the second voltage comparator, the second input of the first multiplication unit is connected to the output of the division unit, the second input of the second multiplication unit is connected to the first output of the control unit, the output of the second peak detector is connected to the first input of the information output unit, the first The Q input of the second time converter is connected to the output of the third voltage comparator, and the second to the output of the fourth voltage comparator, the second input 15 of the third multiplier unit is connected to the output of the division unit, the output of the third peak detector is connected to the second input of the second subtraction unit, the first input of the third converter is a time-voltage converter connected to the output of the second voltage comparator, the second input is connected to the fourth voltage comparator, and the output is with the second input of the summation unit, the output of the integration unit is connected to the second input of the information output unit, the input of the fourth peak detector is connected to the output of the fourth multiplication unit, and output 30 with the third the output of the information output unit; the second output of the control unit is connected to the second input of the first, second, third and fourth peak detectors; the second input of the first and third voltage comparators is connected to the output of the first reference voltage source; the second input of the second and fourth voltage comparators is connected to way out The AQ of the second reference voltage source, the first input of the fourth multiplication unit is connected to the output of the amplifier, and the second input to the output of the second peak detector. ZHIHZH fЈ-X (/ tXi i Editor oh, arrogant Fiz.g Compiled by K.Hilkov Tehred L. Serdgokova Proofreader M. Sharoshi © -Kp t