RU2431139C1 - Method of acoustic-emission control of pressurised vessels and device to this effect - Google Patents

Abstract

FIELD: physics. ^ SUBSTANCE: object acoustic properties are pre-examined and primary transducers are installed. Acoustic-emission hardware serviceability is checked to calibrate channels. Controlled object is loaded to test pressure to register acoustic emission signals exceeding preset thresholds to determine signal parameters to allow determining coordinates of developing defects therefrom and deciding on their danger. Note here that in loading reservoir additionally measured is mean square signal amplitude in equal time intervals for all primary transducers for which thresholds are set for every next time interval and through defects are defined. ^ EFFECT: higher accuracy and validity of through defect detection. ^ 2 cl, 1 dwg

Description

The invention relates to non-destructive testing and can be used for the diagnosis of vessels operating under pressure by acoustic emission.

A known method for diagnosing vessels operating under pressure, which is that they preliminarily study the acoustic properties of the reservoir, determine the propagation speed of the stress waves, the degree of attenuation, the type of oscillations, place the primary transducers on the test object using the data obtained, load the test object, registering signals acoustic emission until the first false pulse of acoustic emission arrives at the primary transducer, acoustic signals are processed missions, at the same time, during processing the equipment that records acoustic emission signals is blocked, and registration is resumed after the oscillations caused by acoustic emission pulses are completely damped, the technical condition of the test object is judged by acoustic emission signals (Patent for the invention RU 2226272 C2, 08.08.1999, taken as analog).

The disadvantage of this method is the lack of accuracy and reliability of defect detection when monitoring the technical condition of pressure tanks, due to the inability to detect and evaluate the parameters of through defects emitting continuous noise, since after the first acoustic emission signal is received, the equipment is blocked until the oscillations are completely damped.

A multi-channel acoustic emission device for controlling products is known, which contains identical channels for receiving and processing acoustic emission signals, each of which consists of a piezoelectric acoustic transducer, preamplifier, filter, main amplifier, connected in series to the output of which a peak detector and strobe driver are connected, as well as digital-to-analog converter and recorder. In addition, in each channel, the device contains a comparator, a memory element, as well as a generator, a counter, a memory unit connected in series, and in each channel the output of the peak detector is connected to the inverting input of the comparator, the output of the gate driver is connected to the gate gate of the comparator, the output of which is connected to the peak detector reset input and the memory element input of each channel. The output of the memory element of each channel is connected to the corresponding input of the switch. The memory block has an input that sets the mode, and its second input is connected to the counter output and the second inputs of the gate former of the memory element of each channel. The output of the memory block is connected to the input of the digital-to-analog converter, the output of which is connected to the non-inverting inputs of the comparators of each channel. The output of the switch is connected to the input of the recorder. The output of the “OR-NOT” element of the gate driver is connected to the first input of the “AND” element and the first input of the second AND element, the second input of the first AND element is connected to the output of the third AND element, and the output of the first AND element is with the input of the first trigger, the non-inverting output of which is connected to the second input of the second element "And" and the output of the shaper, and the inverting output is connected to the second input of the third element "And". The output of the amplifier is connected to the input of the comparator, the input of which is connected to the input of the delay element. The output of the latter is connected to the S-input of the second trigger, the output of which is connected to the first input of the third element "AND". The reset inputs of the first and second triggers are combined and connected to the output of the second AND element. (A.S. 1589204, M. cl. ⁴ G01N 29/04, priority from 4.10.88, adopted as an analogue).

The disadvantage of this device is that it does not allow to determine the arrival times of acoustic emission signals exceeding the set threshold to the measuring channels, and therefore cannot determine the coordinates of the sources of acoustic emission with high accuracy.

Closest to the proposed technical solution is a method of acoustic emission monitoring of vessels, which consists in the fact that they conduct a preliminary study of the control object, including a study of the acoustic properties of the control object, then install primary transducers, check the operability of the acoustic emission equipment and carry out channel calibration, conduct preliminary tests during which the noise level at which the threshold is set is determined. Next, the control object is loaded to the test pressure and at the same time the acoustic emission signals are recorded that exceed the set threshold by which the coordinates of the sources are determined. The parameters of the registered acoustic emission signals judge the degree of danger of the defect (Rules for the organization and conduct of acoustic emission monitoring of vessels, apparatuses, boilers and process pipelines. (ПБ 03-593-03). Series 03. Issue 38 / Coll. Ed. - M .: State Unitary Enterprise "Scientific and Technical Center for Safety and Industry of Gosgortekhnadzor of Russia", 2003. - 56 p., Adopted as a prototype).

The disadvantages of this method is the inability to detect and evaluate the parameters of through defects associated with the fact that only discrete acoustic emission signals are recorded and evaluated. Another disadvantage is the low reliability and accuracy of defect detection, due to the fact that the method does not take into account changes in noise levels when loaded to test loads.

The closest in technical essence is a multi-channel acoustic emission device for product monitoring, consisting of 1 ... n blocks, each of which contains four measuring channels, consisting of a series-connected acoustic transducer, pre-amplifier, filter, peak detector, the output of which is connected to an inverting the input of the comparator, and also contains a digital-to-analog converter, the output of which is connected to the non-inverting input of the comparator, as well as a channel switch, the main amplifier, analog-to-digital converter, random access memory and timer, characterized in that the device is connected in series with a channel switch, the main amplifier, analog-to-digital converter, random access memory, the output of which is connected to the first input of the interface device, with four inputs of the switch channels are connected to the outputs of the channel filters and the inputs of the peak detectors of the corresponding channels, and the inputs of the digital-to-analog converters of the four channels of the unit are combined s and connected to the first output of the interface device, the outputs of the comparators of each channel are connected to the inputs of the timer, the output of which is connected to the second input of random access memory, the second output of the interface device is connected to the third input of the timer, and the third output of the interface device is connected to the computer bus (patent for invention RU 2150698 C1, 10.06.2000, adopted as a prototype).

The disadvantages of this device are the high probability of missing defects and sensitivity to noise, since there is no way to adjust the threshold during monitoring without stopping the registration of signals. In addition, the disadvantage of this device is the inability to detect and determine the area of through defects, due to the impossibility of recording parameters of continuous acoustic emission signals.

The technical task is to increase the reliability and accuracy of the detection and evaluation of developing non-through defects, as well as the detection and evaluation of through defects.

The problem is solved due to the fact that pre-determine the acoustic properties of the material of the control object. Then the primary converters are installed, the operability of the acoustic emission equipment is checked, and the channels are calibrated. Next, the control object is loaded to the test load and at the same time the root-mean-square value of the amplitude of the acoustic emission signals is measured and recorded at equal time intervals, the duration of which is determined by the rate of change of load from minimum to maximum value:

Δt = (0.001 ... 0.01) · T _naked ,

where T _nag - the duration of the load change from the minimum to the maximum value, s.

Based on the results of the measured values of the standard deviation of the signal amplitude, a threshold is set for each channel subsequent to the measurement for each channel, equal to:

P _i = 3 · σ _i ,

where σ _i is the standard deviation of the amplitude of the signal from the i-th channel; i is the channel number from 0 to n.

At the same time, acoustic emission signals from the i-th channel are recorded that exceed the set threshold P _i , and the parameters of these signals are determined by which the coordinates of developing defects are determined and their degree of danger is judged.

Using the registered values of the standard deviation of the amplitude of the acoustic emission signals, the area of the through defects of the experimentally established dependence is determined:

- среднее значение по всем n каналам среднеквадратического отклонения, мВ; Р - текущее значение давления в сосуде, МПа;

.Where

- the average value for all n channels of the standard deviation, mV; P is the current value of the pressure in the vessel, MPa;

.

The problem is also solved due to the fact that a multichannel acoustic emission device for monitoring vessels operating under pressure is used, consisting of n measuring channels, each of which consists of a series-connected acoustic transducer, pre-amplifier, filter, main amplifier, peak detector, the output of the peak detector is connected to the inverting input of the comparator, comparator, timer, interface device, computer bus, the device also contains the analog-to-digital converter, the input of which is connected to the output of the main amplifier, RAM, the output of which is connected to the first input of the interface device and the second input to the first output of the timer, the device also contains a digital-to-analog converter connected to the fourth output of the interface device. The device also has a series-connected detector of the rms value of the signal, the input of which is connected to the output of the main amplifier, a sampling and storage device, the output of the detector of the rms value of the signal connected to the analog input of the sampling and storage device, an analog multiplier, and the first input of the analog multiplier is connected to the output sampling and storage devices and a second input with an output of a digital-to-analog converter, and the output of an analog multiplier is connected to a non- with the comparator’s input, the device also comprises a continuous acoustic emission recording unit, consisting of a series-connected analog-to-digital converter, random access memory, the input of the analog-to-digital converter connected to the output of the sampling and storage device, and the output of the random access memory connected to the fifth input interface devices, a device for recording continuous acoustic emission signals includes a timer, the input of which is connected to by interfacing, the first output is connected to a control input of a sampling and storage device, and the second output is connected to random access memory.

The drawing shows a functional diagram of a device that implements the method of acoustic emission monitoring of vessels operating under pressure.

A device that implements the method of acoustic emission monitoring of vessels operating under pressure, contains (see drawing):

1 - primary (acoustic) transducer;

2 - pre-amplifier;

3 - filter;

4 - main amplifier;

5 - peak detector;

6 - comparator;

7 - timer;

8 - interface device;

9 - computer bus;

10 - analog-to-digital Converter;

11 - random access memory;

12 - digital-to-analog converter;

13 - detector rms value of the signal;

14 - device sampling and storage;

15 - analog multiplier;

16 - block recording continuous signals of acoustic emission;

17 - analog-to-digital Converter block recording continuous signals of acoustic emission;

18 is a random access memory of a unit for recording continuous acoustic emission signals;

19 is a timer unit for recording continuous signals of acoustic emission.

The practical implementation of the proposed device is performed according to well-known schemes using domestic and foreign microcircuits, the main characteristics of which are described in the following sources:

1. www.ni.com;

2. www.analog.com;

3. Horowitz P., Hill W. The art of circuitry: Per. from English - M .: Mir, 2003 .-- 704 p.

4. Shilo V.L. Popular digital circuits. - M .: Radio and communications, 1987, p. 19.

A multi-channel acoustic emission device for monitoring vessels operating under pressure consists of n measuring channels, each of which consists of a series-connected acoustic transducer 1, pre-amplifier 2, filter 3, main amplifier 4, peak detector 5, while the output of the peak detector 5 is connected to the inverting input of the comparator 6, timer 7, interface device 8, computer bus 9, the device also contains a series-connected analog-to-digital converter 10, the input of which the second is connected to the output of the main amplifier 4, random access memory 11, the output of which is connected to the first input of the interface device 8, and the second input to the first output of the timer 7, the device also contains a digital-to-analog converter 12 connected to the fourth output of the interface device 8. The device also a series 13 rms detector of signal 13 is installed, the input of which is connected to the output of the main amplifier 4, and the output is connected to the analog input of the sampling and storage device 14, an analog multiplier 15, the first input of which is connected to the output of the sampling and storage device 14 and the second input with the output of a digital-to-analog converter 12, and the output is connected to the non-inverting input of the comparator 6, the device also contains a unit for recording continuous acoustic emission signals 16, consisting of in series connected analog-to-digital Converter 17, random access memory 18, and the input of the analog-to-digital Converter 17 is connected to the output by the sampling and storage device 14, and the output about the iterative memory device 18 is connected to the fifth input of the interface device 8, and the acoustic emission continuous signal recording unit 16 includes a timer 19, the input of which is connected to the interface device 8, the first output is connected to the control input of the fetch and store device 14, and the second output is connected to random access memory 18.

The proposed device and method work as follows. The acoustic properties are preliminarily determined: the speed of ultrasonic waves and the attenuation coefficient, then the primary transducers are installed, the operability of the acoustic emission equipment is checked, and the channels are calibrated. After that, in the multi-channel device, the computer through the bus 9 and the interface device 8 transmits to the timer 7 the time interval for recording the discrete acoustic emission signal of the recorded window and simultaneously to the timer 19 the measurement interval Δt of the rms amplitude of the noise signals, determined by the ratio:

Δt = (0,001 ... 0,01) · T _naked;

where T _nag - the length of time the load changes from minimum to maximum values, which are selected based on the data of preliminary measurements and calibration.

They begin to load the vessel with a test load. The timer 7, on command from the comparator 6, counts the set time interval and instructs to stop the registration of discrete acoustic emission signals in the random access memory 11 and in the interface device 8. The timer 19 sends time, at time intervals Δt, to the digital input of sampling and storage 14 and to the random access memory device 18. The computer through the bus 9 instructs the interface device 8 to start measuring acoustic emission signals, the interface device 8 sends a command to the digital-to-analogue conversion spruce 12, which supplies a voltage of 3 V to the first input of the analog multiplier 15. The converter converts the acoustic signal of acoustic emission into an electrical signal and passes it through a pre-amplifier 2 and a filter 3 to the main amplifier 4. A rms detector 13 measures the rms value of the signal and feeds it to the analog input of the sampling and storage device 14, which, upon a command from the timer 19, transfers it to the second input of the analog multiplier 15 and the input of the analog-to-digital converter 17. Anal The digital-to-digital converter 17 converts the value of the rms value of the signal into a digital code and transfers it to the random access memory 18, which, by the command of the timer 19, stores the digital code. The digital code of the rms value of the signal from the random access memory 18 is transmitted to the computer through the interface device 8 and the bus 9. The analog multiplier 15 transmits to the second input of the comparator 6 a signal equal to the channel threshold:

P _i = 3 · σ _i ,

where σ _i is the standard deviation of the amplitude of the signal from the i-th channel, measured by the detector of the mean square value of the signal 13; i is the channel number from 0 to n.

The signal from the main amplifier 4 is fed to a peak detector 5, which determines the maximum amplitude and transfers it to the first input of the comparator 6. At the same time, the signals are converted into a digital code on the analog-to-digital converter 10 and recorded in the random access memory 11. The comparator 6 determines the time exceeding the signal at the first input of the threshold set at the second input and sends a signal to the timer 7, which determines the time of arrival of the signal and writes it to the random access memory 11, and it is transmitted to the computer through the interface device 8 and bus 9. After loading the vessel operating under pressure up to the test load and its endurance, the computer through the bus 8 instructs the interface device 8 to stop the registration of acoustic emission signals. The registered discrete signals of acoustic emission from n channels exceeding the set thresholds P _i determine the parameters of these signals, which determine the coordinates of developing defects and judge their degree of danger. Using the registered values of the standard deviation of the amplitude of the acoustic emission signals, the area of the through defects of the experimentally established dependence is determined:

- среднее значение по всем n каналам среднеквадратического отклонения, мВ; Р - текущее значение давления в сосуде, МПа;

.Where

- the average value for all n channels of the standard deviation, mV; P is the current value of the pressure in the vessel, MPa;

.

The proposed technical solution, compared with existing ones, allows controlling thresholds in the control process without stopping the registration of signals and, therefore, reduces the probability of missing defects and reduces sensitivity to noise. In addition, the proposed system registers the parameters of continuous acoustic emission signals, which determine the area of through defects.

Claims (2)

1. The method of acoustic emission monitoring of vessels operating under pressure, which consists in conducting a preliminary study of the acoustic properties of the test object, then installing the primary transducers, checking the operability of the acoustic emission equipment and calibrating the channels, then the test object is loaded to the test pressure and at the same time, acoustic emission signals exceeding the established thresholds are recorded, the parameters of these signals are determined by which the coordination s developing defects and judged of their severity, characterized in that the process vessel further loading at regular time intervals measured RMS amplitudes of the signals from all the primary devices in which for each successive time interval set thresholds and define an area through defects. 2. A multi-channel acoustic emission device for monitoring vessels operating under pressure, consisting of n measuring channels, consisting of a series-connected acoustic transducer, pre-amplifier, filter, main amplifier, peak detector, the output of which is connected to the inverting input of the comparator, and also contains digital-to-analog converter, analog-to-digital converter, random access memory and timer, in the device an analog-to-digital pre-connected an educator, random access memory, the output of which is connected to the first input of the interface device, and the input of the digital-to-analog converter is connected to the fourth output of the interface device, the output of the comparator is connected to the timer input, the output of which is connected to the second input of the random access memory, the second output of the interface device is connected to the third timer input, and the third output of the interface device is connected to the computer bus, characterized in that in each measuring channel an additional input given are a rms detector of a signal, a sampling and storage device, an analog multiplier and a unit for recording continuous acoustic emission signals, consisting of a series-connected analog-to-digital converter, random access memory and a timer, the input of the rms detector of the signal being connected to the output of the main amplifier, and the output connected to the analog input of the sampling and storage device, the first input of the analog multiplier is connected to the output of the device ki and storage and the second input with the output of the digital-to-analog converter, and the output of the analog multiplier is connected to the non-inverting input of the comparator, the input of the analog-to-digital converter of the unit for recording continuous acoustic emission signals is connected to the output of the sampling and storage device, and the output of random access memory is connected to the fifth input of the device pairing, the timer input of the unit for recording continuous acoustic emission signals is connected to the pairing device, and the first output is connected to the control they input sample and hold, and a second output connected to a random access memory.