RU2178150C1 - Device for ultrasonic test of level or presence of liquid in pipe-line - Google Patents

Abstract

FIELD: chemical, metallurgical, petroleum refining industries, water treatment. SUBSTANCE: invention is related to equipment for automatic test of level and presence of liquid in technological pipe-lines. Device includes two emitting and one receiving electroacoustic converters which are located on outer surface of wall of pipe-line. Second emitting converter is placed diametrically opposite to first emitting converter. First and second emitting converters are equidistant from receiving converter. Pulse generator is connected with output to emitting converters. Receiving converter, amplifier, first single-shot blocking oscillator, first adder, integrator, D C amplifier and second adder are connected in series. Input of second single-shot blocking oscillator is connected to output of pulse generator and its output is linked to input of first adder. Input of peak detector is connected to output of amplifier and its output is linked to first input of second adder. Pulse generator, third single-shot blocking oscillator, selector and amplifier are connected in series. Output of second adder is connected to first input of comparator and source of reference voltage is connected to second input of comparator. Output of comparator is connected to input of indicator. EFFECT: raised reliability and accuracy of test of level or presence of liquid in pipe-lines with various thicknesses of walls and various diameters. 2 dwg

Description

 The invention relates to techniques for controlling the level or presence of liquid in technological pipelines and tanks with a cylindrical or close to it shape and can find application in metallurgical, chemical, oil refining, water treatment and other industries.

 A device for controlling the level of liquid media by attenuation of ultrasonic waves propagating in the tank wall, containing a generator, acoustic emitter and receiver, amplifier and recorder, as well as a time-measuring unit connected to one of the inputs to the delay unit of the signal generator and the other input to the amplifier and the adder, the inputs of which are connected to the output of the amplifier and time-measuring unit, and the outputs to the registrar [1].

 The disadvantages of the known device are low reliability and low accuracy, due to the fact that when filling a reservoir or pipeline with liquid, particles of air dissolved in it can settle on the wall in the installation area of the acoustic emitter and receiver, distorting (decreasing) the damping effect of the liquid on the propagation of ultrasonic waves in controlled area.

 There is also known a device for ultrasonic level control of liquid media in closed tanks, containing emitting and receiving electro-acoustic transducers (EAP) of normal waves mounted vertically on the wall of the tank, a pulse generator, amplifier and indicator and which is equipped with a circuit consisting of a series of connected first waiting blocking a generator, a first adder, an integrator, a DC amplifier and a second adder, as well as a second waiting blocking generator and a peak detector, moreover the input of the first standby blocking generator and the input of the peak detector are connected to the output of the pulse generator, the output of the peak detector is connected to one of the inputs of the second adder, the output of the adder is connected to the indicator; the second waiting blocking generator, connected by an input to a pulse generator, and an output with one of the inputs of the first adder [2].

 A disadvantage of the known device is also low accuracy, due to the dependence of the damping properties of the liquid on the geometric dimensions of the tank, in particular the wall thickness, since normal waves are formed only in thin sheets, pipes and shells.

 Another disadvantage of the known device is its low reliability, due to the dependence of the amplitude of a normal ultrasonic wave carrying level information on other types of waves that are simultaneously excited in the wall of the tank or pipeline.

 The objectives of the present invention is to increase the reliability and accuracy of level control or the presence of liquid in industrial tanks and pipelines with different wall thicknesses and diameters.

 Closer (prototype) of the proposed device is the second [2]. The proposed device differs from the selected prototype in that it additionally contains a second emitting EAP connected to the output of the pulse generator and installed diametrically opposite the first emitting EAP in the plane of the horizontal horizontal section of the pipeline, and the first and second emitting EAP are equidistant from the receiving EAP; the third waiting blocking generator and the selector, the output of which is connected to the second input of the amplifier, and the input of the third waiting blocking generator to the output of the pulse generator, a comparator connected to the first input to the output of the second adder, a reference voltage source connected to its output to the second input a comparator, the output of which is connected to the indicator input.

 This allows you to increase the reliability and accuracy of level control or the presence of various liquid media in tanks and pipelines with different wall thicknesses and diameters.

 Functional diagram of the device and pulse potential diagrams explaining its operation are shown in FIG. 12.

 The device contains two identical emitting EAP 1, 2, which are installed on the outer surface of the pipeline or reservoir on diametrically opposite sides in the plane of the horizontal cross section, receiving EAP 3, which is installed at a fixed distance L from the emitting EAP and equidistant from them; pulse generator 4, the output is connected to the inputs of the radiating EAP 1, 2; in series connected receiving EAP 3, amplifier 5, peak detector 6, second adder 7, comparator 8, indicator 9; a selector 10, connected to the second input of the amplifier 5 by an output, the first adder 11, the integrator 12, the DC amplifier 13, the output of which is connected to the second input of the second adder 7, are connected in series; the first standby blocking generator 14 is connected by input to the output of amplifier 5, and by output, to the input of the first adder 11; the second standby blocking generator 15 is connected by the input to the output of the pulse generator 4, and by the output to the second input of the first adder 11; the third waiting blocking generator 16 is connected by the input to the pulse generator 4, and by the output to the input of the selector 10; a reference voltage source 17, the output of which is connected to the second input of the comparator 8, and the output is connected to the input of an indicator 9, signaling the level or presence of liquid in the pipeline.

 The operation of the device is as follows.

 Inclined emitting electroacoustic transducers (EAP) 1, 2 (Fig. 1) with cylindrical waveguides 18, 19, (Fig. 1) and piezoelectric transducers 20, 21 (Fig. 1) are installed on the outer surface of the wall 23 (Fig. 1) of the pipeline reservoir 24 on diametrically opposite sides in the plane of the horizontal cross section of the pipeline (opposite).

 In the waveguides 18, 19, longitudinal ultrasonic waves (USWs) are excited, which are directed into the pipeline wall at an angle α. Longitudinal ultrasonic excitation is carried out using a pulse generator 4 (Fig. 1), which generates a sequence of rectangular pulses 22 (Fig. 2) supplied to the piezoelectric transducers 20, 21.

 At the interface, the waveguides 18, 19, - the wall 23 of the pipeline 24 (Fig. 1), the longitudinal ultrasound is converted into normal or transverse ultrasound by selecting the input angle α. The angle α is selected, knowing the thickness of the wall 23 of the pipeline 24, the material of the waveguides 18, 19, and also sounding frequency. Excited in the wall 23 by two radiating EAP 1, 2, the ultrasound guides are directed to the receiving point 25 (Fig. 1), in which the receiving EAP 3 is located (Fig. 1), and the receiving point 25 is equidistant from the emitting EAP 1, 2.

The opening angle of the radiation pattern of the emitting EAP 1, 2 is selected so that the extreme ultrasonic rays A, B corresponding to the level 0.1 of the main lobe of the radiation pattern of each EAP 1, 2 fall into the receiving zone of the receiving EAP 3. Walking along the wall the path from the emitting EAA 1, 2 to the receiving point 25 and having experienced a change in the amplitude depending on the level of the controlled fluid or its presence on the inner surface 26 of the pipe 24, as well as changes in the amplitude and propagation velocity depending on the wall temperature, ultrasound with with amplitudes 27 and 28 (Fig. 2) from the first and second EAPs, respectively, are directed to the receiving point 25 to the input of the receiving EAP 3. The receiving EAP 3 is identical to the emitting EAP 1, 2. Since the reception point 25 is equidistant from the emitting EAP 1, 2 then the excited ultrasonic vibrations with amplitude values of 27 and 28 from the first and second EAP are added in phase and form at the output of the EAP 3 a total information signal with an amplitude of 29 (Fig. 2). The information signal 29 from the output of the receiving EAP 3 is directed to the input of the amplifier 5 (Fig. 1). In addition to the information signal 29, signals from other types of waves, also propagating in the wall with their amplitudes 30, 31, 32, 33 (Fig. 2) and velocities, are received from the output of the receiving EAP 3 to the input of amplifier 5. When liquid enters the inner surface of the pipeline 26 (Fig. 1), the amplitude of the total information signal 29 (Fig. 2) decreases sharply. A change in the total amplitude is a sign of the presence of fluid in the pipeline. To isolate the information signal 29 and suppress noise in the form of other types of waves with amplitudes 30, 31, 32, 33, a strobe pulse 34 is formed (Fig. 2) with a duration τ ₁ , which is directed to the second input of the amplifier 5. The formation of a strobe pulse 34 is carried out in the selector 10 on the trailing edge of the pulse 35 (Fig. 2) at the output of the third standby blocking generator 16. In turn, the third standby blocking generator 16 is started by pulse 22 at the output of the pulse generator 4.

The duration τ _{2 of the} pulse 35 of the third waiting blocking generator is chosen to be shorter by the time τ ₃ than the delay time τ of the information signal 29 relative to the leading edge of the pulse 22: τ ₃ = 2t, where t = 1 / f; t is the period of the fundamental frequency of the information signal.

Accordingly, the duration τ _{1 of the} strobe pulse 34 is set equal to 2τ ₃ and exceeds the range of previously measured temperature changes Δτ. To generate a signal about the liquid level, the gated signal 36 (Fig. 2) from the output of the amplifier 5 is fed to the input of the peak detector 6 (Fig. 1), which remember its amplitude value and convert to a constant voltage 37 (Fig. 2). From the output of the peak detector 6, a constant voltage 37 is applied to the input of the second summing device 7 (Fig. 1). At the same time, to correct the changes in the amplitude of the information signal 29 depending on the temperature of the pipeline wall, an impulse 40 (FIG. 2) is generated at the output of the first adder 11 (Fig. 1), the duration of which τ ₆ changes with wall temperature. To this end, the output signal of the amplifier 5 is fed to the input of the first standby blocking generator 14 (FIG. 1), which generates a pulse 38, normalized in amplitude, (FIG. 2) of constant duration τ ₄ . According to the pulse 22 of the pulse generator 4, a second waiting blocking generator 15 (Fig. 1) is launched, at the output of which a normalized pulse 39 (Fig. 2) of constant duration τ _{5 is formed} . From the outputs of the first 14 and second 15 waiting blocking generators, the normalized pulses τ ₄ and τ _{5 are} fed to the input of the adder 11. Since the pulse durations τ ₄ and τ _{5 are} constant, and the start time of the first waiting blocking generator 14 depends on the propagation velocity of the ultrasonic emitting EAP 1, 2, and the ultrasonic velocity, in turn, depends on the temperature of the pipeline wall, then at the output of the first adder 11, as a result of logical summation, a pulse 40 of variable duration τ ₆ will be generated. The pulse 40 is fed to the input of the integrator 12 (Fig. 1), in which it is converted into a DC voltage 41 (Fig. 2). The correction was carried out by applying a voltage 41 to the second input of the second adder 7 through a matching DC amplifier 13 (Fig. 1).

 The output of the second adder 7 generates an information signal 42 (Fig. 2), equal to the algebraic sum of the two voltages 37 and 41, which is sent to the first input of the comparator 8. The second input of the comparator receives a voltage 43 (Fig. 2) from the source of the reference voltage 17 ( Fig. 1), the level of which corresponds to a certain amount of liquid on the inner surface of the pipeline wall. When the signal 42 decreases while damping the wall 26 with the liquid below the level of the reference voltage 43 (Fig. 2), a signal 44 is generated at the output of the comparator 8 (Fig. 1), which is sent to the input of the indicator 9 (Fig. 1).

 The proposed invention is new, because it is unknown from the prior art relating to the determination of the level or presence of liquid in tanks and pipelines, and uses an unknown device that contains: two identical radiating EAP installed on the outer surface of the pipeline or tank on diametrically opposite sides in the plane of the transverse horizontal section, the receiving EAT installed at a fixed distance from the radiating EAT and equidistant from them; connected in series with a first radiating EAP, a pulse generator, a second blocking generator, a first adder, an integrator, a DC amplifier, a second adder, a comparator and an indicator; serially connected receiving EAP, amplifier, peak detector, the output of which is connected to the second input of the second adder; connected in series to a third standby blocking generator, a selector whose output is connected to the second input of the amplifier, and the input of a third standby blocking generator to the output of a pulse generator, a first standby blocking generator connected to the output of the amplifier, and the output to the second input of the first adder; a reference voltage source connected to the second input of the comparator, the second radiating EAP connected to the output of the pulse generator.

 The proposed invention has an inventive step, because it uses an unknown device that improves the reliability and accuracy of level control or the presence of liquid filling the tank or pipeline due to the expansion of the control zone and increase sensitivity as a result of in-phase addition of signals from radiating EAPs in the receiving area EAP, as well as the signal separation of the information signal from interference as a result of the strobing of the amplifier.

 The proposed invention is applicable in industry to control the level or “leakage” of liquid in gas-exhaust pipelines and tanks with liquid chlorine and ammonia, pressure vessels of hydraulic presses, in evaporators, receivers, etc.

 Literature.

 1. A. S. USSR 798492, part 2172770, BI 3, 1981, G 01 F 23/28.

 2. A. S. USSR 877342, part 2879411, BI 40, 1981, G 01 F 23/28.

Claims (1)

 A device for ultrasonic control of the level or presence of liquid in a pipeline, comprising emitting and receiving electro-acoustic transducers (EAP) of ultrasonic waves mounted vertically on the outer surface of the pipe or reservoir wall at a fixed distance from each other, a pulsed generator connected to the emitting EAP by the output, a chain of series-connected receiving EAA, an amplifier, a first standby blocking generator, a first adder, an integrator, a DC amplifier, the second adder, the second standby blocking generator, connected to the output of the pulse generator by the input, and the output to the input of the first adder, a peak detector connected to the output of the amplifier, and the output to the first input of the second adder, an indicator characterized in that it additionally contains a second emitting EAP, which is connected to the output of the pulse generator and installed diametrically opposite to the first emitting EAP in the plane of the horizontal cross section of the pipeline, and the first and second emitting EAP equidistant from the receiving EAP, the third waiting blocking generator and a selector are connected in series, the output of which is connected to the second input of the amplifier, and the input of the third waiting blocking generator to the output of the pulse generator, the comparator is connected to the first input to the output of the second adder, the reference voltage source is connected to the second input of the comparator, the output of which is connected to the input of an indicator signaling the level or presence of liquid in the pipeline.

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