RU2239793C2 - Method of ultrasonic monitoring of interface between immiscible fluids in tanks - Google Patents

Abstract

FIELD: indicating or measuring liquid level.

SUBSTANCE: first acoustical transducer generates periodically ultrasonic wave into the wall of a tank. The ultrasonic pulses multiply reflected from the internal side of the wall are received, converted into the electrical signal, amplified, extracted by strobing, detected, and bounded from below.

EFFECT: enhanced reliability and accuracy of ultrasonic monitoring.

3 dwg

Description

The present invention relates to techniques for controlling the presence of liquid in technological tanks and pipelines of various industries and may find application in metallurgical, chemical, oil refining, water treatment and other industries.

A known method of ultrasonic control of the interface of immiscible media, which consists in the fact that using an acoustic transducer in the tank wall, an ultrasonic (ultrasonic) wave is excited, which is introduced along the normal to its surface, and is repeatedly reflected from the same acoustic transducer (AP) from internal surfaces of the tank wall oscillations, convert them into pulsed electrical signals, isolate the envelope of the pulsed signals, set two temporary locations of the trailing edge of the envelope at a fixed amplitude level less than the peak value of the amplitude of the envelope, form a reference pulse corresponding to the middle of the specified time locations, determine the sign of the time interval between the reference pulse and pulse generated at the moment of equal amplitude of the trailing edge of the electric pulse signal to a fixed amplitude level nu, and the interface between immiscible media is judged by the sign of this interval [1].

The disadvantage of this method is the low accuracy and reliability due to the blurring of the interface between two media due to the smooth decline of the trailing edge of the envelope of the reverberation pulses.

There is another way to control the parameters of the media, which consists in the fact that using an acoustic transducer in the wall of the tank excite ultrasound the wave, which is introduced along the normal to its surface, is received by the same AP pulses repeatedly reflected from the inner surfaces of the wall. oscillations, convert them into a pulsed electrical signal, isolate the envelope of the reflected pulse signals, cut off the envelope from below in proportion to its amplitude, form a pulse in magnitude proportional to this amplitude, and integrate this pulse in duration equal to the duration of the truncated envelope, compare the result with the reference value, corresponding to the regulated environment parameter, and the difference is used to judge the controlled parameter [2].

The disadvantage of this method is also low reliability and accuracy, due to the dependence of the amplitude of the reverberation pulses not only on the physicochemical state of the medium and, accordingly, its acoustic resistance to ultrasound, but also on the area of contact of the medium with the tank wall.

The objective of the present invention is to increase the reliability and accuracy of ultrasonic monitoring of the interface between two media with different acoustic impedances.

Closer (prototype) of the proposed method is the second.

The proposed method differs from the known method in that the longitudinal ultrasound the wave is introduced at an angle to the outer surface of the tank wall, is formed at the point of entry of the longitudinal ultrasound transverse ultrasonic waves the wave, which is directed along the wall, receive the transverse ultrasonic waves of the second AP, offset from the first AP vertically by a distance relative to the entry point equal to twice the projection of the path that has passed the transverse ultrasonic a wave from the reflection point to the receiving point, on the outer surface of the tank, and as the selected information signal, the first transverse ultrasonic signal reflected from the inner surface of the wall is received waves, measure its amplitude, form a reference signal, a constant value of which is chosen as the arithmetic mean value between the amplitudes of the signals of the transverse ultrasonic waves reflected from the wall interface with controlled media having different specific acoustic impedances compare the detected information signal with the reference one and judge the interface between immiscible media by the difference in values.

The technical result of this method is to increase the accuracy and reliability of obtaining information about the interface of immiscible media in the wall thickness range of process tanks and pipelines from 200 to 1 mm in steel.

Figure 1 presents a functional diagram of one of the implementation of the proposed method, and figure 2 is a potential pulse diagram explaining the operation of the device.

The device comprises: a first AP 1 with an inclined waveguide 2 mounted on the outer surface 3 of the tank 4, and a generator 5 connected in series to the second AP 9 with an inclined waveguide 13 mounted on the outer surface 3 of the tank 4, amplifier 16 (first input), limiter 21 , detector 22, comparator 24 (first input), indicator 28, driver of the strobe pulse 19, connected to the output of the generator with an output, and output to the second input of the amplifier, the reference voltage source 26, connected to the second input of the comparator 24 as an output.

The implementation of the method and the operation of the device is as follows.

AP 1 with an inclined waveguide 2 is installed on the outer surface 3 of the reservoir 4. The generator 5 generates a periodic sequence of pulses 6 (Fig.2), with which a longitudinal ultrasonic wave is excited in waveguide 2. wave 7 (figure 1). At entry point 8, a longitudinal ultrasound the wave is introduced into the wall at an angle β, which is selected depending on the wall thickness of the tank and the linear geometric dimensions of the AP.

At the interface, the waveguide 2 - wall 3 longitudinal ultrasound wave 7 is transformed into a transverse ultrasound wave 9. Transverse ultrasound repeatedly reflected from the inner surface of the wall wave 9 is directed along the wall to the receiving AP 10. The receiving AP 10 is placed at the exit point 11 of the first reflection 12 of the transverse ultrasonic waves 9 from the inner surface of the wall 13. Accepted oscillations of the first reflection of the transverse ultrasonic the waves are sent to the waveguide 14 of the receiving AP 10, in which they convert to an electrical information signal 15 (figure 2). From the output of the receiving AP 10, the signal 15 is transmitted to the input of the amplifier 16, in which amplification is carried out to the required amplitude. In the received signal 15, only its amplitude 17 is isolated, for which the amplifier 16 is gated by a pulse 18, which is generated in the shaper 19 of the strobe pulse (Fig. 1). Thus highlighted information signal 17 is limited from below to a zero level, leaving only its positive amplitude 20 (figure 2). The limitation is carried out in the limiter 21. The limited signal 20 is detected in the peak detector 22, converting it to a constant voltage 23, equivalent to the information signal 15. This voltage 23 is applied to the first input of the comparator 24. The amplitude of the information signal 20 carries information about the acoustic impedance of each controlled medium 1 or II, in contact with the inner surface of the wall of the tank or pipeline in the installation area of the emitting and receiving AP.

When in contact with the wall of the controlled environment with less acoustic impedance, the information signal 20 (Fig. 3) has a large amplitude, and vice versa. Therefore, to register the interface of immiscible media, a reference voltage (U _op ) 25 is formed, the level of which is the arithmetic average between the amplitudes of the received information signals reflected from the interface of the wall with controlled media having different specific acoustic impedances for transverse ultrasonic the waves. The reference voltage 25 is generated in the source of the reference voltage 26 and fed to the second input of the comparator 24. At the output of the comparator 24, the detected information signal 23 and the reference signal 25 are compared, and in the case of a positive difference, a positive voltage level 27 is generated at the output of the comparator, by which interface immiscible media. To indicate the interface, the output signal 27 of the comparator 24 is fed to the input of the indicator 28.

The proposed invention is new, because it is unknown from the prior art relating to the determination of the interface between immiscible media, and uses an unknown method, namely, that a longitudinal longitudinal waveguide is installed in the tank wall with an inclined waveguide mounted on the outer surface of the pipeline US a wave that is refracted at the input point is transformed into a transverse ultrasonic wave wave and propagates along the wall with multiple reflections from its inner surface, this wave is received by the second AP with an inclined waveguide, also installed on the outer surface of the tank and shifted vertically relative to the first AP equal to the doubled projection of the path that has passed transverse y. h. waves from the reflection point to the reception point, on the outer surface of the tank, isolate in the received signal by gating the first reflection of the transverse ultrasonic waves from the inner surface of the wall, limit the selected information signal from below, at zero level, detect the positive amplitude of the selected signal, form a reference signal, the constant value of which is chosen as the arithmetic mean value between the amplitudes of the transverse ultrasound waves reflected from the wall interface with controlled media having different specific acoustic impedances compare the detected information signal with the reference one and judge the interface between immiscible media by difference.

The proposed invention has an inventive step, because it uses an unknown method that increases the reliability and accuracy of the control of the interface of immiscible media in tanks and pipelines with wall thicknesses from 200 mm to 1 mm for steel.

The proposed invention is applicable in industry to control the interface of immiscible media located in separators, evaporators, pipelines and tanks at normal and overpressure in them.

LITERATURE

1. A.S. USSR No. 1348656, G 01 F 23/28, publ. 10/30/1987

2. A.S. USSR No. 892293, G 01 N 29/02, publ. 12/23/1981

Claims (1)

The method of ultrasonic (ultrasonic) control of the interface of immiscible media, which consists in the fact that using the first acoustic transducer (AP) in the tank wall periodically enter ultrasonic wave, take pulses repeatedly reflected from the inner surface of the wall waves, convert them into an electrical signal, amplify, isolate by gating, detect and limit from below, characterized in that the longitudinal ultrasound the wave is introduced at an angle to the outer surface of the tank wall, is formed at the point of entry of the longitudinal ultrasound transverse ultrasonic waves the wave, which is directed along the wall, receive the transverse ultrasonic waves of the second AP, displaced vertically relative to the first AP by a distance relative to the insertion point, equal to twice the projection of the path that has passed the transverse ultrasonic a wave from the reflection point to the reception point on the outer surface of the tank, and as the selected information signal take the first signal transverse from the inner surface of the wall waves, measure its amplitude, form a reference signal, a constant value of which is chosen as the arithmetic mean value between the amplitudes of the signals of the transverse ultrasonic waves reflected from the wall interface with controlled media having different specific acoustic impedances compare the informational, detected signal with the reference one and judge the interface between immiscible media by the difference in values.

Images