RU2626744C1 - Intratubal ultrasonic flaw detector - Google Patents

Abstract

FIELD: measuring equipment.

SUBSTANCE: intratubal ultrasonic flaw detector is equipped with a device for measuring the sound speed in the pumped liquid V and the unit for automatically adjusting the time window duration ΔT during the monitoring by the formula: ΔT=ΔT°V°/V, where ΔT° is the window duration when monitoring in a liquid with a minimum sound velocity V°. The design of the carrier p of ultrasonic piezoelectric transducers provides the path length of the ultrasonic pulse, from the point of reflection from the inner pipe surface to the nearest carrier element, not less than ΔT°V°/2+ΔHp, where ΔHp is the maximum permissible wear of a runner of the carrier of ultrasonic piezoelectric transducers.

EFFECT: expanding the range of monitored thicknesses of the pipe wall towards the increase while pumping various liquids and simplifying the requirements for the design of a carrier of ultrasonic piezoelectric transducers.

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Description

The invention relates to the field of ultrasonic non-destructive testing and can be used for in-line inspection of pipelines.

Known ultrasonic flaw detector (Non-destructive testing: Reference: In 8 volumes / Under the general editorship of V.V. Klyuev. T. 3: I.N. Ermolov, Yu.V. Lange. Ultrasonic testing. - 2nd edition. , rev. - M.: Mashinostroenie, 2008-864 p.: ill.), equipped with contact oblique ultrasonic piezoelectric transducers, with the help of which they excite transverse wave pulses in the control object. The flaw detector includes an electronic unit for excitation of transducers and registration of echo signals, an analysis unit for echo signals registered in the zone of operation of a time window of a fixed duration, which begins at the moment the pulse enters the control object, and the window duration is equal to the time it takes for a single reflected beam to pass through the control object.

Such a time window duration makes it possible to register defects irrespective of their position in the pipe wall. With the contact method of introducing ultrasonic vibrations into the control object, the time of registration of the echo signal from the surface of the control object is invariable during the control. This allows you to accurately set the beginning of the time window after the echo from the surface.

A flaw detector with a contact method for introducing ultrasonic vibrations into a test object can be used for expert assessment when monitoring pipelines from the outside.

Known ultrasonic automatic installations for immersion control (through a liquid layer of large thickness), for example sheet metal [Methods of acoustic control of metals / N.P. Aleshin, V.E. White, A.Kh. Vopilkin et al .: Ed. N.P. Alyoshina. - M.: Mechanical Engineering, 1989. - 456 p.]. The units include a flaw detector, similar to that used in the contact control method, in which a time window of fixed duration is used. The installation includes a large number of ultrasonic transducers mounted on a carrier that provides the required orientation of the transducers relative to the surface of the control object.

Automatic installations allow you to control at high speed. However, when controlling large-sized products, for example, sheet metal with an uneven surface, it is difficult to maintain a constant distance between the transducers and the surface of the test object. Because of this, an echo signal from the surface of the product, which can be taken as an echo signal from a defect, can fall into the effective area of a time window of a fixed duration.

A flaw detector for an immersion automatic installation is known [copyright certificate No. 166160, 1964, BI No. 24], in which an echo signal from the surface of the product is recorded, and the action of the time window starts with a delay relative to this moment equal to the duration of the echo signal from the surface of the product. The duration of the time window is fixed, based on the results of calculating the transit time of the ultrasonic pulse to the most remote defect in the controlled product of a given thickness.

Automatic immersion plants use a fluid with a known sound velocity, such as water. Therefore, in the control process, the angle of entry of ultrasonic vibrations into the control object remains constant. In addition, the thickness of the test object is known in advance. This allows you to set the required time window duration without any problems.

With in-line flaw detection, control is performed when pumping dissimilar liquids with different sound speeds. Pipelines are made of pipes with different wall thicknesses, which can vary greatly even in one controlled area. This must be taken into account when setting the duration of the time window.

Known in-line flaw detector [Operation manual for the device Pipetronix UltraScan 28 '' / 32 '' company Pipetronix (Germany)], including many ultrasonic piezoelectric transducers oriented at a given angle to the surface of the pipe to excite the shear wave pipe material, the carrier of the transducers, consisting of devices for mounting transducers mounted on skids of a given height, an electronic unit for exciting transducers and registering echo signals, an echo signal analysis unit, registered GOVERNMENTAL in the zone of action of fixed duration of the time window which starts after registering the echo from the inner surface and has a duration of not less than the propagation time of the reflected beam only once through the pipe wall.

With in-pipe inspection, the duration of the time window should allow for the monitoring of pipes with a maximum wall thickness of a once-reflected beam when the speed of sound in the pumped liquid changes over a wide range.

The flaw detector has the disadvantage of using a time window of fixed duration. This limits the ability to control pipes with a large wall thickness and tightens the requirement for the design of the media when pumping liquids with different sound speeds.

The technical result of the claimed in-line ultrasonic flaw detector is to expand the range of controlled pipe wall thicknesses upward when pumping dissimilar liquids and simplify the design requirements for the carrier of ultrasonic piezoelectric transducers.

The technical result is achieved by the fact that an in-tube ultrasonic flaw detector including a plurality of ultrasonic piezoelectric transducers oriented at a given angle to the pipe surface to excite a shear wave in the pipe material, a carrier of ultrasonic piezoelectric transducers, consisting of devices for mounting ultrasonic piezoelectric transducers mounted on skids of a given height , electronic excitation block of ultrasonic piezoelectric trans of the echo signals and the echo signals registration unit, the echo signals analysis unit registered in the time window validity zone, which begins after the echo signal is recorded from the pipe’s inner surface and has a duration not less than the time of the passage of a once reflected beam through the pipe wall, is additionally equipped with a device for measuring the speed of sound in the pumped liquid V and block automatic adjustment of the duration of the time window ΔT during monitoring according to the formula:

ΔT = ΔT ° V ° / V,

Where

ΔТ ° - window duration during control in a liquid with a minimum sound speed V °.

In addition, the design of the carrier of ultrasonic piezoelectric transducers provides a path length of the ultrasonic pulse from the reflection point from the inner surface of the pipe to the nearest structural element of the carrier; the carrier of ultrasonic piezoelectric transducers is not less than

ΔT ° V ° / 2 + ΔНп,

Where

ΔNp is the maximum allowable wear of the carrier carrier, carrier of ultrasonic piezoelectric transducers.

In FIG. 1 shows a carrier of ultrasonic piezoelectric transducers.

In FIG. 1 adopted the following notation:

1. Ultrasonic piezoelectric transducer.

2. A device for mounting an ultrasonic piezoelectric transducer.

3. Ultrasonic beam emitted by an ultrasonic piezoelectric transducer in a liquid.

4. The pumped liquid.

5. The wall of the pipe.

6. Runner carrier ultrasonic piezoelectric transducers.

7. The distance from the ultrasonic piezoelectric transducer to the inner surface of the pipe.

8. Ultrasonic beam in the pipe wall.

9. Defect on the inner surface of the pipe.

In FIG. 2 shows an oscillogram of signals recorded by an ultrasonic piezoelectric transducer.

In FIG. 2 adopted the following notation:

10. The sounding signal.

11. The echo from the inner surface of the pipe.

12. Echo from a defect in the pipe wall.

13. The echo from the structural elements of the media.

14. A time window for recording echoes from the pipe wall.

In FIG. Figure 3 shows the dependences of the change in the time of registration of echo signals relative to the moment of registration of the echo signal on the inner surface ΔT depending on the speed of sound in the pumped liquid V, constructed for different pipe wall thickness N.

In FIG. Figure 4 shows the dependences ΔT (V) constructed for different values of the angle of incidence β (Fig. 1) and the beam length L (Fig. 1).

In FIG. 5 shows an exemplary block diagram of the proposed flaw detector.

In FIG. 5 adopted the following notation:

1. Ultrasonic piezoelectric transducer.

15. The excitation unit of the ultrasonic piezoelectric transducer 1 and registration of echo signals.

5. The wall of the pipe.

16. Block analysis of echo signals.

17. The data storage device.

18. Block automatic adjustment of the duration of the time window.

19. A device for measuring the speed of sound in a pumped liquid.

20. Ultrasonic transducer for measuring the speed of sound.

21. Reflector.

22. The flow of fluid pumped through the pipeline.

23. Block excitation transducer and receiving ultrasonic pulses.

24. The unit for calculating the speed of sound.

25. Sealed enclosure for electronic components.

When in-tube ultrasonic testing, an immersion echo monitoring method is used. To identify defects such as crack and risk, the ultrasonic piezoelectric transducer 1 (Fig. 1) is fixed in the device 2 (Fig. 1) in such a way as to provide a given angle of incidence β of the ultrasonic rays 3 (Fig. 1) from the liquid 4 (Fig. 1) pumped through the pipeline to the inner surface of the pipe wall 5 (Fig. 1) to excite a shear wave pulse in the pipe material. The in-line ultrasonic flaw detector is equipped with a large number of ultrasonic piezoelectric transducers operating in a combined mode (radiation / reception) to monitor the entire cross section of the pipe. The attachment device for ultrasonic piezoelectric transducers 2 (Fig. 1) is mounted on skids 6 (Fig. 1), usually made of polyurethane, which provide a predetermined distance 7 (Fig. 1) from the ultrasonic piezoelectric transducer 1 (Fig. 1) to the internal the surface of the pipe wall 5 (Fig. 1). The device 2 (Fig. 1) and skids 6 (Fig. 1) together with the fastening elements are a structural unit - a carrier of ultrasonic piezoelectric transducers.

An in-line ultrasonic flaw detector moves inside the pipeline under the pressure of the pumped liquid. The transducer 1 (Fig. 1) excites a pulse of an elastic wave of an ultrasonic beam 3 (Fig. 1) in the pumped liquid 4 (Fig. 1). A smaller part of the energy of the ultrasonic beam 3 (Fig. 1) enters the wall of the pipe 5 (Fig. 1) at an angle α (beam 8 (Fig. 1)) and is reflected from defect 9 (Fig. 1) if it exists (in this case the defect is located on the inner surface of the pipe wall). The main part of the wave energy (approximately 90%) is reflected from the inner surface of the pipe wall 5 (Fig. 1) towards the ultrasonic piezoelectric transducer 1 (Fig. 1) and the structural elements of the carrier of ultrasonic piezoelectric transducers - beam L (Fig. 1).

The ultrasonic piezoelectric transducer 1 (Fig. 1) after its excitation by an electric pulse registers several signals. The first probe pulse 10 is recorded (Fig. 2) - the response of the ultrasonic piezoelectric transducer to excitation. The second recorded the echo 11 (Fig. 2) - reflection from the inner surface of the pipe 5 (Fig. 1), the third - the echo 12 (Fig. 2) from the defect 6 (Fig. 1), if any. The fourth is the echo signal 13 (Fig. 2), resulting from contact with the structural elements of the carrier of an ultrasonic pulse reflected from the inner surface of the pipe.

To register the echo signals from the pipe wall, a time window 14 (Fig. 2) is used, which starts after the registration of the echo signal 11 (Fig. 2) and has a duration of at least the time of passage of a once reflected beam through the pipe wall.

The duration of the window 14 (Fig. 2) determines the maximum value of the controlled wall thickness.

The beginning of the time window is rigidly “tied” to the echo signal from the inner surface of the pipe 11 (Fig. 2), so that when the distance 7 (Fig. 1) increases from the transducer 1 (Fig. 1) to the pipe surface, what happens when the ultrasonic piezoelectric carrier is run over transducers to the reinforcement bead of the weld or to a dent in the pipe wall, the echo 11 (Fig. 2) did not fall into the coverage area of the time window 14 (Fig. 2).

The reason for the appearance of the echo signal 13 (Fig. 2) can be not only reflection from the attachment device of the ultrasonic piezoelectric transducer 2 (Fig. 1), but also reflection from other ultrasonic piezoelectric transducers, which can occur when they are densely located on the carrier of ultrasonic piezoelectric transducers, as , for example [utility model patent No. 159204], or from the edge of the carrier skid 6 (FIG. 1). The signal can greatly increase in amplitude if dirt adhering to the test appears at the reflection site. In order for the echo signal 13 (Fig. 2) not to be interpreted as an echo signal from a defect, it should not fall into time window 14 (Fig. 2). Otherwise, problems arise when using the program for automatic search for defects in the processing of registered information. In addition, due to the registration of the echo signal 13 (Fig. 2), a large amount of unnecessary information will be continuously recorded in the in-tube ultrasonic flaw detector storage device, which can lead to its overflow until the end of the control of the pipeline section.

The design of a carrier for ultrasonic piezoelectric transducers of an in-line ultrasonic flaw detector for monitoring pipes with a thick wall is associated with solving a difficult problem. So that the echo 13 (Fig. 2) does not fall into the time window 14 (Fig. 2), it is necessary to increase the beam length L (Fig. 1), but without increasing the distance 7 (Fig. 1), which is selected from the condition for reliable registration of the echo from the inner surface of the pipe 11 (Fig. 2) used in the on-board algorithm for processing registered information. In this case, it is necessary to securely fasten the converter 1 (Fig. 1) in the device 2 (Fig. 1).

In-pipe inspection takes place when pumping heterogeneous liquids with different speeds of sound through a pipeline. The greatest time of registration of the echo signal from the defect 12 (Fig. 2) will be in the control once reflected beam, as shown in Fig. 1, in a liquid with a minimum speed of sound, when the angle of entry α (Fig. 1) of ultrasonic vibrations into the pipe wall will be maximum. If you use a time window 14 (Fig. 2) of a fixed duration, as is done in the prototype, and the echo 13 (Fig. 2) will be recorded at the window border, as shown in FIG. 2, with an increase in the speed of sound in the liquid, this signal will fall into the coverage area of the time window 14 (Fig. 2). Therefore, the registration time of the echo 13 (Fig. 2) must be moved away from the time window. For this, the carrier design must provide the necessary beam length L (Fig. 1) - the path length of the ultrasonic pulse, from the reflection point from the inner surface of the pipe to the nearest structural element of the carrier.

In FIG. 3 shows the calculation result by formulas (1) and (2) of the time of registration of the echo signal from the defect ΔТd and from the elements of the carrier ΔТн relative to the moment of registration of the echo signal from the inner surface of the pipe 11 (Fig. 2):

where H is the wall thickness of the pipe; L is the beam length L (Fig. 1); Vt is the shear wave velocity in the pipe wall material; V is the speed of sound in the pumped liquid.

The value of the input angle α (Fig. 1) can be determined from the well-known Snellius relation:

α = arcsin [(Vt / V) sinβ].

The calculations were performed for the case of the fall of ultrasonic rays on the inner surface of the pipe at an angle β (Fig. 1) equal to 17 ° and a shear wave velocity in the metal Vt equal to 3230 m / s. At an angle of 17 ° in oil with an average value of the speed of sound, the input angle α (Fig. 1) is 45 °. This is the recommended value for in-line inspection [Current state of in-line ultrasonic non-destructive testing of welds / G. Dobman, O.A. Barbian, H. Willems: Defectoscopy. 2007. No.11. S. 63-71].

In FIG. 3, the solid lines show the change in ΔТd value when a pipe wall with a different value of thickness N is monitored by a single reflected beam. The dashed line shows the change in ΔТd value at different beam lengths L (Fig. 1).

The dependencies in FIG. 3 are built for the real range of sound velocities in piped liquids. At the Transneft Diascan test pipeline test site, which is a closed pipeline, liquid (water with glycerin addition) is used with a sound speed of approximately 1580 m / s. During the first control of the constructed pipelines, water is usually used from the nearest water bodies with a sound speed of 1480 ... 1500 m / s. In different grades of oil at a temperature of approximately 20 ° C, the speed of sound can be in the range of 1300 ... 1420 m / s. If we take into account that the oil temperature during control can be 0 ... 50 ° C, and the temperature coefficient of the speed of sound in oil is minus 4 m / s per degree, then the range of possible values of the speed of sound in oil significantly expands - 1180 ... 1500 m / s.

When the speed of sound in a liquid changes, the time of registration of the echo signal 13 (FIG. 2) and the echo signal from the defect 12 (FIG. 2) changes unidirectionally, as can be seen from the data in FIG. 3. With a decrease in the speed of sound, the echo signal 13 (Fig. 2) will be recorded later in time, with an increase - on the contrary. It will be similar with the time of registration of the echo signal from the defect. For example, with a decrease in the speed of sound, the angle of entry of the ultrasonic wave into the pipe wall α (Fig. 1) will increase, which will increase the path length of the ultrasonic pulse in the pipe wall and, accordingly, the time of registration of the echo signal from defect 12 (Fig. 2).

The claimed in-line ultrasonic flaw detector proposes the duration of the time window 14 (Fig. 2) to change in the process of control inversely with the value of the speed of sound in the pumped liquid according to the law, which coincides with the dependence of the change in the relative time of registration of the echo signal 13 (Fig. 2) when V. is changed.

If a specific carrier of ultrasonic piezoelectric transducers has a length L (Fig. 1) of 40 mm, then the echo signal from the carrier elements does not fall into the coverage area of the window with a fixed duration, which is used in the prototype, at the highest sound speed in the liquid 1580 m / s duration windows should be no more than 50 μs, as can be seen from the data in FIG. 3. In this case, it is possible to ensure that the pipe walls with a maximum thickness of not more than 24 mm are monitored by a once-reflected beam in the entire range of V variation. With a larger thickness, the echo signal from the defect will not fall into the coverage area of such a time window when tested in a liquid with the lowest sound velocity.

If you change the duration of the time window during the monitoring process depending on the speed V, as proposed in the invention, for example, along the dashed line constructed for L = 40 mm, then with the same carrier of ultrasonic piezoelectric transducers, 32 mm thick walls can be controlled. As can be seen from FIG. 3, the echo from the defect will fall into the coverage area of the window even at the minimum speed of sound in the liquid.

Thus, regardless of the specific design of the carrier, changing the window duration depending on the speed of sound in the pumped liquid allows you to significantly expand the range of controlled thicknesses upward by more than 30%.

If the task is not to control ultra-thick pipes, then the use of the invention can significantly reduce the requirement for the design of the carrier of ultrasonic piezoelectric transducers. For example, as can be seen from FIG. 3, to control the wall with a thickness of 24 mm, it is sufficient that the support structure of the ultrasonic piezoelectric transducers provides a length L (Fig. 1) of about 30 mm instead of 40 mm, as when using a time window with a fixed duration.

The implementation of the invention is as follows.

Prior to pipeline control, it is required to set the initial time window duration ΔТ °. For this, in a liquid with a minimum sound velocity V ° from a given range on a sample with the largest thickness that must be controlled by a given flaw detector, with an artificial defect, for example, in the form of a rectangular groove, for a given angle of incidence β, the time of registration of the echo signal from the defect ΔTd at once reflected beam control. If you prepare a flaw detector for inspection in oil, then A-92 or A-95 gasoline with a sound speed of 1175 ... 1190 m / s can be used as a liquid with a minimum speed.

The ΔТ ° value obtained in this way should be considered as the minimum acceptable value. In order to exclude cases of a defect being missed due to the echo signal leaving the time window with an increase in the angle of incidence, which occurs, for example, when a run is run over a weld reinforcement roller, it is necessary to make the window a little longer. This operation is carried out only once when setting up the flaw detector in workshop conditions.

In the process of monitoring the pipeline, it is required to measure the speed of sound in the pumped liquid V, and set the duration of the time window ΔТ to establish, based on calculations by the formula:

In this case, the ΔT value will change from V, similar to the change in the time of registration of the echo signal from the structural elements of the carrier — along one of the dashed lines in FIG. 3.

In order for the echo signal from the carrier elements not to fall within the coverage area of the time window ΔT defined by formula (3), it is necessary that the design of the flaw detector carrier provide the necessary path length of the ultrasonic pulse from the reflection point from the inner surface of the pipe to the nearest carrier element L (Fig. one). This requirement means that the dashed line of change ΔT in FIG. 3 should be higher than the solid line constructed for the maximum thickness of the pipe wall in the entire specified range of sound velocity values in the pumped liquid. It is especially difficult to achieve the desired value of L at a minimum speed of sound and angles of incidence of more than 17 °. In FIG. Figure 4 shows the calculation data according to formula (1) for angles of incidence of 17 °, 18 °, and 19 ° on a wall surface 29 mm thick (solid lines). Dashed lines show the results of the calculation according to the formula (2) for different values of the length L (Fig. 1).

It is proposed to use a carrier in the flaw detector, the design of which provides a length L (Fig. 1), determined from the condition:

where ΔТ ° is the duration of the time window during control in a liquid with a minimum sound speed V °.

In this case, the time of registration of the echo signal from the most distant defect TD will be earlier in time than the time of registration of the echo signal 13 (Fig. 2) - Tn, in the entire range of specified values of the speed of sound in the pumped liquid.

For most pipes, the roughness of the inner surface is 40 ... 50 RZ, and the skids of the carrier of ultrasonic piezoelectric transducers are made of polyurethane. As a result, intensive runner wear occurs and they have to be changed approximately every 600 km of the controlled length of the pipeline. Due to the wear of the runner, the beam length L decreases (Fig. 1). If this is not taken into account when designing the carrier, then the echo signal 13 (Fig. 2) from the structural elements of the carrier of the ultrasonic piezoelectric transducers will fall into the coverage area of the window when the runner is worn.

In the operational documentation for the flaw detector, the maximum permissible wear of the runner ΔНп is set, at which the runner needs to be replaced. The change in the time of registration of the echo signal 13 (Fig. 2) - ΔТн, due to wear of the runner, can be calculated by the formula:

ΔTn = 2ΔNp / (Vcosβ).

The calculation for the case of the angle of incidence β (Fig. 2), equal to 17 °, the speed of sound V, equal to 1180 m / s, and ΔНп, equal to 4 mm, gives the value ΔТн equal to 7 μs. The calculation for the velocity in the liquid of 1580 m / s gives a ΔТн value of 5.5 μs. Those. ΔТн does not strongly depend on the value of V.

It should be noted that the above is also true when using a time window with a fixed duration, which is used in the prototype.

It is proposed, in order to take into account the wear of the carrier runner, to use a carrier that provides the value L (Fig. 1) for the case of the maximum allowable wear of the carrier runner. To do this, the length L calculated by the formula (4) (Fig. 1) must be increased by ΔL calculated by the formula:

ΔL = ΔНп / cosβ.

Usually ΔНп is 4 mm. It turns out that at an angle β equal to 17 °, the ΔL value will be equal to 4.18 mm, at 18 ° - 4.21 mm, at 19 ° - 4.23 mm. Those. at the angles most often used for in-line inspection, we can assume that ΔL = ΔНп.

With that said, the condition for determining the required length L (Fig. 1) will look like this:

In the process of designing the carrier, it is always possible to evaluate the beam length L (Fig. 1) to the nearest reflector, taking into account the curvature of the pipe. Knowing the minimum allowable length L (Fig. 1) obtained from (5) allows you to correctly position a large number of transducers on the carrier so that echo signals resulting from the contact of adjacent transducers and carrier elements of ultrasonic pulses reflected from the inner surface of the pipe do not fall into the time window coverage area.

To implement the invention, it is necessary to equip the flaw detector with a device for measuring the speed of sound in the pumped liquid in the control process.

Widely known devices in which to determine the speed of sound measured the propagation time of the pulse of an elastic wave at a known distance from the transducer to the reflector. The easiest way to excite a pulse is to use a piezoelectric transducer. The main elements of the electronic circuits of the device do not differ from those commonly used in in-tube thickness gauges, which, at least in a small amount, are equipped with all flaw detectors for detecting cracks.

In FIG. 5 shows an exemplary block diagram of the proposed flaw detector. The ultrasonic piezoelectric transducer 1 (Fig. 5) is connected to the excitation unit of the ultrasonic piezoelectric transducer and registration of echo signals 15 (Fig. 5). An ultrasonic pulse falls on the surface of the pipe wall 5 (Fig. 5) at a given angle β. A transverse wave is excited in the pipe wall at an angle α. In the presence of a defect, a reflected pulse arises, which is recorded by the transducer 1 (Fig. 5) and, after processing in block 15 (Fig. 5), enters the echo analysis block 16 (Fig. 5) and then to the data storage 17 (Fig. 5). Only those echo signals are analyzed that, according to the time of registration, are in the area of operation of the time window, the duration of which is regulated in block 18 (Fig. 5). The initial information for changing the duration of the time window is the value of the speed of sound in the pumped liquid V, which is measured using the device 19 (Fig. 5). The device includes an ultrasonic transducer 20 (Fig. 5) and a reflector 21 (Fig. 5). In the housing of the device 19 (Fig. 5), holes are provided for flowing through it of the fluid 22 pumped through the pipeline (Fig. 5). The Converter 20 (Fig. 5) is fixed at a known distance from the reflector 21 (Fig. 5). To excite the transducer 20 (Fig. 5) and receive ultrasonic pulses, a block 23 is used (Fig. 5). In block 24 (Fig. 5), the transit time by an ultrasonic pulse to the reflector and vice versa is measured and V is calculated. In block 18 (Fig. 5), the duration of the time window is calculated by formula (3). Flaw detector electronic units are placed in a sealed enclosure 25 (Fig. 5).

Claims (2)

1. An in-line ultrasonic flaw detector including a plurality of ultrasonic piezoelectric transducers oriented at a given angle to the pipe surface to excite a shear wave pipe material, a carrier of ultrasonic piezoelectric transducers, consisting of devices for attaching ultrasonic piezoelectric transducers mounted on skids of a given height, an electronic excitation unit ultrasonic piezoelectric transducers and registration of echo signals , an analysis unit for echoes recorded in the time window area, which begins after the echo is recorded from the pipe’s inner surface and has a duration not less than the time of a single reflected beam passing through the pipe wall, characterized in that the in-line ultrasonic flaw detector is equipped with a device for measuring the speed of sound in the pumped liquid V and the unit for automatically adjusting the duration of the time window ΔT during monitoring according to the formula: ΔT = ΔT ° V ° / V, where ΔT ° is the window duration for Only in a liquid with a minimum sound velocity V °. 2. An in-line ultrasonic flaw detector according to claim 1, characterized in that the carrier structure of the ultrasonic piezoelectric transducers provides a path length of the ultrasonic pulse from the point of reflection from the inner surface of the pipe to the nearest structural element of the carrier of ultrasonic piezoelectric transducers, not less than ΔT ° V ° / 2 + ΔНп, where ΔНп is the maximum allowable wear of the carrier of ultrasonic piezoelectric transducers.

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