RU2607258C1 - Method of intratubal ultrasonic inspection - Google Patents

Abstract

FIELD: measurement technology.

SUBSTANCE: invention can be used: for detection of defects in pipeline wall. Summary of invention consists in fact that by means of ultrasonic transducers elastic wave pulses are excited in fluid pumped via pipeline at specified angle to pipeline inner surface in direction of flaw detector movement and opposite to flaw detector movement through equal intervals of travel, analyzing echo pulses from pipeline wall, which amplitudes exceed preset threshold level, upon that measuring maximum echo pulse recording time after each ultrasonic transducer excitation, and defect is considered to be recorded, if during, at least, three successive ultrasonic transducer excitations emitting ultrasonic pulses in flaw detector movement direction, echo pulse recording time is constantly decreasing, or in ultrasonic transducer emitting opposite to flaw detector travel, echo pulse recording time is constantly increasing.

EFFECT: higher defects detecting reliability.

1 cl, 5 dwg

Description

The invention relates to the field of ultrasonic non-destructive testing of materials and products and can be used to detect defects in the wall of the pipeline.

Known immersion method of ultrasonic testing (Non-destructive testing: Reference: In 8 volumes / Under the General editorship of V.V. Klyuev. T.Z., I.N. Ermolov, Yu.V. Lange, Ultrasonic control - 2nd edition, rev. - M .: Mashinostroyeniye, 2008 - 864 s: ill.), in which using an ultrasonic transducer, pulses of an elastic wave in a liquid are excited at a given angle to the surface of the control object, echo signals from the control object are recorded, and their amplitude is measured , and the presence of a defect in the object of control is judged by the excess of the amplitude of the echo signal of a given marriage full-time level. This method has several disadvantages. Firstly, the ultrasonic transducer is excited at regular intervals, which is acceptable for manual control or automatic control with a constant speed of movement of the ultrasonic transducer on the surface of the control object, since there is no difficulty in determining the location of the defect in the control object. In in-line diagnostics, control is carried out at different speeds of the flaw detector, which depends on the speed of the fluid pumped through the pipeline and can vary from 0.2 m / s to 2.0 m / s. This method does not allow to determine the location of a registered defect in the pipeline. In addition, the level of the threshold for registration of defects during in-line diagnostics is set much lower than with manual inspection, since in-line inspection takes place in pumped liquids with different attenuation and sound speed, when the temperature of the liquid changes from 0 ° C to 50 ° C, with surface contamination ultrasonic transducers and pipe walls. Using the known method for in-line inspection will lead to the registration of a large number of false defects.

Known immersion method of ultrasonic testing (Current state of in-line ultrasonic non-destructive testing of welds. / G. Dobman, OA Barbian, X. Willems: Flaw detection. 2007. No. 11. P. 63-71), in which ultrasonic transducers are fixed under a given angle to the inner surface of the pipe to excite ultrasonic pulses in the pipe wall in two opposite directions. The transducers move along the axis of the pipe, excite at equal intervals of distance (distance traveled), register the echo signals from the pipe wall. The number of excesses by the amplitude of the echo signal of a given threshold level for a given number of consecutive excitations is calculated, and based on this, a decision is made about the presence of a defect. If the number of excesses of the threshold level is greater than the specified number, then it is considered that a defect is registered. The disadvantage of this method is the low reliability of the control due to the fact that this control method leads to registration on a defect-free pipeline of a large number of places suspected of defects.

In the UltraScan CD. Flaw detector operating manual ”it is recommended to consider a defect detected if, during at least four consecutive excitations of the transducer, excesses of the threshold level echo amplitude were detected. Such a control mode does not allow reliable detection of small defects on thick-walled pipes, since the number of threshold excesses can be less than the required one. If you reduce the number of required excesses and lower the threshold, then the number of false defects increases. This is mainly due to the presence of places on the outer surface of the pipe with increased roughness and metal scale, as well as due to reflections from small inclusions in the pipe wall. The amplitude of the interfering signals in these places is comparable to the amplitude of the echo signals from the defect with the minimum dimensions to be detected.

The technical result of the claimed method of in-line ultrasonic testing is to increase the reliability of detection of defects, in particular, defects in the wall of the pipeline, oriented across the axis of the pipeline.

The technical result is achieved by the fact that in the method of in-line ultrasonic testing using ultrasound transducers, elastic wave pulses are excited in the fluid pumped through the pipeline at a given angle to the inner surface of the pipeline in the direction of the flaw detector and against the flaw detector moving at equal intervals of the distance traveled, the echo pulses from the walls of the pipeline, the amplitudes of which exceeded a predetermined threshold level, while measuring the time of registration of the largest echo pulse after each excitation of the ultrasonic transducer, and the defect is considered registered if, during at least three consecutive excitations of the ultrasonic transducer emitting ultrasonic pulses in the direction of the flaw detector, the registration time of the echo pulse is constantly reduced, or for an ultrasonic transducer radiating upstream flaw detector, the time of registration of an echo pulse is constantly increasing.

In addition, the difference in the time of registration of the largest echo pulse (ΔΤ) in two successive excitations of the ultrasonic transducer is measured, and the value of ΔΤ must satisfy the condition: 2ΔXsinβ / Sr (max) <ΔT <2ΔXsinβ / Sr (min), where Sr (min) and Sf (max) is the smallest and greatest value of the speed of sound in liquids pumped through the pipeline, β is the angle of incidence of the ultrasonic pulse on the inner surface of the pipe wall, ΔΧ is the flaw detector moving between two successive excitations of the ultrasonic transducer.

In the inventive method for detecting a defect requires only three exceeding the amplitude of the echo pulse of the threshold level in three successive excitations of the ultrasonic transducer.

In FIG. 1 shows a control circuit for in-line diagnostics.

In FIG. 1 adopted the following notation:

1. Ultrasonic transducer.

2. The wall of the pipeline.

3. Defect.

In FIG. 2 shows the change in the amplitude of the echo pulse when moving the ultrasonic transducer across the defect regardless of the direction of radiation.

In FIG. 2 adopted the following notation:

4. ΔΧ - moving the flaw detector between two consecutive excitations of the ultrasonic transducer.

5. The threshold level.

In FIG. 3 shows the change in the time of registration of the echo pulse when moving across the defect, the radiation of the ultrasonic transducer along the path of the flaw detector.

In FIG. 3 adopted the following notation:

4. ΔΧ - moving the flaw detector between two consecutive excitations of the ultrasonic transducer.

6. ΔΤ is the difference in the time of registration of the largest echo pulse in two successive excitations of the ultrasonic transducer.

In FIG. 4 shows the change in the time of registration of the echo pulse when moving across the defect, the radiation of the ultrasonic transducer against the flaw detector.

In FIG. 4 the following notation is accepted:

4. ΔΧ - moving the flaw detector between two consecutive excitations of the ultrasonic transducer.

5. ΔΤ is the difference in the time of registration of the largest echo pulse in two successive excitations of the ultrasonic transducer.

In FIG. 5 shows a diagram for calculating the change in the time of registration of an echo pulse.

In FIG. 5 adopted the following notation:

2. The wall of the pipe.

3. Defect.

4. ΔΧ - moving the flaw detector between two consecutive excitations of the ultrasonic transducer.

7. The radiating surface of the ultrasonic transducer.

8. ΔL is the change in the length of the beam in the liquid when the ultrasonic transducer is shifted by ΔΧ.

9. β is the angle of incidence of the ultrasonic pulse on the inner surface of the pipe.

During in-line inspection, a control circuit is used (Fig. 1), in which the ultrasonic pulse from the ultrasonic transducer 1 (Fig. 1) falls on the inner surface of the pipeline 2 (Fig. 1) through a layer of fluid pumped through the pipeline at a given angle. An ultrasonic pulse propagates in the pipe wall in the direction of radiation. In the presence of a defect 3 (Fig. 1), the wave is partially reflected and recorded by ultrasonic transducer 1 (Fig. 1). To increase the reliability of control, especially when checking the weld, ultrasonic transducers 1 (Fig. 1) are oriented in two mutually opposite directions - along the path of the flaw detector (Fig. 3) and against the course (Fig. 4). Ultrasonic transducers 1 (Fig. 1) in the normal control mode excite each time you move to ΔΧ 4 (Fig. 2), which is determined by the design of the odometer flaw detector system. The energy in the beam tube is not evenly distributed, and the intensity of the extreme rays is much less than the central one. Therefore, the first and last echo pulses from the defect are much weaker than the central one. The threshold level 5 (Fig. 2) is selected based on the requirement of detecting a defect with minimum dimensions under the most difficult conditions of in-line inspection. The number of excitations in which the amplitude of the echo pulses when crossing the defect exceeds threshold 5 (Fig. 2) depends on ΔΧ4 (Fig. 2), the size of the piezoelectric element of the ultrasonic transducer 1 (Fig. 1), the depth of the defect, and the threshold level 5 (Fig. 2). 2).

Studies have shown that with real monitoring using a standard ultrasonic transducer with a piezoelectric element with a diameter of 15 mm and an odometer pitch of 3.3 mm from a defect of 1 mm deep on the inner surface of a pipe 30 mm thick (the largest on domestic pipelines), the number of threshold exceeded will be no more than three. The threshold level during research was chosen from the condition of its excess over the noise amplitude on a defect-free pipe by 2 times. With this mode of operation of the flaw detector according to the methods specified in the description of the claimed invention in the "inventive step" section, defect-free spots on the outer surface with increased roughness and with metal scale, as well as places with the accumulation of small inclusions in the pipe wall will be recorded, especially when monitoring thin pipes.

To increase the reliability of inspection, a method of in-line ultrasonic inspection is proposed, in which the time of registration of echo pulses from defects whose amplitude is higher than a predetermined threshold level is analyzed, and which is based on the fact that when a flaw detector moves, the time of recording interfering ("false") signals in sequential excitations of the ultrasonic transducer is a random quantity, and the time of registration of echo pulses from a defect will either constantly increase or decrease depending on from the radiation direction of the ultrasonic transducer with respect to the direction of movement (Fig. 3 and Fig. 4).

If radiation occurs along the path of the flaw detector (Fig. 3), then the recording time will be constantly reduced. If radiation occurs against the movement of the flaw detector (Fig. 4), the recording time will constantly increase. This property is implemented in the claimed method and can significantly increase the reliability of the control compared to prototypes (indicated in the "inventive step" section of the description of the claimed invention), in which the defect detection criterion is that the amplitude of the echo pulse exceeds only the threshold level 5 (Fig. 2) .

Also, in the claimed method of in-line ultrasonic testing, the analysis of the recording time of not all echo pulses with amplitudes above threshold level 5 (Fig. 2) is carried out, but only for the largest amplitude echo pulses recorded in each excitation of the ultrasonic transducer. This is due to the fact that in-tube flaw detectors operate with very high sensitivity, therefore, in addition to echo pulses from a defect, echo signals from the pipe wall (“false”) with an amplitude, as a rule, smaller than the echo pulse from defect 3, are often recorded (Fig. 1), but above threshold level 5 (Fig. 2).

Further, in the claimed method of in-line ultrasonic testing, in order to make a decision on the identification of a defect, it is necessary to continuously decrease or increase the time for recording the largest echo pulse, but not less than in three successive excitations of the ultrasonic transducer. The requirement for a greater number of excitations of the ultrasonic transducer can lead to the omission of a defect with weak reflectivity on pipes with a large wall thickness.

To increase the reliability of the in-line inspection in the claimed method, it is proposed to introduce a restriction on the permissible value ΔΤ 6 (Fig. 3 and Fig. 4). The registered ultrasonic pulses are recognized as echo pulses from the defect if the magnitude of the change in the recording time ΔΤ 6 (Fig. 3 and Fig. 4) of the largest echo pulse in two successive excitations is close to the value calculated by the formula:

ΔT = 2ΔXsinβ / Sr, where

Sg - the speed of sound in the pumped liquid through the pipeline,

β is the angle of incidence of the ultrasonic pulse 9 (Fig. 5).

With the displacement of the ultrasonic transducer 1 (Fig. 1) relative to the defect 3 (Fig. 1), the exit point of the ultrasonic beam on the radiating surface of the ultrasonic transducer 1 (Fig. 1) changes, which falls on the defect 3 (Fig. 1), which leads to a change the time of registration of the echo pulse from defect 3 (Fig. 1). If the ultrasonic transducer 1 (Fig. 1) moves from defect 3 (Fig. 3) to ΔΧ 4 (Fig. 2, Fig. 3 and Fig. 4), then the beam length in the liquid will increase by ΔL 8 (Fig. 5), and the time of registration of the echo pulse from the defect will increase by ΔΤ 6 (Fig. 3 and Fig. 4), since ΔΧ 4 (Fig. 2, Fig. 3, Fig. 4 and Fig. 5) is a constant, then ΔΤ 6 (Fig. 3 and Fig. 4) will also be a constant value, which improves the reliability of the in-line inspection.

ΔΤ 6 (Fig. 3 and Fig. 4) depends on the angle of incidence β 9 (Fig. 5) and the speed of sound in the pumped liquid. The angle of incidence β 9 (Fig. 5) is determined by the design of the carrier of the ultrasonic transducers of the flaw detector and does not change during the in-pipe inspection, while the speed of sound in liquids pumped through pipelines can vary greatly. Therefore, for the implementation of in-line ultrasonic testing in heterogeneous liquids by the claimed method, it is required that the ΔΤ 6 value (Fig. 3 and Fig. 4) satisfy the following condition:

2ΔXsinβ / Sr (max) <ΔT <2ΔXsinβ / Sr (min), where

Sg (min) and Sg (max) - the smallest and greatest values of the speed of sound in the pumped liquids.

For flaw detectors for in-pipe inspection of pipes with a diameter of 28 ... 40 '', the angle of incidence β 9 (Fig. 5) is 17 °. The speed of sound in the pumped fluids varies over a wide range - 1200 ... 1600 m / s, taking into account a possible change in the temperature of the fluid, which can vary from a small minus to 50 ° C. If the value ΔΧ 4 (Fig. 2, Fig. 3, Fig. 4 and Fig. 5) is 3.3 mm, then ΔΤ 6 (Fig. 3 and Fig. 4) can vary from 1.2 to 1.6 μs , and only in this case it is considered that the defect is registered.

Claims (2)

1. The method of in-line ultrasonic testing, in which using ultrasonic transducers they generate pulses of an elastic wave in the fluid pumped through the pipeline at a given angle to the inner surface of the pipeline in the direction of the flaw detector and against the flaw detector at equal intervals of the distance traveled, analyze the echo pulses from the pipeline wall the amplitudes of which exceeded a predetermined threshold level, characterized in that they measure the time of registration of the largest echo pulse after each excitation of the ultrasonic transducer, and the defect is considered to be registered if, during no less than three consecutive excitations of the ultrasonic transducer emitting ultrasonic pulses along the flaw detector, the registration time of the echo pulse is constantly decreasing, or for an ultrasonic transducer radiating upstream of the flaw detector, the time of registration of the echo pulse is constantly increasing. 2. The method of in-line ultrasonic testing according to claim 1, characterized in that the difference in the time of registration of the largest echo pulse (ΔT) in two consecutive excitations of the ultrasonic transducer is measured, while the ΔT value must satisfy the condition: 2ΔXsinβ / Sf (max) <ΔT < 2ΔXsinβ / Cf (min), where Cf (min) and Cf (max) are the smallest and largest values of the speed of sound in the fluids pumped through the pipeline, β is the angle of incidence of the ultrasonic pulse on the inner surface of the pipe wall, ΔX is the defectoscope moving between two sequences excitations of the ultrasonic transducer.

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