RU2488108C2 - Method of ultrasonic control of butt, lap and tee welds of thin-walled pipes of small diameter - Google Patents

Abstract

FIELD: measurement equipment.

SUBSTANCE: control zones are scanned with the help of an inclined combined piezoelectric converter (PEC), PEC position is determined, which corresponds to maximum of an echo-signal from a defect, equivalent area of the detected defect is determined, as well as its coordinates. At the same time acoustic probing of the welded joint is carried out with a multiply reflected beam, in process of control they identify the number of rereflections of an ultrasonic beam, speed of a shift ultrasonic wave in a metal is determined with the help of standard samples, besides, speed measurement is carried out using non-lapped PECs, and the operation of calibration of a depth metre of a flaw detector is carried out in special control samples with the help of lapped PECs using the following operations: installation of the PEC onto the control sample at a certain distance from artificial reflectors, control of delay time in a prism introduced into the flaw detector memory, with a pitch of 0.01 mcs, registration of flaw detector depth metre readings at each step of control, determination of actual values of coordinates of artificial reflectors for each scheme of acoustic probing with a single-reflected, double-reflected or triple-reflected beam, measurement of coordinates of artificial reflectors in the control sample with the help of ordinary measurement tools, completion of the process of delay time calibration-control in the prism.

EFFECT: increased accuracy and reliability of defect coordinates detection in process of ultrasonic control of butt, lap and tee welds of thin-walled pipes of small diameter.

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Description

The proposed method relates to acoustic non-destructive testing methods and is intended for use in ultrasonic testing systems - ultrasonic testing of thin-walled welded joints of small-diameter pipes that are part of technological installations of petrochemical industries, and can also be used in other industries.

When controlling welded joints, the main way to identify the echo signal from a defect against the background of false signals associated with the structural elements of the weld: reinforcing roller, sag, etc. - the exact determination of the coordinates of the reflector.

For example, the reflection point F (Fig. 1) lies outside the time corresponding to the arrival of an echo signal from possible defects in the welded joint. False signals of this type arise as a result of reflection from the sag P or reinforcement roller Q of the weld - the positions of the transducer 1 and 2, false signals associated with specular reflection from the sag surface at some point F. In the position of the transducer 3, mirror reflection does not occur, but remain weaker echoes resulting from diffraction of ultrasonic waves at the edges of the weld M and L.

Diffraction can generate such surface waves propagating along the LM arc [5]. False signals also arise as a result of reflection from local mechanically stressed zones of the control object - OK, where the speed of sound changes, for example, zones of thermal influence.

In some cases, ultrasonic testing of difficulties in determining the coordinates of defects is due to the geometry of the OC. For example, when ultrasonic testing of tee welds with a wall thickness H <20 mm, it is not possible to accurately measure the coordinates of defects, therefore, the presence of defects is judged by the position of the piezoelectric transducer - NEP, relative to the edge of the seam convexity; the coordinates of defects in products with a curved surface, for example a cylindrical one, are determined using special nomograms [6], etc.

A known method of ultrasonic testing of butt welds along their entire thickness, including the operations of input and receiving ultrasonic vibrations, moving the probe along and across the weld, identifying defects, determining their magnitude, measuring the distance to identified defects from the measurement source, determining their depth and distance between defects [1].

A known method of measuring the height of lack of penetration in the welds of thin-walled products, including discrete rotation of the product, reciprocating motion above the weld of the probe focused on the inner surface of the product with the simultaneous measurement and reception of ultrasonic signals, fixing the amplitude of the reflected signal and the position of the probe, setting the probe at an angle to the product, determining the coordinates of the probes in which the amplitude is 0.25 of the maximum amplitude of the reflected signal and determining the height of the lack of penetration from the form obtained by the authors le [2].

There is also known a method of ultrasonic testing of welded joints of pipes of a small diameter, including scanning a weld seam using an inclined aligned probe, identifying the received signal against a background of false interference signals, determining the characteristics of the detected defects and comparing them with normal ones [3]. At the same time, ultrasonic testing of butt, lap and tee welded joints of pipes of small diameter is conducted by a multiple-reflected beam.

The closest in technical essence is the method of ultrasonic testing of welded joints, which includes the following operations: scanning the control zone — the weld using an inclined aligned probe, determining the position of the probe corresponding to the maximum echo signal from the defect, determining the equivalent area of the detected defect and its coordinates — the depth Y and position X relative to the input point of the ultrasonic vibrations using known operations: measuring the depth of propagation of the ultrasonic pulse from the emitter with a flaw detector depth meter The probe to its receiver t ₀ through the entire acoustic path: emitter → prism → OK → reflector → OK → prism → receiver, measurement of the delay in the probe _pr t _pr , measurement of the input angle a, input of the reference value of the velocity of shear ultrasonic vibrations C _t into the flaw detector memory and determining the coordinates of the defect by the formulas (figure 2):

.X = S sinα; Y = S cos; Where $$S=\frac{C_t(t_0-t_{PR})}{2}[\mathrm{four}]$$

.

A disadvantage of the known methods for determining the coordinates of defects is their low reliability in ultrasonic testing of thin-walled welded joints of pipes of small diameter, due to the significant curvature of the surface of the welded joint, the difficulty of determining the intrinsic parameters of the probe, adapted to the shape of the welded joints, the need for ultrasonic testing of the repeatedly reflected beam.

The technical result of the proposed invention is to increase the accuracy and reliability of determining the coordinates of defects during ultrasonic testing of butt, lap and T-welds of thin-walled pipes of small diameter using inclined coupled probes and acoustic sounding circuits with a multiple-reflected beam.

The technical result is realized with ultrasonic testing with a repeatedly reflected beam — once, twice or three times reflected, in the process of control, the number of ultrasound beam reflections is determined - 1, 2 or 3, shear wave velocity C _{t is} measured using standard samples СО-2 and СО-3 , and the speed C _t is determined by the formula:

$$$$

$$C_t=\frac{2\cdot \left(R-\sqrt{X_0^2+{\mathrm{<figure-callout\; id="0"\; label="Y"\; filenames="00000027.png"\; state="\{\{state\}\}">Y</figure-callout>}}_0^2}\right)}{t_{\mathrm{one}}-{\mathrm{<figure-callout\; id="2"\; label="t"\; filenames="00000025.png"\; state="\{\{state\}\}">t</figure-callout>}}_2}$$

where R is the radius of curvature of the cylindrical surface of the standard sample СО-3; X ₀ and Y ₀ - measurement of the coordinates of a cylindrical hole with a diameter of 2.0 mm on a sample of CO-2, obtained by measuring the angle of entry α; t ₁ - measurement of the depth probe of the probe installed on СО-3 through the entire acoustic path - meter → prism → СО-3 → reflector-bottom СО-3, cylindrical surface → СО-3 → prism → receiver, when measuring the delay in the prism t _ol ; t ₂ - measured by the depth gauge of the flaw detector ultrasonic pulse propagation from the emitter to the probe receiver installed on the sample СО-2 through the entire acoustic path - emitter → prism → СО-2 → reflector-hole ⌀2 mm → СО-2 → prism → receiver , when measuring the angle of entry α. Moreover, the shear vibration velocity С _t is measured using non-rubbed probes, that is, transducers with a flat working surface, and the flaw detector’s depth gauge calibration operation is performed on control samples — SOPs made in the form of half-cylinders of the same radius, wall thickness, and material as those controlled welded joints, moreover, on the outer and inner cylindrical surfaces of the SOP, IO are deposited - artificial angular reflectors - notches, the coordinates of which are easily determined by conventional measuring instruments; the flaw detector depth gauge is calibrated using ground probes, that is, probes, working surfaces that have a concave cylindrical shape with radii of curvature corresponding to the radius of the pipe elements of the weld; a flaw detector depth gauge is calibrated at a fixed position of the ground probe in the control sample relative to the IO notch by changing the delay time in the prism t _pr inserted into the flaw detector memory with a resolution of 0.01 μs, and the specified calibration is performed using a once, twice, and triple reflected beam; in the process of ultrasonic testing, the readings of the depth gauge of the flaw detector X _ISM and Y _ISM are recorded, where Y _ISM is the apparent depth of the defect in the thickness of the weld measured by the flaw detector, relative to the input-receiving surface of ultrasonic vibrations; X _ISM - measured by the flaw detector the distance from the input point of ultrasonic vibrations to the defect; the actual values of the coordinates Y _i and X _i , the defect are determined for each scheme of ultrasonic testing according to the formulas:

- with ultrasound with a single-reflected beam:

Y ₁ = 2H-Y _1ism ; X ₁ = X _{1 ism.} ;

- with ultrasonic scanning by a double reflected beam:

Y ₂ = Y _2ism -2H; X ₂ = X ₂ ;

- with ultrasound triple-reflected beam:

Y ₃ = 4H-Y _3ism ; X ₃ = X _3ism. ;

where H is the measured thickness of the weld;

measure the coordinates of artificial reflectors on a control sample using conventional measuring instruments, for example, digital caliper - X _W , Y _W ;

fix the end of the calibration process - regulation of the delay time in the prism t _pp. under the conditions:

; $$\frac{\left|X_i-X_{iш}\right|}{X_{iш}}\le {\epsilon }_i^{\text{'}}$$

; i=1; 2; 3; $$\frac{\left|Y_i-Y_{iw}\right|}{Y_{iw}}\le {\epsilon }_i$$

; $$\frac{\left|X_i-X_{iw}\right|}{X_{iw}}\le {\epsilon }_i^{\text{'}\text{'}}$$

; i = 1; 2; 3;

- заданные погрешности измерения координат ИО на контрольном образце.where ε _i and $${\epsilon }_i^{\text{'}\text{'}}$$

- the specified errors in measuring the coordinates of the EUT on the control sample.

Consider the content of the proposed method. It contains the following operations:

1. Acoustic sounding of a welded joint - butt, lap or tee is carried out repeatedly by a reflected beam - once, twice or three times reflected.

2. The determination in the process of monitoring the number of reflections of the ultrasound beam - 1, 2 or 3;

3. The determination of the velocity of the shear ultrasonic wave C _t in the metal using standard samples СО-2 and СО-3 according to the formula:

$$C_t=\frac{2\cdot \left(R-\sqrt{X_0^2+{\mathrm{<figure-callout\; id="0"\; label="Y"\; filenames="00000027.png"\; state="\{\{state\}\}">Y</figure-callout>}}_0^2}\right)}{t_{\mathrm{one}}-{\mathrm{<figure-callout\; id="2"\; label="t"\; filenames="00000025.png"\; state="\{\{state\}\}">t</figure-callout>}}_2}$$

The measurement of speed C _{t is} carried out using non-rubbed probes, that is, transducers with a flat working surface;

4. Calibration of the depth gauge of the flaw detector is carried out on special control samples - SOP using ground probes using the following operations:

- Installation of the probe on the control sample at a certain distance from the IO-notch implementing one of the acoustic sounding schemes: once, twice or three times with a reflected beam.

- regulating the delay time t in a prism, _etc., inputted to the memory flaw, in increments of 0.01 microseconds.

- Registration of the readings of the depth gauge of the flaw detector X _ISM and Y _ISM at each regulation step t _ex

- Determination of the actual values of the coordinates Y _i and X _i , i = 1, 2 or 3, artificial reflectors for each acoustic sounding scheme: once-reflected Y _i , twice-reflected Y ₂ or three-reflected Y ₃ beam, respectively, according to the formulas:

Y ₁ = 2 · H-Y _1ism ; X ₁ = X _{1 ism.} ;

Y ₂ = Y _2ism -2 · N; X ₂ = X ₂ ;

Y ₃ = 4 · H-Y _3ism ; X ₃ = X _3ism. ;

- Coordinate measurement - X _W , Y _{W of} artificial reflectors on a control sample using conventional measuring instruments, for example, digital caliper.

- The completion of the calibration process-regulation of the delay time in the prism t _PR when the conditions are met:

_; $$\frac{\left|{\text{X}}_{\text{i}}-{\text{X}}_{\text{iш}т}\right|}{{\text{X}}_{\text{iш}т}}\le {\text{ε}}_{\text{i}}^{\text{'}}$$

; i=1; 2; 3; $$\frac{\left|{\text{Y}}_{\text{i}}-{\text{Y}}_{iw\text{t}}\right|}{{\text{Y}}_{\text{ish}t}}\le {\text{ε}}_{\text{i}}$$

_; $$\frac{\left|{\text{X}}_{\text{i}}-{\text{X}}_{\text{ish}t}\right|}{{\text{X}}_{\text{ish}t}}\le {\text{ε}}_{\text{i}}^{\text{''}}$$

; i = 1; 2; 3;

- заданные, допустимые погрешности измерения координат ИО глубиномером дефектоскопа на контрольном образце.where ε _i and $${\epsilon }_i^{\text{'}\text{'}}$$

- specified, permissible errors in measuring the coordinates of the IO with the depth gauge of the flaw detector on the control sample.

Consider the basic operations of the proposed method.

Acoustic sounding of butt, lap and tee welded joints with repeatedly reflected rays is one of the technological methods for increasing the reliability of control of welds of small thicknesses and diameters of pipe elements, since it allows you to control the entire thickness of the weld, take into account the design features of the welded joint when developing scanning schemes, and control not only the seam itself, but also the adjacent zones of thermal influence, to conduct ultrasonic testing in the conditions of one-way access.

The determination in the process of monitoring the number of reflections of the ultrasound beam is necessary to determine the actual depth of the defect Y. This operation is performed automatically if there is a W-scan in the flaw detector or by calculation and experimental methods in its absence.

To improve the accuracy of determining the coordinates of defects, the measurement of the velocity of the shear ultrasonic wave C _{t is} carried out using standard samples СО-2 and СО-3 (Fig. 3) made of the same material as the object to control the probe with a flat working surface, first set in sequence to CO-3, then to CO-2. At the same time, the readings of the depth detector of the flaw detector t ₁ and t ₂ are recorded - the propagation time of the ultrasonic wave from the emitter to the receiver through the entire acoustic path for samples СО-3 and СО-2, respectively. The values of t ₁ and t ₂ associated with the parameters of the Converter and samples by the equations:

, $$\begin{array}{c}\mathrm{FROM}-3:t_{\mathrm{one}}=t_{PR}+\frac{2\cdot R}{C_t}\\ CO-2:{\mathrm{<figure-callout\; id="2"\; label="t"\; filenames="00000025.png"\; state="\{\{state\}\}">t</figure-callout>}}_2=t_{PR}+\frac{2\sqrt{X_0^2+{\mathrm{<figure-callout\; id="0"\; label="Y"\; filenames="00000027.png"\; state="\{\{state\}\}">Y</figure-callout>}}_0^2}}{C_t}\end{array}\}$$

,

where R is the radius of curvature of the cylindrical surface of CO-3; X ₀ and Y ₀ - the measured coordinates of the cylindrical hole ⌀2 mm on CO-2; t _ol - the delay in the prism of the probe. From these equations determine the speed C _t by the formula:

$$C_t=\frac{2\cdot \left(R-\sqrt{{\mathrm{<figure-callout\; id="0"\; label="X"\; filenames="00000027.png"\; state="\{\{state\}\}">X</figure-callout>}}_0^2+{\mathrm{<figure-callout\; id="0"\; label="Y"\; filenames="00000027.png"\; state="\{\{state\}\}">Y</figure-callout>}}_0^2}\right)}{t_{\mathrm{one}}-{\mathrm{<figure-callout\; id="2"\; label="t"\; filenames="00000025.png"\; state="\{\{state\}\}">t</figure-callout>}}_2}$$

According to the known method of setting the depth gauge of the flaw detector [3, 7], the delay in the prism t _{pr is} determined using a standard sample СО-3 (Fig. 3a). In this case, C _t = 3260 m / s is entered into the flaw detector memory, and the delay time in the prism is calculated by the formula:

_ave t = t ₁ -33.7 (microseconds).

In other sources, for example [4], another value of the velocity of a shear ultrasonic wave in steel is given: С _t = 3230 m / s.

The flaw detector depth gauge is calibrated on special control samples - SOPs made in the form of half-cylinders of the same radius, wall thickness and material as the welded joints being controlled, and on the outer and inner cylindrical surfaces of the SOP, IOs are applied - artificial angular reflectors - nicks, coordinates which are easily determined by conventional measuring instruments (figure 4). In this case, ground probes are used, that is, transducers whose working surfaces have a concave cylindrical shape with radii of curvature corresponding to the radius of the pipe elements of the weld. Depth gauge calibration is performed using the following operations:

- installation of the probe on the control sample at a certain distance X = (n + 1) X ₀ from the IO notch, which implements one of the acoustic sounding schemes: a once-reflected beam - X = 2 · X ₀ , X ₀ = H · tα; n = 1, twice reflected beam - X = 3 · X ₀ , n = 2; X = 4 · X ₀ , n = 3 (Fig. 4). Then, with small movements of the probe near the nominal position X, along the SOP axis, the maximum value of the echo signal from the reflector is achieved, this position of the transducer is fixed, and the following operations are performed:

- regulation of the delay time in the prism t _ave. , entered into the memory of the flaw detector with a step of 0.01 μs.

- registration of the readings of the depth gauge of the flaw detector X _ISM and Y _ISM at each regulation step t _ex The diagrams for the formation of the readings of the depth gauge X _ISM and Y _ISM with ultrasonic testing of a once reflected, twofold reflected and threefold reflected beam are shown in Fig. 5.

- determination of the actual values of the coordinates Y _i , and X _i , i = 1, 2 or 3, artificial reflectors for each acoustic sounding scheme: once reflected Y ₁ , X ₁ , twice reflected Y ₂ , X ₂ or three times reflected Y ₃ , X ₃ beam, respectively, according to the formulas:

Y ₁ = 2H-Y _1ism ; X ₁ = X _{1 ism.} ;

Y ₂ = Y _2ism -2H; X ₂ = X ₂ ;

Y ₃ = 4H-Y _3ism ; X ₃ = X _3ism. ;

- measuring the coordinates X _W , Y _W artificial reflectors on the control sample using conventional measuring instruments, such as a digital caliper. The depth of the IO-notch on the SOP (figure 4) can take only two values Y = 0 and Y = H, where H is the wall thickness of the SOP.

- completion of the calibration process - regulation of the delay time in the prism t _etc. when the conditions are met:

; $$\frac{\left|X_i-X_{iш}\right|}{X_{iш}}\le {\epsilon }_i^{\text{'}}$$

; i=1; 2; 3; $$\frac{\left|Y_i-Y_{iw}\right|}{Y_{iw}}\le {\epsilon }_i$$

; $$\frac{\left|X_i-X_{iw}\right|}{X_{iw}}\le {\epsilon }_i^{\text{'}\text{'}}$$

; i = 1; 2; 3;

- допустимые погрешности измерения координат ИО глубиномером дефектоскопа на контрольном образце.where ε _i and $${\epsilon }_i^{\text{'}\text{'}}$$

- permissible errors in measuring the coordinates of the IO with a flaw detector depth gauge on a control sample.

Laboratory tests of the proposed method were carried out on the installation of UIU "SCANER" using a certified control sample SOP-OK-3.0 / 16-65-4, made in the form of a half-cylinder ⌀16.0 mm, wall thickness H = 3.0 mm, material Article 20, with artificial reflectors in the form of “notch” dimensions: width b = 2.0 mm; depth h = 1.0 mm. In the experiments, the certified P121-4.0-655-⌀16 mm transducer was used.

The test results are shown in table 1. A flaw detector depth gauge was calibrated by sounding a sample with a direct beam.

- the position of the probe was determined at which the echo signal from the IO is maximum.

- correction of the position of the PES coordinate of X was carried out taking into account the theoretical value of X _from = H · tgα = 6.43 mm. In this case, the change in the level of the echo pulse on the screen of the flaw detector did not exceed 1.0 ÷ 1.2 dB.

- by changing the delay in the prism t _ave , the depth gauge was adjusted. Criterion for accuracy: readings of the depth gauge X _0izm. , Y _0ism. Correspond to the actual values of the coordinates of the IE: X ₀ = 6.4 mm; Y ₀ = 3.0 mm. The minimum deviation of the measured coordinate values from the actual values was obtained with a delay in the prism of t _ave = 4.12 μs. The readings of the flaw detector depth gauge in this case: X _0ism = 6.4 mm; Y _0ism. = 3.0 mm. A digital vernier caliper measured the value of the X coordinate: X _0ш = 6.4 mm. Other ultrasonic testing parameters were also determined:

- recorded the time of the signal from the reflector to the receiver t ₀ through the entire acoustic path;

- determined the transit time of the ultrasonic wave in the metal t _m : t _M = t ₀ + t, _etc.

- the distance along the central beam from the probe emitter to the IO was determined:

; $${\mathrm{<figure-callout\; id="0"\; label="S"\; filenames="00000027.png"\; state="\{\{state\}\}">S</figure-callout>}}_0=\frac{C_t(t_0-t_{PR.})}{2}$$

;

- the theoretical value of the path of ultrasonic waves in the metal was determined:

; $$S_{0T}=\frac{H}{\cos \alpha }$$

;

After adjusting the depth gauge of the flaw detector, the coordinates of the EUT were measured for ultrasonic testing with a multiple reflected beam: once, twice and three times reflected. The calculated values of the control parameters with a 1-fold reflected beam, i = 1, 2 or 3, were determined by the formulas:

; $$S_0=\frac{C_t(t_0-t_{пр.})}{2}$$

;X _iT = (i + 1) H tgα; $$S_{iT}=\frac{(i+\mathrm{one})\cdot H}{\cos \alpha }$$

; $${\mathrm{<figure-callout\; id="0"\; label="S"\; filenames="00000027.png"\; state="\{\{state\}\}">S</figure-callout>}}_0=\frac{C_t(t_0-t_{PR.})}{2}$$

;

The above data show the high efficiency of the proposed method of ultrasonic testing, as well as a fairly accurate match of the experimental and calculated data obtained by the method of geometric acoustics.

The proposed method of ultrasonic testing has the following advantages:

1. Allows to carry out ultrasonic testing of welded joints of thin-walled pipes of small diameter of various types: butt, lap and tee with the use of repeatedly reflected ultrasound waves.

2. To make accurate measurements of the coordinates of defects during acoustic sounding of welded joints with a repeatedly reflected beam.

3. to regulate the accuracy of measuring the coordinates of defects, and consequently, the effectiveness of their identification against a background of interference - false echo signals.

4. To increase the objectivity of the sorting of welded joints.

Used sources

1. Patent of the Russian Federation No. 23958020, IPC G01 No. 29/04, publication date 07/27/2010

2. Patent of the Russian Federation No. 2256907 C1, IPC G01 29/04, publication date 07/20/2005

3. Patent of the Russian Federation No. 2394235 C1, IPC G01 No. 29/26, publication date 07/10/2010.

4. Ermolov I.N., Lange Yu.V. Ultrasonic inspection Directory. V.3., M.: Mechanical Engineering, 2004, 859 p.

5. Ermolov I.N., Aleshin N.P. Acoustic control methods. Book 2. M .: Higher school, 1991, 282 p.

6. Aleshin N.P. Physical methods of non-destructive testing of welded joints. M .: Engineering. 2006.367 s.

7. Scherbakov O.N. The application technique of the installation of the measuring ultrasonic series “SCANER” (hand-held scanner - “Scaruch”) for ultrasonic testing of welded joints and the base metal of pipelines. SCAN 2.01.00000yum MNTP "ALTES", M .: 2001, 84 p.

Claims (1)

A method for ultrasonic testing of butt, lap and tee welds of thin-walled pipes of small diameter, including scanning a control zone - a weld using an inclined aligned probe, determining the probe position corresponding to the maximum echo signal from the defect, determining the equivalent area of the detected defect and its coordinates - the occurrence depth Y and position X relative to the entry point of the ultrasonic vibrations using known operations: measuring the depth of time of a flaw detector with a depth meter Ia ultrasonic pulse from the transducer probe to its receiver t ₀ through the acoustic path: radiator → prism → OK → reflector → OK → prism → receiver, measuring the delay in the probe wedge t _ave, measuring the input angle α, the input to the memory reference speed values flaw shear ultrasonic vibrations C _t and defect coordinates determination by the formulas:
X = S sinα; Y = S cosα,
Where $$S=\frac{C_t(t_0-t_{PR})}{2},$$

characterized in that the coordinates of the defects are measured during ultrasonic testing with a repeatedly reflected beam — once, twice or three times reflected, in the process of control, the number of re-reflections of the ultrasound beam is determined - 1, 2 or 3, the velocity of the shear ultrasound wave C _{t is} measured using standard samples of CO -2 and СО-3 made of OK material, and the speed C _t is determined by the formula:
$$C_t=\frac{2\cdot \left(R-\sqrt{X_0^2+Y_0^2}\right)}{t_{\mathrm{one}}-t_2}$$

,
where R is the radius of curvature of the cylindrical surface of the standard sample СО-3;
X ₀ and Y ₀ - the measured coordinates of a cylindrical hole with a diameter of 2.0 mm on a sample of CO-2, obtained by measuring the angle of entry α;
t ₁ - measured by the depth gauge of the flaw detector, the propagation time of the ultrasonic pulse from the emitter to the probe receiver installed on SO-3 when measuring the delay in the prism t _CR ;
t ₂ - measured by the depth gauge of the flaw detector, the propagation time of the ultrasonic pulse from the emitter to the probe receiver installed on the sample СО-2 when measuring the input angle α,
moreover, the shear vibration velocity C _t is measured using non-rubbed probes, that is, transducers with a flat working surface, and the flaw detector depth gauge is calibrated using control samples — SOPs made in the form of half-cylinders of the same radius, wall thickness, and material as those of the controlled ones welded joints, moreover, on the outer and inner cylindrical surfaces of the SOP are deposited IO - artificial angular reflectors - nicks, the coordinates of which are easily determined by conventional measurements fir-tree tools; a flaw detector depth gauge is calibrated using ground probes, that is, probes whose working surfaces have a concave cylindrical shape with radii of curvature corresponding to the radius of the pipe elements of the weld; a flaw detector depth gauge is calibrated at a fixed position of the ground probe in the control sample relative to the IO notch by changing the delay time in the prism t _pr introduced into the flaw detector memory with a resolution of 0.01 μs, and the specified calibration is performed using a once, twice and triple reflected beam; in the process of ultrasonic testing, the readings of the depth gauge of the flaw detector X _ISM and Y _ISM are recorded, where Y _ISM is the apparent depth of the defect in the thickness of the weld measured by the flaw detector, relative to the input-receiving surface of ultrasonic vibrations; X _ISM - measured by the flaw detector the distance from the input point of ultrasonic vibrations to the defect; the actual values of the coordinates Y _i and X _{i of the} defect are determined for each scheme of ultrasonic testing according to the formulas:
with ultrasound once reflected beam:
Y ₁ = 2H-Y _1ism ; X ₁ = X _1ism
with ultrasound twice reflected beam:
Y ₂ = Y _2ism -2H; X ₂ = X _2ism ;
with ultrasound triple reflected beam:
Y ₃ = 4H-Y _3ism ; X ₃ = X _3ism
where N is the measured thickness of the welded joint,
measure the coordinates of artificial reflectors on a control sample using conventional measuring instruments, for example, digital caliper - X _W , Y _W ;
fix the end of the calibration process - regulation of the delay time in the prism t _PR when the conditions are met:
$$\frac{\left|Y_i-Y_{iw}\right|}{Y_{iw}}\le {\epsilon }_i$$

; $$\frac{\left|X_i-X_{iw}\right|}{X_{iw}}\le {\epsilon }_i^{\text{'}\text{'}}$$

; i = 1; 2; 3
where ε _i and $${\epsilon }_i^{\text{'}\text{'}}$$

- the specified errors in measuring the coordinates of the EUT on the control sample.

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