RU2243586C1 - Method for determining quality of product on basis of reliable and possible sections of remaining defectiveness - Google Patents

Abstract

FIELD: non-destructive control of irregularities.

SUBSTANCE: method includes measuring critical sizes of defects in operation mode, and also sizes allowed during operation and sizes allowed during manufacture. Control results are presented as bar graph. Possibility of detection of defect, source defectiveness and remaining defectiveness are determined. Remaining defectiveness is separated on reliable part and possible part. Received defects size is compared to critical size of defect, to operation-allowed defect and manufacture-allowed defect. On basis of comparison quality of product its possible use in operation are determined.

EFFECT: higher efficiency.

5 dwg

Description

The invention relates to the field of non-destructive testing (hereinafter referred to as NC) of discontinuities, inhomogeneities and other defects in the material of a product or a group of products (parts, structural elements, etc.), including ultrasonic, eddy current, radiographic and other methods of NC. The invention can be used in assessing the quality, reliability and safety of a product based on the results of a tax code, assessing the suitability of the means and methods of a tax code, the adequacy of the qualifications of the operators of a tax code, and organizing product control during operation and / or manufacture.

There is also a method for determining the defectiveness of a product (GOST 14782-86), according to which a standard sample is manufactured with a small defect obtained by drilling or milling, according to which sensitivity is determined, which determines the reliability of this control method (and control means). It is believed that the higher the sensitivity, the higher the reliability of the NK, but the quantitative characteristics of this relationship in the specified method has not been established, i.e. the method does not allow to evaluate the real defectiveness after repair of the identified defects.

In accordance with existing practice in modern technology, NK of critical products is carried out after manufacture, before operation and during operation. At the same time, it is assumed that as a result of the NC, all defects that are available for detection by this control method are detected. All discontinuities, inhomogeneities and similar metal anomalies, if they exceed the permissible dimensions, are classified as defects and are repaired by repair. It is believed that after repair and repair of defects, there are no other defects in the product (see, for example, Equipment and pipelines of nuclear power plants. Welded joints and surfacing. Control rules, PNAEG-7-010-89, Gosatomnadzor of Russia, Energoatomizdat, 1991 .). The same practice has developed abroad. Thus, it is believed that initially (before the ND) in the product there were those defects that were revealed during the inspection, and after inspection and repair of the detected defects there were no more.

The drawback of the described approach is that when assessing both the initial defectiveness of the product and the residual defectiveness (i.e., the defect remaining in the product after it was inspected and the detected defects were repaired) they do not take into account the real possibility of skipping defects using the inspection methods used by NK operators with a certain skill level. It is known (for example, Gurvich AK, Reliability of flaw detection control as the reliability of the complex “Flaw detector - operator - medium”, Flaw detection, 1992, No. 3, pp. 5-13) that in almost all cases of NC there is a significant probability of missing a defect large sizes exceeding permissible sizes. In practice, it turns out that almost always after ND and repair of detected defects in the product, defects still remain. It is these defects that ultimately determine the reliability and performance of the product.

The technical result to which this invention is directed is that it allows you to evaluate the actual defectiveness of the product after checking and repairing the detected defects and to establish a boundary between the sizes of defects that reliably exist in the product (the probability of their existence is 1), and the sizes defects that may or may not be in the product (the probability of their existence is less than 1). Knowing the size of the defects that reliably exist in the product (after checking and repairing the detected defects) will allow us to more accurately assess the real state of the product, the possibility of reliable and safe operation, the acceptability of certain NK methods, the quality of the manufacturing technology of the product, and if necessary, accept reasonable measures to improve the quality and reliability of the product to an acceptable level.

Technical result is achieved by a method for determining the quality of products comprising defective products NDT determine critical dimensions χ _cr defects during operation, operation permissible dimensions [χ] _d.e defects in the manufacture and allowable dimensions [χ] _mfd defects

the control results are presented in the form of a histogram in the coordinates (N _obn , χ), where N _obn is the number of defects detected during the control, χ is the characteristic size of the defect, the probability of detecting a _water defect P is determined, the initial defect is determined N _ref = f (χ), determined residual defectiveness N _ost = (χ) as the difference N _ref and N _obn , residual defectiveness is divided into the reliable part χ ≤ χ _d and the probabilistic part χ> χ _d , where χ is the characteristic size of the defect, χ _d is the size of the defects on the border between the reliable and probabilistic parts, predelyaemy from:

where χ _max - the maximum possible defect sizes in this product;

the value of χ _{d is} compared with χ _cr, [χ] _{d.e and} [χ] _ex , and the results of the comparison make a conclusion about the quality of the product and the possibility of its operation.

As a rule, the linear size of the defect, or a combination of the linear dimensions of the defect, or the area of the defect, or the volume of the defect, is chosen as the characteristic size χ of the defect.

In one embodiment, the histogram is approximated (N _obn, χ) by the equation

N _obn (χ) = Aχ ^-n {1- (1-η) exp [-α (χ -χ ₀ )] - η}, (2)

where A, n, α, η are constants, which are determined from the condition of approximation of the equation N _obn (χ) to the control results presented in the form of a histogram,

χ ₀ is the minimum defect size available for detection,

the initial defectiveness N _ref is determined by the formula:

N _ref = Aχ ^-n , (3)

and the probability of detecting a _water defect P by the formula:

In the particular case, the minor axis α of the ellipse is taken as the characteristic size, which schematizes the defect, while the a / c ratio is taken constant for all a, determined from the condition of the maximum defect development rate under operating conditions.

Moreover, χ _cr, [χ] _doe and [χ] _izg , determine for a particular product or group m of the same type of products, moreover, when controlling m of the same type of products, all the control results are summarized and presented in the form of a single histogram.

в области дефектов, важных для безопасности, определяют в виде числа дефектов в изделии, размеры которых равны или больше критических размеров [χ ]_кр в режиме эксплуатации изделия:In this case, residual defectiveness

in the field of defects important to safety, it is determined as the number of defects in the product, the dimensions of which are equal to or greater than the critical dimensions [χ] _cr in the operation mode of the product:

в области дефектов, важных для надежности, определяют в виде числа дефектов, размеры которых превышают размеры дефектов [χ ]_д.э предельно допустимых в эксплуатации изделия:residual defectiveness

in the field of defects important for reliability, they are determined in the form of the number of defects whose dimensions exceed the dimensions of the defects [χ] _{qe of the} maximum permissible product operation:

в области дефектов, определяющих качество изготовления, в виде числа дефектов, размеры которых превышают размеры [χ ]_изг допустимых при изготовлении несплошностей:residual defectiveness

defects in determining the quality of manufacture, as the number of defects that are larger than the dimensions of [χ] _mfd permissible in the manufacture of discontinuities:

where χ _before - the maximum possible characteristic size of the defect,

m is the number of similar products.

At the same time, the minimum defect size χ _{0 that} is available for detection is determined when setting up the flaw detector used to control the product, or as the minimum defect size that was detected during inspection.

To simplify the calculations, the constant η is taken equal to 0.

In another embodiment, a test sample is manufactured to determine the characteristics of non-destructive testing of discontinuities in the product material, this test sample is tested by the non-destructive testing method, and the product is controlled using the same method as the test sample, and the test the sample is made in the form of the product or its most critical part from the same material and according to the same technology as the product, with defects located at random with different characteristic p χ measures, determine the probability of detecting defects P _water (χ):

P _water (χ) = N _obn. (Χ) / N _closed (χ), (8)

where n _obn is the number of defects detected during the control of the test sample,

N _{Hall then} - the number of defects in the manufacture of the test sample, the initial defect is determined as;

N _ref = N _{obd ed} / R _water (χ) (9)

the histogram (N _ref , χ) is approximated by the equation N _ref = f (χ) or N _ref = f (a, c), where a, c are the linear dimensions of the defects, and when determining the residual defect N _{rest, the} value of N _{obn ed} is determined from the analytical expression N _{obn ed} = N _ref · R _waters (χ).

в области дефектов, важных для безопасности, определяют в виде числа дефектов в изделии, размеры которых равны или больше критических размеров χ _кр в режиме эксплуатации изделия:At the same time, the test sample contains three groups of defects: defects whose sizes lie in the range from the sizes of defects admissible during operation to the dimensions critical for the product in operation; defects, the sizes of which lie in the range from the dimensions allowed during the manufacture of the product, to the sizes of defects permitted during operation; defects, the sizes of which lie in the range from the minimum dimensions available for detecting defects to the sizes of defects acceptable during manufacture, while the first two types of defects mimic defects of an operational nature, and the third type mimic technological defects, residual defects

in the field of defects important to safety, they are determined as the number of defects in the product, the dimensions of which are equal to or greater than the critical dimensions χ _cr in the operation mode of the product:

в области дефектов, важных для надежности, определяют в виде числа дефектов, размеры которых превышают размеры дефектов χ _д.э., предельно допустимых в эксплуатации изделия:residual defectiveness

in the field of defects important for reliability, they are determined in the form of the number of defects, the sizes of which exceed the dimensions of the defects χ _{doe, the} maximum permissible in the operation of the product:

в области дефектов, определяющих качество изготовления, в виде числа дефектов, размеры которых превышают размеры χ _изг допустимых при изготовлении несплошностей:residual defectiveness

defects in determining the workmanship, as the number of defects that are larger than the dimensions χ _mfd permissible in the manufacture of discontinuities:

where χ _before - the maximum possible characteristic size of the defect.

In this case, the histogram (N _ref , χ) is approximated by an equation of the type

, или N_исх=А_а,с(а²/с

, или

N _ref = A _x exp (-nχ χ), or N _ref = A _a exp (-n _a ), or N _ref = A _{a, c} exp [-n _{a, s,} (a ² / s)], or N _ref = A _F exp (-nF), or N _ref = Ax χ ^-nx , or N _ref = A _a

, or N _ref = A _{a, s} (a ² / s

, or

where a, c are the linear dimensions of the defect,

F is the area of the defect,

n, A are the coefficients selected from the condition of maximum approximation of the analytical curve to the experimental data.

Figure 1 shows a schematic diagram of a defect in a pipeline with an ellipse with half shafts a and c, figure 2 shows a set of defects of critical sizes, dimensions acceptable for operation and sizes of discontinuities during fabrication (the corresponding fabrication standards are given in table NTD PNAEG-7 010- 89)), in Fig. 3, a characteristic of the reliability of the ND in the form of the dependence of the probability of detecting defects P _water on their size a, in Fig. 4 is a histogram of defects detected in the product, and in Fig. 5 is a diagram of residual defectiveness.

The method can be applied to a specific product or group of similar products, the quality of manufacture, the reliability and safety of which must be ensured using the well-known PC method during monitoring by an operator of known skill.

The methods of fracture mechanics determine the critical sizes of defects in the operating mode for a given product χ _cr , the maximum permissible defects [χ] _doe in operation allowable manufacturing sizes of defects [χ] _izg (product defect standards), determined by the applicable regulatory documents and / or technical specifications for manufacturing (χ - characteristic defect size, for example, the linear size of the defect, or a combination of the linear dimensions of the defect, or the area of the defect, or defect volume). It should be noted that defects that determine quality are defects whose sizes are in the range from the minimum sizes available for detecting defects (search) to the sizes of defects acceptable during manufacture and higher; defects that determine reliability are defects whose sizes are in the range from defective during manufacture to acceptable during operation and above; defects defining safety - from acceptable during operation to critical sizes and above.

The set of defects of critical dimensions (curve 3), allowable for operation dimensions (curve 2), as well as the allowable sizes of discontinuities in the manufacture (curve 1) are shown in Fig.2.

Non-destructive testing of the product (ND) is carried out by the selected method (ultrasonic, eddy current, radiographic and other ND methods) and technical means of control by operators of a certain qualification.

The control results are presented in the form of a histogram in the coordinates “characteristic defect size χ is the number of detected defects of a given size N _ed .”

Next, determine the probability of detecting a defect P _water , the initial defect N _ref = f (χ) and residual defect N _est = φ (χ) as the difference N _ref and N _obn .

These dependencies can be determined by various methods.

According to one of the options, the results of NK are presented in the form of analytical expressions.

The structure of the equation that can describe the results of NK presented on the histogram is as follows:

N _obn (χ) = N _ref (χ) P _water (χ) (14)

where N _ref is the number of defects detected during inspection per unit of characteristic size. If the semimajor axis of the ellipse with which the defect is schematized is selected as the characteristic size, then the dimension N _obn - mm ^-1 ;

N _ref is the function of the initial (to the NC) defectiveness with the same dimension as N _obn ;

P _water - the probability of detecting a defect of a given size χ.

The form of the functions N _ref and P _water is determined on the basis of the condition of the greatest simplicity of expression, the minimum number of constants and the correspondence of the physically determined dependence of N _ref and P _water on χ. In a first approximation, the following equations can be used:

N _ref = Aχ ^-n , (14)

N _obn (χ) = Аχ ^-n {1- (1-η) exp [-α (χ -χ ₀ )] - η}, (16)

where A, n, α, η, χ ₀ are constants.

The numerical values of the constants A, n, α, η are determined from the condition that the equation N _obn (χ) is as close as possible to the results of the NC presented in the form of a histogram.

In this case, χ ₀ is the minimum defect size that is available for detection — it is determined when setting up the flaw detector used to control the product, or as the minimum defect size that was detected during the inspection; As a first approximation, η can be taken equal to 0. As a result, three unknowns remain, which greatly simplifies the task of determining them.

The constants A, n, α can be determined either by solving a system of three equations for A, n, and α, which are obtained by taking three points on the histogram, or they are determined using the least squares method.

Residual defectiveness N _ost is defined as the difference N _ref and N _obn :

N _ost (χ) = N _ref (χ) -N _obn (χ). (17)

в области дефектов, важных для безопасности, определяют в виде числа дефектов в изделии, размеры которых равны или больше критических размеров χ _кр в режиме эксплуатации изделия:The number of remaining defects in the product is determined in three ranges: residual defectiveness

in the field of defects important to safety, they are determined as the number of defects in the product, the dimensions of which are equal to or greater than the critical dimensions χ _cr in the operation mode of the product:

в области дефектов, важных для надежности, определяют в виде числа дефектов, размеры которых превышают размеры дефектов [χ ]_д.э., предельно допустимых в эксплуатации изделия:residual defectiveness

in the field of defects important for reliability, they are determined in the form of the number of defects, the sizes of which exceed the dimensions of the defects [χ] _doe, maximum permissible in the operation of the product:

в области дефектов, определяющих качество изготовления, в виде числа дефектов, размеры которых превышают размеры [χ ]_изг допустимых при изготовлении несплошностей:residual defectiveness

defects in determining the quality of manufacture, as the number of defects that are larger than the dimensions of [χ] _mfd permissible in the manufacture of discontinuities:

where χ _before - the maximum possible characteristic size of the defect in this design with a given geometry (e.g., in the direction of the pressure vessel wall thickness equal to the maximum size of the defect wall thickness)

m is the number of similar products.

When constructing a histogram, the horizontal axis χ must include the critical size of the defect, even if, as a result of the control, all detected defects did not reach critical sizes.

In the case of control of several products of the same type, all control results are summarized and presented in the form of a single histogram. The more products were monitored, the more reliable the final result.

According to another embodiment, to determine the dependences P _water (probability of detecting a defect), N _ref = f (χ) (initial defectiveness) and N _ost = φ (χ) (residual defectiveness), a test sample is made.

Taking into account real operational loads and conditions, defects (discontinuities) are determined for the product (for example, the pipeline, Fig. 1) by the methods of fracture mechanics (taking into account safety factors):

The set of defects of critical dimensions (curve 3), allowable for operation dimensions (curve 2), as well as the allowable sizes of discontinuities in the manufacture (curve 1) are shown in figure 2

The test sample is made in the shape of the product and on a scale of about 1: 1 to the product or its most critical part. The most critical part of the product is that part of the product in which the most likely occurrence of defects (welds, places of maximum operational influences, etc.) or the destruction of which is dangerous. The test sample is made of the same material and using the same technology as the product. Three types of artificial defects are laid in test samples:

- defects, the sizes of which lie in the range from the sizes of defects admissible during operation, to sizes critical for the product in operation,

- defects, the sizes of which lie in the range from the dimensions allowed during manufacture, to the sizes of defects acceptable during operation,

- defects, the sizes of which lie in the range from the minimum sizes available for detecting defects to the sizes of defects admissible in the manufacture (it is also permissible that the upper boundary of the interval exceed the dimensions of the defects admissible in the manufacture).

In this case, the first two types of defects (discontinuities) should simulate defects of an operational nature, and the third type of technology defects. Operational defects - defects that can develop from technological defects or arise and develop under the action of operational loads (fatigue cracks, stress corrosion cracking cracks, etc.) .p.) technological defects are defects whose occurrence is associated with the peculiarities of the manufacturing or installation technology (lack of fusion, non-fusion, pores, etc.). In this case, it is possible to bookmark a different combination of types of defects (one, any two, three), if necessary, it is also possible to produce a different number of samples, in each of which one type of defects or their different combination will be laid.

All embedded defects must be hidden from the operators of the tax code, i.e. be internal (subsurface) or, if the defect is superficial, be located in a place inaccessible to visual detection (or have dimensions that cannot be visually fixed).

It should also be noted that defects are placed randomly in the sample, for example, using random number tables.

The minimum permissible distance between defects is determined on the basis of the condition for the existence of single defects (if single defects are laid) or less for group cracks (the conditions of mutual influence are known, for example, Methodological Recommendations MR 108.7-86, M .: TSNIITMASH, 1986).

The number of defects of each type should be sufficient for statistical processing of the results, for example, at least 9 pieces. (With less results are less reliable).

Any defect can be conservatively modeled by a crack, and any crack can be described by an ellipse with semi-axes: short a and long c.

There are various options for bookmarking defects in the test sample.

Defects in the form of ellipses are laid in the test sample, and the ratio of the axes of the ellipse is taken on the basis of the condition for the maximum growth rate of the defect in the operational stress field;

Defects in the form of ellipses are laid in the test sample, while the ratio of the axes of the ellipse is arbitrary, and the area of the plane defect or the projection area of the volume defect on the plane of the probable development of the defect is taken as characterizing the size of the defect;

Defects in the form of ellipses are placed in the test sample, while the number of defects and the ratio of the axes of the ellipse are selected using mathematical methods for planning the experiment, based on the condition of minimizing the number of defects to be laid (K. Daniel, Application of statistics in an industrial experiment. M .: Mir, 1979 );

If the defects to be inserted into the test sample do not have the shape of an ellipse, then they are schematized by ellipses.

After the manufacture of the test sample, it is controlled using the same means and methods of control and by operators of the same qualifications, which will then be used to control the product, the results of the monitoring are compared with real defects embedded in the test sample.

For each characteristic size of the defect, reliability is determined as a function of the probability of detection of defects P _water (χ):

P _water (χ) = N _obn. (Χ) / N _closed (χ), (8)

where N _obn is the number of defects detected during the control of the test sample,

N _{Hall then} - the number of defects in the manufacture of the test sample,

Based on the control results, a probability curve for detecting defects for a given part is constructed using this PC method, depending on the characteristic size of the defects. The probability curve for detecting defects from the dimensions of defects “a” and “c” (any defect in the material can be conservatively described by an ellipse with half axes a and c) can be approximated by the equation that most closely describes the experimental results of control, for example

P _water = 1- (1-ε) exp [-α _NK (a-a ₀ ) (s-s ₀ )] - ε, or (18)

P _water = 1- (1-ε) exp [-α _NK (χ -χ ₀ )] - ε (20)

where α _nk - confidence factor NC, characterizes the increase detectability of defects depending on its size;

ε is a constant characterizing the ultimate detectability of the control by this method for an arbitrarily large defect size; if the dimensions of the part are small, then this value can be neglected by introducing an appropriate adjustment of α _nk .

χ is the characteristic size of the defect, for example, its area;

χ ₀ is the minimum characteristic size of the defect;

and _o , c _o are the minimum defect sizes available for detecting ND.

Next, the product is inspected, and the inspection results are presented in the form of a histogram in the coordinates “characteristic defect size χ is the number of detected defects of a given size N _{obn ed} .”

или

или

The initial defectiveness N _ref is defined as the ratio of N _{obn ed} / P _water (χ); the resulting histogram is approximated by an equation of the type N _ref = Ax exp (-nχ χ), or

or

or

or

илиor

or

where a, c are linear dimensions of the defect, ρ _c is the distribution function of c, for example, the normal distribution law,

F is the area of the defect,

- коэффициенты, выбираемые из условия максимального приближения аналитической кривой к экспериментальным данным, при этом

- среднее значение с, а D - дисперсия.n, A, D,

- coefficients selected from the condition of maximum approximation of the analytical curve to the experimental data, while

is the average value of c, and D is the variance.

As the characteristic size, we can take the semi-minor axis a of the ellipse, which schematize the defect, while the ratio a / c is taken constant for all a, based on the condition for the maximum growth rate of the defect under operating conditions; wherein

например, в случае нормального закона, однородного поля напряжений а/с=2, D=a/2, получаем

for example, in the case of a normal law, a uniform stress field a / c = 2, D = a / 2, we obtain

Residual defectiveness is obtained as the difference between N _ref and N _ed. At the same time, N _{obd ed} is determined from the analytical expression N _ex · P _water (χ), i.e. residual defectiveness N _ost can be represented as the equation

в области дефектов, важных для безопасности, определяют в виде числа дефектов в изделии, размеры которых равны или больше критических размеров χ _кр в режиме эксплуатации изделия:Residual

in the field of defects important to safety, they are determined as the number of defects in the product, the dimensions of which are equal to or greater than the critical dimensions χ _cr in the operation mode of the product:

в области дефектов, важных для надежности, определяют в виде числа дефектов, размеры которых превышают размеры дефектов χ _д.э, предельно допустимых в эксплуатации изделия:residual defectiveness

in the field of defects important for reliability, they are determined in the form of the number of defects, the sizes of which exceed the dimensions of the defects χ _doe , the maximum permissible in the operation of the product:

в области дефектов, определяющих качество изготовления, в виде числа дефектов, размеры которых превышают размеры χ _изг допустимых при изготовлении несплошностей:residual defectiveness

defects in determining the workmanship, as the number of defects that are larger than the dimensions χ _mfd permissible in the manufacture of discontinuities:

where χ _before - the maximum possible characteristic size of the defect.

Further, residual defects are divided into a reliable part χ ≤ χ _d in which defects with dimensions χ ≤ χ _d exist reliably, and the probabilistic part χ> χ _d , in which defects with sizes χ> χ _d may or may not exist.

The border between the reliable and probabilistic parts of the residual defect is determined from the condition:

where χ _max - the maximum possible defect sizes in this product.

The value of χ _{d is} compared χ _cr [χ] _d.e [χ] out _, and the results of the comparison make conclusions about the quality, reliability and safety of the product.

The invention is illustrated by the following example.

It is necessary to ensure the quality of two pipelines with an inner diameter of D = 800 mm and a wall thickness of S = 34 mm made of pearlite steel. The critical dimensions of the defects in the transverse welds are shown in figure 2 (curve 1). Permissible defects in operation were determined using the equations of fracture mechanics and safety factors (curve 2 in FIG. 2). Norms of defects in operation are presented in figure 2 of curve 3.

As a result, the NC using the standard method and means before the start of operation (after installation), 47 discontinuities were discovered.

All identified discontinuities (defects) are presented in the form of a histogram in figure 3.

In this case, the defect width in the direction of the wall thickness, or rather, the semi-minor axis of the ellipse, with which all the identified defects were schematized, was chosen as the characteristic size of the defect.

When the ratio a / 0.5 s≈ critical size defect corresponds to α = 15 mm, [α] _d.e = 6 mm, [α] _mfd = 1.15 mm (Figure 2).

Despite the fact that the maximum size of the detected defect was α _max = 13 mm, the abscissa axis contains a critical size of α = 15 mm.

The equation describing the number of detected defects N _OB depending on the size of a:

According to the results of the control, the minimum detected defect had a = 0.6 mm.

To determine the constants A, n, α solve a system of three equations with respect to these constants:

The 1st equation is obtained for a point with coordinates (a = 1 mm, N _obn = 20) of FIG. 3:

20 = A · 1 ^-n [1-exp [-α (1-0.6)]]; (26)

The 2nd equation is obtained for a point with coordinates (a = 5 mm, n _obn = 4) of FIG. 3:

4 = A · 5 ^-n [1-exp [-α (5-0.6)]]; (27)

The 3rd equation is obtained for a point with coordinates (a = 13 mm, n _obn = 0.66 in FIG. 3:

0.66 = A · 13 ^-n [1-exp [-α (13-0.6)]]. (28)

For the 3rd equation, n _obn = 0.66 was obtained as an averaging of the number of detected defects in the range from 11 to 13 mm, which was 2/3, where 2 is the number of detected defects, 3 is the number of intervals.

Finally, the system of equations has the form:

20 = A · [1-exp (-0,4α)]

4 = A · 5 ^-n [1-exp (-4,4α)] (29)

0.66 = A · 13 ^-n [1-exp (-12,4α)]

The solution of the system of equations for A, n, α gave the following results:

A = 1000 mm, n = 2.56, α = 0.05 mm ^-1

Substituting the constants A, n, α in the corresponding equations, we obtain: the equation of the initial defectiveness:

N _ref = 1000a ^-2.56 ; (thirty)

defect detection probability equation:

P _water = 1-exp [-0.05 (a-0.6)]; (31)

residual defectiveness equation

N _ost (χ) = N _ref (χ) -N _obn (χ). (17)

The obtained equations are presented in Fig. 4.

Solve the equation

relative to α _d . Moreover, α _max = S, where S is the thickness of the pipeline wall. The results of the solution are presented in figure 5 in the form of a curve 2.

The value thus determined is a _d = 14 mm.

For the given operating conditions, the fastest increase in the defect area will be ensured at a / s ≅ 0.5. The critical size of the defect will have a _cr = 15.5 mm, which is close to a _d = 14 mm. Given that in operation a defect with a _d = 14 mm can quickly grow to a critical value of 15.4 mm, the operation of the product should be prohibited, despite the fact that all identified defects are repaired and after repair the product meets the quality requirements of the current technical documentation, for example PNAES -7-010-89.

Claims (11)

1. The method of determining the quality of the product, including determining the defectiveness of the product by non-destructive testing, characterized in that they determine the critical dimensions χ _cr defects in the operating mode, the allowable dimensions [χ] _doe defects and the dimensions [χ] _of defects allowed in the manufacture, the control results are presented in the form of a histogram in the coordinates (N _obn , χ), where N _obn is the number of defects detected during the inspection, χ is the characteristic defect size, determine the probability of detection of _water defect P, determine the initial defect N _ref = f (χ), determine the residual defect N _rem = φ (χ) as the difference N _ref and N _obn , residual defect is divided into the reliable part χ ≤ χ _d and the probabilistic part χ> χ _d , where χ - the characteristic size of the defect, x _d - size of de OBJECTS at the boundary between the parts reliable and probability determined from

where χ _max - the maximum possible defect sizes in this product; the value of χ _d compared with χ _cr , [χ] _BC and [χ] _izg and according to the results of comparison make a conclusion about the quality of products and the possibility of its operation. 2. The method according to claim 1, characterized in that the linear size of the defect, or a combination of the linear dimensions of the defect, or the area of the defect, or the volume of the defect, is selected as the characteristic size χ of the defect. 3. The method according to claim 1 or 2, characterized in that approximate the histogram (N _obn , χ) by the equation N _obn (χ) = Ax- ⁿ {1- (1-η) exp [-α (χ-χ ₀ )] - η}, where A, n, α, η are constants, which are determined from the condition of approximation of the equation N _obn (χ) to the control results presented in the form of a histogram, χ ₀ is the minimum defect size available for detection, the initial defectiveness N _ref is determined by the formula: N _ref = Aχ ^-n , and the probability of detecting a _water defect P by the formula: P _water = 1- (1-η) exp [-α (χ -χ ₀ )] - η. 4. The method according to claim 2 or 3, characterized in that the characteristic axis is the semi-axis a of the ellipse by which the defect is schematized, and the a / c ratio is assumed to be constant for all a, determined from the condition of the maximum defect development rate under operating conditions . 5. The method according to any one of claims 1 to 4, characterized in that χ _cr , [χ] _doe and [χ] _exg is determined for a particular product or a group of m of the same type of products, and when monitoring m of the same type of products, all the control results are summarized and presented in the form of a single histogram. 6. The method according to claim 5, characterized in that N _OST is determined in three ranges: residual defectiveness

in the field of defects important to safety, they are determined as the number of defects in the product, the dimensions of which are equal to or greater than the critical dimensions χ _cr in the operation mode of the product:

residual defectiveness

in the region of defects important for reliability, it is determined as the number of defects whose dimensions exceed the dimensions of the defects [χ] _doe maximum permissible in the operation of the product:

residual defectiveness

defects in determining the quality of manufacture, as the number of defects that are larger than the dimensions of [χ] _mfd permissible in the manufacture of discontinuities:

where χ _before - the maximum possible characteristic size of the defect, m is the number of similar products. 7. The method according to any one of claims 3 to 6, characterized in that the minimum defect size χ ₀ , which is available for detection, is determined when setting up the flaw detector used to control the product, or as the minimum defect size that was detected during the control. 8. The method according to any one of claims 3 to 7, characterized in that the constant η is taken equal to 0. 9. The method according to claim 1 or 2, characterized in that they produce a test sample designed to determine the characteristics of non-destructive testing of discontinuities in the product material, control this test sample by the method of non-destructive testing, and control the product, which is performed by the same method, as the control of the test sample, while the test sample is made in the form of the product or its most critical part from the same material and according to the same technology as the product, with randomly located defects with different characteristic dimensions χ, determine the probability of detecting defects _waters P (χ): P _water (χ) = N _{obn. then} (χ) / N _{hall then} (χ), where N _{obn. then} - the number of defects detected during the control of the test sample; N _{Hall then} - the number of defects in the manufacture of the sample, the initial defect is determined as N _ref = N _{obn. ed} / R _water (χ), histogram (N _ref, χ) is approximated by the equation N _ref = f (χ) or N _ref = f (a, c) where a, c - the linear dimensions of the defects, and in the determination of residual defectiveness N _ost value N _{upd. ed} determined from the analytical expression N _{obn. ed} = N _ref · R of _water (χ). 10. The method according to claim 9, characterized in that the test sample contains three groups of defects: defects, the sizes of which lie in the range from the sizes of defects acceptable during operation, to sizes critical for the product in operation; defects, the sizes of which lie in the range from the sizes allowed during the manufacture of the product to the sizes of defects allowed during operation; defects, the sizes of which lie in the range from the minimum dimensions available for detecting defects to the sizes of defects acceptable during manufacture, while the first two types of defects mimic defects of an operational nature, and the third type mimic technological defects, residual defects

in the field of defects important to safety, they are determined as the number of defects in the product, the dimensions of which are equal to or greater than the critical dimensions χ _cr in the operation mode of the product:

residual defectiveness

in the area of defects important for reliability, they are determined as the number of defects whose dimensions exceed the dimensions of the defects χ _doe maximum permissible in the operation of the product:

residual defectiveness

defects in determining the workmanship, as the number of defects that are larger than the dimensions χ _mfd permissible in the manufacture of discontinuities:

where χ _before - the maximum possible characteristic size of the defect. 11. The method according to claim 9 or 10, characterized in that the histogram (N _ref , χ) is approximated by an equation of the type N _ref = A _x exp (-n _xχ ), or N _ref = A _a exp (-n _a a), or N _ref = A _{a, s} exp [-n _{a, s,} (a ² / s)], or N _ref = A _F exp (-nF), or

or N _ref = A _a

, or

or

where a, c are linear dimensions of the defect; F is the area of the defect; n, A are the coefficients selected from the condition of maximum approximation of the analytical curve to the experimental data.

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