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capillary control. Capillary flaw detection. Capillary method of non-destructive testing.

Capillary method for studying defects is a concept that is based on the penetration of certain liquid formulations into the surface layers necessary products carried out by means of capillary pressure. Using this process, you can significantly increase the lighting effects, which are able to determine more thoroughly all the defective areas.

Types of capillary research methods

A fairly common occurrence that can occur in flaw detection, this is not a sufficiently complete identification of the necessary defects. Such results are very often so small that the general visual inspection is not able to recreate all the defective areas of the various products. For example, using such measuring equipment as a microscope or a simple magnifying glass, it is impossible to determine surface defects. This occurs as a result of insufficient contrast in the existing image. Therefore, in most cases, the most qualitative control method is capillary flaw detection. This method uses indicator liquids that completely penetrate the surface layers of the material under study and form indicator prints, with the help of which further registration is carried out visually. You can get acquainted with our website.

Requirements for the capillary method

The most important condition qualitative method detection of various defective violations in finished products by the type of capillary method is the acquisition of special cavities that are completely free from the possibility of contamination, and have additional access to the surface areas of objects, and are also equipped with depth parameters that far exceed their opening width. The values ​​of the capillary method of research are divided into several categories: basic, which support only capillary phenomena, combined and combined, using a combination of several methods of control.

Basic actions of capillary control

Defectoscopy, which uses the capillary method of control, is designed to study the most secretive and inaccessible defective places. such as cracks, various kinds corrosion, pores, fistulas and others. This system is used to correctly determine the location, extent and orientation of defects. Its work is based on the thorough penetration of indicator liquids into the surface and heterogeneous cavities of the materials of the controlled object. .

Using the capillary method

Basic data of physical capillary control

The process of changing the saturation of the picture and displaying the defect can be changed in two ways. One of them involves polishing upper layers controlled object, which subsequently carries out etching with acids. Such processing of the results of the controlled object creates a filling with corrosion substances, which gives a darkening and then development on a light material. This process has several specific restrictions. These include: unprofitable surfaces that can be poorly polished. Also, this method of detecting defects cannot be used if non-metallic products are used.

The second process of change is the light output of defects, which implies their complete filling with special color or indicator substances, the so-called penetrants. Be sure to know that if there are luminescent compounds in the penetrant, then this liquid will be called luminescent. And if the main substance belongs to dyes, then all flaw detection will be called color. This method of control contains dyes only in saturated red shades.

Sequence of operations for capillary control:

Basic capillary methods non-destructive testing subdivided depending on the type of penetrating substance into the following:

· The penetrating solution method is a liquid method of capillary non-destructive testing based on the use of a liquid indicator solution as a penetrating agent.

· The filtering suspension method is a liquid method of capillary non-destructive testing based on the use of an indicator suspension as a liquid penetrating agent, which forms an indicator pattern from filtered particles of the dispersed phase.

Capillary methods, depending on the method of revealing the indicator pattern, are divided into:

· Luminescent method, based on registering the contrast of a visible indicator pattern luminescent in long-wave ultraviolet radiation against the background of the surface of the test object;

· contrast (color) method, based on the registration of the contrast of the color in the visible radiation of the indicator pattern against the background of the surface of the test object.

· fluorescent color method, based on the registration of the contrast of a color or luminescent indicator pattern against the background of the surface of the test object in visible or long-wave ultraviolet radiation;

· brightness method, based on the registration of the contrast in the visible radiation of an achromatic pattern against the background of the surface of the test object.

Always available! Here you can (color flaw detection) at a low price from a warehouse in Moscow: penetrant, developer, cleaner Sherwin, capillary systemsHelling, Magnaflux, ultraviolet lights, ultraviolet lamps, ultraviolet illuminators, ultraviolet lamps and control (standards) for color flaw detection of CD.

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Capillary flaw detection - a flaw detection method based on the penetration of certain liquid substances into the surface defects of the product under the action of capillary pressure, as a result of which the light and color contrast of the defective area increases relative to the undamaged one.

Capillary flaw detection (capillary inspection) designed to detect invisible or poorly visible to the naked eye surface and through defects (cracks, pores, shells, lack of penetration, intergranular corrosion, fistulas, etc.) in test objects, determining their location, extent and orientation along the surface.

indicator liquid(penetrant) is a colored liquid designed to fill open surface defects and the subsequent formation of an indicator pattern. The liquid is a dye solution or suspension in a mixture of organic solvents, kerosene, oils with additives of surface-active substances (surfactants), which reduce the surface tension of water in the defect cavities and improve the penetration of penetrants into these cavities. Penetrants contain colorants (color method) or luminescent additives (luminescent method), or a combination of both.

Purifier– serves to pre-clean the surface and remove excess penetrant

developer called a flaw detection material designed to extract a penetrant from a capillary discontinuity in order to form a clear indicator pattern and create a background that contrasts with it. There are five main types of developers used with penetrants:

Dry powder; - aqueous suspension; - suspension in a solvent; - solution in water; - plastic film.

Devices and equipment for capillary control:

Materials for color flaw detection, Luminescent materials

Sets for capillary flaw detection (cleaners, developers, penetrants)

Pulverizers, Hydropistols

Sources of ultraviolet illumination (ultraviolet lamps, illuminators).

Test panels (test panel)

Control samples for color flaw detection.

The capillary control process consists of 5 stages:

1 - preliminary cleaning of the surface. In order for the dye to penetrate into defects on the surface, it must first be cleaned with water or an organic cleaner. All contaminants (oils, rust, etc.) and any coatings (paintwork, plating) must be removed from the controlled area. After that, the surface is dried so that no water or cleaner remains inside the defect.

2 - application of penetrant. The penetrant, usually red in color, is applied to the surface by spraying, brushing, or immersing the object in a bath for good impregnation and complete penetrant coverage. As a rule, at a temperature of 5 ... 50 ° C, for a time of 5 ... 30 minutes.

3 - removal of excess penetrant. Excess penetrant is removed by wiping with a tissue, rinsing with water, or with the same cleaner as in the pre-cleaning step. In this case, the penetrant should be removed only from the control surface, but not from the defect cavity. The surface is then dried with a lint-free cloth or air jet.

4 - application of the developer. After drying, a developer (usually white) is applied to the control surface in a thin, even layer.

5 - control. The identification of existing defects begins immediately after the end of the developing process. During the control, indicator traces are detected and recorded. The color intensity of which indicates the depth and width of the defect, the paler the color, the smaller the defect. Intense coloration has deep cracks. After the control, the developer is removed with water or a cleaner.

To disadvantages capillary control should be attributed to its high labor intensity in the absence of mechanization, the long duration of the control process (from 0.5 to 1.5 h), as well as the complexity of mechanization and automation of the control process; decrease in the reliability of results at negative temperatures; subjectivity of control - the dependence of the reliability of the results on the professionalism of the operator; limited shelf life of flaw detection materials, dependence of their properties on storage conditions.

The advantages of capillary control are: simplicity of control operations, simplicity of equipment, applicability to a wide range of materials, including non-magnetic metals. Main advantage capillary flaw detection is that with its help it is possible not only to detect surface and through defects, but also to obtain valuable information about the nature of the defect and even some of the reasons for its occurrence (stress concentration, non-compliance with technology, etc.) ).

Flaw detection materials for color flaw detection are selected depending on the requirements for the controlled object, its condition and control conditions. As a parameter of the size of the defect, the transverse size of the defect on the surface of the test object is taken - the so-called width of the defect opening. The minimum value of disclosure of the detected defects is called the lower threshold of sensitivity and is limited by the fact that a very small amount of penetrant, retained in the cavity of a small defect, is insufficient to obtain a contrast indication for a given thickness of the developing agent layer. There is also an upper sensitivity threshold, which is determined by the fact that from wide, but shallow defects, the penetrant is washed out when excess penetrant on the surface is eliminated. The detection of indicator traces corresponding to the above main features serves as the basis for an analysis of the acceptability of a defect in terms of its size, nature, and position. GOST 18442-80 establishes 5 sensitivity classes (according to the lower threshold) depending on the size of the defects

With sensitivity according to class 1, the blades of turbojet engines, sealing surfaces of valves and their seats, metal sealing gaskets of flanges, etc. are controlled (detected cracks and pores up to tenths of a micron). According to the 2nd class, they check the bodies and anti-corrosion surfacing of reactors, the base metal and welded joints of pipelines, bearing parts (detectable cracks and pores up to several microns in size). For class 3, fasteners of a number of objects are checked, with the possibility of detecting defects with an opening of up to 100 microns, for class 4 - thick-walled casting.

Capillary methods, depending on the method of revealing the indicator pattern, are divided into:

· Luminescent method, based on registering the contrast of a visible indicator pattern luminescent in long-wave ultraviolet radiation against the background of the surface of the test object;

· contrast (color) method, based on the registration of the contrast of the color in the visible radiation of the indicator pattern against the background of the surface of the test object.

· fluorescent color method, based on the registration of the contrast of a color or luminescent indicator pattern against the background of the surface of the test object in visible or long-wave ultraviolet radiation;

· brightness method, based on the registration of contrast in the visible radiation of an achromatic pattern against the background of the surface of an object.

PERFORMED: VALUKH ALEXANDER

Capillary control

Capillary method of non-destructive testing

CapillIflaw detectorandI - a flaw detection method based on the penetration of certain liquid substances into the surface defects of the product under the action of capillary pressure, as a result of which the light and color contrast of the defective area increases relative to the undamaged one.

There are luminescent and color methods of capillary flaw detection.

In most cases, according to technical requirements, it is necessary to detect defects so small that they can be noticed when visual control almost impossible to the naked eye. The use of optical measuring instruments, such as a magnifying glass or a microscope, does not make it possible to detect surface defects due to the insufficient contrast of the image of the defect against the background of the metal and the small field of view at high magnifications. In such cases, the capillary control method is used.

During capillary testing, indicator liquids penetrate into the cavities of surface and through discontinuities in the material of the test objects, and the resulting indicator traces are recorded visually or using a transducer.

Control by capillary method is carried out in accordance with GOST 18442-80 “Non-destructive control. capillary methods. General requirements."

Capillary methods are divided into basic, using capillary phenomena, and combined, based on a combination of two or more non-destructive testing methods that are different in physical essence, one of which is capillary testing (capillary flaw detection).

Purpose of capillary inspection (capillary flaw detection)

Capillary flaw detection (capillary inspection) designed to detect invisible or poorly visible to the naked eye surface and through defects (cracks, pores, shells, lack of penetration, intergranular corrosion, fistulas, etc.) in test objects, determining their location, extent and orientation along the surface.

Capillary methods of non-destructive testing are based on capillary penetration of indicator liquids (penetrants) into the cavities of surface and through discontinuities in the material of the test object and registration of the indicator traces formed visually or using a transducer.

Application of the capillary method of non-destructive testing

The capillary method of control is used in the control of objects of any size and shape, made of ferrous and non-ferrous metals, alloyed steels, cast iron, metal coatings, plastics, glass and ceramics in energy, aviation, rocket technology, shipbuilding, chemical industry, metallurgy, construction nuclear reactors, in the automotive, electrical, mechanical engineering, foundry, stamping, instrumentation, medicine and other industries. For some materials and products, this method is the only one for determining the suitability of parts or installations for work.

Capillary flaw detection is also used for non-destructive testing of objects made of ferromagnetic materials, if they magnetic properties, shape, type and location of defects do not allow achieving the required sensitivity according to GOST 21105-87 by the magnetic particle method and the magnetic particle method of control is not allowed to be used according to the operating conditions of the object.

A necessary condition for the detection of defects such as material discontinuity by capillary methods is the presence of cavities free of contaminants and other substances that have access to the surface of objects and a propagation depth that is much greater than their opening width.

Capillary control is also used in leak detection and, in combination with other methods, in monitoring critical objects and objects in the process of operation.

The advantages of capillary methods of flaw detection are: simplicity of control operations, simplicity of equipment, applicability to a wide range of materials, including non-magnetic metals.

The advantage of capillary flaw detection is that with its help it is possible not only to detect surface and through defects, but also to obtain valuable information about the nature of the defect and even some of the reasons for its occurrence (stress concentration, non-compliance with technology, etc.) ).

As indicator liquids, organic phosphors are used - substances that give a bright glow of their own under the action of ultraviolet rays, as well as various dyes. Surface defects are detected using means that allow extracting indicator substances from the cavity of defects and detecting their presence on the surface of the controlled product.

capillary (crack), coming to the surface of the object of control only on one side, is called a surface discontinuity, and connecting the opposite walls of the object of control, - through. If the surface and through discontinuities are defects, then it is allowed to use the terms "surface defect" and "through defect" instead. The image formed by the penetrant at the location of the discontinuity and similar to the shape of the section at the exit to the surface of the test object is called an indicator pattern, or indication.

With regard to a discontinuity such as a single crack, instead of the term "indication", the term "indicator trace" is allowed. Discontinuity depth - the size of the discontinuity in the direction inside the test object from its surface. The discontinuity length is the longitudinal dimension of the discontinuity on the surface of the object. Opening of a discontinuity - the transverse size of a discontinuity at its exit to the surface of the test object.

A necessary condition for reliable detection by the capillary method of defects that have access to the surface of an object is their relative uncontamination with foreign substances, as well as the propagation depth, which significantly exceeds the width of their opening (at least 10/1). A cleaner is used to clean the surface before applying the penetrant.

Capillary methods of flaw detection are divided into on the main, using capillary phenomena, and combined, based on a combination of two or more methods of non-destructive testing, different in physical essence, one of which is capillary.

capillary control. Color flaw detection. Capillary method of non-destructive testing.

_____________________________________________________________________________________

Capillary flaw detection- a flaw detection method based on the penetration of certain contrast agents into the surface defective layers of the controlled product under the action of capillary (atmospheric) pressure, as a result of subsequent processing with a developer, the light and color contrast of the defective area increases relative to the undamaged one, with the identification of the quantitative and qualitative composition of damage (up to thousandths of millimeter).

There are luminescent (fluorescent) and color methods of capillary flaw detection.

Mainly according to technical requirements or conditions, it is necessary to detect very small defects (up to hundredths of a millimeter) and it is simply impossible to identify them with a normal visual inspection with the naked eye. The use of portable optical instruments, for example, a magnifying loupe or a microscope, does not allow revealing surface damage due to insufficient visibility of the defect against the background of the metal and the lack of a field of view at multiple magnifications.

In such cases, the capillary control method is used.

During capillary testing, indicator substances penetrate into the cavities of surface and through defects in the material of the test objects, and as a result, the resulting indicator lines or points are recorded visually or using a transducer.

Control by capillary method is carried out in accordance with GOST 18442-80 “Non-destructive control. capillary methods. General requirements."

The main condition for the detection of defects such as discontinuity of the material by the capillary method is the presence of cavities free from contaminants and other technical substances that have Free access to the surface of the object and the depth of occurrence, several times greater than the width of their opening at the exit. A cleaner is used to clean the surface before applying the penetrant.

Purpose of capillary inspection (capillary flaw detection)

Capillary flaw detection (capillary control) is designed to detect and inspect surface and through defects invisible or poorly visible to the naked eye (cracks, pores, lack of penetration, intergranular corrosion, shells, fistulas, etc.) in controlled products, determining their consolidation, depth and orientation on the surface.

Application of the capillary method of non-destructive testing

The capillary method of control is used in the control of objects of any size and shape, made of cast iron, ferrous and non-ferrous metals, plastics, alloyed steels, metal coatings, glass and ceramics in power engineering, rocket technology, aviation, metallurgy, shipbuilding, chemical industry, in the construction of nuclear reactors, in mechanical engineering, automotive, electrical engineering, foundry, medicine, stamping, instrumentation, medicine and other industries. In some cases, this method is the only one for determining the technical serviceability of parts or installations and their admission to work.

Capillary flaw detection is also used as a non-destructive testing method for objects made of ferromagnetic materials, if their magnetic properties, shape, type and location of damage do not allow achieving the sensitivity required by GOST 21105-87 by the magnetic particle method or the magnetic particle testing method is not allowed to be used according to the technical operating conditions of the object .

Capillary systems are also widely used for tightness control, in conjunction with other methods, in monitoring critical objects and objects in operation. The main advantages of capillary flaw detection methods are: simplicity of operations during testing, ease of handling devices, a wide range of tested materials, including non-magnetic metals.

The advantage of capillary flaw detection is that using a simple control method, one can not only detect and identify surface and through defects, but also obtain them by their location, shape, length and orientation over the surface. full information about the nature of the damage and even some of the reasons for its occurrence (concentration of power stresses, non-compliance with technical regulations during manufacture, etc.).

Organic phosphors are used as developing liquids - substances that have their own bright radiation under the action of ultraviolet rays, as well as various dyes and pigments. Surface defects are detected by means that allow the penetrant to be removed from the cavity of defects and detected on the surface of the controlled product.

Devices and equipment used in capillary control:

Sets for capillary flaw detection Sherwin, Magnaflux, Helling (cleaners, developers, penetrants)
. Spray guns
. Pneumohydroguns
. Sources of ultraviolet illumination (ultraviolet lamps, illuminators).
. Test panels (test panel)
. Control samples for color flaw detection.

The "sensitivity" parameter in capillary method flaw detection

The sensitivity of capillary control is the ability to detect discontinuities of a given size with a given probability when using a specific method, control technology and penetrant system. According to GOST 18442-80, the control sensitivity class is determined depending on the minimum size of the detected defects with a transverse size of 0.1 - 500 μm.

The detection of surface defects with an opening size of more than 500 µm is not guaranteed by capillary inspection methods.

Sensitivity class Defect opening width, µm

II From 1 to 10

III From 10 to 100

IV From 100 to 500

technological Not standardized

Physical bases and technique of the capillary control method

The capillary method of non-destructive testing (GOST 18442-80) is based on the penetration of an indicator substance into a surface defect and is designed to detect damage that has a free exit to the surface of the test item. The color flaw detection method is suitable for detecting discontinuities with a transverse size of 0.1 - 500 microns, including through defects, on the surface of ceramics, ferrous and non-ferrous metals, alloys, glass and other synthetic materials. Found wide application when monitoring the integrity of adhesions and welds.

A colored or coloring penetrant is applied with a brush or sprayer to the surface of the test object. Due to the special qualities that are provided at the production level, the choice physical properties substances: density, surface tension, viscosity, penetrant under the action of capillary pressure, penetrates into the smallest discontinuities that have an open exit to the surface of the controlled object.

The developer, applied to the surface of the test object in a relatively short time after careful removal of the unassimilated penetrant from the surface, dissolves the dye located inside the defect and, due to mutual penetration into each other, “pushes” the penetrant remaining in the defect onto the surface of the test object.

Existing defects are visible quite clearly and contrast. Indicator traces in the form of lines indicate cracks or scratches, individual color dots indicate single pores or exits.

The process of detecting defects by the capillary method is divided into 5 stages (carrying out capillary control):

1. Preliminary cleaning of the surface (use a cleaner)
2. Application of the penetrant
3. Removal of excess penetrant
4. Applying the developer
5. Control

capillary control. Color flaw detection. Capillary method of non-destructive testing.

§ 9.1. General information about the method
The capillary control method (CMC) is based on the capillary penetration of indicator liquids into the cavity of discontinuities in the material of the test object and registration of the resulting indicator traces visually or using a transducer. The method makes it possible to detect surface (i.e., emerging on the surface) and through (i.e., connecting opposite surfaces of the OC walls.) Defects that can also be detected by visual inspection. Such control, however, requires high costs time, especially when revealing weakly disclosed defects, when performing close examination surfaces using magnification. The advantage of KMC is in multiple acceleration of the control process.
Detection of through defects is part of the task of leak detection methods, which are discussed in Chap. 10. In leak detection methods, along with other methods, CMC is used, and the indicator liquid is applied on one side of the OK wall, and recorded on the other. This chapter discusses a variant of CMC, in which the indication is performed from the same surface of the OK, from which the indicator liquid is applied. The main documents regulating the use of CMC are GOST 18442 - 80, 28369 - 89 and 24522 - 80.
The capillary control process consists of the following main operations (Fig. 9.1):

a) cleaning the surface 1 of the OC and the cavity of the defect 2 from dirt, grease, etc. by their mechanical removal and dissolution. This ensures good wettability of the entire surface of the test tube by the indicator liquid and the possibility of its penetration into the defect cavity;
b) impregnation of defects with indicator liquid. 3. To do this, it must well wet the material of the product and penetrate into defects as a result of the action of capillary forces. On this basis, the method is called capillary, and the indicator liquid is called an indicator penetrant or simply a penetrant (from Latin penetro - I penetrate, I get it);
c) removal of excess penetrant from the surface of the product, while the penetrant remains in the defect cavity. For removal, the effects of dispersion and emulsification are used, special liquids are used - cleaners;

Rice. 9.1 - Basic operations for capillary flaw detection

d) detection of the penetrant in the defect cavity. As noted above, this is done more often visually, less often - with the help of special devices - converters. In the first case, special substances are applied to the surface - developers 4, which extract the penetrant from the defect cavity due to sorption or diffusion phenomena. The sorption developer is in the form of a powder or a suspension. All mentioned physical phenomena discussed in § 9.2.
The penetrant impregnates the entire layer of the developer (usually quite thin) and forms traces (indications) 5 on its outer surface. These indications are detected visually. A distinction is made between the luminance or achromatic method, in which the indications have more dark tone compared to white developer; the color method, when the penetrant has a bright orange or red color, and the luminescent method, when the penetrant glows under ultraviolet radiation. The final operation for KMK is the cleaning of OK from the developer.
In the literature on capillary testing, flaw detection materials are designated by indices: indicator penetrant - "I", cleaner - "M", developer - "P". Sometimes after letter designation followed by numbers in brackets or in the form of an index, indicating the peculiarity of the application of this material.

§ 9.2. Basic physical phenomena used in capillary flaw detection
Surface tension and wetting. Most important characteristic indicator liquids is their ability to wetting the material of the product. Wetting is caused by the mutual attraction of atoms and molecules (hereinafter referred to as molecules) of the liquid and solid body.
As is known, forces of mutual attraction act between the molecules of the medium. Molecules inside a substance experience, on average, the same action from other molecules in all directions. Molecules located on the surface are subject to unequal attraction from the side of the inner layers of the substance and from the side bordering the surface of the medium.
The behavior of a system of molecules is determined by the free energy minimum condition, i.e. that part potential energy, which can be converted to work isothermally. The free energy of molecules on the surface of a liquid and a solid is greater than the internal energy when the liquid or solid is in a gas or vacuum. In this regard, they tend to acquire a shape with a minimum outer surface. In a solid body, this is prevented by the phenomenon of form elasticity, while a liquid in weightlessness, under the influence of this phenomenon, acquires the shape of a ball. Thus, the surfaces of a liquid and a solid tend to shrink, and a surface tension pressure arises.
The value of surface tension is determined by the work (at constant temperature) required to form a unit, the area of ​​the interface between two phases in equilibrium. It is often referred to as the surface tension force, lowering the following under this. At the interface, media allocate an arbitrary area. Tension is considered as the result of the action of a distributed force applied to the perimeter of this area. The direction of forces is tangential to the interface and perpendicular to the perimeter. The force per unit length of the perimeter is called the surface tension force. Two equal definitions of surface tension correspond to the two units used to measure it: J/m2 = N/m.
For water in air (more precisely, in air saturated with evaporation from the water surface) at a temperature of 26 ° C normal atmospheric pressure surface tension force σ = 7.275 ± 0.025) 10-2 N/m. This value decreases with increasing temperature. In various gaseous media, the surface tension of liquids practically does not change.
Consider a drop of liquid lying on the surface: a solid body (Fig. 9.2). We neglect the force of gravity. Let us single out an elementary cylinder at point A, where the solid body, liquid and surrounding gas come into contact. Three forces of surface tension act per unit length of this cylinder: solid body - gas σtg, solid body - liquid σtzh and liquid - gas σlg = σ. When the drop is at rest, the resultant of the projections of these forces onto the surface of the solid is zero:
(9.1)
Angle 9 is called the wetting angle. If σtg>σtzh, then it is sharp. This means that the liquid wets the solid (Fig. 9.2, a). The smaller 9, the stronger the wetting. In the limit σtg>σtzh + σ, the ratio (σtg - σtzh)/st in (9.1) is greater than unity, which cannot be, since the cosine of the angle is always modulo less than one. The limiting case θ = 0 will correspond to complete wetting, i.e. spreading of a liquid over the surface of a solid up to the thickness of a molecular layer. If σtzh>σtg, then cos θ is negative, therefore, the angle θ is obtuse (Fig. 9.2, b). This means that the liquid does not wet the solid.


Rice. 9.2. Wetting (a) and non-wetting (b) of the surface with a liquid

Surface tension σ characterizes the property of the liquid itself, and σ cos θ is the wettability of the surface of a given solid body by this liquid. The component of the surface tension force σ cos θ, which “stretches” the drop along the surface, is sometimes called the wetting force. For most well-wetting substances, cos θ is close to unity, for example, for the border of glass with water it is 0.685, with kerosene - 0.90, with ethyl alcohol - 0.955.
Surface cleanliness has a strong influence on wetting. For example, an oil layer on the surface of steel or glass sharply impairs its wettability with water, cos θ becomes negative. The thinnest layer of oil, sometimes remaining on the surface of OK and cracks, greatly interferes with the use of water-based penetrants.
The microrelief of the OC surface causes an increase in the area of ​​the wetted surface. To estimate the contact angle θsh on a rough surface, use the equation

where θ is the contact angle for a smooth surface; α is the true area of ​​the rough surface, taking into account the unevenness of its relief, and α0 is its projection onto the plane.
Dissolution consists in the distribution of molecules of the solute among the molecules of the solvent. In the capillary method of control, dissolution is used when preparing an object for control (to clean the cavity of defects). The dissolution of gas (usually air) collected at the end of a dead-end capillary (defect) in the penetrant significantly increases the maximum penetration depth of the penetrant into the defect.
To assess the mutual solubility of two liquids, the rule of thumb is used, according to which "like dissolves like." For example, hydrocarbons dissolve well in hydrocarbons, alcohols in alcohols, etc. The mutual solubility of liquids and solids in a liquid tends to increase with increasing temperature. The solubility of gases generally decreases with increasing temperature and improves with increasing pressure.
Sorption (from Latin sorbeo - I absorb) is physical and chemical process, as a result of which there is an absorption by any substance of gas, vapor or a dissolved substance from the environment. Distinguish between adsorption - the absorption of a substance on the phase interface and absorption - the absorption of a substance by the entire volume of the absorber. If sorption occurs mainly as a result of the physical interaction of substances, then it is called physical.
In the capillary control method, development mainly uses the phenomenon of physical adsorption of a liquid (penetrant) on the surface of a solid body (developer particles). The same phenomenon causes the deposition on the defect of contrast agents dissolved in liquid base penetrant.
Diffusion (from Latin diffusio - spreading, spreading) - the movement of particles (molecules, atoms) of the medium, leading to the transfer of matter and equalizing the concentration of particles different sort. In the capillary control method, the phenomenon of diffusion is observed when the penetrant interacts with air compressed at the dead end of the capillary. Here, this process is indistinguishable from the dissolution of air in the penetrant.
An important application of diffusion in capillary flaw detection is development using developers such as quick-drying paints and varnishes. The particles of the penetrant enclosed in the capillary come into contact with such a developer (at the first moment - liquid, and after hardening - solid) deposited on the surface of the OK, and diffuse through a thin film of the developer to its opposite surface. Thus, the diffusion of liquid molecules is used here, first through a liquid, and then through a solid body.
The diffusion process is caused by the thermal motion of molecules (atoms) or their associations (molecular diffusion). The rate of transfer across the boundary is determined by the diffusion coefficient, which is constant for a given pair of substances. Diffusion increases with temperature.
Dispersion (from lat. dispergo - I scatter) - fine grinding of a body into environment. Dispersion of solids in a liquid plays an essential role in cleaning the surface from contaminants.
Emulsification (from lat. emulsios - milked) - the formation of a dispersed system with a liquid dispersed phase, i.e. liquid dispersion. An example of an emulsion is milk, which consists of tiny drops of fat suspended in water. Emulsification plays an essential role in cleaning, removal, excess penetrant, preparation of penetrants, developers. Emulsifiers are used to activate emulsification and maintain the emulsion in a stable state.
Surfactants (surfactants) - substances that can accumulate on the contact surface of two bodies (media, phases), lowering its free energy. Surfactants are added to the means for cleaning the surface of OK, injected into penetrants, cleaners, since they are emulsifiers.
The most important surfactants dissolve in water. Their molecules have hydrophobic and hydrophilic parts, i.e. wetted and non-wetted with water. Let us illustrate the action of surfactants when washing off the oil film. Usually water does not wet it and does not remove it. Surfactant molecules are adsorbed on the surface of the film, their hydrophobic ends are oriented towards it, and their hydrophilic ends are oriented towards the aqueous medium. As a result, a sharp increase in wettability occurs, and the fatty film is washed off.
Suspension (from Latin supspensio - I hang) is a coarse-dispersed system with a liquid dispersion medium and a solid dispersed phase, the particles of which are large enough and precipitate or float rather quickly. Suspensions are usually prepared by mechanical grinding and stirring.
Luminescence (from lat. lumen - light) - the glow of certain substances (phosphors), excess over thermal radiation, with a duration of 10-10 s or more. An indication of a finite duration is necessary in order to distinguish luminescence from other optical phenomena, for example, from light scattering.
In the capillary control method, luminescence is used as one of the contrast methods for visual detection of indicator penetrants after development. To do this, the phosphor is either dissolved in the main substance of the penetrant, or the substance of the penetrant itself is a phosphor.
Brightness and color contrasts in KMC are considered from the point of view of the ability of the human eye to fix the luminescent glow, color and dark indications on a light background. All data refer to the eye of an average person, the ability to distinguish the degree of brightness of an object is called contrast sensitivity. It is determined by the change in the reflection coefficient that is visible to the eye. In the color control method, the concept of brightness-color contrast is introduced, which simultaneously takes into account the brightness and saturation of the trace from the defect to be detected.
The ability of the eye to distinguish small objects with sufficient contrast is determined by minimum angle vision. It has been established that an object in the form of a strip (dark, colored or luminescent) can be seen by the eye from a distance of 200 mm when it is minimum width more than 5 microns. Under working conditions, objects are distinguished by an order of magnitude larger - 0.05 ... 0.1 mm wide.

§ 9.3. Capillary flaw detection processes

Rice. 9.3. To the concept of capillary pressure

Filling a through macrocapillary. Let's analyze a well-known experiment from a physics course: a capillary tube with a diameter of 2r is vertically immersed at one end in a wetting liquid (Fig. 9.3). Under the action of wetting forces, the liquid in the tube rises to a height l above the surface. This is the phenomenon of capillary absorption. Wetting forces act per unit length of the meniscus circumference. Their total value Fк=σcosθ2πr. This force is counteracted by the weight of the column ρgπr2 l, where ρ is the density and g is the acceleration due to gravity. In the state of equilibrium σcosθ2πr = ρgπr2 l. Hence the height of the rise of the liquid in the capillary l= 2σ cos θ/(ρgr).
In this example, the wetting forces were considered as being applied to the line of contact between the liquid and the solid (capillary). They can also be considered as the tension force on the surface of the meniscus formed by the liquid in the capillary. This surface is, as it were, a stretched film that tends to shrink. From here, the concept of capillary pressure is introduced, which is equal to the ratio of the force FK acting on the meniscus to the cross-sectional area of ​​the tube:
(9.2)
Capillary pressure increases with increasing wettability and decreasing capillary radius.
A more general Laplace formula for pressure from the tension of the meniscus surface has the form pk=σ(1/R1+1/R2), where R1 and R2 are the radii of curvature of the meniscus surface. Formula 9.2 is used for a round capillary R1=R2=r/cos θ. For slot width b with plane-parallel walls R1®¥, R2= b/(2cosθ). As a result
(9.3)
The impregnation of defects with a penetrant is based on the phenomenon of capillary absorption. Estimate the time required for impregnation. Consider a horizontal capillary tube, one end of which is open and the other is placed in a wetting liquid. Under the action of capillary pressure, the meniscus of the liquid moves towards the open end. Distance traveled l is related to time by an approximate dependence.
(9.4)

where μ is the coefficient of dynamic shear viscosity. It can be seen from the formula that the time required for the penetrant to pass through a through crack is related to the wall thickness l, in which a crack appeared, with a quadratic dependence: it is the smaller the lower the viscosity and the greater the wettability. Orientation curve 1 dependence l from t shown in fig. 9.4. Should have; in mind that when filling with real penetrant; cracks, the noted regularities are preserved only if the penetrant simultaneously touches the entire perimeter of the crack and its uniform width. Failure to comply with these conditions causes a violation of relation (9.4), however, the influence of the noted physical properties of the penetrant on the impregnation time is preserved.

Rice. 9.4. Kinetics of capillary filling with a penetrant:
through (1), dead-end with (2) and without (3) the phenomenon of diffusion impregnation

The filling of a dead end capillary differs in that the gas (air) compressed near the dead end limits the penetrant penetration depth (curve 3 in Fig. 9.4). Calculate the maximum depth of filling l 1 based on the equality of pressures on the penetrant outside and inside the capillary. Outside pressure is the sum of atmospheric R and capillary R to. Internal pressure in the capillary R c is determined from the Boyle-Mariotte law. For capillary constant cross section: p a l 0S= p in( l 0-l 1)S; R in = R a l 0/(l 0-l 1), where l 0 is the total depth of the capillary. From the equality of pressures we find
Value R to<<R a, therefore, the filling depth calculated by this formula is no more than 10% of the total depth of the capillary (task 9.1).
Consideration of filling a dead-end gap with non-parallel walls (simulating real cracks well) or a conical capillary (simulating pores) is more difficult than capillaries of constant cross section. A decrease in the cross section as it fills causes an increase in capillary pressure, but the volume filled with compressed air decreases even faster, so the filling depth of such a capillary (with the same mouth size) is less than that of a capillary of constant cross section (task 9.1).
In reality, the limiting depth of filling a dead-end capillary is, as a rule, greater than the calculated value. This is due to the fact that air compressed near the end of the capillary partially dissolves in the penetrant and diffuses into it (diffusion filling). For long dead-end defects, sometimes a situation favorable for filling occurs when filling begins at one end along the length of the defect, and the displaced air exits from the other end.
The kinetics of motion of the wetting liquid in a dead-end capillary is determined by formula (9.4) only at the beginning of the filling process. Later, when approaching l to l 1, the rate of the filling process slows down, asymptotically approaching zero (curve 2 in Fig. 9.4).
According to estimates, the filling time of a cylindrical capillary with a radius of about 10-3 mm and a depth l 0 = 20 mm to level l = 0,9l 1 no more than 1 s. This is significantly less than the exposure time in the penetrant recommended in control practice (§ 9.4), which is several tens of minutes. The difference is explained by the fact that after the process of fairly fast capillary filling, a much slower process of diffusion filling begins. For a capillary of constant cross section, the kinetics of diffusion filling obeys the laws of the type (9.4): l p= KÖt, where l p is the depth of diffusion filling, but the coefficient To thousands of times less than for capillary filling (see curve 2 in Fig. 9.4). It grows in proportion to the increase in pressure at the end of the capillary pk/(pk + pa). Hence the need for a long impregnation time.
Removal of excess penetrant from the surface of OK is usually performed using a cleaning fluid. It is important to choose a cleaner that would remove the penetrant well from the surface, washing it out of the defect cavity to a minimum extent.
manifestation process. In capillary flaw detection, diffusion or adsorption developers are used. The first are quick-drying white paints or varnishes, the second are powders or suspensions.
The process of diffusion development consists in the fact that the liquid Developer contacts the penetrant at the mouth of the defect and sorbs it. The penetrant diffuses into the developer first - as in a liquid layer, and after the paint dries - as in a solid capillary-porous body. At the same time, the process of dissolution of the penetrant in the developer takes place, which in this case is indistinguishable from diffusion. In the process of impregnation with a penetrant, the properties of the developer change: it becomes denser. If the developer is used in the form of a suspension, then in the first stage of development, diffusion and dissolution of the penetrant in the liquid phase of the suspension occur. After the suspension has dried, the development mechanism described earlier operates.

§ 9.4. Technology and controls
The scheme of the general technology of capillary control is shown in fig. 9.5. Let's take a look at its main steps.

Rice. 9.5. Technological scheme of capillary control

Preparatory operations are aimed at bringing the mouths of defects to the surface of the product, eliminating the possibility of background and false indications, and cleaning the cavity of defects. The method of preparation depends on the condition of the surface and the required sensitivity class.
Mechanical cleaning is carried out when the surface of the Product is covered with scale or silicate. For example, the surface of some welds is coated with a layer of hard silicate "birch bark" flux. Such coatings cover the mouths of defects. Electroplated coatings, films, varnishes are not removed if they crack along with the base metal of the product. If such coatings are applied to parts that may already have defects, then the control is carried out before coating is applied. Cleaning is performed by cutting, abrasive grinding, processing with metal brushes. These methods remove part of the material from the surface of the OK. They cannot clean blind holes, threads. When grinding soft materials, defects can be covered by a thin layer of deformed material.
Mechanical cleaning is called blowing with shot, sand, stone chips. After mechanical cleaning, its products are removed from the surface. Cleaning with detergents and solutions is subjected to all objects entering the control, including those that have undergone mechanical cleaning and cleaning.
The fact is that mechanical cleaning does not clean the cavities of defects, and sometimes its products (grinding paste, abrasive dust) can contribute to their closure. Cleaning is carried out with water with surfactant additives and solvents, which are alcohols, acetone, gasoline, benzene, etc. They are used to remove preservative grease, some paintwork: If necessary, solvent treatment is performed several times.
For a more complete cleaning of the surface of the OC and the cavity of defects, methods of cleaning intensification are used: exposure to organic solvent vapors, chemical etching (helps to remove corrosion products from the surface), electrolysis, heating of the OC, exposure to low-frequency ultrasonic vibrations.
After cleaning, the surface is dried OK. This removes the remnants of washing liquids and solvents from the defect cavities. Drying is intensified by increasing the temperature, blowing, for example, using a jet of thermal air from a hair dryer.
Penetrant impregnation. There are a number of requirements for penetrants. Good wettability of the OK surface is the main one. To do this, the penetrant must have a sufficiently high surface tension and a contact angle close to zero when spreading over the OC surface. As noted in § 9.3, most often, substances such as kerosene, liquid oils, alcohols, benzene, turpentine, which have a surface tension of (2.5 ... 3.5) 10-2 N / m, are used as the basis for penetrants. Less often, water-based penetrants with surfactant additives are used. For all these substances cos θ is not less than 0.9.
The second requirement for penetrants is low viscosity. It is needed to reduce the time of impregnation. The third important requirement is the possibility and convenience of detecting indications. By contrast, the KMC penetrant is divided into achromatic (brightness), color, luminescent and luminescent-color. In addition, there are combined CMCs, in which indications are detected not visually, but with the help of various physical effects. According to the types of penetrants, more precisely, according to the methods of their indication, the KMC is classified. There is also an upper threshold of sensitivity, which is determined by the fact that from wide, but shallow defects, the penetrant is washed out when excess penetrant is removed from the surface.
The sensitivity threshold of a particular selected CMC method depends on the control conditions and flaw detection materials. Five sensitivity classes have been established (according to the lower threshold) depending on the size of the defects (Table 9.1).
To achieve high sensitivity (low threshold of sensitivity), it is necessary to use well-wetting high-contrast penetrants, paint developers (instead of suspensions or powders), increase UV irradiation or illumination of the object. The optimal combination of these factors makes it possible to detect defects with an opening of tenths of a micron.
In table. 9.2 provides recommendations for choosing the method and control conditions that provide the required sensitivity class. Illumination is given combined: the first number corresponds to incandescent lamps, and the second - to fluorescent ones. Positions 2,3,4,6 are based on the use of commercially available sets of flaw detection materials.

Table 9.1 - Sensitivity classes

One should not unnecessarily strive to achieve higher sensitivity classes: this requires more expensive materials, better surface preparation of the product, and increases the inspection time. For example, the application of the luminescent method requires a darkened room, ultraviolet radiation, which has a harmful effect on personnel. In this regard, the use of this method is advisable only when high sensitivity and productivity are required. In other cases, color or the simpler and cheaper luminosity method should be used. The filtered suspension method is the most highly productive. In it operation of manifestation disappears. However, this method is inferior to others in sensitivity.
Due to the complexity of their implementation, combined methods are used quite rarely, only if it is necessary to solve any specific problems, for example, achieving very high sensitivity, automating the search for defects, and testing non-metallic materials.
Checking the sensitivity threshold of the CMC method according to GOST 23349 - 78 is performed using a specially selected or prepared real sample of OK with defects. Samples with initiated cracks are also used. The manufacturing technology of such samples is reduced to causing the appearance of surface cracks of a given depth.
According to one of the methods, the samples are made from sheet alloy steel in the form of plates with a thickness of 3...4 mm. The plates are straightened, ground, nitrided on one side to a depth of 0.3 ... 0.4 mm, and this surface is again ground to a depth of about 0.05 ... 0.1 mm. Surface roughness parameter Ra £ 0.4 µm. Due to nitriding, the surface layer becomes brittle.
The samples are deformed either by tension or by bending (by pressing a ball or cylinder from the side opposite to the nitrided one). The deformation force is gradually increased until a characteristic crunch appears. As a result, several cracks appear in the sample, penetrating to the entire depth of the nitrided layer.

Table: 9.2
Conditions for achieving the required sensitivity

Samples produced in this way are certified. Determine the width and length of individual cracks with a measuring microscope and enter them in the sample form. Attached to the form is a photograph of the sample with indications of defects. Samples are stored in cases to protect them from contamination. The sample is suitable for use no more than 15...20 times, after which the cracks are partially clogged with dry residues of the penetrant. Therefore, the laboratory usually has working samples for everyday use and control samples for arbitration issues. Samples are used to test flaw detection materials for the effectiveness of joint use, to determine the correct technology (impregnation time, development), certification of flaw detectors and determine the lower threshold of CMC sensitivity.

§ 9.6. Objects of control
The capillary method controls products made of metals (mainly non-ferromagnetic), non-metallic materials and composite products of any configuration. Products made of ferromagnetic materials are usually controlled by the magnetic particle method, which is more sensitive, although the capillary method is also sometimes used to control ferromagnetic materials if there are difficulties with the magnetization of the material or the complex surface configuration of the product creates large magnetic field gradients that make it difficult to detect defects. Control by the capillary method is carried out before ultrasonic or magnetic particle control, otherwise (in the latter case) it is necessary to demagnetize the OK.
The capillary method detects only defects that come to the surface, the cavity of which is not filled with oxides or other substances. In order for the penetrant not to be washed out of the defect, its depth must be significantly greater than the opening width. Such defects include cracks, lack of penetration of welds, deep pores.
The vast majority of defects detected during capillary inspection can be detected during ordinary visual inspection, especially if the product is pre-etched (defects turn black) and magnification tools are used. However, the advantage of capillary methods is that when they are used, the angle of view on the defect increases by 10–20 times (due to the fact that the width of indications is greater than that of defects), and the brightness contrast increases by 30–50%. Due to this, there is no need for a thorough inspection of the surface and the inspection time is greatly reduced.
Capillary methods are widely used in power engineering, aviation, rocket technology, shipbuilding, and the chemical industry. They control the base metal and welded joints made of austenitic steels (stainless), titanium, aluminum, magnesium and other non-ferrous metals. Class 1 sensitivity is used to control blades of turbojet engines, sealing surfaces of valves and their seats, metal gaskets of flanges, etc. Class 2 is used to check reactor bodies and anti-corrosion surfacing, base metal and welded joints of pipelines, bearing parts. According to class 3, the fasteners of a number of objects are checked, according to class 4 - thick-walled castings. Examples of ferromagnetic products controlled by capillary methods: bearing cages, threaded connections.


Rice. 9.10. Defects in the shoulder blades:
a - fatigue crack, revealed by the luminescent method,
b - zakov, identified by color method
On fig. 9.10 shows the detection of cracks and shackles on the blades of an aircraft turbine using luminescent and color methods. Visually, such cracks are observed at a magnification of 10 times.
It is highly desirable that the test object has a smooth, for example machined, surface. Surfaces after cold stamping, rolling, argon-arc welding are suitable for testing in classes 1 and 2. Sometimes mechanical treatment is carried out to level the surface, for example, the surfaces of some welded or welded joints are treated with an abrasive wheel to remove the frozen welding: flux, slag between the weld beads.
The total time required to inspect a relatively small object such as a turbine blade is 0.5...1.4 h, depending on the used flaw detection materials and sensitivity requirements. Time spent in minutes is distributed as follows: preparation for inspection 5...20, impregnation 10...30, removal of excess penetrant 3...5, development 5...25, inspection 2...5, final cleaning 0...5. Typically, exposure during the impregnation or development of one product is combined with the control of another product, as a result of which the average time of product control is reduced by 5–10 times. In task 9.2, an example of calculating the time of monitoring an object with a large area of ​​the controlled surface is given.
Automatic control is used to check small parts such as turbine blades, fasteners, ball and roller bearing elements. The installations are a complex of baths and chambers for sequential processing of OK (Fig. 9.11). In such installations, means of intensifying control operations are widely used: ultrasound, temperature increase, vacuum, etc. .

Rice. 9.11. Scheme of an automatic installation for the control of parts by capillary methods:
1 - conveyor, 2 - pneumatic lift, 3 - automatic gripper, 4 - container with parts, 5 - trolley, 6 ... 14 - baths, chambers and furnaces for processing parts, 15 - roller table, 16 - place for inspection of parts UV irradiated, 17 - place for inspection in visible light

The conveyor feeds the parts to the ultrasonic cleaning bath, then to the bath for rinsing with running water. Moisture is removed from the surface of parts at a temperature of 250...300°C. Hot parts are cooled with compressed air. Penetrant impregnation is carried out under the action of ultrasound or in vacuum. The removal of excess penetrant is carried out sequentially in a bath with a cleaning liquid, then in a chamber with a shower unit. Moisture is removed with compressed air. The developer is applied by spraying paint in the air (in the form of fog). Details are inspected at workplaces where UV irradiation and artificial lighting are provided. The responsible inspection operation is difficult to automate (see §9.7).
§ 9.7. Development prospects
An important direction in the development of KMK is its automation. The tools discussed earlier automate the control of the same type of small products. Automation; control of products of various types, including large-sized ones, is possible with the use of adaptive robotic manipulators, i.e. having the ability to adapt to changing conditions. Such robots are successfully used in painting operations, which are in many ways similar to CMC operations.
The most difficult thing to automate is the inspection of the surface of products and the decision on the presence of defects. At present, to improve the conditions for performing this operation, high-power illuminators and UV irradiators are used. To reduce the effect on the controller of UV radiation, light guides and television systems are used. However, this does not solve the problem of full automation with the elimination of the influence of the subjective qualities of the controller on the results of control.
The creation of automatic systems for evaluating the results of control requires the development of appropriate algorithms for computers. The work is carried out in several directions: determination of the configuration of indications (length, width, area) corresponding to unacceptable defects, and correlation comparison of images of the controlled area of ​​objects before and after processing with flaw detection materials. In addition to the marked area, computers in KMC are used to collect and analyze statistical data with the issuance of recommendations for adjusting the technological process, for the optimal selection of flaw detection materials and control technology.
An important area of ​​research is the search for new flaw detection materials and technologies for their application, with the goal of increasing the sensitivity and productivity of testing. The use of ferromagnetic liquids as a penetrant has been proposed. In them, in a liquid base (for example, kerosene), ferromagnetic particles of very small size (2 ... 10 microns), stabilized by surfactants, are suspended, as a result of which the liquid behaves as a single-phase system. The penetration of such a liquid into defects is intensified by a magnetic field, and the detection of indications is possible by magnetic sensors, which facilitates the automation of control.
A very promising direction for improving capillary control is the use of electron paramagnetic resonance. Substances of the type of stable nitroxy radicals have been obtained comparatively recently. They contain weakly bound electrons that can resonate in an electromagnetic field with a frequency from tens of gigahertz to megahertz, and the spectral lines are determined with a high degree of accuracy. Nitroxyl radicals are stable, low toxic, and can dissolve in most liquid substances. This makes it possible to introduce them into liquid penetrants. The indication is based on the registration of the absorption spectrum in the exciting electromagnetic field of the radio spectroscope. The sensitivity of these instruments is very high; they make it possible to detect accumulations of 1012 paramagnetic particles and more. Thus, the issue of objective and highly sensitive means of indication for capillary flaw detection is solved.

Tasks
9.1. Calculate and compare the maximum depth of penetrant filling of a slit capillary with parallel and non-parallel walls. Capillary depth l 0=10 mm, mouth width b=10 µm, kerosene-based penetrant with σ=3×10-2N/m, cosθ=0.9. Atmospheric pressure accept R a-1.013×105 Pa. Diffusion filling is ignored.
Decision. We calculate the filling depth of a capillary with parallel walls using formulas (9.3) and (9.5):

The solution is designed to demonstrate that the capillary pressure is about 5% atmospheric and the filling depth is about 5% of the total capillary depth.
Let us derive a formula for filling a slot with non-parallel surfaces, which has the form of a triangle in cross section. From the Boyle-Mariotte law we find the pressure of air compressed at the end of the capillary R in:

where b1 is the distance between the walls at a depth of 9.2. Calculate the required number of flaw detection materials from the set in accordance with position 5 of Table. 9.2 and time to perform CMC anti-corrosion surfacing on the inner surface of the reactor. The reactor consists of a cylindrical part with a diameter of D=4 m, a height of H=12 m with a hemispherical bottom (welded to the cylindrical part and forms a body) and a lid, as well as four branch pipes with a diameter of d=400 mm and a length of h=500 mm. The time for applying any flaw detection material to the surface is taken to be τ=2 min/m2.

Decision. Calculate the area of ​​the controlled object by elements:
cylindrical S1=πD2Н=π42×12=603.2 m2;
part
bottom and cover S2=S3=0.5πD2=0.5π42=25.1 m2;
nozzles (each) S4=πd2h=π×0.42×0.5=0.25 m2;
total area S=S1+S2+S3+4S4=603.2+25.1+25.1+4×0.25=654.4 m2.

Taking into account that the controlled surface of the hardfacing is uneven, located mainly vertically, we accept the penetrant consumption q=0.5 l/m2.
Hence the required amount of penetrant:
Qp = S q\u003d 654.4 × 0.5 \u003d 327.2 liters.
Taking into account possible losses, re-inspection, etc., we assume that the required amount of penetrant is 350 liters.
The required amount of developer in the form of a suspension is 300 g per 1 liter of penetrant, hence Qpr=0.3×350=105 kg. The cleaner is required 2...3 times more than the penetrant. We take the average value - 2.5 times. Thus, Qoch \u003d 2.5 × 350 \u003d 875 liters. Liquid (eg acetone) for pre-cleaning requires approximately 2 times more than Qoch.
The control time is calculated taking into account the fact that each element of the reactor (housing, cover, branch pipes) is controlled separately. Exposure, i.e. the time the object is in contact with each flaw detection material is taken as the average of the standards given in § 9.6. The most significant exposure for the penetrant. - on average t n=20 min. Exposure or time spent in contact with other flaw detection materials is less than with a penetrant, and it can be increased without compromising the effectiveness of the control.
Based on this, we accept the following organization of the control process (it is not the only possible one). The body and cover, where large areas are controlled, are divided into sections, for each of which the time of applying any flaw detection material is equal to t uch = t n = 20 min. Then the application time of any flaw detection material will be no less than the exposure for it. The same applies to the execution time of technological operations not related to flaw detection materials (drying, inspection, etc.).
The area of ​​such a plot Sch = tch/τ = 20/2 = 10 m2. The inspection time of an element with a large surface area is equal to the number of such areas, rounded up, multiplied by t uch = 20 min.
We divide the body area into (S1 + S2) / Such \u003d (603.2 + 25.1) / 10 \u003d 62.8 \u003d 63 sections. The time required to control them is 20×63 = 1260 min = 21 h.
We divide the cover area into S3 / Such \u003d 25, l / 10 \u003d 2.51 \u003d 3 sections. Control time 3×20=60 min = 1 hour.
We control the nozzles at the same time, i.e., having performed any technological operation on one, we move on to another, after that we also perform the next operation, etc. Their total area 4S4=1 m2 is much less than the area of ​​one controlled area. The inspection time is mainly determined by the sum of the average exposure times for individual operations, as for a small product in § 9.6, plus a relatively short time for applying flaw detection materials and inspection. In total, it will be approximately equal to 1 hour.
The total control time is 21+1+1=23 hours. We assume that the control will require three 8-hour shifts.

UNBRAKABLE CONTROL. Book. I. General questions. Penetrant control. Gurvich, Ermolov, Sazhin.

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