Flaw detectors for the production of small pipelines. Pipeline flaw detection - an ultrasonic method for testing pipes, welds and joints

The end of welding work is the beginning of quality control of welded joints. After all, it is clear that the long-term operation of the prefabricated structure depends on the quality of the work performed. Flaw detection of welded seams are methods of control of welded joints. There are several of them, so it is worth understanding the topic thoroughly.

There are visible defects in the weld and invisible (hidden). The first can be easily seen with the eyes, some of them are not very large, but with a magnifying glass it is not a problem to detect them. The second group is more extensive, and such defects are located inside the body of the weld.

Hidden defects can be detected in two ways. The first method is non-destructive. The second is destructive. The first option, for obvious reasons, is used most often.

Non-destructive method for quality control of welds In this category, several methods are used to check the quality of welds.

Visual inspection (external).
Magnetic control.
Radiation flaw detection.
Ultrasonic.
Capillary.
Control of welded joints for permeability.

There are other ways, but they are rarely used.

visual inspection

With the help of an external examination, it is possible to identify not only visible defects in the seams, but also invisible ones. For example, the unevenness of the seam in height and width indicates that there were interruptions in the arc during the welding process. And this is a guarantee that the seam inside has lack of penetration.

How to conduct an inspection.

The seam is cleaned of scale, slag and metal drops.
Then it is treated with technical alcohol.
After another treatment with a ten percent solution of nitric acid. It's called etching.
The surface of the seam is clean and matte. The smallest cracks and pores are clearly visible on it.

Attention! Nitric acid is a material that corrodes metal. Therefore, after inspection, the metal weld must be treated with alcohol.

The loop has already been mentioned. With this tool, you can detect scanty flaws in the form of thin cracks less than a hair thick, burns, small undercuts, and others. In addition, with the help of a magnifying glass, you can control whether the crack is growing or not.

When examining, you can also use a caliper, templates, ruler. They measure the height and width of the seam, its even longitudinal location.

Magnetic control of welds

Magnetic methods of flaw detection are based on the creation of a magnetic field that penetrates the body of the weld. For this, a special apparatus is used, in the principle of operation of which the phenomena of electromagnetism are embedded.

There are two ways to identify a defect within a connection.

With the use of ferromagnetic powder, usually iron. It can be used both dry and wet. In the second case, iron powder is mixed with oil or kerosene. It is sprinkled on the seam, and a magnet is installed on the other side. In places where there are defects, the powder will collect.
With the help of a ferromagnetic tape. It is laid on the seam, and on the other hand, the device is installed. All defects that appear at the junction of two metal blanks will be displayed on this film.

This version of flaw detection of welded joints can be used to test only ferromagnetic joints. Non-ferrous metals, nickel-chromium-plated steels and others are not controlled in this way.

Radiation control

It's basically an x-ray. Expensive devices are used here, and gamma radiation is harmful to humans. Although this is the surest way to detect defects in the weld. They are clearly visible on the film.

Ultrasonic flaw detection

This is another accurate option for detecting flaws in a weld. It is based on the property of ultrasonic waves to be reflected from the surface of materials or media with different densities. If the weld does not have defects inside it, that is, its density is uniform, then sound waves will pass through it without interference. If there are defects inside, and these are cavities filled with gas, then two different media are obtained inside: metal and gas.

Therefore, ultrasound will be reflected from the metal plane of the pore or crack, and will return back, being displayed on the sensor. It should be noted that different flaws reflect waves differently. Therefore, it is possible to classify the result of flaw detection.

This is the most convenient and fastest way to control welded joints in pipelines, vessels and other structures. Its only drawback is the difficulty of decoding the received signals, therefore only highly qualified specialists work with such devices.

Capillary control

Methods for controlling welds by the capillary method are based on the properties of certain liquids to penetrate into the body of materials through the smallest cracks and pores, structural channels (capillaries). Most importantly, this method can control any materials of different density, size and shape. It does not matter if it is metal (black or non-ferrous), plastic, glass, ceramics and so on.

Penetrating liquids seep into any imperfections in the surface, and some of them, such as kerosene, can pass through fairly thick products through and through. And most importantly, the smaller the size of the defect and the higher the absorption of the liquid, the faster the process of detecting the flaw, the deeper the liquid penetrates.

Today, specialists use several types of penetrating liquids.

Penetrants

From English, this word is translated as absorbent. Currently, there are more than a dozen penetrant formulations (water or based on organic liquids: kerosene, oils, and so on). They all have low surface tension and strong color contrast, making them easy to see. That is, the essence of the method is as follows: a penetrant is applied to the surface of the weld, it penetrates inside, if there is a defect, it is painted on the same side after cleaning the applied layer.

Today, manufacturers offer different penetrating fluids with different flaw detection effects.

Luminescent. From the name it is clear that they include luminescent additives. After applying such a liquid to the seam, you need to shine on the joint with an ultraviolet lamp. If there is a defect, then the luminescent substances will shine, and this will be visible.
Colored. Liquids contain special luminous dyes. Most often, these dyes are bright red. They are clearly visible even in daylight. Apply such a liquid to the seam, and if red spots appear on the other side, then the defect is detected.

There is a division of penetrants by sensitivity. The first class is liquids, which can be used to determine defects with a transverse size of 0.1 to 1.0 microns. The second class is up to 0.5 microns. This takes into account that the depth of the flaw should exceed its width by ten times.

You can apply penetrants in any way, today cans with this liquid are offered. They are supplied with cleaners for cleaning the defective surface and a developer, with the help of which the penetration of the penetrant is detected and the pattern is shown.

How to do it right.

The seam and seam areas must be thoroughly cleaned. Mechanical methods cannot be used, they can cause dirt to enter the cracks and pores themselves. Use warm water or soapy water, the last step is cleaning with a cleaner.
Sometimes it becomes necessary to pickle the surface of the seam. The main thing after that is to remove the acid.
The entire surface is dried.
If the quality control of welded joints of metal structures or pipelines is carried out at sub-zero temperatures, then the seam itself must be treated with ethyl alcohol before applying penetrants.
An absorbent liquid is applied, which must be removed after 5-20 minutes.
After that, a developer (indicator) is applied, which draws out a penetrant from defects in the weld. If the defect is small, then you will have to arm yourself with a magnifying glass. If there are no changes on the surface of the seam, then there are no defects.

Kerosene

This method can be designated as the simplest and cheapest, but this does not reduce its effectiveness. It is carried out using this technology.

Clean the joint of two metal blanks from dirt and rust on both sides of the seam.
On the one hand, a chalk solution is applied to the seam (400 g per 1 liter of water). It is necessary to wait for the applied layer to dry.
Kerosene is applied on the reverse side. It is necessary to moisten abundantly in several approaches for 15 minutes.
Now you need to observe the side where the chalk solution was applied. If dark patterns (spots, lines) appear, it means that there is a defect in the weld. These drawings will only expand over time. Here it is important to accurately determine the exit points of kerosene, therefore, after the first application of it to the seam, it is necessary to immediately monitor. By the way, dots and small spots will indicate the presence of fistulas, lines - the presence of cracks. This method is very effective in connection options, for example, pipe to pipe. When welding overlapped metals, it is less effective.

Methods for quality control of welded joints for permeability

Basically, this method of control is used for containers and tanks that are made by welding. To do this, you can use gases or liquids that fill the vessel. After that, excess pressure is created inside, pushing the materials out.

And if there are defects in the places where the containers are welded, then liquid or gas will immediately begin to pass through them. Depending on which control component is used in the verification process, there are four options: hydraulic, pneumatic, pneumohydraulic and vacuum. In the first case, a liquid is used, in the second, a gas (even air), and the third is a combined one. And the fourth is the creation of a vacuum inside the tank, which, through defective seams, will draw coloring substances applied to the outside of the seam into the tank.

With the pneumatic method, gas is pumped into the vessel, the pressure of which exceeds the nominal one by 1.5 times. From the outside, a soapy solution is applied to the seam. Bubbles will show the presence of defects. During hydraulic flaw detection, liquid is poured into the vessel at a pressure 1.5 times higher than the working one, and the near-weld section is tapped. The appearance of liquid indicates the presence of a defect.

These are the options for flaw detection of pipelines, tanks and metal structures today are used to determine the quality of the weld. Some of them are quite complex and expensive. But the main ones are simple, and therefore often used.

Demanded method of control of welded joints - flaw detection of welded seams. This technique provides an impressive service life of products, structures and materials; allows you to maintain their reliability; get an assessment of the properties of parts; determine poor-quality work, etc. Using this technique, the lack of tightness of joints is revealed, the admission of which is strictly prohibited and dangerous.

Flaw detection of pipeline welds and other structures must be carried out immediately after the completion of highly specialized actions without fail. Unlike destructive methods of quality control and verification, these technologies are more popular and more actively distributed everywhere. There are several ways to carry out the procedure, which are determined depending on the object being checked and its features.

Types of verification

Non-destructive testing methods combined into a common group "defectoscopy of welded seams" have become widespread in all branches of work, one way or another connected with welding joints. It is customary to structure the methods into several types.

Visual and measuring control. External inspection, which allows you to determine the presence of defects and identify both external and internal problems. The presence of uncooked places is judged by the unevenness of the folds, the width and height of the seams. To achieve maximum effectiveness, visual control is carried out using a powerful magnifying glass and specialized lighting devices.
Capillary flaw detection of welded seams. A popular control method based on the ability of a liquid to fill the smallest cracks and channels. This system is suitable for all materials and various shapes. Improving the quality of the check is provided by penetrants - substances that can color defects, facilitating the work of specialists.
Magnetic flaw detection of welded seams. A method created on the basis of the characteristics of electromagnetism. Registration of distortions is carried out by creating a magnetic field in a certain place.
Ultrasonic check. The procedure is carried out using devices for ultrasonic flaw detection of welded seams. Specialized sensors allow you to fix wave distortion and determine the location of the problem. Deciphering signals requires a strong theoretical base and extensive practical experience.
radiographic methods. The heart of the technology is the knowledge of the unique features of x-rays and gamma rays, and their penetrating capabilities. This method is the most accurate and reliable of all types of control, but also more expensive.

Flaw detection of welded seams— a mandatory process for efficient, productive and safe activities.

1. INTRODUCTION

1.1. The instruction was developed taking into account the accumulated experience in defectoscopy of bends of unheated pipes of boilers and pipelines in the process of their manufacture, installation and operation. 1.2. With the release of this Instruction, the effect of the "Instruction on the flaw detection quality control of the metal of bends of various standard sizes of unheated pipes of boilers and steam pipelines of live steam and hot reheating of thermal power plants" (M.: SCNTI ORGRES, 1974) is canceled. 1.3. This Instruction was compiled on the basis of experimental and production control of a large number of bends of various sizes of unheated pipes of boilers and steam pipelines that are in operation at power plants of the USSR Ministry of Energy, as well as new pipe bends manufactured by boiler plants, installation and repair enterprises. 1.4. The instruction was developed taking into account the requirements of the Rules of the Gosgortekhnadzor of the USSR, TU-14-3-460-75 "Seamless steel pipes for steam boilers and pipelines. Specifications", OST 108.030.129-79 "Shaped parts and assembly units of station and turbine pipelines of thermal power plants General specifications", GOST 20415-75 "Non-destructive testing. Acoustic methods. General provisions", GOST 21105-75 "Non-destructive testing. Magnetic powder method", OST 108.030.40-79 "Tube elements of heating surfaces. Connecting pipes within the boiler . Collectors of stationary steam boilers. General specifications". 1.5. The Instruction takes into account the recommendations of GOST 14782-76 "Non-destructive testing. Welded seams. Ultrasonic methods", GOST 17410-78 "Seamless cylindrical metal pipes. Method of ultrasonic flaw detection", "Basic provisions for ultrasonic flaw detection of welded joints of boiler units and pipelines of thermal power plants (OP No. 501-CD-75)" (M.: SPO Soyuztekhenergo, 1978). The term of introduction is set from January 1, 1982.

2. GENERAL PROVISIONS

2.1. The instruction defines methods for flaw detection of unheated pipe bends within boilers, steam and hot water station pipelines, pipelines within a turbine and other pipes made of pearlitic class steels with an outer diameter of 57 mm or more, a wall thickness of 3.5 mm or more. The instruction does not apply to cast elbows. (Revised edition, Rev. 1987). 2.2. The instruction is designed to detect defects such as pores, scratches, sunsets, delaminations, cracks*, corrosion pits, shells on the outer and inner surfaces of bends and in their sections. * If it is necessary to detect defects such as transverse cracks, control is carried out according to the method of Appendix 1. 2.3. The volumes and frequency of control of pipeline bends are determined by the relevant instructive documents of the USSR Ministry of Energy and the Ministry of Energy Machinery. 2.4. Control includes: - visual inspection and measurement of ovality; - magnetic particle flaw detection (MPD); - measurement of wall thickness by ultrasonic method; - ultrasonic flaw detection (USD). 2.5. The control of new bends is carried out over the entire surface of the bent section using the methods according to clause 2.4, except for MTD. Pipe bends with a diameter of 273 mm or more are additionally subjected to MPD. 2.6. Bends that are in operation are subject to control by methods according to clause 2.4, except for MTD. Pipe bends with a diameter of 273 mm or more, as well as bends with a diameter of 133 mm or more with an ambient temperature of 450 °C or more, are additionally subjected to MTD. Inspection of bends in operation is carried out on at least two thirds of the bend surfaces, including tension and neutral zones (Fig. 1).

Rice. 1. Sketch of the bend:

1 - controlled surface; 2 - uncontrolled surface; 3 - line of conjugation of the bent section with a straight pipe; I - stretched zone; II, IV - neutral zone; III - compressed zone

2.7. The bends included in the control groups are subjected to all types of control, according to clause 2.4, over the entire surface of the bend (in tension, compression and neutral zones). 2.8. The control of bends according to clause 2.4 (except visual) is carried out by flaw detectorists of at least the 4th category, who have been trained and certified in the prescribed manner according to the "Rules for the control of welded joints in pipe systems of boiler units and pipelines of thermal power plants" (PK-03-TsS-66) and OP No. 501 TsD-75. 2.9. Visual inspection and measurement of out-of-roundness in the factory is performed by inspectors.

3. VISUAL INSPECTION AND MEASUREMENT OF OVALITY

3.1. Visual inspection of the bends is carried out in order to identify defects on the outer surface that are not allowed according to TU-14-3-460-75 for the manufacture of pipes and OST 108.030.129-79 for the manufacture of bends. Visual inspection of the surface is carried out without the use of magnifying devices after stripping, performed for new bends in accordance with OST 108.030.129-79, and for bends in operation, after stripping, performed in accordance with clause 6.16 of this Instruction. 3.2. According to the results of a visual inspection, bends are rejected if films, sunsets, cracks, delaminations, flaws, deep risks and coarse ripples are found on the outer or inner surface. (Revised edition, Rev. 1987). 3.3. Surface defects without sharp corners (dents from scale), small ripples and other small defects due to the production method, which do not prevent inspection, are allowed, with a depth of not more than 5% of the nominal wall thickness, but not more than 2 mm for hot-worked pipes and 0.2 mm for cold and heat-formed pipes with an outer diameter to wall thickness ratio of more than 5 and 0.6 mm; for cold- and heat-formed pipes with a diameter to wall thickness ratio of 5 or less, provided that the wall thickness does not go beyond the nominal allowable values. 3.4. On the concave (compressed) part of the bends, irregularities of the corrugation type are allowed, and in the places of transitions of the bent sections into straight lines, single smooth irregularities are allowed. In this case, the allowable dimensions of corrugations and irregularities are determined by OST 108.030.129-79. 3.5. Out-of-roundness (ovality) control is performed according to OST 108.030.129-79 by measuring the largest and smallest diameters: for bends with a rotation angle equal to or less than 30° - in the middle section; for bends with an angle of rotation of more than 30 ° - at least in three sections, bend; on average and at distances equal to 1/6 of the arc length (but not less than 50 mm) from the beginning and end of the bend, while the ovality of the bend is determined by the maximum of the three measured values. 3.6. At manufacturing plants, out-of-roundness control is performed by direct measurement or by applying non-going templates for each pipe size according to the factory instructions approved by the chief engineer of the factory. 3.7. At repair enterprises and power plants, ovality is determined by direct measurement using micrometric instruments with a division value of not more than 0.01 mm. 3.8. The ovality value is fixed as a percentage for each bend separately and is determined by the formula

Where DMax , Dmin- the largest and smallest outer diameters measured in one section. The value of the ovality of the bends should not exceed the values specified in OST 108.030.129-79. 3.9. The results of measuring the ovality are drawn up in accordance with clause 7 of this Instruction.

4. MAGNETIC POWDER DEFECTOSCOPY (MPD)

4.1. Magnetic particle flaw detection is performed before ultrasonic testing in order to detect surface defects such as cracks, sunsets, ripples, etc. Under operating conditions at a thermal power plant, it is allowed to use ultrasonic testing by surface waves instead of MPD, the methodology of which is described in Appendix 2. Control is performed after cleaning the bend surface in accordance with clause 6.16 of this Instructions. 4.2. Magnetic particle flaw detection is performed in accordance with GOST 21105-75 by the method of circular magnetization by passing current through the controlled part of the product or longitudinal (pole) magnetization by an electromagnet. 4.3. Magnetic particle inspection is carried out according to the method described in Appendix 3. (Revised edition, Rev. 1987). 4.4. Defective places can be selected with a grinding machine and re-inspected by MTD or etching or capillary flaw detection. The decision on the suitability of bends after the removal of defects is made based on the results of measurements of the wall thickness at the sampling site according to clause 5.5. (Revised edition, Rev. 1987) 4.5. The results of the MTD are drawn up in accordance with clause 7 of this Instruction. 4.4, 4.5. (Revised edition, Rev. 1987).

5. ULTRASONIC THICKNESS METERING

5.1. Ultrasonic thickness measurement is performed in order to determine the minimum thickness of the bend wall, including at the sampling sites, if any. 5.2. Ultrasonic thickness measurement of bends is carried out by ultrasonic thickness gauges "Quartz-6", "Quartz-14", "TITs-3" and others in accordance with the Instructions for Use of Instruments with measurement accuracy: ± 0.15 mm for thickness up to 10 mm; ± 0.3 mm - up to 25 mm; ± 0.6 mm - more than 25 mm. It is allowed to perform thickness measurement with UDM-1m and UDM-3 devices according to the method recommended in Appendix 4. Thickness measurements are made after surface preparation in accordance with clause 6.16 of this Instruction. 5.3. Before thickness measurement, the devices must be prepared for operation: set up according to the factory operating instructions for the device and tested on a test sample used for ultrasonic bending of this size (Fig. 2). 5.4. Measurement of the wall thickness of the bend is made on the stretched part along the entire length of the bend. Under the conditions of TPP (installation, incoming inspection), wall thickness measurements are additionally carried out on both neutrals in sections 100-150 mm long, 30-50 mm wide in places where ovality is measured and in one of the straight sections near the bend along the perimeter on a ring 30-50 mm wide . 5.5. For connecting pipelines within the boiler, turbine and station pipelines, the wall thinning value is determined by the formula

Where S- nominal pipe wall thickness; Smin- the minimum wall thickness of the pipe at the bend on the stretched side. Thinning of the wall of bends for pipes made with deviations from the nominal dimensions in thickness should not exceed the values specified in OST 108.030.40-79. (Revised edition, Rev. 1987). 5.6. The results of thickness measurement are drawn up in accordance with clause 7 of this Instruction.

Rice. 2. Test specimen for bend control:

1 - remote risks; 2 - marking

Note. On samples of pipe bends up to 15 mm thick, the upper reflector is located in section II, the lower one - in section I; over 15 mm - the upper and lower reflectors are located in section I. (Revised edition, Rev. 1987).

6. ULTRASONIC DEFECTOSCOPY

6.1. Ultrasonic flaw detection of bends is performed to detect defects both on the inner and outer surfaces, and in the section of the bend without determining the type of defect. 6.2. The most common defects in bends can be: delamination, risks, looseness, corrosion-fatigue cracks, corrosion pits. 6.3. Ultrasonic flaw detection of bends is recommended after visual inspection, measurement of ovality, MPD and wall thickness measurement. 6.4. The quality of the bends is assessed based on a comparison of the parameters of echo signals from a defect and a corner reflector of the notch type on a test specimen of the corresponding size. 6.5. Bend inspection test specimens are made from straight sections of pipe. The material of the samples must match the material of the controlled bend. When testing bends that have been in operation for more than 50 thousand hours, it is recommended to make samples from pipes that have worked for the same period. To adjust the flaw detector on the inner and outer surfaces of the test sample (see Fig. 2), corner reflectors ("notches") are made according to the technology given in Appendix 5 of OP No. 501-PD-75. The dimensions of the corner reflectors and the bend control parameters depending on the wall thickness are given in Table. 1. Table 1

Pipe wall thickness, mm

Corner reflector dimensions ("notches"), mm

Operating frequency, MHz

Emitter diameter, mm

Up to 15.0 incl.

St. 15.0 to 18.0 incl.

St. 18.0 to 22.0 incl.

Note. When inspecting bends with a wall thickness of up to 15.0 mm, it is allowed to use prisms for a frequency of 2.5 MHz with a piezoelectric plate for a frequency of 5.0 MHz. When using piezoplates with a diameter of 8.0 mm (5.0 MHz) in a 2.5 MHz finder prism, it is recommended to use a centering washer made of textolite or getinaks of the appropriate thickness.

(Revised edition, Rev. 1987). The correctness of the manufacture of reflectors is recommended to be checked by the lead impression method. The shape of the print using an instrumental microscope checks the angular and linear dimensions of the reflector. The following tolerances are set for the deviation of the angular and linear dimensions of the reflectors: ± 0.1 mm - along the width and height of the reflector; ±2.0° - by the angle of inclination of the reflecting face. A marking is applied on the sample containing the outer diameter, wall thickness, steel grade, remote risks of the location of the reflecting faces, reflector, reflector area, registration number of the sample according to the logbook. 6.6. For ultrasonic bending, UDM-1M, UDM-3, DUK-66P (DUK-66PM) and other ultrasonic devices equipped with prismatic finders are used. To control bends with a ratio of the nominal wall thickness to the nominal diameter of the pipe less than or equal to 0.1, finders with a prism angle of 40 or 30°, more than 0.1 - 30° are used. 6.7. The control of bends with a diameter of less than 273 mm is carried out with ground-in finders. Before lapping, it is allowed to select the finders according to Appendix 5. It is recommended to choose the optimal angle of the finder's prism from fig. 9. (Revised edition, Rev. 1987). 6.8. To increase the sensitivity of the seeker at a frequency of 5 MHz, it is allowed to improve the attachment of the piezoelectric plate in accordance with Appendix 6. 6.9. The finder is suitable for monitoring if the amplitude values A B echo signal from the top notch of the test piece meet the requirements of Table 2. In this case, the amplitude of the echo signal from the lower notch is set equal to 25 div. scale 1 of the "Distance" regulator in the mode Himp for flaw detectors of the UDM type or 20 dB for flaw detectors with an amplitude scale in decibels. table 2 (Revised edition, Rev. 1987). 6.10. It is recommended to check the quality of the detector operation in the process of adjusting the sensitivity of the flaw detector and control according to Table. 2. 6.11. The flaw detector is adjusted according to the notches made on the outer and inner surfaces of the test sample (see Fig. 2) in accordance with the selected scheme (Fig. 3, a). For ultrasonic bending, a direct and once reflected beam control scheme is used (positions I, II in Fig. 3, a). For ultrasonic testing of bends with a wall thickness of less than 12 mm, it is allowed to use a control scheme with a direct, once and twice reflected beam (positions I, II, III in Fig. 3, a). 6.12. The setting is performed after setting the regulators to the following positions: - for the device of the UDM type: TRC - left, "Power" - right; "Cutoff" - zero; "Type of measurement" - Himp; "Distance, cm" - left; "Sensitivity" - right; "Frequency" - according to Table 1; - for the device DUK-66P: VARU - left; "Cutoff" - zero; "Weakening" - left; "Operating mode" - I; "Frequency" - according to Table 1; "sweep smoothly" - left; "Delay" - "off". When operating with devices such as UDM and DUK-66P, the sound range is set according to Table 3.

Rice. 3. Diagram of flaw detector setup:

a - adjustment according to the test sample; b - flaw detector oscillogram; position of the finder when sounding:

I - notches with a direct beam; II - once reflected beam; III - twice reflected beam; b - angle of inclination of the prism of the finder; a is the angle of entry of the ultrasonic beam; L x- distance from the input point to the notch location plane; A, B - sounding zones (A - for positions I, II; B - for positions II, III) Table 3 (Revised edition, Rev. 1987). 6.13. The sequence of operations when adjusting the flaw detector: - the finder is installed on the test sample and, moving it with reciprocating movements perpendicular to the generatrix, one is convinced of the presence of an echo signal from the lower and upper notches. The sweep speed is set using the "Sweep smoothly" controls so that the echo from the top notch is in the second half of the screen. The position of the echo signal on the scan line is fixed on the screen scale or on a strip of graph paper pasted below the scan line; - set the rejection sensitivity level for defects located in the lower two thirds of the bend section. To do this, the seeker is set to the position of the maximum signal from the lower notch (position I in Fig. 3, a). With a fixed position of the regulator "Distance, cm" - 25 divisions of the scale I (UDM) or "Attenuation" - 20 dB, the signal height is reduced to 10 mm on the device screen by the regulators "Cutoff", "Power", "Sensitivity"; - the controls "Distance, cm" (UDM) or "Attenuation" (DUK) are set to zero with the remaining positions of the other controls unchanged; - set the rejection sensitivity level for defects located in the upper third of the bend section. To do this, the searcher is moved to the position of the maximum signal from the upper notch (position II in Fig. 3, a) and its amplitude is reduced to a height of 10 mm on the screen of the flaw detector using the "Distance, cm" or "Attenuation" controls; - set the control level of sensitivity in accordance with Table 4 and measure the range of the echo signal (nominal height) from the upper and lower notches in millimeters on the screen of the flaw detector. Table 4 (Revised edition, Rev. 1987). 6.14. In the process of setting up the flaw detector, the following control parameters are recorded: - amplitude of the echo signal from the top ( A B) and lower ( A N) notch; - distance of the echo signal from the top ( P V) and lower ( P N) notch. 6.15. Ultrasonic flaw detection of bends is carried out according to a combined scheme with one finder. It is allowed to use a separate-combined control scheme by two seekers. Appendix 7 shows the method of control using an acoustic unit. 6.16. Before ultrasonic testing of bends, preparatory work is carried out in accordance with the requirements of OP No. 501 TsD-75 (clauses 1.4.1; 1.4.2; 1.4.7-1.4.10). In order to ensure the reliability of acoustic contact, the surface of the controlled bend along the entire length (up to the junction with straight sections plus 100 mm) is freed from insulation, peeling scale, dirt, cleaned with metal brushes or sandpaper. To remove dense scale, the use of a thermal method is allowed (see Appendix 3 of OP No. 501 TsD-75). Before inspection, the prepared bend surface is wiped with a rag and covered with a thin layer of contact lubricant (avtol, machine oil). Solidol is not recommended. Surface preparation and removal of contact lubricant after the end of ultrasound is performed by specially assigned personnel. 6.17. Scanning of the bend surface is carried out by reciprocating movements of the finder, oriented perpendicular to the bend generatrix, with simultaneous rotation by 10-15° in both directions relative to its own axis (Fig. 4). In places of increased versus nominal curvature, it is recommended to slightly wiggle the finder relative to the beam entry point in a plane perpendicular to the bend generatrix. 6.18. The control of bends is carried out at the search level of sensitivity, which is set using the "Distance" (UDM) or "Weakening" (DUK-66P) regulators as follows: - when testing new bends: 8 cases. scale H imp (UDM); 8 dB scale "Weakening" (DUK-66P); - when inspecting bends in operation: 5 cases. scale H imp (UDM); 4 dB scale "Weakening" (DUK-66P). (Revised edition, Rev. 1987).

Rice. 4. Bend control scheme:

1 - entry point; 2 - left control; 3 - right control

Note. The control sides are determined in relation to the course of the medium. 6.19. A sign of a defect in the bend metal is the appearance of an echo signal in the scanning area, limited by the working area (see Fig. 3, b): zone A - when inspected by a direct and once reflected beam; zone B - under control by once and twice reflected beam. The appearance of an echo signal near the front edge of the working area (position I in Fig. 3, b) or the rear edge (position III in Fig. 3, b) indicates the location of the defect near the inner surface. The echo signal in the working area (near position II in Fig. 3, b) indicates the location of the defect near the outer surface. In this case, the location of the defect can be established by probing the surface of the bend with a finger dipped in oil. 6.20. When a defect is detected, its location is determined along the perimeter of the bend and the parameters are measured: echo signal amplitude A when inspected from opposite sides and echo signal path P when inspected from opposite sides. The amplitude of the echo signal is measured by reducing the height of the echo signal on the device screen to 10 mm using the "Distance, cm" (UDM) or "Attenuation" (DUK-66P) controller. The measured amplitude values are recorded. The run of the echo signal is measured in millimeters on the scale of the screen at the control sensitivity level (according to Table 4). If the envelopes of echo signals at the search sensitivity level (according to clause 6.18) from two defects are superimposed on one another, then it is considered that one defect has been detected. The location of the defect (defects) along the perimeter of the bend is approximately related to one of the zones - stretched, neutral or compressed. If it is necessary to accurately indicate the location of defects, their coordinates are measured L x relative to the middle of each of the zones during transverse scanning on the right and left (see Fig. 4) after setting the sweep speed recommended in Appendix 8. 6.21. The quality of the bends according to the results of ultrasound is evaluated by two ratings "Fail" (marriage) and "Good". The bend is invalid (rejected) if: - defects are found, the amplitude or range of the echo signal from which is equal to or exceeds the rejection values for the corresponding notch. In this case, defects in the lower two thirds of the bend section are evaluated by a notch on the inner surface of the test sample, the rest - by the upper notch; - a defect was found on the inner surface of the neutral zone, exceeding the control sensitivity level in amplitude (see Table 4). The final assessment of the continuity of the metal of the bend is made after the removal of external defects and repeated ultrasound. The bends are suitable if no defects with rejection signs are found during the control process. In case of difficulties in assessing the defects detected at a frequency of 5 MHz in bends with a wall thickness of up to 15 mm, it is recommended to additionally carry out control at a frequency of 2.5 MHz. If the amplitude of the echo signal from a defect during testing at a frequency of 2.5 MHz exceeds the amplitude of the echo signal from a notch, the defect is considered invalid. (Revised edition, Rev. 1987).

7. REGISTRATION OF TECHNICAL DOCUMENTATION ON THE RESULTS OF DETECTOSCOPY

7.1. According to the results of flaw detection, documentation is drawn up separately for the types of control (see clause 2.4). 7.2. At manufacturing plants, information on each type of control is presented according to the form established at the factory. Documentation can be issued for a group of bends. 7.3. The amount of information in the documents is determined by the types of control. The results of control during the manufacture of bends are presented without deciphering the nature of the defects. When inspecting bends at TPPs, the dimensions and zones of location of defects should be presented. 7.4. The documentation for each type of control indicates: - the date of the control and the number of the conclusion (or log entry); - factory stamp (or number, position at the place of installation) and bend standard size; - steel grade; - place of control (in the workshop, on the plaza, on the boiler, etc.); - name of the document regulating the need and scope of control; - results of control and quality assessment; - surname and signature of the person who carried out the control. The number of the flaw detector certificate (for control at TPP); - surname and signature of the engineer responsible for the control (head of the laboratory, group, etc.). (Revised edition, Rev. 1987). 7.5. The amount of information recorded in the control documents: - when measuring ovality - the type of tool, device; - with MTD - method of magnetization, type (brand) of the device or device; characteristics of the detected defects (sizes and areas of location), method of eliminating defects, dimensions of the sample area; - for ultrasonic thickness measurement - type (brand), serial number of the device, type of finder, frequency of ultrasonic vibrations (except for manufacturers), registration number of the test sample, measurement results (minimum wall thickness in the neutral and stretched zones, straight section near the bend); for ultrasonic testing - flaw detector type (brand) serial number, finder type, prism angle, frequency, piezoplate diameter, finder registration number, test sample registration number, settings according to item 6.14, sizes and location of detected defects. (Revised edition, Rev. 1987). 7.6. An example of drawing up a conclusion on the control of bends is given in Appendix 9.

8. SAFETY PRECAUTIONS

8.1. Persons who have been instructed in safety precautions with registration in a special journal are allowed to work on flaw detection of bends. 8.2. The briefing is carried out within the time limits established by the order for the enterprise (organization). 8.3. In the conditions of a power plant, flaw detection control is carried out by a link consisting of two people (when using circular magnetization - at least three people - one worker and two operators) according to an orderly system of admission to work. 8.4. Before any switching on, the flaw detectors (for ultrasonic testing or MTD) must be reliably grounded with an uninsulated flexible copper wire with a cross section of at least 2.5 mm 2 (for circular magnetization at least 10 mm 2). 8.5. If there are no socket outlets at the workplace with indication of voltage, the connection of flaw detectors to the network and their disconnection from it is carried out by the duty personnel of the electrical department (at the plant - by the electrician on duty). 8.6. Flaw detectorists must work in overalls that do not restrict movement, and headgear. 8.7. It is forbidden to carry out inspections near the place where welding work is being carried out. 8.8. When performing ultrasound, the requirements of occupational health when working with oils must be observed. 8.9. To prevent fire, oily rags should be stored in a metal box.

Attachment 1
METHODOLOGICAL INSTRUCTIONS ON ULTRASONIC BENDING FOR THE PRESENCE OF TRANSVERSAL CRACKS

1. Inspection for transverse cracks is performed after ultrasonic testing in accordance with Section 6 of this Instruction. 2. Ultrasonic echo-pulse flaw detectors UDM-1M, UDM-3, DUK-66P with prismatic detectors according to Table 5 are used for testing. When inspecting bends with a wall thickness of 20 mm or more, flaw detectors must have overlay scales in accordance with clause 1.3.2 of OP No. 501 TsD-75. Table 5 It is allowed to use flaw detectors of other types if there are additional guidelines that take into account the specifics of the equipment. 3. Ultrasonic flaw detection of pipe bends with a diameter of up to 200 mm is carried out with a ground-in finder in accordance with clause 1.4.6 of OP No. 501 TsD-75. 4. The duration of the sweep should be set so that twice the wall thickness of the controlled bend is within the flaw detector screen. The depth gauge is adjusted in accordance with the operating instructions for flaw detectors. 5. The sensitivity of the flaw detector is adjusted: - when testing bends with a thickness of more than 20.0 mm - along a side cylindrical reflector with a diameter of 6 mm at a depth of 44 mm in a standard sample No. 2 according to GOST 14782-76. At the same time, the handles that regulate the sensitivity of the flaw detector and the power of the probing pulse set the maximum amplitude of the echo signal from this reflector at a level of 10 mm across the screen when the attenuator is installed in accordance with Table 1 of OP No. 501 TsD-75 on control points (for UDM flaw detectors) or at the attenuation values corresponding to these points in decibels (for flaw detectors DUK-66P); - when testing bends with a thickness of 5.0 to 20.0 mm - along notches on test specimens for testing welded joints of pipelines without backing rings in accordance with Table 6 and in accordance with clause 2.4 of OP No. 501 TsD-75. In this case, the handles that regulate the sensitivity of the flaw detector and the power of the probing pulse set the maximum amplitude of the echo signal from the notch on the inner surface of the sample at a level of 10 mm on the screen when the attenuator is installed: - 25 mm on the "Distance I" scale in the mode Himp for flaw detectors of UDM type; - 20 dB for flaw detectors DUK-66P. Table 6 6. In the mode of searching for defects, the attenuator is set to the positions: 0-5 div. - for UDM flaw detectors; 0 dB - for flaw detectors DUK-66P. The control is carried out according to the scheme of a direct and once reflected beam. Scanning is carried out along the generatrix of the bend with a transverse step of no more than 5 mm. 7. If an echo signal from a defect is detected, the bends are rejected if: - when inspecting bends up to 20 mm thick, the value of the echo signal amplitude from the defect is equal to or exceeds 15 mm on the "Distance I" scale for UDM flaw detectors or 14 dB for DUK flaw detectors -66P; - when testing bends with a thickness of 20 mm or more, the value of the amplitude of the echo signal from a defect is equal to the value of the control level, determined taking into account the depth of the defect, or exceeds it (on the internal scale 3 for flaw detectors of the UDM type or by 6 dB less than the level value set for given depth on an additional scale on the coordinate ruler of the DUK-66P flaw detector). 8. The results of the control are drawn up in accordance with the requirements of Sec. 7 present Instructions.

Annex 2
METHODOLOGICAL INSTRUCTIONS FOR ULTRASONIC CONTROL OF BENDS BY SURFACE WAVES

1. Surface wave ultrasonic testing is used to detect cracks on the outer surface of the stretched portion of steam pipe bends. 2. Instruments UDM-1M, UDM-3 are used for testing, equipped with non-serial prism finders for a frequency of 1.8 MHz with a prism tilt angle of 68° (Fig. 5), and test samples used for ultrasonic testing (see Fig. 2) . 3. Seeker prisms are made of Plexiglas. The piezoelectric element fastening unit is used from serial prismatic seekers at a frequency of 1.8 MHz. 4. The constancy of the entry point of ultrasound into the metal is achieved using a U-shaped retainer made of a metal plate 1-2 mm thick. The latch is fixed on the prism with screws in the slots of the plate. 5. The flaw detector is adjusted according to the test samples by moving the latch until an echo signal 40 mm high is received on the screen from the upper notch of the established area. The latch is fixed with screws. The location of the echo signal on the device screen is marked with a strobe pulse and is measured by the distance from the finder to the notch ( L x). The maximum signal from the notch and from the defect must be measured at a constant distance of the finder from the notch (for example, 50 mm across the surface). Control is carried out by longitudinal movement of the finder, oriented perpendicular to the generatrix of the bend (Fig. 6). 6. A sign of defects is a series of pulses with a height of more than 10 mm, appearing on the screen of the flaw detector in the control zone. The location of the defects is determined after combining the pulses from the defects with the mark on the screen. In this case, the defect will be located at a distance L x from the seeker. 7. Defective places are polished and again checked by MTD or etching;

Rice. 5. Search head

Rice. 6. Scheme of sounding bends:

1 - creep zone

Annex 3

1. Means for magnetic particle testing 1.1. As magnetizing devices for circular and longitudinal type of magnetization, flaw detectors DMP-ZM, MD-10Ts, MD-50P and other types can be used, providing similar parameters. 1.2. For longitudinal (pole) magnetization, alternating current electromagnets are used with the parameters specified in the "Instructions for the use of portable magnetizing devices for magnetic particle inspection of power equipment parts without surface cleaning" (M.: SPO Soyuztekhenergo, 1978), DME-20Ts and others, ensuring the magnetic field strength in the center of the interpolar space on the product is not lower than the value calculated according to the recommended Appendix 2 of GOST 21105-75 (conditional sensitivity level "B"). Longitudinal magnetization of the pipeline bend section for the presence of transverse defects is allowed to be carried out using a flexible power cable wound on the pipe on both sides of the controlled section. 1.3. The equipment for magnetic particle testing must provide an applied magnetic field strength of at least 30 A/cm for soft magnetic (coercive force N s< 10 А/см, остаточная индукция B r >1 T) steels. 1.4. As an indicator of defects, magnetic powders and pastes are used, which are applied to the controlled surface of the bend in the form of a suspension. The dispersion medium of the suspension is water with anti-corrosion and wetting agents. 1.5. The content of the magnetic powder in 1 liter of the dispersion medium is: black (TU 5-14-1009-79) or colored - 25 ± 5 g magnetic-luminescent - 4 ± 1 g The compositions of the magnetic suspension are given in the recommended Appendix 4 OST 108.004.109-80 "Products and seams of welded joints of NPP power equipment. Methods of magnetic particle control". The viscosity of the dispersion medium should not exceed 30·10 -6 m 2 /s (30cSt) at the control temperature. 2. Control technology 2.1. During magnetic particle testing of pipeline bends, the following operations are performed: preparation of the equipment and the surface of the pipeline bend for testing; magnetization; applying the indicator in the form of powder or suspension to the controlled area; marking of defective places and evaluation of control results. 2.2. Before the control, the operability of the components of the magnetizing device is checked. The operation is performed using the measuring instruments included in the device kit, magnetic field meters and a control sample made in accordance with the recommended Appendix 6 of OST 108.004.109-80, or a cracked sample selected from the number of rejected pipe bends. At the same time, the technological properties of the magnetic suspension are checked on a controlled sample by signs of the presence of a dense powder bead on existing cracks. 2.3. The choice of the value of the applied field for the controlled steel grade is made according to the recommended Appendix 2 of GOST 21105-75 (conditional sensitivity level "B"). When calculating the value of the magnetizing current according to the value of H pr for circular and longitudinal magnetization, one can be guided by the recommendations of Appendix 8 (clauses 2, 3, 4) of OST 108.004.109-80. 2.4. The surface of pipeline bends to be inspected must have a roughness no worse than Ra= 10 µm ( Rz= 40 µm) according to GOST 2789-73. 2.5. The magnetization of the bend is carried out in sections by the method of the applied field. With circular magnetization, the distance l between electrical contacts should be within 70-250 mm; while the width of the control zone should be no more than 0.6 l. 2.6. To detect differently oriented defects, the bend section is magnetized in mutually perpendicular directions. 2.7. The application of the magnetic suspension to the controlled area using the applied field method should stop 2-3 seconds before the field source is turned off. 2.8. Illumination of the controlled surface must be at least 500 lux (when using incandescent lamps). 2.9. The results of the control are evaluated by the presence of a dense roller of magnetic powder on the controlled surface, which is reproduced each time during multiple (2-3 times) checks. 2.10. The results of magnetic particle testing are recorded in a journal (clause 7 of this Instruction), and if necessary, a defective place is photographed or a defectogram is taken using a transparent adhesive tape. The place of the defect is marked with paint, chalk and other means. 2.11. After the control, if necessary, cleaning of the installation sites of electrical contacts is carried out. Annex 3. (Revised edition, Rev. 1987).

Appendix 4
THICKNESS METERING TECHNIQUE USING UDM-1M and UDM-3 DEVICES

1. When measuring the thickness of bends with UDM-1M or UDM-3 devices, the following finders are used: - separate-combined at a frequency of 5 MHz with a thickness of up to 20 mm; - separately-combined (PC) for a frequency of 2.5 MHz with a thickness of 20-45 mm; - direct normal, combined at a frequency of 1.8 (1.25) MHz with a thickness of more than 45 mm. In this case, if normal finders are used, the setting of the depth gauge and thickness measurement is carried out in accordance with the factory operating instructions, when using PC-finders - in accordance with clause 4 of this appendix. 2. Before using flaw detectors with PC-detectors, their suitability is checked, for which the device controls are set to the following positions: - "Power", "Sensitivity", "Sweep smoothly" - extreme right; - "Cut-off", "TRC", "Distance" - extreme left; - "Measurement type" - sweep smoothly; - "Sound range" - 1; - the "Measurement type" switch is set to the "Sweep smoothly" position and the alignment of the leading edges of the probing and strobe pulses is checked. If there are coincidences, the leading edge of the strobe pulse must be between the sweep start point and the leading edge of the probing pulse when the "Distance, cm" control is set to zero. If the pulses are combined, the "Measurement type" switch is switched to the "DN" position and the device is set up. If there is no alignment, the device should be replaced. 3. Adjustment of the flaw detector is carried out using stepped samples made of steel of the same grade as the controlled bend. To control bends with a diameter of up to 133 mm inclusive, samples are made according to Fig. 7, a, for bends with a diameter of more than 133 mm - fig. 7b. The surface of the test specimen shall be marked with the nominal diameter and thickness of the pipe, the steel grade, the numerical values of the step height, and the minimum and maximum wall thicknesses of the specimen. 4. Adjustment of flaw detectors for measuring thickness up to 20 mm is carried out in the following order: - the finder is installed on the step of the test sample with the maximum negative tolerance ( Smin). Regulators "Cutoff" and "Sensitivity" the signal amplitude is reduced to 15-20 mm on the screen of the device; - the "Distance, cm" regulator is set to the mark corresponding to the nominal value of the thickness of the measured step in the appropriate scale; - potentiometer "Begin Du" the leading edge of the strobe pulse is combined with the leading edge of the echo signal; - the finder is mounted on the step of the test piece with the maximum positive tolerance ( SMax). With the "Cutoff" regulator, the elo-signal is increased to a height of 15-20 mm across the screen; - the "Distance, cm" regulator is set to the mark corresponding to the nominal value of the thickness of the measured step in the appropriate scale; - the "End Du" potentiometer combines the leading edges of the strobe pulse and the echo signal. To ensure the required accuracy of adjustment, all of the above operations are repeated several times. 5. Thickness measurement using PC-finders is carried out in the following order: - through a layer of contact lubricant, the finder is applied to the measured surface in such a way that the radiation-reception plane is oriented along the generatrix and there is a clear bottom echo signal; - the "Power" and "Sensitivity" knobs set the height of the echo signal 10-15 mm on the screen of the device; - with the "Distance", cm" regulator, the leading edge of the strobe pulse is combined with the leading edge of the echo signal. The value of the measured thickness is recorded on the scale 1 "Distance, cm".

Rice. 7. Test specimens for thickness measurement of bends with a diameter:

a - up to 133 mm; b - over 133 mm; 1 - marking

Annex 5
PROCEDURE FOR CHECKING THE SUITABILITY OF FINDERS FOR BEND CONTROL

1. The methodology determines the method for selecting seekers by sensitivity and checking the correctness of their grinding in accordance with Table 2. 2. Verification is performed according to a standard sample (GOST 14782-76). In this case, the amplitude of the echo signal from the side drillings of S.O. is measured. N 1 with control sensitivity adjusted by a hole with a diameter of 6 mm at a depth of 44 mm to a given level according to S.O. N 2 in accordance with table.7. Table 7

Nominal frequency of the seeker, MHz

Finder prism angle, deg.

The sensitivity level of the device, configured according to S.O. N 2

Signal amplitude H imp from side drilling С.О. N 1, located at a depth, mm

The difference in the amplitudes of the signals (dB) from side drilling S.O. N 1, located at a depth, mm

St. 3 to 10 incl.

(Revised edition, Rev. 1987). The finder is considered suitable for inspection if the amplitude of the echo signal from side drillings with a diameter of 2 mm C.O. N 1 corresponds to the values of table.7. To measure the amplitude of the echo signal with instruments of the UDM type, the switch "Measurement type" is set to the position " Himp". The amplitude is read on a scale of 1 "Distance, cm", the full value of which is taken equal to 100 cases, " Himp". Measurement of the sensitivity of the seekers is performed with prisms with angles of 30 and 40 ° that are not lapped along the curvature of the bends. If it is necessary to check the sensitivity of the seekers with lapped prisms, the carriage with the piezoelectric plate is moved to a non-lapped prism and the operations listed in paragraph 2 are performed. 3. The working surface of the finders is ground according to the curvature of the pipe as follows: - determine the position of the entry point according to S.O. N 3 GOST 14782-76; - on a sheet of paper depict the full contour of the finder prism on a scale of 1: 1 (Fig. 8), on which the entry point is marked (m ); - according to the graph (Fig. 9) set the value of the optimal angle of the prism (b 0) to control the given size of the bends; - on the contour of the finder (see Fig. 8) draw a straight line ( Kn) at an angle b 0 to the electroacoustic contact surface ( Kl) through the top of the right angle of the rear part of the prism; - at the intersection point B of the specified line with the line dm connecting the center of the piezoelectric plate d with the entry point of the finder m restore the perpendicular; - along the perpendicular from point B lay a segment equal to the radius of curvature of the working surface of the finder R, and from the obtained point 0 draw an arc of a circle abc ;

R = R T ,

Where R T- pipe radius; - the contour obtained as a result of construction is transferred to the prism of the finder; - the prism is filed along the contour, and then rubbed on an emery cloth superimposed on the surface of a test sample of a given size. Example. It is required to control a bend with a diameter of 159 mm and a thickness of 12 mm. The ratio of wall thickness to diameter is 0.075. From the graph in Fig. 9 (solid line) determine that the optimal angle of the prism (which provides an angle of impact with the defect equal to 45°) is 30°. (Revised edition, Rev. 1987).

Rice. 8. Scheme of constructing the working surface of the finder

Rice. 9. Graph for choosing the optimal angles of the prism

Appendix 6
IMPROVEMENT OF THE MOUNTING OF THE PIEZO PLATE

The body of the unit is made of plexiglass according to TU 26-57, TU 1783-53 or class 1 GOST 9389-60. Plexiglas is cut into bars 15 × 15 mm 150-250 mm long and turned on a lathe to a diameter of 10 mm. Further processing is carried out in the following order (Fig. 10, a): - a cylindrical workpiece is machined to a diameter of 9 mm and faceted; - hole 1 is drilled with a drill with a diameter of 5 mm; - cavity 2 is bored to a diameter of 7 mm; - cavity 3 is bored along the diameter of the piezoelectric plate, taking into account its tight fit. After landing the piezoelectric plate on the collar of the cavity 3, the outer edge of the housing must be machined flush with the surface of the piezoelectric plate; - the processed part of the workpiece is cut along the line 4-4; - contact patch 5, spring 6 and piezoelectric plate 7 are inserted inside the housing 4 (see Fig. 10, b);

Fig.10. Mounting point of the piezo plate:

a - manufacturing technology; b - assembly technology

To install the assembly in a standard finder at a frequency of 5 MHz, the tension sleeve of the piezoplate attachment assembly is cut off and a M6x0.75 thread is cut in the central hole. A sketch of the piezoelectric plate attachment point is shown in fig. 11. To improve the reliability of electrical contact, a feeder connector is used, shown in fig. 12.

Rice. 11. Sketch of the piezoplate attachment point:

1 - prism; 2 - carriage; 3 - tension nut; 4 - body; 5 - contact pad; 6 - contact spring; 7 - piezoplate

Rice. 12. Sketch of finder connector:

1 - the central core of the feeder; 2 - insulation of the central core of the feeder; 3 - feeder braid;

4 - feeder insulation; 5 - contact sleeve; 6 - centering washers; 7 - clamping sleeve; 8 - connector body; 9 - connector shank

Appendix 7
BEND CONTROL METHOD USING ACOUSTIC UNIT

1. The acoustic unit (Fig. 13) consists of a housing 1, which contains two seekers 2 placed in a magnetic circuit 3. One of the seekers is fixed in the housing, and the other can move in the slots 4. 2. The operating frequency of the seekers must correspond to the values given in Table 1. 3. Searchers should have the same sensitivity and should not differ from one another in echo signal amplitude by more than 2-3 units. scale "Distance, cm" or 1 dB scale "Attenuation". 4. The angles of the prism of the finders should not differ by more than ±2° from the nominal values determined from the graph (see Fig. 9). 5. Block seekers are switched on according to a separate-combined scheme (clause 3.1, drawing 15, 16 of GOST 14782-76) in accordance with Fig. 14. Bends with a wall thickness of more than 10 mm are controlled by a direct beam (Fig. 14, a), and bends with a wall thickness of up to 10 mm - by a once reflected beam (see Fig. 14, b). 6. Control of bends with the use of an acoustic block is performed by devices such as UDM or DUK. When working with devices of the UDM type, control is carried out in the H imp mode. It is allowed to use devices of other types if there are additional guidelines that take into account the specifics of the equipment. 7. The flaw detector is adjusted according to the test sample after the regulators are set to the following positions: "TRC", "Cutoff" (DUK / 66P) and "TRC", "Cutoff" (UDM) - to the extreme left, "Power" - to the extreme right for all types. Sounding range - "1", regulators "Attenuation" - 4 dB (DUKP), "Distance, cm" (UDM) - 5 div. H imp. 8. The acoustic unit is placed on the test piece and held there by the magnetic circuits. The finder 2 is moved along the guides until an impulse F appears on the device screen, conditionally called "service" and at its maximum value it is fixed with screws 5 of the finder 2 (see Fig. 13). 9. While moving the block over the test piece, receive the signal from the lower reflector F, set the "Distance" or "Attenuation" controls to 25 div. H imp(or 20 dB) and the "Sensitivity" regulator of the UDM type device or "Power" ("Cutoff") of the DUK type device set the echo signal amplitude at a level of 10-15 mm on the device screen. 10. With the sensitivity adjusted, the amplitude is measured from the upper reflector. 11. If the location of the echo signal from the reflector and the "service" pulse coincide, they are separated by moving the finder 2 in one direction or another, after which the amplitude of the echo signal from the reflectors is measured again. 12. The quality of the surface of the controlled bend is assessed by comparing the amplitude of the "service" pulse on the test sample and on two or three sections of the controlled surface. 13. If the amplitude of the "service" pulses on the test sample and on the controlled bend differs by more than 5 divisions. H imp(4 dB) due to exfoliating oxides, poor acoustic contact, roughness, the bend surface is subject to additional cleaning with a file, sandpaper or thermal method. 14. The control of the bends is carried out by moving the block along the surface perpendicular to the generatrix by reciprocating movements. The "service" pulse must be on the screen of the device during the entire time of sounding. If it disappears, it is necessary to establish the cause (bad contact, malfunction of the device, finder, cable, etc.). 15. When an echo signal from a defect is detected, it is evaluated in accordance with paragraphs. 6.20, 6.21 of this Instruction.

Rice. 13. Acoustic block

Rice. 14. Bend control schemes

Annex 8
METHOD FOR ADJUSTING THE SCANNING SPEED OF DEVICES OF THE TYPE UDM AND DUK

1. Adjustment of the scanning speed of the instruments is carried out to establish a correspondence between the values of the distance from the point of entry of the detector to the defect, measured on the scale of the instrument "Distance, cm" and on the surface of the inspected product. The sweep speed when working with prismatic finders is adjusted according to the corner reflectors of the test sample in accordance with the selected control scheme. 2. Adjustment of the sweep speed of the device type UDM is carried out in the following order: - the "Cutoff" and "TRC" regulators are set to the left position, "Power" - to the right; "Type of measurement" - D X; "Frequency" - to the position corresponding to the operating frequency of the selected seeker; - the searcher is installed on the test sample in the position of the maximum signal from the lower reflector (position I in Fig. 3, a); - measure distance with a ruler D X 1 from the point of entry of the finder to the plane in which the reflective surface of the bottom notch is located, and this value is set on the scale "Distance, cm"; - potentiometer "Scale start D X "combine the leading edge of the strobe pulse with the leading edge of the echo signal; - the finder is set to the position of the maximum signal from the upper reflector (position II in Fig. 3, a). The "Sensitivity" regulator reduces the amplitude of the echo signal to 10-15 mm above the scan line; - the ruler measures the distance D X2 from the point of entry of the finder to the reflective surface of the upper notch, and this value is set on the scale "Distance, cm"; - the potentiometer "End of the scale D X "combines the leading edge of the echo signal with the leading edge of the strobe - pulse; - to ensure the accuracy of the adjustment (± 1 mm) all of the above operations should be repeated several times. H imp". To do this, on the UDM screen, mark the location of the echo signals from the upper and lower reflectors. The switch "Measurement type" is switched to the position H imp, and with the "Ultrasound Speed" regulator, the sweep is set such that the echo signals are in the positions fixed during the adjustment of the DX. (Revised edition, Rev. 1987). 3. Adjustment of the sweep speed of the DUK-66P device is carried out in the following order: - the finder is installed on the test sample in the position of the maximum signal from the upper reflector (position II in Fig. 3, a); - measure the distance from the entry point to the reflective surface of the upper notch D X2 with a ruler and mark it on a convenient scale on the screen scale. The scale should be chosen so that the echo signal is in the second third of the scale; - with the "Sweep smoothly" knob, the echo signal from the upper notch is combined with the mark (position I, in Fig. 3, b); - the seeker is set to the position of the maximum signal from the lower reflector (position I in Fig. 3, a); - a ruler measures the distance D X1 from the input point to the plane in which the reflecting surface of the lower notch is located; - on the scale of the screen in the selected scale mark the value D X1; - if the mark D X1 on the screen scale does not coincide with the position of the echo signal from the bottom notch, the device must be replaced.

Appendix 9
METHODOLOGICAL INSTRUCTIONS ON BENDING SPLIT WHEN THE RATIO OF THE WALL THICKNESS TO THE OUTER DIAMETER MORE THAN 0.17

1. To control bends with a ratio of the nominal wall thickness to the nominal outer diameter of more than 0.17, standard piezoelectric transducers with a frequency of 1.8 (1.25) and 2.5 MHz are used, providing an angle of encounter (g) of an ultrasonic beam with a defect equal to 90°. The optimal tilt angles of the prism are selected according to the attached chart (Fig. 15). 2. Adjustment of the flaw detector is carried out according to a test sample made from a straight section of the pipe. The sample material must match the material of the controlled bend (Fig. 16). 2.1. When testing bends with a wall thickness of up to 30 mm, a corner reflector ("notch") is made on the inner surface of a sample of the appropriate size; . 16). 2.2. The dimensions of the corner reflectors and the parameters of the piezoelectric transducer, depending on the wall thickness of the bends, are given in Table. eight.

Rice. 15. Graph for choosing the optimal angles of the prism:

b - prism tilt; g - encounters with a defect; a - input

Note. When the angle of inclination of the prism is less than the 1st critical angle, due to the presence of a curved surface, the longitudinal wave does not play a role and the main one is the transverse (shear) wave.

Rice. 16. Test piece:

R H - nominal radius of the pipe; S H - nominal thickness of the pipe; a - notch height; b - notch width

Table 8 3. Adjustment of the flaw detector is performed in the following order: 3.1. In accordance with the operating instructions for the device, the depth gauge is adjusted by lateral drilling and a notch on the inner surface of the test sample (Fig. 17).

Rice. 17. Setting the depth gauge:

Start, , - end

3.2. The sweep speed is adjusted by smoothly moving the transducer over the sample surface. At the same time, echo signals from the notch and side drilling are found and placed on the device screen, as shown in Fig. 18. The position of the echo signal on the scanning line is fixed on a scale on the instrument screen.

Rice. 18. Sweep speed setting

3.3. Sensitivity setting consists in setting control sensitivity levels: 3.3.1. Search level - at which defects are searched. 3.3.2. Control level - at which the assessment is made of the admissibility of a defect detected on the inner surface of the neutral zone by the amplitude of the echo signal or by the path of the echo signal (nominal height) in any place. 3.3.3. The first rejection level - at which the assessment of the admissibility of a defect found on the inner surface is made, according to the amplitude of the echo signal. 3.3.4. The second rejection level - at which the assessment of the admissibility of a defect found in the upper 3/4 of the section of the bend is made, according to the amplitude of the echo signal. 3.4. The setting of the 1st rejection level of sensitivity is made according to the notch. To do this, by smoothly moving the transducer along the working surface of the sample, the position of the maximum echo signal from the notch is found at a fixed position of the "Distance, cm" regulator - 25 divisions of scale 1 (UDM) or "Attenuation" - 20 dB (DUK). The height of the echo signal is reduced to 10 mm on the instrument screen by the "Cutoff", "Power", "Sensitivity" controls. The control level is 14 dB, or 15 units, the 2nd rejection level is 26 dB, or 35 units. 3.5. The control of bends is carried out at the search level of sensitivity, which is set using the "Distance, cm" or "Weakening" controls as follows: - when testing new bends: 8 divisions of the scale H imp(UDM), 8 dB of the "Attenuation" scale (DUK); - when checking bends in operation: 5 divisions of the scale H imp(UDM), 4 dB of the "Attenuation" scale (DUK). 4. The quality of the bends is evaluated according to the results of ultrasound as follows: "Fail" (marriage) and "Good". Unsuitable (rejection) if: - defects are found on the outer surface of the bend, the amplitude or range of the echo signal from which is equal to or exceeds the 1st rejection level; - a defect was found on the inner surface of the neutral zone of the bend, exceeding the control sensitivity level in amplitude; - in the section of the bend, a defect was found that exceeds the 2nd rejection level of sensitivity in amplitude. The bends are considered fit if no defects with rejection signs are found during the control process. Annex 9. (Introduced additionally, Rev. 1987). Appendix 10 The control was carried out: ultrasonic device UDM-3 (serial number 1705), thickness gauge "Quartz-6" (serial number 1407), magnetic particle device DMP-2 (serial number 1211), micrometric clamp (serial number 325). On the basis of Circular No. T-3/77, in accordance with the "Instruction for the flaw detection of pipeline bends made of pearlite steel (I No. 23 SD-80) (M.: SPO Soyuztekhenergo, 1981) Control was carried out by: Ultrasound - 4th category flaw detector Ivanov I.I. (certificate No. 127-19k), MTD - Ivanov I.I. (magnetization method - circular), Ivanov I.I.

Bend number according to the scheme

Nominal
pipe diameter, mm

Steel grade

Operating parameters of the medium in the bend

Number of starts / including from cold

Ovality measurement, %

Wall thickness measurement, mm

Ultrasonic Inspection and Magnetic Particle Inspection

Control results and locations
zheniya detected-
defects (according to the results of MTD, ultrasound and wall thickness measurements)

Troubleshooting Method

Note -
chanting

Pressure MPa (kgf / cm 2)

Tempera-
tour, °С

Operating time, thousand hours

Straight section ring

stretched zone

Neutral zones

Finder type

Frequency, MHz

Prism angle, deg.

Piezo diameter
plates, mm

Evaluation of control results

Prismatic

On the outer surface of the stretched part of the bend

Removed with a sample size of 21x10x1.0 mm. Left in service

On the inner surface of the right neutral defects And d =32 cases. on a length of 30 mm

Gib replaced

Not conducted

Not carried out

Rejected and replaced

Not carried out

Inadmissible wall thinning

Prismatic

No defects

Signature of the person who carried out the control __________________________ (surname, signature). Signature of the person responsible for control _______________________ (last name, signature) Head of the metal laboratory (site) ______________________ (last name, signature) (Revised edition, Rev. 1987).

Test results

The developed search engine complex hardware (A2075 SoNet,A1550 lntroVisoN, Vector 2008.) was tested in operation both on test samples of pipes and in real conditions on the pipeline in the process of its re-insulation. The results of tests of A2075 SoNet on a test pipe with a diameter of 1420 mm with artificially applied defect models and natural defects are shown in Fig. 4 and in the table,

where the interpretation of the obtained images and conclusions about the detection of defects are given. The pipe is located on the territory of the experimental base (0E6) 000 VNIIGAZ. At the top of fig. 4 shows a diagram of the location of defects and models of defects in the test pipe. Below the scheme is a scan of this pipe with images of defects in the form of spots. The X-axis on the diagram and scan is directed along the pipe axis and is graduated in meters. The Y-axis (Z-axis on the scans) is directed along the circumference of the pipe and has divisions corresponding to the 12-hour system with the origin from the upper generatrix of the pipe. The counting direction along the Y axis is chosen clockwise when viewed from the pipe end on the left in Fig. 4. It can be seen that the positions of defects and models on the diagram and scan image coincide quite well. The shift of all images of the scan image down along the Y axis, relative to the scheme, by approximately 0.5 h is due to the fact that the trajectory of the scanning device was not laid exactly along the upper generatrix of the pipe, but at the position of 11.5 h. It is also seen that concentrated defects in the form of drillings with a diameter of 10 mm to a depth of about half the wall thickness lie at the detection threshold. A transverse cut 260 mm long was not detected due to the fact that for an ultrasonic wave propagating along it, its beginning and end are inhomogeneities of small wave sizes. At the same time, all longitudinal defects in the pipe walls. SCR and longitudinal cut are clearly visible on the scan. Scanogram in fig. 5

received at scanning of a single-seam pipe with a diameter of 1420 mm., which was in long-term operation and cut out of the pipeline due to the appearance of SCC in it. The pipe is located on the territory of DOAO Orgenergogaz. Two SCC zones and many centers of pitting corrosion were found in it, the first SCC zone (its photograph on the left in Fig. 5) contains cracks with a maximum depth of 2 mm. The depth of cracks after their detection by the A1550 IntroVisor was measured with a conventional flaw detector. The opening of cracks is so small that they are almost invisible on the surface of the pipe. This zone has coordinates of 6.75 m along the X axis (along the distance from the start of scanning) and 0.5 m along the Z axis (along the circumference of the pipe). The second SCC zone (Photo in Fig. 5 on the right) is a chain of opened cracks with a total length of about 180 mm and a maximum depth of 7 mm. Its coordinates are: 9.75 m in range and 0.7 m along the circumference of the pipe. The scan also shows the image of a longitudinal weld - 155 m in circumference. Two longitudinal red lines (0 and 23 m) correspond to the beginning and end of the control zone. Tests A2075 SoNet flaw detector scanner in real conditions (Fig. 6)

were carried out on a linear section of a gas pipeline with a diameter of 1220 mm near the city of Ukhta. At the same time, the influence of the quality of pipe stripping, prime residues, rain and snow, adhering soil on the results of control was studied. In addition, the noise immunity of the device was evaluated during testing under conditions of acoustic and electromagnetic interference from a working cleaning machine. On fig. 7

shown scanogram defect-free section of the pipeline without insulation with a pothole on the surface, apparently resulting from a blow with a metal pipe gripper. The pothole is 15 mm long, 5 mm wide and 3 mm deep. It is deviated from the longitudinal axis of the pipe by about 30. The image of the pothole on the scan is clearly visible in the zone with coordinates 1.3 1.4 m in range and 0.39 m along the circumference of the pipe. Images of longitudinal welds at positions 0.75 and 1.25 m around the circumference. The dashed red stripes at the bottom of the scan are images of the signals that have passed around the pipe. All defects found during testing of the scanner - flaw detector A2075 SoNet, were examined in detail using an A1550 IntroVisor tomograph, and their parameters were measured. On fig. eight

A tomogram of the wall (17.2 mm thick) of a main gas pipeline pipe with a diameter of 1420 mm with a corrosion crack 10 mm deep is shown. The vertical coordinate axis on the tomogram is the depth axis, and the horizontal axis coincides with the longitudinal axis of the tomograph antenna array aperture. The control was performed by an antenna array of transverse waves at a frequency of 4 MHz. The crack image on the tomogram is located at a distance of 26 mm from the origin of coordinates, which coincides with the center of the antenna array aperture. The crack is shown by two red spots (Fig. 8). The top spot is caused by the signal from the corner reflector formed by the crack mouth and the outer surface of the pipe. The lower spot at a depth of 10 mm is the result of ultrasound diffraction at the crack tip. Intermediate points of the crack are not visible due to the inner surface of the crack that is mirror-like for ultrasound, which does not give back reflection of signals along trajectories coinciding with the trajectories of propagation of probing signals. As you can see, the operator can measure the real height of cracks directly on the device screen without resorting to scanning. antenna array in the direction perpendicular to the crack, it should be noted that this tomogram was reconstructed using both direct ultrasonic radiation and reflected from the bottom surface of the pipe wall. Tests confirmed the effectiveness of the proposed solutions and demonstrated the high sensitivity of the equipment, its stable operation under the influence of a wide range of adverse factors, noise immunity and the ability to control at distances up to 10 m from the cleaning machine, reliability and sufficient safety margin of mechanical and electronic components. Created flaw detector scanner well compatible with the equipment used in the pipeline re-insulation process and can be introduced into the technological chain. Its scanning device should move directly behind the stripping machine at a distance of 30-40 meters. Then the impact of noise and prime dust on equipment and the operator will be minimal.

Conclusion

1. As a result of research, an innovative combination of NDT methods for diagnosing pipelines during their re-insulation has been proposed and technical tools have been developed that provide a comprehensive solution to this problem.

2. A mobile ultrasonic flaw detector A2075 SoNet has been developed, designed to inspect the base metal of the pipe body with a capacity of up to six linear meters per minute without the use of contact liquids.

3. On-line inspection of suspicious areas detected by a flaw scanner can be performed using a manual multi-channel eddy current flaw detector Vector 2008, which allows visualizing and localizing the location of stress-corrosion cracks.

4. The problem of measuring the depth of stress-corrosion cracks is successfully solved by the A1550 IntroVisor handheld ultrasonic tomograph using phased antenna arrays operating on transverse waves.

5. The practical work of the complex of the created flaw detection equipment confirmed the effectiveness of the proposed methods, the operability of the equipment in difficult climatic and operational conditions and showed the possibility of including the complex in the technological chain of pipeline re-insulation.

b. With a certain refinement and improvement of the developed technical means, they will improve the reliability of pipeline diagnostics and the quality of repair work during a major overhaul, which will invariably entail an increase in the operational reliability of pipelines.

A lot depends on the quality and reliability of pipelines today. These are the productivity of work at enterprises, and the uninterrupted supply of water through the water supply system, and the safe operation of heating mains. In addition, the quality of pipes is very important in oil production and other operations that require the use of pipes. We will talk about the cases in which flaw detection is necessary and how it is carried out in this article.

When is defectoscopy needed?

The main purpose of flaw detection is to check the integrity of pipes without destroying their structure. Such studies are necessary before putting the pipeline into operation, especially if the system will operate under significant pressure, or at high temperatures. In addition, such a study must be carried out periodically after the pipeline is put into operation - this will help determine the condition of the pipes, detect corrosion, and make repairs in time to prevent a rupture.

In addition to checking the pipes themselves, flaw detection of welds is also important. As a rule, in pressurized systems, these are the most vulnerable points. Several non-destructive testing methods are used to check the quality of welds and the integrity of pipes.

Methods of flaw detection

Often, ultrasonic testing is used to check the thickness of pipe walls and the quality of welds. Such a study allows you to identify possible defects without taking the pipeline out of service, which is convenient, since most systems require continuous operation. The use of the ultrasonic method makes it possible to detect a large number of damages, including defects in welds, internal corrosion of pipes, etc.

The eddy current testing method makes it possible to detect microcracks in pipes at their bends even at high surface temperatures. This method of control also does not require the shutdown of the pipeline.

Capillary flaw detection can also be used to determine surface defects in pipes.