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Ball joints are a very serious element of the front suspension, this is especially true for VAZ classic cars. There are twice as many ball joints there as in front-wheel drive cars (4 pieces), due to which the car becomes more dangerous. After all, if you don’t take care and drive a car whose ball joints have failed, the wheel may simply fall on its side. If you drive at this time, the car will immediately lose control and it will be very, very difficult to stop it. We would like to show you a striking example in the video below, where the ball joint fails and the right wheel of the car simply falls on its side.

Note!
To diagnose ball joints, you will need a mount or a mounting blade or a crowbar; In addition, you will need a very thin stick, either metal or just a twig, but, very importantly, the stick should be smooth, without bends or the like. (It is best to use a 5.6 cm long metal stick). And besides all this, you will also need a ruler and a small knife. Or instead of a stick, ruler and knife, take a good caliper that will replace all these tools!

It all depends on the area where the car is used. If you operate it in very large cities (such as Moscow), in the very center of the city, mostly on ideal roads, or in St. Petersburg, where the roads are clearly not inferior, then you don’t even have to bother with diagnosing the suspension. Just look there once a year or every 100,000 km, check everything and move on. But, basically, Lada cars are used in small towns, villages and similar places where the roads, as they say, leave much to be desired. In this case, diagnostics of the entire suspension as a whole, as well as diagnostics of ball joints, should be performed as often as possible, approximately once every 20,000 km. Or after a good collision into a deep hole at speed. This way, you will always be confident in your car and will not be afraid to use it, since after a thorough check you will know with high accuracy that the suspension is fully operational.

Note!
Few people adhere to this, because every 20,000 km it is quite expensive to look into the car’s suspension for people who drive almost every day, and these 20,000 km will be covered in a very short period. In this case, diagnostics of ball joints can be carried out immediately after a dull knock appears in the front of the car or when hitting a hole. Usually this sound appears when one of the bearings fails, but until you hear this sound, you will not understand whether the ball joints are working correctly or not. Perhaps these knocks can even be imagined. Therefore, to prevent this from happening and to prevent you from just messing with the car’s suspension, take a close look at the video below, which shows a car with a faulty and noisy ball joint.

How to diagnose ball joints on a VAZ 2101-VAZ 2107?

Note!
Ball joints are diagnosed in several ways, the most correct of which is the last (third) method. If you act according to it, you will immediately understand whether the support needs to be replaced or not yet. But there is a big disadvantage in this method, because in order to implement it, you will need to remove the ball joints from the car, and this takes time. Therefore, few people check ball joints for serviceability in this way. On the other hand, if you perform the other two verification methods correctly, they will also give their results. And if the ball joints are very badly damaged, then by checking them in this way, it will also be possible to understand that they are faulty and must be replaced.

Method one (hanging the car and loading the front suspension):

1. First, remove all the nuts securing the wheel to the car, and then raise the car using a jack. As soon as it hangs in the air, completely unscrew the nuts and remove the desired wheel from the car (read the article “”). After the operation has been completed, place planks (indicated by a red arrow) under the lower suspension arm and lower the car on them. After this, you should be able to get the car to rest completely on the suspension, or, to be more precise, on the spring. The part on which the wheel is put on (indicated by the blue arrow) will have to hang in the air. That's all, start checking.

1. To check the ball joints on a car by hanging the car, do the following. To begin, pick up a pry bar (optionally, a crowbar or a mounting blade), and then insert it as shown in the photos below. The large photo shows how to fix the mounting blade when checking the upper ball joint, the small photo shows how to fix it when checking the lower ball joint. The small photo shows little and it is difficult to understand where the mounting blade should be inserted. But when you work with a car live, you will immediately understand everything and, using the spatula as a lever, move it down, then up, then down, then up, etc. During this procedure, do not damage the boot, be careful. If the support is severely damaged, the suspension will move a lot and will move with a little effort. In this case, the ball joints must be replaced.

Note!
This method is best to check only the upper ball joints, because the lower joints are checked a little differently. For more details on how to do this, read Method 2 below!

Method two (checking the lower ball joints using a caliper):

Let's start with the fact that not all car enthusiasts have calipers. If you find yourself in this number, then take a knife, a thin wire and rulers and also start checking. First, you will need to use a 7 mm wrench (or a socket) and use it to completely unscrew the lower plug of the ball joint (indicated by the red arrow). Then insert a caliper into the hole (some calipers have a special thin part) and measure the distance to which it will go. If you can’t insert the caliper (it rests on the ground, for example, but there is no jack) or if you don’t have one, then take a thin wire, push it into the hole until it stops, make a cut with a knife flush with the end of the ball joint and take it out. Then measure the distance from the end of the wire to this cut using a ruler. If this distance is greater than 11.8 mm, then the ball joint must be replaced.

Method three (removing the ball joints and visually inspecting them):

This is the longest method, but you will know for sure whether the ball joints are working properly or whether they already have play and they are all broken. In order to carry out this method, remove the ball joints you need from the car (How to do this, read the article “”), and then carefully inspect the boot of the ball joints. There should be no cracks, breaks or similar defects on it. Then remove the boot completely; Make sure there is lubrication in the ball joint and that there is no water, dirt, etc. in the ball joint. Next, grab the tip of the ball finger with your hand (see photo below) and swing it from side to side. The finger will have to move with the force of the hand, but it will be difficult. If the pin dangles and moves easily, or if you cannot even move it, then the ball joint is considered faulty and must be replaced.

Contact network

Currently, the main part of the supporting structures of the contact network consists of reinforced concrete supports and metal supports on reinforced concrete foundations. Let's consider the diagnostics of reinforced concrete structures.

There are two types of diagnostics of supports: diagnostics of the above-ground part and underground part of the supports. Based on the results of diagnostics of the above-ground part, the bearing capacity of the supports is assessed, the change in which should occur due to the aging of concrete and a decrease in its strength characteristics. Diagnostics of the underground part of the supports is carried out to assess the condition of the wire reinforcement and the level of reduction in bearing capacity due to electrocorrosion of the reinforcement.

Depending on the type of traction current in electrified areas, it is necessary to carry out the following types of diagnostics:

· in AC sections, diagnostics of the overhead part should mainly be carried out. Diagnostics of the underground part can be carried out only in exceptional cases when corrosion damage to concrete in this part is detected;

· in DC areas, it is imperative to carry out diagnostics of both parts of the supports: above-ground and underground.

Diagnostics of the above-ground part of supports can be carried out in two ways: it can be selective or continuous.

Selective diagnostics are carried out to establish the load-bearing capacity of supports, which during operation have developed visible damage in the form of longitudinal cracks, weathering of the surface layer, a network of small cracks, etc., as well as deflections of the cantilever. It is mandatory to check the condition of anchor supports and supports in small radius curves, regardless of the presence of damage on them. The first selective diagnostics must be carried out no later than 3 years after the site is put into operation. Subsequent inspection must take place at least once every three years.

Complete diagnostics of the above-ground part should be carried out 20 years after the start of operation of the site. If the same operating conditions are maintained, the second continuous diagnostic is carried out 10 years after the first. Subsequent examinations are prescribed individually for each area, depending on the condition of the supports, taking into account the data from previous diagnoses.

Degraded supports are identified in several ways. At the first stage, places where corrosion is possible are determined. To do this, measure the average values ​​of the rail-to-ground potentials and the support resistance. By dividing the potential by the resistance, you can obtain the value of the leakage current that would flow through the fittings. In this way, potentially dangerous structures are identified from the point of view of electrocorrosion.

But the danger of electrocorrosion depends not only on the ratio of potential and resistance, but also on the number of aggressive ions in the soil, the duration of the potential, etc. A more reliable assessment of the danger of electrocorrosion using integrating sensors. An integrating sensor is an electrochemical cell of steel in concrete, immersed in the soil and capable of passing current.

The sensor is a concrete parallelepiped with sides 20 x 20 mm and a length of 150 mm with a centrally reinforced steel rod protruding 20 mm above the end face and having a protective layer at the other end face. The electrode is made of wire of the same diameter and class as that used for the manufacture of supports. Before installation in the soil, the device is weighed to the nearest 0.01g. The number of installed integrating electrocorrosion sensors depends on the path profile and measurement of soil parameters (on average after 1.5...2 km). The steel rod of each sensor is connected to the rails. After a specified period of time (3–4 months), the sensors are removed and weighed again. Based on the results of the initial weighing and weighing after electrochemical action, metal losses are determined and the specific metal removal in g/dm 2 days is calculated for each sensor. Electrocorrosion diagrams are calculated based on Faraday's law.

To diagnose the degree of electrocorrosion of the reinforcement of reinforced concrete supports, the ADO-2M, “Diakor”, IDA-2 devices, and the “PK-1M” device are used.

When using the PK-1M device, it is necessary to clean the descent (above the protective device) and the base of the rail or the butt connector. Then you need to connect the connector of the “Rail” device using a cable to the rail, connecting the rail clamp to the base of the rail or to the butt connector. Next, you need to connect the connector of the “Descent” device to the grounding connection of the support above the protective device. All connections and cleaning should be carried out using dielectric gloves. Next, turn on the power of the device and take measurements. Measurements are carried out only when there is a load. Technical characteristics of the device: range of measured potentials -250 - +250V; range of measured resistances 0 – 100 kOhm; measurement accuracy – 5%. The device contains a memory block for storing the results of examining 1000 support resistances and 250 potential diagrams.

ADO-2M uses two methods - electrochemical and vibration. The electrochemical method is designed to assess the condition of high-strength wire reinforcement of prestressed supports. The method can be used to determine whether there is or is not corrosion of rods or anchor bolts. With the electrochemical method, the support reinforcement is polarized from a current source from 0 to 1.5 A for a specified period of time (Fig. 50). Then the current source is turned off with switch S2, and a voltmeter with a measuring range of ±1.99 V is connected to the reinforcement. The degree of corrosion is determined by the rate of decrease in the potential of the reinforcement.

The fact is that the potential of reinforcement depends on the state of its surface; passive steel is highly polarized.

If the surface of the reinforcement has traces of corrosion, then its potential decreases. The armature can be pre-polarized, therefore, to eliminate errors, measurements are carried out twice, changing the sign of polarization with switch S1. To measure an unknown potential, one pole of the voltmeter is connected to a zero element (NE), which is immersed in the ground. The zero element has a known constant potential.

The disadvantage of this method is the need to connect to the fittings, which is not always easy to do. In addition, the polarization current must be significant, which is why the ADO-2M power supply has a large mass (8...10 kg).

Rice. 50. Electrochemical method

The vibration method (Fig. 51) is based on the dependence of the decrement of damped vibrations of the support on the degree of corrosion of the reinforcement. The support is set into oscillatory motion, for example, using a guy rope and a release device, which is calibrated for a given force. A vibration sensor, for example an accelerometer, is installed on the support. The decrement of damped oscillations is defined as the logarithm of the ratio of the oscillation amplitudes:

where A 2 A 7 are the amplitudes of the second and seventh oscillations, respectively.

Rice. 51. Vibration method

ADO-2M devices measure vibration amplitudes of 0.01...2 mm with a frequency of 1...3 Hz. The greater the degree of corrosion, the faster the vibrations die out.

The disadvantage of the method is that the vibration decrement largely depends on the soil parameters, the method of embedding the support, deviations in the manufacturing technology of the support, and the quality of the concrete. The noticeable influence of corrosion appears only with significant development of the process.

ADO-2M can also be used to measure rail-ground potentials (up to 2000 V), support resistances, checking spark gaps and diode grounding conductors, and searching for low-resistance supports in group groundings.

The operating principle of the combined device for diagnosing the corrosion state of supports (DIACOR) is based on the electrochemical method. When diagnosing, the current density is 2.5 μA/cm 2, the polarization duration is up to 5 minutes. During this time, the potential of the reinforcement of a serviceable support should rise to 0.6...0.7 V. If the measured value is less than 0.6 V, then a diagnosis of “corrosion” is made. In alternating and cathode zones, the source power is not enough to polarize the reinforcement. There it is proposed to use a pin grounding switch and double the supply voltage.

To diagnose support reinforcement, an IDA-2 flaw detector is used. The operation of the IDA-2 inductive flaw detector of reinforcement is based on the method of measuring the inductance of a coil when steel is introduced into it (Fig. 52).

Rice. 52. Inductive flaw detector of fittings

An inductive coil inserted into one of the arms of the bridge, powered by a measuring generator, is applied to the above-ground and underground parts of the support. The total resistance of the coil depends on the amount of reinforcement metal.

The advantage of this method is that the mass of metal in the above-ground and underground parts is directly compared. The disadvantages are the need to excavate the supports and the fact that the readings of the device depend on fluctuations in the thickness of the protective layer of concrete.

The thickness of the protective layer of concrete with a constant mass of reinforcement and the position of the reinforcement can be determined using IZ devices. The IZS-10N plastic case contains magnets and a movable frame, on the axis of which there is an arrow-pointer and a magnet. The presence and location of reinforcing elements is determined by moving the device along the surface of the structure. The thickness of the protective layer is determined by a calibration curve, the number of which depends on the diameter of the reinforcement.

The IZS-10N device consists of an alternating voltage generator, an autonomous power supply, an inductive sensor, a detector and a pointer device. Its action is based on the same principle as the action of IDA-2. Two measurements are taken: when the sensor axis coincides with the direction of the reinforcement and at a right angle. Thickness measurement range - 5...60 mm, reinforcement diameter - 4...8 mm class A-1 and 10...32 mm class A-1P.

The device provides:

· measuring the thickness of the protective layer of concrete over reinforcing bars 4, 5, 6, 8, 10, 12, 14, 16, 18, 20...25, 28...32 mm;

· measurement of the thickness of the protective layer of concrete depending on the diameter of the reinforcement bars within the following limits: with a diameter of 4 ... 10 mm - from 5 to 30 mm; with a diameter of 12 ... 32 mm - from 10 to 60 mm;

· determination of the location of projections of reinforcement bars on the concrete surface: with a diameter of 12...30 mm - with a thickness of the protective layer of concrete of no more than 60 mm; with a diameter of 4 ... 10 mm - no more than 30 mm.

Measurement error 5%, weight - 4.2 kg.

The IZS-10N device is also used to determine the types of supports. To do this, the diameter indicator on the front panel of the device is set to number 4, and the transducer moves along the circumference of the support. If the instrument readings change from 3-4 mm to 10-15 mm, then this indicates that this rack is of the RCC type (with rod reinforcement). If the arrow of the device points to 15-18 mm, then this indicates that this rack is of the type SZhBK, SK (pre-stressed).

The strength of concrete is determined by the ultrasonic method using the Beton-5, UKV-1M and UK-12P devices. To ensure reliable acoustic contact between concrete and the working surfaces of ultrasonic transducers, grease and technical petroleum jelly are used. This method allows you to determine the depth of propagation of cracks in concrete, the sizes of cavities and zones of uncompacted concrete.

Ultrasonic devices UK-1401 (UK-14PM) are designed to measure the time and speed of propagation of longitudinal ultrasonic waves in solid materials when sounded on a fixed base in order to determine the strength and integrity of reinforced concrete supports of the contact network. Sounding base - 150 mm, time measurement range - 15... 70 μs; time measurement discreteness - 0.1 μs; sound speed measurement range - 2150 ... 9900 m/s. Usually two measurements are taken - along and across the body of the support.

Areas of use:

· determination of concrete strength by ultrasonic speed according to GOST 17624-87 “Concrete. Ultrasonic method for determining strength";

· determination of the strength of concrete in operating structures in combination with the “separation with chip” method;

· assessment of the load-bearing capacity of concrete supports and pillars made of centrifuged concrete through the ratio of the speeds of ultrasound propagation in the directions along and across the support;

· search for near-surface defects in concrete structures by an abnormal decrease in speed or increase in the propagation time of ultrasound in a defective area compared to areas without defects;

· assessment of the similarity or difference in the elastic properties of materials or samples of the same material from each other, as well as the age of the material, subject to changes in its properties over time.

The order of measurements is as follows:

· inspect the outer surface of the support, establish any existing damage, their quantity, location;

· determine measurement areas. The number of these areas depends on the type of rack and the degree of damage. For SRC-type racks that do not have holes in the top part, at least 2 measurements are required at a height of 1.2 - 1.5 m from the ground surface. In the area below the console heel by 0.5 - 0.7 m. For other types of racks (type SK) with holes in the top part, one section is sufficient - in the lower part of the support;

· the areas for measurements must be located in the compressed zone of the structure, located on the side of the track or in the plane of action of the greatest bending moment;

· it is considered mandatory to carry out measurements in the area of ​​the crack network, regardless of the height of its location above the ground;

· in selected areas, in the presence of longitudinal cracks, measurements are taken between the cracks;

· in the area of ​​contact of ultrasonic transducers with the concrete surface there should be no cavities, potholes or air pores with a depth of more than 3 mm and a diameter of more than 6 mm. The measurement sites must be cleaned of dirt, paint, dust, etc.;

· measurements start from the bottom of the support;

· measurements must be carried out in dry weather at a temperature not lower than +50C;

· the sounding device is applied to the concrete surface with a force of about 4 kgf;

· excavation of the support to measure the propagation time of ultrasound should be carried out to a depth of 0.5-0.7 m from the side of the neutral zone of the support.

The condition of the above-ground part of the support can be checked by applying a series of blows with a special measuring hammer. The strength of reinforced concrete is determined by the acceleration of the hammer rebound. Due to the fact that the structure of concrete is heterogeneous - it contains sand and gravel - the diagnosis is made based on estimates of the mathematical expectation and dispersion of measurement parameters.

Even a household voice recorder is used to analyze sound vibrations in the support body. A blow is applied to the above-ground part of the support, and the damped sound vibrations are recorded on a voice recorder. Then, in laboratory conditions, it is connected to the sound card (card) of the computer, and the electrical vibrations are converted into an array of data using an analog-to-digital converter. This array can be processed by all known methods, starting with a purely visual comparison of oscillograms for supports with known degrees of loss of concrete strength.

Diagnostics of the above-ground and underground parts of supports can be carried out with a low-frequency ultrasonic flaw detector A1220 Figure 53. The device consists of an electronic unit with a screen and keyboard and a 24-element (6 * 4) matrix antenna device (AU). The design of the AC device elements ensures testing without contact liquid, i.e. with dry point contact. The AC elements are spring-loaded and make it possible to measure on curved and rough surfaces.

Rice. 53. Ultrasonic flaw detector A1220

Metal support structures can be diagnosed with the VIT-3M device (Fig. 54). The VIT-3M eddy current flaw detector is designed to detect and evaluate the depth of surface cracks on products made of steel, as well as alloys based on aluminum, copper, titanium, and magnesium. The flaw detector can be used to detect defects on flat and curved surfaces, both with finishing and with high roughness, as well as under a layer of non-metallic coating.

The operation of the device is based on the amplitude-frequency method of eddy current flaw detection.

The flaw detector is assembled in one housing, including the battery compartment. An eddy current transducer (EC), in the housing of which an indication LED is mounted, is connected to the flaw detector housing by a cable through a connector on the rear panel.

The flaw detector has three types of indication of inspection results:

· light, triggered when the transducer crosses a crack (structurally combined with the sensor).

· pointer, operating in static mode and allowing one to estimate the depth of a detected crack by comparing the deviations of the pointer on a specially made sample and on the crack.

· sound, with information output to headphones. Duplicates the arrow. The change in tone frequency is proportional to the deflection of the needle.

Rice. 54. Eddy current flaw detector VIT-3M

When checking metal structures, it is necessary to install the VI on the controlled area perpendicular to the surface. When moving the VI perpendicular to the surface along the controlled area, monitor the deflection of the arrow. When the VI passes over a crack, the arrow will deviate to the right. If the needle deviation is more than 4-5 scale divisions, then when the VI crack crosses, a light indicator will work. When using headphones, a beep will be heard.

Specifications:

· minimum crack depth - no more than 0.2 mm;

· the minimum value of the crack length is no more than 3 mm;

· dimensions no more than 140x90x35 mm;

· weight no more than 0.3 kg.

Ultrasonic thickness gauges series “26” and “MG2” Figure 55.

Portable, pocket-type thickness gauges of the 26 series are designed primarily for studying the destruction of materials.

Ultrasonic thickness gauge MG2 series with advanced technical characteristics:

· possibility of measuring thickness through insulation;

· thickness of the controlled material from 0.5 to 635 mm;

· fast measurement mode MIN/MAX;

· freeze frame mode;

zero offset compensation

· continuous operation time from built-in batteries - 150 hours

· operating temperature from -10 to +1500С

· weight 340 g.

Rice. 55. Ultrasonic thickness gauges series “26” (a) and “MG2” (b)

Ultrasonic flaw detectors “Epoch LT” (Fig/ 56)

Rice. 56. Ultrasonic flaw detector “Epoch LT”

A digital broadband flaw detector with built-in low-pass and high-pass filters is designed for inspecting welds and joints, measuring thickness, identifying corrosion and erosion, finding and determining the size of cracks and pores.

The device has a square or peak pulse generator:

· pulse frequency from 30 Hz to 1 kHz;

· operating frequency range from 0.5 to 25 MHz;

VGA, USB data output port

· Large capacity NiMH battery, continuous operation time 8 hours

· large, bright liquid crystal or electroluminescent display.

· automatic calibration of the ultrasonic transducer.

· improved data logging function with editing capabilities

· expanded memory (500 A-scan images/12000 thickness values)

· the ability to determine the position of a defect in three coordinates.

The metal hardness of metal supports can be determined using the MEIT-7 device. The surface of the support is first protected, then a ball with a diameter of 10 mm is pressed into the surface with a certain force. The indentation force is selected so that the impression from the ball has a diameter of 0.9 mm. The indentation force is measured and converted into the yield strength of the metal. It is recommended to evaluate the condition of metal structures based on an analysis of visual inspections, aggressiveness of the environment, remaining thickness, deflections and metallographic studies. Metallographic studies are carried out when there is a need to determine the grade of steel. To determine the thickness of the flanges of structural elements, indicator brackets are used (Fig. 57). Signs of cracking are the destruction of the paint layer and protruding stripes of red-brown rust. Very thin cracks are detected using a magnifying glass or an MPB-2 microscope. In general, several methods are recommended for diagnosing metal structures and their joints: ultrasonic, eddy current, analysis of hysteresis loop parameters.

Fig.57. Indicator bracket

Diagnostics of overhead lines

Overhead power line (OTL) is a device for transmitting and distributing electrical energy through wires located in the open air and attached to supports or brackets and racks on engineering structures using insulators and fittings. Branches to inputs into buildings are classified as overhead lines.

Diagnostics of insulators. An important place in ensuring reliable operation of power supply devices is occupied by modern and high-quality diagnostics of network insulation. Today there are no sufficiently reliable methods for remote detection of defective insulators and technical means that allow these methods to be implemented. Porcelain disc insulators are tested with a voltage of 50 before installation kV power frequency for 1 min, then use a megohmmeter for a voltage of 2.5 kV their resistance is measured, which must be at least 300 MOhm. Diagnosis of insulators in operation is carried out using remote monitoring devices or measuring rods (Figures 2.6 – 2.8). Let's consider what physical effects arise as a result of applying high voltage to an insulator. It is known from theory that if an electric field of sufficient strength is applied to two electrodes separated by an insulator, then an electrically conductive layer is formed on the surface or in the body of the insulator, in which an electric discharge - a streamer - appears and develops. The occurrence and development of a discharge is accompanied by the generation of oscillations in a wide range of frequencies (in the infrared, i.e. thermal, sound, ultrasonic frequency ranges, in the visible spectrum and in a wide range of radio frequencies). It is therefore obvious that the receiving part of the diagnostic device must detect one or another of the listed consequences of the formation and development of the streamer. Polymer insulators fail in different ways than porcelain or glass insulators, and it is difficult to determine the condition of such insulators in the absence of any observable physical defects such as cracks or blackening.

On VL 110 kV Only suspension insulators are used; on VL 35 kV and below, both pendant and pin insulators can be used. When an insulator in a garland breaks down, its dielectric “skirt” is destroyed and falls to the ground if the skirt is made of glass, but when a porcelain insulator breaks down, the skirt remains intact. Therefore, faulty glass insulators are visible to the naked eye, while diagnostics of failed porcelain insulators is possible only with the help of special devices, for example, the Filin ultraviolet diagnostic device.

Overhead power lines (OHL) with voltage 35 kV and higher are basic in power transmission systems. And therefore, defects and malfunctions occurring on them require immediate localization and elimination. Analysis of overhead line accidents shows that numerous overhead line failures occur annually as a result of changes in the material properties of wires and their contact connections (CS): destruction of wires due to corrosion and vibration effects, abrasion, wear, fatigue, oxidation, etc. In addition, The number of damages to porcelain, glass and polymer insulators is growing every year. There are many methods and systems for diagnosing the above elements, however, they are usually labor-intensive, have increased danger and, in addition, require disconnecting the equipment from voltage. The method of inspecting overhead lines using helicopter patrols is characterized by high productivity. Per day of work (5 - 6 h) are inspected up to 200 km lines. During helicopter patrols the following types of work are carried out:

Thermal imaging diagnostics of overhead lines, insulators, contact connections and fittings in order to identify elements subject to thermal heating due to emerging defects (Figure 5.8);

Ultraviolet diagnostics of overhead lines, insulators, contact connections in order to detect corona discharges on them (Figure 5.10);

Visual inspection of supports, insulators, contact connections (Figure 5.9, a high-resolution video camera is used).

The use of thermal imagers makes it possible to greatly simplify the process of monitoring the condition of arresters installed on overhead lines 35, 110 kV. Based on the thermogram, it is possible to determine not only the phase of the spark gap with an increased conduction current, but also the specific defective element that influenced the increase in this current. Timely replacement and repair of defective elements allows the further operation of the arresters to continue.

The use of aviation inspections is increasing in foreign countries as inspection technologies develop. For example, TVA is working on the use of high-resolution infrared cameras on a stabilized suspension and a DayCor camera for detecting corona on overhead power line elements in the daytime, a radar for

identifying rotting wooden supports, etc. The formation of a corona on overhead power line elements indicates short circuits, cracks or contamination of ceramic insulators or broken wire strands. Corona produces weak ultraviolet radiation that cannot be seen during the daytime. DayCor camera thanks to a filter that transmits only ultraviolet radiation in the wavelength range 240 - 280 nm, allows you to detect the corona in the daytime.

For rapid diagnostics of the condition of support-rod insulators and ceramics of high-voltage bushings, a small-sized portable vibration diagnostic device “Ajax-M” is used. To obtain diagnostic information, an impact is applied to the support insulator shoe, after which resonant oscillations are excited in it. The parameters of these vibrations are related to the technical condition of the insulator. The appearance of defects of any type leads to a decrease in the frequency of resonant oscillations and an increase in the rate of their attenuation. To eliminate the influence of resonant vibrations of structures associated with the insulator, vibrations are recorded after two impacts - on the upper and lower shoes of the insulator. Based on a comparison of the spectra of resonant vibrations upon impact on the upper and lower parts of the insulator, the technical condition is assessed and defects are searched for.

Using the Ajax-M device, you can diagnose the condition of the support insulation and search for the following types of defects: the presence of cracks in the ceramics of the insulator or the places where ceramics are embedded in the support shoes; the presence of porosity in the ceramics of the insulator; determination of the technical condition coefficient of the insulator. Based on the diagnostic results, categories of the insulator condition are determined - “requires replacement”, “requires additional monitoring” or “can be used”. The recorded parameters of the insulator state can be recorded in the long-term memory of the device and, subsequently, in the computer memory for storage and processing. Using an additional program, it is possible to evaluate changes in insulator parameters from measurement to measurement. Using the device, the condition of insulators of almost any type and brand can be diagnosed.

To assess the condition valve arresters

resistance measurement;

measurement of conduction current at rectified voltage;

breakdown voltage measurement;

thermal imaging control.

To assess the condition surge suppressors The following tests are used:

resistance measurement;

conduction current measurement;

thermal imaging control.

Diagnostics of wires. To identify possible problem areas on power lines caused by vibration, a power line wire vibration monitoring and analysis device is used. The device allows you to evaluate on-site in real weather conditions the vibration characteristics of power lines with different designs, wire tensions and technical support, and determine the nominal service life of wires exposed to vibration. The instrument is a vibration instrument used on site to monitor and analyze the vibration of overhead power lines caused by wind. It measures the frequencies and amplitudes of all vibration cycles, stores the data in a high-definition matrix, and processes the results to provide an estimate of average life expectancy

wires being tested. The measurement and evaluation methods are based on the IEEE international standard and the CIGRE procedure. The device can be installed directly on the wire near any type of clamp. The instrument consists of a calibrated beam sensor bracket that attaches to a wire clamp that supports a short cylindrical body. The sensing element in contact with the wire transmits movement to the sensor. Inside the case there is a microprocessor, an electronic circuit, a power supply, a display and a temperature sensor. Using bending amplitude ( Yb) as a measurement parameter to evaluate the vibration severity of a wire is a well-established practice. Differential displacement measurement at 89 mm from the last point of contact between the wire and the metal hanger clamp is the starting point for the IEEE standardization of wire vibration measurements. The sensor is a cantilever beam that senses the bend of the wire near the hanging or hardware clamps. For each vibration cycle, the strain sensors generate an output signal proportional to the bending amplitude of the wire. Vibration frequency and amplitude data are stored in an amplitude/frequency matrix according to the number of events. At the end of each monitoring period, the built-in microprocessor calculates the nominal wire life index. This value is stored in memory, after which the microprocessor returns to standby mode for the next startup. The microprocessor can be directly accessed from any I/O terminal or computer via an RS-232 communication line.

Flaw detection of wires and lightning protection cables of overhead power lines. The reliability of overhead lines depends on the strength of steel ropes used as current-carrying, load-bearing elements in combined wires, lightning protection cables, and guy wires. Monitoring the technical condition of the overhead line and its elements is based on comparison of identified defects with the requirements of the standards and tolerances given in the design materials of the inspected overhead line, in state standards, PUE, SNiP, TU and other regulatory documents. The condition of wires and cables is usually assessed by visual inspection. However, this method does not allow detecting breaks inside the wires. To reliably assess the condition of overhead line wires and cables, it is necessary to use a non-destructive instrumental method using a flaw detector, which allows you to determine both the loss of their cross-section and internal wire breaks.

Thermal method for diagnosing overhead lines. It is possible to detect heat leaks and prevent accidents associated with overheating on overhead lines at the earliest stages of its occurrence. Thermal imagers or pyrometers are used for this purpose.

Assessment of the thermal state of current-carrying parts and insulation of overhead lines, depending on their operating conditions and design, is carried out:

According to standardized heating temperatures (temperature rises);

Excessive temperature;

Dynamics of temperature changes over time;

With load changes;

By comparing measured temperature values ​​within a phase, between phases, with known-good areas.

Limit values ​​for heating temperature and its excess are given in the regulatory directives RD 153-34.0-20363-99 “Basic provisions of the methodology for infrared diagnostics of electrical equipment and overhead lines”, as well as in the “Instructions for infrared diagnostics of overhead power lines”.

For contacts and contact connections, calculations are carried out at load currents (0.6 - 1.0) I nom after appropriate recalculation. Recalculation of the excess of the measured temperature value to the normalized value is carried out based on the ratio:

, (2.5)

where Δ T nom - temperature rise at I nom;

Δ T slave - temperature rise at I slave;

For contacts at load currents (0.3 - 0.6) I However, their condition is assessed based on excess temperature. The temperature value recalculated by 0.5 is used as a standard I nom. The following ratio is used for recalculation:

, (2.6)

where: Δ T 0.5 - excess temperature at load current 0.5 I nom.

Thermal imaging control of equipment and live parts at load currents below 0.3 I nom is not effective for identifying defects at an early stage of their development. Defects detected at the specified loads should be classified as defects at an emergency degree of malfunction. And a small part of defects should be classified as defects with a developing degree of malfunction. It should be noted that there is no assessment of the degree of failure of defects on indirectly overheated surfaces of equipment. Indirect overheating can be caused by hidden defects, such as cracks, inside the disconnector insulators, the temperature of which is measured externally, and often the defective parts inside the object are very hot and severely burned. Equipment with indirect overheating should be classified as the second or third degree of overheating. The condition of welded and crimped joints should be assessed based on excess temperature.

Inspection of all types of overhead power line wires using the thermal imaging method is carried out:

For newly commissioned overhead lines - in the first year of their commissioning at a current load of at least 80%;

Overhead lines operating with maximum current loads, or supplying critical consumers, or operating in conditions of increased atmospheric pollution, high wind and ice loads - annually;

Overhead lines that have been in operation for 25 years or more, with the rejection of 5% of contact connections - at least once every 3 years;

For other overhead lines - at least once every 6 years.

Ultrasonic diagnostics of overhead line supports. Assessment of the condition of reinforced concrete supports using an ultrasonic surface sounding device. Constant monitoring of the condition of overhead line supports allows not only to prevent accidents, but also to significantly increase the profitability of operating electrical networks by repairing only those supports that really need repair or replacement. A significant proportion of overhead line supports in our country and abroad are made of reinforced concrete. A common type of reinforced concrete support is a stand in the form of a thick-walled pipe, made by centrifugation. Under the influence of climatic factors, vibration and work load, the concrete of the rack changes its structure, cracks, receives various damages and, as a result, the rack gradually loses its load-bearing capacity. Therefore, regular inspections of all electrical service racks are required to determine whether a rack needs to be replaced. Such inspections also prevent unnecessary rejection of supports.

The possibility of an objective assessment of the load-bearing capacity of centrifuged reinforced concrete pillars is based on the fact that with a change in the structure of concrete and the appearance of defects in it, the strength of concrete deteriorates, which manifests itself in a decrease in the speed of propagation of ultrasonic vibrations. Moreover, due to the design features of the racks and the nature of the loads on them, changes in the properties of concrete in the directions along and across the rack are not the same: the ultrasound speed in the transverse direction decreases faster over time, which, apparently, can be explained by an increase in the concentration of microcracks with a predominantly longitudinal orientation . By changing the speed of ultrasound propagation along and across the rack during its operation, as well as by their ratio, one can judge the degree of loss of the bearing capacity of the rack and make a decision about its replacement.

SECTION 1. MATHEMATICAL MODELS AND METHODS IN THE THEORY OF TECHNICAL DIAGNOSTICS

Topic 6. Physical control methods in technical diagnostics

Lecture outline

6.5. Acoustic control methods

6.6. Radio wave methods of non-destructive testing

6.7. Thermal non-destructive testing

6.7.1. Temperature controls

6.7.2. Non-contact thermometry methods

6.5. Acoustic control methods

For the acoustic NDT method, vibrations in the ultrasonic and sound ranges with a frequency from 50 Hz to 50 MHz are used. The intensity of vibrations is usually low, not exceeding 1 kW/m2. Such oscillations occur in the region of elastic deformations of the medium, where stress and deformation are related by a proportional relationship (the region of linear acoustics).

The amplitude of acoustic waves in liquids and gases is characterized by one of the following parameters:

acoustic pressure (Pa) or pressure change relative to the average pressure in the medium:

p = ρ c v,

where c is the speed of propagation of acoustic waves; ρ is the density of the medium;

displacement in (m) of particles of the medium from the equilibrium position in the process of oscillatory motion;

speed (m/s) of oscillatory motion of particles of the medium

v = ∂ ∂ u, t

where t is time.

There are many known acoustic methods of non-destructive testing, which are used in several versions. The classification of acoustic methods is shown in Fig. 23. They are divided into two large groups - active and passive methods.

Active methods are based on the emission and reception of elastic waves, passive methods are based only on the reception of waves, the source of which is the controlled object itself.

Active methods are divided into transmission, reflection, combined (using both transmission and reflection), impedance and natural frequency methods.

Fig.23. Classification of acoustic types of non-destructive testing

Passage methods use emitting and receiving converters located on one or different sides of the controlled product. Pulsed or continuous (less often) radiation is used. Then the signal passing through the controlled object is analyzed.

Rice. 24. Passage methods:

a- shadow; b – temporary shadow; c – velocimetric; 1 – generator; 2 emitter; 3 – object of control, 4 – receiver; 5 – amplifier,

6 – amplitude meter; 7 – travel time meter; 8 – phase meter

Passage methods include:

amplitude shadow method, based on recording a decrease in the amplitude of the wave passing through the controlled object due to the presence of a defect in it (Fig. 24, a);

temporary shadow method, based on recording the delay of the pulse caused by an increase in its path in the product when going around a defect (Fig. 24, b). The wave type does not change;

velocimetric method, based on recording changes in the speed of propagation of dispersive modes of elastic waves in the defect zone and used for one-sided and two-sided access to the controlled object (Fig. 24, c). This method typically uses dry point contact transducers. In the version with one-way access (Fig. 24, c above), the speed of the zero-order antisymmetric wave (a0) excited by the emitter in the layer separated by the defect is less than in the defect-free zone. With double-sided access (Fig. 24, c below), in the defect-free zone, energy is transmitted by a longitudinal wave L, in the defect zone - by waves a0, which travel a longer distance and propagate at lower speeds than the longitudinal wave. Defects are noted by a change in phase or an increase in transit time (only

V pulse version) for the controlled product.

IN reflection methods pulsed radiation is used. This subgroup includes the following flaw detection methods:

The echo method (Fig. 25, a) is based on recording echo signals from a defect. On the indicator screen, the sent (probing) pulse I, pulse III reflected from the opposite surface (bottom) of the product (bottom signal) and the echo signal from defect II are usually observed. The arrival time of pulses II and III is proportional to the depth of the defect and the thickness of the product. With a combined control circuit (Fig. 25, a), the same converter performs the functions of emitter and receiver. If these functions are performed by different converters, then the circuit is called separate.

The echo-mirror method is based on the analysis of signals that have experienced specular reflection from the bottom surface of the product and the defect, i.e. passed the path ABCD (Fig. 25, b). A variant of this method, designed to detect vertical defects in the EF plane, is called the tandem method. To implement this, when moving transducers A and D, they are kept constant

value I A + I D = 2Н tgα ; to obtain specular reflection from non-vertical defects, the value of I A + I D varies. One of the variants of the method, called "oblique tandem", provides for the location of the emitter and receiver not in the same plane (Fig. 25, b, plan view below), but in different planes, but in such a way as to receive a specular reflection from the defect. Another option, called K-method, involves placing the transducers on different sides of the product, for example, placing the receiver at point C.

Rice. 25. Reflection methods:

a – echo; b – echo - mirror; c – delta method; d – diffraction-time; d – reverberation;

1 – generator; 2 – emitter; 3 – object of control; 4 – receiver; 5 – amplifier; 6 – synchronizer; 7 – indicator

The delta method (Fig. 25, c) is based on the reception of longitudinal waves by a transducer 4 located above the defect, emitted by a transverse wave transducer 2, and scattered on the defect.

Diffraction-time method (Fig. 25,d), in which emitters 2 and 2’,

receivers 4 and 4' emit and receive either longitudinal or transverse waves, and can emit and receive different types of waves. The transducers are positioned so as to receive the maximum echo signals of waves diffracted at the ends of the defect. The amplitudes and arrival times of signals from the upper and lower ends of the defect are measured.

Reverberation method(Fig. 25, d) uses the influence of the defect on the decay time of repeatedly reflected ultrasonic pulses in the controlled object. For example, when testing a glued structure with an outer metal layer and an inner polymer layer, a bond defect prevents energy transfer to the inner layer, which increases the decay time of multiple echoes in the outer layer. Pulse reflections in the polymer layer are usually absent due to the high attenuation of ultrasound in the polymer.

IN combined methods use the principles of both passing and

And reflections of acoustic waves.

Mirror-shadow The method is based on measuring the amplitude of the bottom signal. In this case, the reflected beam is conventionally shifted to the side (Fig. 26, a). According to the technique of implementation (records the echo signal), it is classified as a reflection method, and according to the physical nature of the control (measures the attenuation of the signal of a product that has passed twice in the defect area), it is close to the shadow method.

The echo-shadow method is based on the analysis of both transmitted and reflected waves (Fig. 26, b).

Rice. 26. Combined methods using transmission and reflection:

a – mirror-shadow; b – echo-shadow; c – echo-through: 2 – emitter; 4 – receiver; 3 – object of control

In the echo-through method (Fig. 26, c), through signal I and signal II, which has experienced double reflection in the product, are recorded. If a translucent defect appears, signals III and IV are recorded, corresponding to the reflections of waves from the defect and also experienced reflection from the upper and lower surfaces of the product.

Leah A large opaque defect is detected by the disappearance or strong decrease in signal I, i.e. shadow method, as well as signal II. Translucent or small defects are detected by the appearance of signals III and IV, which are the main information signals.

Natural frequency methods are based on the measurement of these frequencies (or spectra) of vibrations of controlled objects. Natural frequencies are measured when both forced and free vibrations are excited in products. Free vibrations are usually excited by mechanical shock, while forced vibrations are excited by the influence of a harmonic force of varying frequency.

There are integral and local methods. Integral methods analyze the natural frequencies of a product oscillating as a whole. In local methods, vibrations of its individual sections.

In the natural frequency method, forced oscillations are used. IN

integral method generator 1 (Fig. 27, a) of adjustable frequency is connected to emitter 2, which excites elastic vibrations (usually longitudinal or bending) in the controlled product 3. Receiver 4 converts the received vibrations into an electrical signal, which is amplified by amplifier 5 and sent to resonance indicator 6. By adjusting the frequency of generator 1, the natural frequencies of product 3 are measured. The range of applied frequencies is up to 500 kHz.

Rice. 27. Natural frequency methods. Oscillation methods:

- forced: a – integral; b – local;

- free: in – integral; g – local;

1 – generator of continuous oscillations of varying frequency; 2 – emitter; 3 – object of control; 4 – receiver; 5 – amplifier; 6 – resonance indicator; 7 – frequency modulator; 8 – indicator; 9 – spectrum analyzer; 10 – impact vibrator; 11 – information processing unit

The local method using forced oscillations is known as ultrasonic resonance method. It is mainly used for measuring thickness. In the wall of the product 3 (Fig. 27.6), using converters 2, 4, elastic waves (usually longitudinal) of continuously varying frequency are excited. The frequencies at which resonances of the converter-product system are observed are recorded. The resonant frequencies determine the wall thickness of the product and the presence of defects in it. Defects parallel to the surface change the measured thickness, and those located at an angle to the surface lead to the disappearance of resonances. The range of frequencies used is up to several megahertz.

IN integral method in product 3 (Fig. 27, c), freely damped vibrations are excited by the blow of hammer 2. These vibrations are received by microphone 4, amplified by amplifier 5 and filtered by bandpass filter 6, which transmits only signals with frequencies corresponding to the selected vibration mode. The frequency is measured with a frequency meter 7. A sign of a defect is a change (usually a decrease) in frequency. As a rule, the main natural frequencies are used, not exceeding 15 kHz.

IN local method(Fig. 27, d) vibrator 10, excited by generator 1, creates periodic impacts on the controlled product. Electrical signals from the receiving microphone 4 through the amplifier 5 are sent to the spectrum analyzer 9. The spectrum of the received signal, isolated by the latter, is processed by the decision device 11, the result of the processing appears on the indicator 8. In addition to microphones, piezoreceivers are used. Defects are detected by changes in the spectrum of the received pulse signal. Unlike the integral method, control is performed by scanning products. Typical operating frequency range is from 0.3 to 20 kHz.

Acoustic-topographic the method has features of integral and local methods. It is based on excitation of intense bending vibrations of a continuously changing frequency in a product and recording the distribution of vibration amplitudes using powder applied to the surface. Elastic vibrations are excited by a transducer pressed against a dry product. The converter is powered by a powerful (about 0.4 kW) generator of continuously varying frequency. If the natural frequency of the zone separated by a defect (delamination, failure of connection) falls within the range of excited frequencies, the vibrations of this zone are amplified, the powder covering it is shifted and concentrated along the boundaries of the defects, making them visible. Frequency range used

From 40 to 150 kHz.

Impedance methods use the dependence of the impedances of products during their elastic vibrations on the parameters of these products and the presence of defects in them. Mechanical impedance is usually estimated Z = F v, where F and v are complex

amplitudes of the disturbing force and oscillatory speed, respectively. Unlike characteristic impedance, which is a parameter of the medium, mechanical impedance characterizes the structure. Impedance methods use bending and longitudinal waves.

When using bending waves, a rod-type transducer (Fig. 28, a) contains 2 radiating and receiving 4 piezoelements connected to the generator 1. Through a dry point contact, the transducer excites 3 harmonic bending vibrations in the product. In the defect zone, the Z modulus of mechanical

impedance Z = Z e j ϕ decreases and its argument φ changes. These

changes are recorded by electronic equipment. In the pulsed version of this method, pulses of freely damped oscillations are excited in the converter-product system. A sign of a defect is a decrease in the amplitude and carrier frequency of these oscillations.

Rice. 28. Control methods: a- impedance; b – acoustic emission; 1 – generator; 2 – emitter; 3 – object of control; 4 – receiver; 5 – amplifier; 6 – processing block

information boxes with indicator

In addition to the combined converter, separate-combined converters are used, which have separate emitting and receiving vibrators in a common housing. These converters operate in pulse mode. When working with combined converters, frequencies up to 8 kHz are used. For separate-combined ones, pulses with carrier frequencies of 15-35 kHz are used.

In another embodiment, in a controlled multilayer structure, a flat piezoelectric transducer is used to excite longitudinal elastic waves fixed frequency. Defects are recorded by changes in the input electrical impedance Z E of the piezoelectric transducer. ImpedanceZ E is determined by the input acoustic impedance of the controlled structure, depending on the presence and depth of defects in the connection between the elements. Changes Z E are represented as a point on the complex plane, the position of which depends on the nature of the defect. Unlike methods using bending waves, the transducer contacts the workpiece through a layer of contact lubricant.

Contact impedance method, used for hardness control, is based on an assessment of the mechanical impedance of the contact zone of the diamond indenter of the transducer rod, pressed against the test object with a constant force. A decrease in hardness increases the area of ​​the contact zone, causing an increase in its elastic mechanical impedance, which is noted by an increase in the natural frequency of the longitudinal oscillating transducer, which is uniquely related to the measured hardness.

Passive acoustic methods are based on the analysis of elastic vibrations of waves arising in the controlled object itself.

The most typical passive method is acoustic emission method(Fig. 28.6). The phenomenon of acoustic emission is that elastic waves are emitted by the material itself as a result of internal dynamic local restructuring of its structure. Phenomena such as the appearance and development of cracks under the influence of external loads, allotropic transformations during heating or cooling, and the movement of dislocation clusters are the most

more typical sources of acoustic emission. Piezoelectric transducers in contact with the product receive elastic waves and make it possible to determine the location of their source (defect).

Passive acoustic methods are vibration-

diagnostic and noise diagnostic. At first, vibration parameters are analyzed any individual part or assembly using contact-type receivers. In the second, the noise spectrum of the operating mechanism is studied, usually using microphone receivers.

Based on frequency, acoustic methods are divided into low-frequency and high-frequency. The first include vibrations in the audio and low-frequency (up to several tens of kHz) ultrasonic frequency ranges. The second includes vibrations in the high-frequency ultrasonic frequency range: usually from several 100 kHz to 20 MHz. High frequency methods are usually called ultrasonic.

Areas of application of methods. Of the acoustic control methods considered, the echo method finds the greatest practical application. About 90% of objects. Using various types of waves, it is used to solve problems of flaw detection of forgings, castings, welded joints, and many non-metallic materials. The echo method is also used to measure the dimensions of products. The time of arrival of the bottom signal is measured and, knowing the speed of ultrasound in the material, the thickness of the product is determined with unilateral access. If the thickness of the product is unknown, then the speed is measured using the bottom signal, the attenuation of ultrasound is assessed, and the physical and mechanical properties of the materials are determined from them.

The echo-mirror method is used to detect defects oriented perpendicular to the input surface. At the same time, it provides higher sensitivity to such defects, but requires that there be a sufficiently large area of ​​​​a flat surface in the area where the defects are located. In rails, for example, this requirement is not met, so only the mirror-shadow method can be used there. The defect can be detected by a combined inclined transducer. However, in this case, the specularly reflected wave goes to the side and only a weak scattered signal reaches the converter. The echo-mirror method is used to detect vertical cracks and lack of penetration when inspecting welded joints.

Delta and diffraction-time methods are also used for semi-

obtaining additional information about defects during inspection of welded joints.

The shadow method is used to control products with a high level of structural reverberation, i.e. noise associated with the reflection of ultrasound from inhomogeneities, large grains, flaw detection of multilayer structures and products made of laminated plastics, when studying the physical and mechanical properties of materials with high attenuation and scattering of acoustic waves, for example, when monitoring the strength of concrete by ultrasound speed.

The local forced vibration method is used to measure small cracks with one-sided access.

The integral method of free vibrations is used to test carriage wheel tires or glassware “by ringing purity” with a subjective assessment of the results by ear. The method using electronic equipment and objective quantitative assessment of the results is used to control the physical and mechanical properties of abrasive wheels, ceramics and other objects.

Reverberation, impedance, velosymmetric, acoustic

topographic methods and the local free vibration method are used mainly for testing multilayer structures. Reverb The method mainly detects defects in the connections of metal layers (skin) with metal or non-metallic load-bearing elements or fillers. The impedance method detects defects in connections in multilayer structures made of composite polymer materials and metals used in various combinations. Velosymmetric The method and local method of free vibrations mainly control products made of polymer composite materials. Acoustic-topographic The method is used to detect defects mainly in metal multilayer structures (honeycomb panels, bimetals, etc.).

Vibration diagnostic and noise diagnostic methods are used to diagnose working mechanisms. The acoustic emission method is used as a means of studying materials, structures, monitoring products and diagnostics during operation. Its important advantages over other inspection methods are that it reacts only to developing, truly dangerous defects, as well as the ability to test large areas or even the entire product without scanning it with a converter. Its main drawback as a means of monitoring is the difficulty of isolating signals from developing defects against a background of noise.

6.6. Radiation methods of non-destructive testing

Radiation monitoring uses at least three main elements (Fig. 29):

source of ionizing radiation;

controlled object;

detector that records flaw detection information.

Rice. 29. Transmission scheme:

1 – source; 2 – product; 3 - detector

When passing through a product, ionizing radiation is attenuated - absorbed and scattered. The degree of attenuation depends on the thickness δ and density ρ of the controlled object, as well as on the intensity M 0 and energy E 0 of radiation. If there are internal defects of size ∆δ in a substance, the intensity and energy of the radiation beam change.

Radiation monitoring methods (Fig. 30) differ in the methods of detecting flaw detection information and are accordingly divided into radio-

graphic, radioscopic and radiometric.

Radiation monitoring methods

Radiographic:			Radioscopic:				Radiometric:
Fixing the image			Image observation				Electronic registration
on film			marriages on the screen.				tric signals.
(on paper).

Rice. 30. Radiation monitoring methods

Radiographic Radiation non-destructive testing methods are based on converting a radiation image of a controlled object into a radiographic image or recording this image on a storage device with subsequent conversion into a light image. In practice, this method is the most widely used due to its simplicity and documentary evidence of the results obtained. Depending on the detectors used, a distinction is made between film radiography and xeroradiography (electroradiography). In the first case, a photosensitive film serves as a latent image detector and a static visible image recorder; in the second, a semiconductor wafer is used, and ordinary paper is used as a recorder.

Depending on the radiation used, several types of industrial radiography are distinguished: radiography, gammagraphy, accelerator and neutron radiography. Each of the listed methods has its own scope of use. These methods can be used to illuminate steel products with a thickness of 1 to 700 mm.

Radiation introscopy- a method of radiation non-destructive testing, based on converting the radiation image of the controlled object into a light image on the output screen of the radiation-optical converter, and the analysis of the resulting image is carried out during the control process.

The sensitivity of this method is somewhat less than radiography, but its advantages are the increased reliability of the results obtained due to the possibility of stereoscopic vision of defects and viewing products from different angles, “express” and continuity of control.

Radiometric flaw detection- method of obtaining information about internal

the early state of the controlled product, illuminated by ionizing radiation, in the form of electrical signals (of varying magnitude, duration or quantity).

This method provides the greatest possibilities for automating the control process and implementing automatic feedback of control and the technological process of product manufacturing. The advantage of the method is the possibility of carrying out continuous high-performance quality control of the product, due to the high speed of the equipment. This method is not inferior in sensitivity to radiography.

6.7. Thermal non-destructive testing

In thermal methods of non-destructive testing (TDT), thermal energy propagating in the test object is used as test energy. The temperature field of the surface of an object is a source of information about the features of the heat transfer process, which, in turn, depend on the presence of internal or external defects. A defect is understood as the presence of hidden cavities, cavities, cracks, lack of penetration, foreign inclusions, etc., all possible deviations of the physical properties of an object from the norm, the presence of places of local overheating (cooling), etc.

There are passive and active TNCs. With passive TNC, the thermal fields of products are analyzed during their natural functioning. Active TNC involves heating an object with an external energy source.

Non-contact thermal control methods are based on the use of infrared radiation emitted by all heated bodies. Infrared radiation occupies a wide range of wavelengths from 0.76 to 1000 microns. The spectrum, power and spatial characteristics of this radiation depend on the temperature of the body and its emissivity, determined mainly by its material and the microstructural characteristics of the emitting surface. For example, rough surfaces emit more radiation than mirrored ones.

This information can be used as an example for compiling support inspection reports.

Explanatory note

to the report on the results of inspection of the condition of reinforced concrete supports

Basis for work

The work is carried out within the framework of Agreement No. 07/11 for repair, maintenance and diagnostic inspection of electrical grid facilities

General provisions.

Scope of diagnostic work:

Checking the condition of reinforced concrete supports using a non-destructive ultrasonic express method

Checking the position of the supports

List of lines and number of reinforced concrete supports to be diagnosed:

220 kV overhead line D-1 Ulyanovskaya - Zagorodnaya 169 supports

220 kV overhead line D-9 Luzino - Nazyvaevskaya 466 supports

220 kV overhead line D-13 Tavricheskaya - Moskovka 130 supports

220 kV overhead line D-14 Tavricheskaya - Moskovka 130 supports

220 kV overhead line L-225 Irtyshskaya - Valikhanovo 66 supports

A total of 961 reinforced concrete supports were subject to inspection.

Results of inspection of overhead line supports.

In total, 1036 intermediate reinforced concrete supports were actually examined

220 kV overhead line D-1 Ulyanovskaya - Zagorodnaya 165 supports

220 kV overhead line D-9 Luzino - Nazyvaevskaya 504 supports

220 kV overhead line D-13 Tavricheskaya - Moskovka 130 supports

220 kV overhead line D-14 Tavricheskaya - Moskovka 130 supports

220 kV overhead line L-224 Irtyshskaya - Mynkul 53 supports

220 kV overhead line L-225 Irtyshskaya - Valikhanovo 52 supports

Condition of centrifuged racks

220 kV overhead line D-1 Ulyanovskaya - Zagorodnaya (165 pcs.)

54 centrifuged wastewater (32.7%) are in normal condition

There are 102 pieces in the worker. (61.8%)

In deteriorated 9 pcs. (5.4%)

220 kV overhead line D-9 Luzino - Nazyvaevskaya (506 units)

260 centrifuged racks (51.4%) are in normal condition

There are 170 pieces in a worker. (33.6%)

In deteriorated 42 pcs. (8.3%)

In pre-accident 34 pcs. (6.7%)

220 kV overhead line D-13 Tavricheskaya - Moskovka (130 pcs.)

75 centrifuged racks (57.7%) are in normal condition

There are 48 pieces in a worker. (36.9%)

In deteriorated 5 pcs. (3.8%)

In pre-emergency 2 pcs. (1.54%)

220 kV overhead line D-14 Tavricheskaya - Moskovka (130 pcs.)

79 centrifuged rack (60.7%) are in normal condition

There are 39 pieces in the worker. (30.0%)

In deteriorated 11 pcs. (8.46%)

In pre-emergency 1 pc. (0.76%)

220 kV overhead line L-224 Irtyshskaya - Mynkul (53 pcs.)

37 centrifuged racks (69.8%) are in normal condition

There are 11 pieces in the worker. (20.8%)

In deteriorated 2 pcs. (3.8%)

In pre-emergency 3 pcs. (5.7%)

220 kV overhead line L-225 Irtyshskaya - Valikhanovo (52 pcs.)

31 centrifuged racks (59.6%) are in normal condition

There are 18 pieces in a worker. (34.6%)

In deteriorated 1 piece. (1.9%)

In pre-emergency 2 pcs. (3.8%)

Conclusion

The examined reinforced concrete supports of the 220 kV overhead line of the Omsk enterprise MES of Siberia are in working condition, with some operational deviations of the values ​​of the monitored parameters of individual elements from the normal state.

The main visible defects of reinforced concrete conical and cylindrical racks SK-5, SK-7 and SN-220, from which the reinforced concrete supports of most of the surveyed overhead lines are made, identified during their inspection are:

Local exposure of reinforcement and slight longitudinal cracking of concrete (working condition)

Tilts of centrifuged racks exceed permissible limits (deteriorated condition)

The presence of transverse cracks in concrete above the permissible size (pre-emergency condition).

However, in a number of cases, instrumental testing did not confirm the pre-accident danger of transverse cracks in the support struts. In this regard, those supports that still have a sufficient design life in terms of the bearing capacity of concrete and reinforcement, and which are classified as a pre-failure condition only by the presence of transverse cracks in the dangerous section of the racks, less costly measures were chosen as repair and preventive work. Recommended measures for some of these supports instead of replacing steel: additional control condition once every 3 years, protection from environmental influences, installation of temporary metal bandages. To verify the correct rejection of centrifuged pillars of reinforced concrete supports based on data from instrumental monitoring of their condition, it is desirable to conduct mechanical tests of the maximum load-bearing capacity of the pillars in operation. We have already carried out such tests earlier (Appendix 1) and showed the degree of danger of certain defects for the load-bearing capacity of the racks.

According to the Operating Instructions for overhead lines, supports that are in working condition require cosmetic repairs, and supports that are tilted above the permissible limit (more than 3.0 degrees) must be straightened immediately. However, in some cases, straightening reinforced concrete supports is undesirable because it causes more harm than good. We are talking about the initially non-vertical installation of a reinforced concrete support in a prepared pit. This happens when the topography of the overhead line route does not make it possible to obtain a strictly vertical pit for installing a reinforced concrete support, or when the crossbars are installed incorrectly (Fig. 1). In any case, if the verticality of the support is not ensured during the construction of the overhead line, and during its operation there has been no significant change in the value of the initial inclination of the support, then bringing such a support to a vertical position, for example, using the ORGRES method, can lead to the premature appearance of transverse cracks at the support and weakening of the support concrete in the zone of maximum bending moment (Fig. 2). In such cases, it is more correct to either organize observation of inclined supports in order to determine the trends and rates of their tilt, or to reinstall the supports in a new pit.

Rice. 1. The tilt of support No. 193 along the 220 kV overhead line D-9 “Luzino - Nazyvaevskaya”

It is known that random (or constant) eccentricities from the external load on the support are perceived by the reinforcement of the reinforced concrete rack, and the concrete itself mainly carries a compressive load. Therefore, as long as the reinforcement of a reinforced concrete post is capable of providing prestressing concrete at a level significantly higher than the tensile force arising in the concrete due to the tilt of the post, the support is able to perform its operational functions without straightening.

It is also known that under a layer of intact concrete, corrosion of reinforcement is impossible due to passivation of its surface under the action of an alkaline pore solution of concrete (the pH value of the concrete solution is about 10-12).

Therefore, in order to maintain the long-term performance of a reinforced concrete support that has a slope and deep cracks, it is sometimes more important to redecorate the damaged concrete and protect it from environmental influences. For example, by impregnating its surface and existing cracks with highly adhesive protective materials (such as Siberia-Ultra) and closing the upper hole of the rack to prevent atmospheric moisture from entering it.

For example, the 274 units we examined in 2010. reinforced concrete supports of the 220 kV Tyumen-Tavda overhead line (MES of Western Siberia), built in 1964 using cylindrical centrifuged racks SN-220, galvanized traverses and galvanized metal covers covering the upper hole of the rack, almost completely retained their load-bearing capacity ( Fig 3). Although among them there were also inclined racks (Fig. 4).

Rice. 2. Transverse cracks that appeared in the concrete of the inclined centrifuged pillar of support No. 875 VL 225 due to its alignment.

Rice. 3. The top of support No. 45 of the 220 kV Tyumen - Tavda overhead line, covered with a galvanized metal cover since the construction of the overhead line

Rice. 4. The tilt of support No. 44 of the 220 kV Tyumen-Tavda overhead line is visible.

conclusions

1. In each specific case of detecting a tilt of a reinforced concrete support that exceeds the permissible limit, it is initially necessary to organize monitoring of it in order to determine trends and rates of tilt, as well as the development of existing defects. In the event of dangerous trends or threats, it is necessary to either reinstall the support in a new pit or replace it. A similar approach can be applied to racks that have undeveloped (non-dangerous) transverse cracks.

2. The pre-failure state of some racks (less than 4.5% of those examined) is caused by the presence of transverse cracks, the appearance of which is associated both with the alignment of the supports and with supercritical external influences. There are 42 such racks in total, which need to be replaced by 2016. In particular, support racks No. 9 on each 220 kV overhead line D-13 and D-14 and support racks No. 74, 85, 120, 181 and 183 on each 220 kV overhead line D-1 must be replaced.

Within a year, it is necessary to reinstall or replace support No. 152 on the 220 kV D-9 overhead line, which has a slope of more than 7 degrees, and install metal bands on supports No. 172 and 350 of this overhead line in the zone of their intense cracking.