RU2802253C1 - Method for manufacturing a solid-state insulator for an x-ray machine - Google Patents

Abstract

FIELD: X-ray engineering.

SUBSTANCE: invention relates to X-ray equipment comprising X-ray tubes and can be used in the development of X-ray generators for non-destructive testing of industrial objects, for obtaining X-ray images for industrial transillumination, medical diagnostics and scientific research. To manufacture the insulator, Al₂O₃ is first treated with high-energy activation in a planetary mixer at a speed of 1800 rpm⋅ min^-1 for 300 s. Then Al₂O₃ is introduced into the organosilicon polymer, a tin-based catalyst is added and mixed with a mixer, followed by evacuation to a residual pressure of 1.5⋅10^-3 Pa. The product is shaped in stages by filling the injection mold in volumes of 150 ml with the resulting polymer mixture followed by placing the polymer matrix on a vibration stand for 10 minutes.

EFFECT: increased electrical strength of the solid-state insulator.

3 cl, 2 dwg

Description

The invention relates to X-ray engineering, and more specifically to X-ray equipment (RA) containing X-ray tubes and can be used in the development of X-ray generators for non-destructive testing of industrial objects, for obtaining X-ray images for industrial transillumination, medical diagnostics and scientific research.

Known small-sized X-ray apparatus ARINA, designed for non-destructive testing of materials by X-ray method (LLC "Spectroflesh", L.Ya. Morgovsky, E.Ya. Peliks. Pulsed radiography. Devices of the Arina series, St. Petersburg, 1999) [1 ].

This device contains assembled in a common housing:

x-ray machine, which houses the x-ray unit, battery and pulse voltage converter; a control unit including a low-voltage switch, the input of which is connected to the battery output, a reference voltage stabilizer, a pulse counter for counting the irradiation dose by inductively converting an electrical signal into a signal for counting pulses, and a pulse converter; and a control panel, the output of which is connected to the input of the pulse counter. The device also has a control panel connected to the X-ray machine via a high-voltage cable.

According to its design, the ARINA device is designed to operate on low currents, but high voltage - the operating voltage is approximately 150 kV per nanosecond pulse. In connection with the foregoing, this device poses a danger to the operator as a source of high voltage current and X-ray radiation synchronous with it, because during the exposure the operator is located at a distance of no more than 20 meters from the X-ray radiation unit, since the device is controlled from the control panel associated with the X-ray machine with a cable about 20 meters long.

Known monoblock source of x-rays of their patent RF 51854, publ. March 10, 2006 [2].

The X-ray source monoblock belongs to X-ray engineering and can be used to obtain X-ray images for industrial transillumination, medical diagnostics, etc. To reduce the mass of the monoblock and reduce its dimensions in the monoblock of the X-ray source, containing an X-ray tube, consisting of a housing, cathode and anode units, as well as a generator device, the high-voltage output of which is connected to the cathode unit, the internal volume of the monoblock body is filled with a solid-state high-voltage insulator. The anode unit is made in the form of an anode tube placed outside the vacuum cylinder of the X-ray tube, at the end of which the target is installed. The design of the target can be of a perforated or massive type and provides the smallest possible focal length. The design of the insulator ensures prompt installation of the x-ray tube.

A disadvantage of the well-known utility model is the lack of the ability to diagnose and repair a high-voltage power source placed in a solid-state high-voltage insulator.

Known monoblock portable x-ray machine from RF patent 82980, publ. May 10, 2009 [3].

The utility model relates to the field of flaw detection of materials by transilluminating them with X-rays, namely to radiation sources of portable X-ray machines for detecting defects in metallic materials and products, in particular, steels and alloys. The proposed technical solution can be implemented both in industrial devices and in devices for working in the field. EFFECT: optimization of heat exchange conditions in the monoblock, which provides increased reliability and increased time of its continuous operation, and, as a result, increased productivity of x-ray control.

The monoblock of a portable X-ray apparatus contains a thermionic X-ray tube and a high-voltage direct voltage source placed in a metal case filled with a liquid dielectric. In contrast to the well-known, in the proposed monoblock, an X-ray tube placed in a metal case filled with a liquid dielectric is located inside a hollow cylinder made of a solid dielectric, the inner diameter of which is equal to the outer diameter of the X-ray tube, and the minimum wall thickness is equal to the ratio of the maximum value of the output voltage of the high-voltage source to the maximum tension electric field, which does not lead to the destruction of this dielectric. Transformer oil can be chosen as a liquid dielectric. Fluoroplast can be chosen as a solid dielectric. The disadvantage of the well-known PM is the lack of heat removal from the anode of the tube.

Known generator of x-rays from patent RU204394, publ. May 24, 2021 [4]. The utility model relates to X-ray engineering, and more specifically to X-ray equipment containing X-ray tubes, with the installation of at least part of the supply equipment in the same housing, and can be used in the development of X-ray generators (GRI) for non-destructive testing, mainly in the field , in particular, to control the welds of oil pipelines, gas pipelines and oil product pipelines with the location of the GRI inside the pipe. The X-ray generator contains a housing, an X-ray tube mounted with its cathode and an anode on support insulators, and a bipolar high voltage source with a midpoint output, the negative output of the source being connected to the X-ray tube cathode, the positive one to its anode, and the midpoint to the housing. The bipolar source includes two pulse transformers, and the anode support insulator is made of a ceramic material with a high thermal conductivity of at least 15 W/(m⋅°K) and electrical resistance of at least 10 ¹² Ohm⋅cm. The utility model provides a significant heat removal of the anode while maintaining the insulating properties (electrical strength).

The disadvantage of the known utility model is the high complexity of manufacturing a ceramic insulator with specified geometric parameters. The geometric parameters are set before the insulator is baked. During baking at high temperatures, deformation of the surfaces that come into contact with the anode of the X-ray tube and the body of the X-ray machine occurs, as a result of which the heat transfer from the anode of the tube to the body is disturbed.

Known for obtaining polymer insulators from patent RU2143147, publ. December 20, 1999 [5]. The method includes installing an insulator rod inside a split mold, supplying a dosed amount of insulating material under pressure and curing on the rod in two stages, the insulating material being subjected to preliminary shear deformation at a certain deformation rate and time.

The disadvantage of this method is the high cost of the resulting polymer insulator.

A known method for producing polymer insulators from patent RU2389096, publ. May 10, 2010 [6].

The invention relates to methods for producing high-voltage polymer insulators by injection molding and can be used in the electrical industry. The method includes preliminary shear deformation of an insulating material based on filled siloxane compositions at a certain shear rate and deformation time, installing an insulator rod inside a split mold, supplying a dosed amount of insulating material under pressure and curing it on the rod in two stages, while in the insulating material regenerate is preliminarily introduced in the form of a high-viscosity pasty mass of the same material, which is added in an amount of 5-20 wt.h. per 100 wt.h. insulating material, and the time of preliminary shear deformation is reduced in proportion to the amount of introduced regenerate. The technical result is the ability to obtain polymer insulators at a lower cost.

The disadvantage of this method is the production of polymer insulators with low electrical insulating properties.

It is an object of the present invention to provide a method for manufacturing a solid state insulator for an X-ray machine, in which the solid state insulator has a high degree of heat dissipation and a reduced probability of electrical breakdown and failure.

The specified technical result is achieved by the fact that the method of manufacturing a solid-state insulator for an X-ray machine includes preparing a mixture of a polymer with a ceramic filler powder and subsequent shaping of the product, while a two-component silicone polymer is used to prepare the polymer mixture: a compound, a tin-based catalyst and a ceramic filler - oxide powder aluminum (Al ₂ O ₃ ), taken respectively in a volume ratio of 100/(3-5)/(5-7), and first aluminum oxide powder (Al ₂ O ₃ ), treated with high-energy activation in a planetary mixer at a speed of 1800 rpm min ^-1 for 300 sec, then its organosilicon polymer (compound) is introduced using a mixer at a speed of 120 rpm ^-1 for 60 min, a tin-based catalyst is added and the resulting mixture is mixed with a mixer at a speed of 300 rpm ^-1 for 2 min, followed by evacuation to a residual pressure of 1.5⋅10 ^-3 Pa, the shaping of the product is carried out in stages, filling the injection mold in volumes of 150 ml with the resulting polymer mixture, followed by placing the polymer matrix on a vibrating stand for 10 min. After the high-energy activation treatment, the alumina powder particles have an average size of the order of 10 µm.

An X-ray apparatus in which solid-state insulators are used consists of: an emitter, a power supply unit, a control panel interconnected by electric cables, while the emitter contains an X-ray tube, which is fed by two multipolar high-voltage multiplier blocks: cathode and anode, which are powered through isolation transformers from the alternating voltage driver; a high-potential heating block, a pump for circulating oil through the anode oil cooler; anode heatsink; liquid cooling radiator; fan block; device for compensating excess oil pressure when it is heated. All internal elements of the emitter are mounted in a welded cylindrical housing, the inner surface of which is covered with electrical paper, laid in several layers; the ends of the case are made as covers for access to the internal parts of the emitter, sealed connectors are installed on the outside of the covers; an oil-filling hole plugged with a plug is installed on the cover of the anode compartment. The high-voltage heating unit and the anode radiator are installed in solid-state insulators manufactured according to the claimed method.

Disclosure of the essence of the invention.

X-ray sources are most widely used in practical applications in various branches of science, medicine and industry. Issues related to the improvement of X-ray machines (RA) continue to be relevant due to the practical need for small-sized X-ray sources, which are characterized by high reliability, durability and safety in operation.

At present, due to a number of undeniable advantages, portable X-ray machines made in the form of a monoblock are widely used.

Improving approaches to increasing the electrical strength of dielectric materials and elements in X-ray machines under conditions of their operation, complicated by high-intensity temperature and radiation fields, is an important direction to improve their fault tolerance, durability and safety.

The invention is illustrated by figures 1-2.

In FIG. 1 proposed the layout of a bipolar monoblock X-ray apparatus with high-voltage combined insulation, where: A - emitter, B - power supply, C - control panel.

This layout provides the device with the ability to power both from a conventional electrical network 220 V, 50-60 Hz, and from a battery with a voltage of 120 V. If necessary, you can easily switch to a different battery voltage.

In FIG. 2 shows the emitter, where:

1 - two bipolar high-voltage multiplier blocks cathode and anode, 2 - high-potential heating block, 3 - pump for oil circulation through the anode oil cooler, 4 - device for compensating excess oil pressure when it is heated, 5 - welded cylindrical body, 6 - solid-state emitter insulators , 7 - x-ray tube, 8 - isolation transformers, 9 - electrical paper laid in several layers (paper insulation), 10 - alternating voltage driver, 11 - anode heatsink, 12 - liquid cooling heatsink, 13 - fan unit.

The total voltage on the X-ray tube (7) is the sum of two voltages, approximately in amplitude, formed by the anode and cathode multipliers (1). These multipliers are located on separate frames and are fed through isolation transformers (8), incandescent power windings, measuring resistors.

The isolation transformers (8) supplying the multipliers (1) are supplied with an amplitude-adjustable alternating current voltage with a frequency of 50 kHz.

Isolating transformers (8) increase the voltage to an amplitude value of 4 kV and feed the multipliers (1). The temperature sensor is located in the cathode compartment of the emitter. When manufacturing an experimental sample, the number of temperature sensors (not shown in Fig. 2) can be increased (in both compartments) for more accurate temperature measurement. The thermal protection circuit is configured in such a way that if the oil temperature exceeds 60 °C, the high voltage supply to the X-ray tube is stopped. The possibility of restarting the device is restored after the temperature drops to 40 °C. All internal elements of the emitter are mounted in a welded cylindrical housing (5). The oil filling hole, plugged with a plug, is installed on the cover of the anode compartment (3). The emitter can work in any position. The insulating medium in the emitter is dried and purified transformer oil. To seal the joints, rubber oil and petrol resistant gaskets and glue-sealant are used.

RA works as follows.

The voltage from the network 220 V 50 Hz is supplied to the power supply unit (B), which generates an adjustable constant voltage from 100 to 250 V. Further, this voltage is supplied to the alternating voltage generation unit (10) of the emitter, where an alternating voltage of a rectangular shape with a frequency of 50 kHz is generated, which, in turn, is fed to the decoupling step-up transformers (8) of the anode and cathode multipliers (1). Isolating transformers (8) increase the voltage to an amplitude value of 4 kV and feed the multipliers (1). The voltage of the multipliers is applied to the x-ray tube (7). The total voltage on the X-ray tube is the sum of two voltages approximately equal in amplitude, generated by the anode and cathode multipliers (1). On the cathode isolation transformer (8) there is a winding supplying the high-voltage heating unit (2). The heating block (2) feeds the heating of the X-ray tube with the specified voltage.

During RA operation, the heat generated at the anode of the X-ray tube (7) is removed in two ways from the anode radiator (11):

- through the solid-state insulator (6) to the housing (5);

- through a forced liquid cooling system (12.13).

During the operation of the RA, the transformer oil is heated and its volume increases. To compensate for changes in the volume of oil, a device for compensating for excess oil pressure during its heating (4) is used.

The operator sets and controls the operating parameters of the X-ray machine, and also controls its operation using the control panel (B).

Combined insulation of oil and solid dielectrics takes place in PA designs also in those cases where in general it would be possible to use only solid insulation. However, for reasons of cooling and papering insulation by oil impregnation of increased penetration strength, it is more acceptable to have insulation from layers of oil and solid insulation. For radio electronics, combined insulation is often used, consisting of materials of various nature. In the developed RA, the use of combined insulation was carried out, consisting of: cast insulation based on solid polymers, paper insulation with oil impregnation and transformer oil.

Highly polymerized plastics are used as high voltage insulation. Polymers have relatively low thermal stability. The density of polymers is very low compared to porcelain or glass. Relatively low mechanical strength is improved by reinforcement (composite materials). Relatively low thermal conductivity is increased with mineral-based fillers. The resistance of polymers to moisture, radiation, chemicals varies depending on the material. The highest possible dielectric strength can be achieved with polymers, but it is highly process dependent. Unfortunately, partial discharges at defects can often lead to very rapid erosion of polymer insulators. The electrical conductivity of polymers is very low compared to ion-conducting materials such as porcelain and glass. The advantage of many polymers is thermoplasticity, which allows the formation of insulators of almost any shape from such plastics. These materials can also be used in combination with mineral powders in order to improve the insulating, heat-conducting and mechanical properties. The technological chain for the manufacture of such polymeric materials includes degassing, moisture removal, molding (3D printing) under pressure. A mandatory requirement for the quality of polymeric insulating materials is their uniformity in density and powder content (for composites with powders). When using hardening compositions, it is necessary to achieve homogeneity of insulating products in terms of mechanical and electrical properties.

The manufacture of a solid-state insulator according to the proposed method includes the preparation of a mixture of polymer with ceramic filler powder and subsequent shaping of the insulator. To prepare the mixture, the initial components are taken: a two-component silicone polymer - a compound and a catalyst based on tin and aluminum oxide powder, respectively, in a volume ratio of 100/(3-5)/(5-7).

Before being introduced into the polymer mixture, the Al ₂ O ₃ ceramic filler is treated with high-energy activation in a planetary mixer at a speed of 1800 rpm ^-1 for 300 s. After the high-energy activation treatment, the alumina powder particles have an irregular shape with an average size of about 10 µm.

Alumina powder (Al ₂ O ₃ ) treated with high-energy activation is introduced into the liquid silicone polymer (compound) using a mixer at a speed of 120 rpm ^-1 for 60 minutes. The share of the introduced ceramic filler in the polymer matrix is 5-7 vol. %. The volume fraction of the ceramic filler of aluminum oxide powder in the polymer matrix is more than 7 vol. % complicates the process of manufacturing a solid-state insulator, due to an increase in the viscosity of the polymer mixture. At less than 5 vol. % content of ceramic filler, the necessary characteristics of a solid-state insulator are not achieved, namely, its mechanical strength and electrical insulating properties at elevated temperatures, i.e. at temperatures above 100 °C.

Then add the catalyst based on tin in the amount of 3-5 vol. % and mix the polymer mixture with a mixer at a speed of 300 rpm^-1 for 2 min, followed by evacuation to a residual pressure of 1.5⋅10^-3 Pa. The shaping of the insulator is carried out in stages, by filling the injection mold with volumes of 150 ml of polymer mixture with ceramic filler and subsequent placement of the polymer matrix on the shaker for 10 min.

Example 1

Two-component organosilicon polymer was used as starting materials: PENTELAST-718 compound, Penta-18P tin-based catalyst, and aluminum oxide (Al ₂ O ₃ ) powder.

Powder of aluminum oxide (Al ₂ O ₃ ) is preliminarily subjected to high-energy activation. To do this, take a sample of aluminum oxide powder and grinding media in a mass ratio of 1:10 and loaded into a planetary mixer. Processing is carried out at a speed of 1800 rpm ^-1 for 300 seconds. After treatment, the alumina powder particles had an average size of about 10 µm. The proportion of aluminum oxide in the polymer matrix was 7 vol. %. The introduction of aluminum oxide into the liquid polymer was carried out using a laboratory mixer at a speed of 120 rpm ^-1 for 60 min. The introduction of the Penta-18P catalyst in the amount of 5 vol. % into the resulting mixture was carried out using a laboratory mixer at a speed of 300 rpm ^-1 for 2 min, followed by evacuation to a residual pressure of 1.5 10 ^-3 Pa. The casting mold was filled in stages, in volumes of 150 ml of the polymer mixture, followed by placing the polymer matrix on a vibrating stand for 10 minutes.

The insulator obtained according to example 1 has the following performance characteristics: relative elongation at break 80%; tensile strength 2.0 MPa; hardness 23 Shore A; electrical strength of the material is 10.3 kV/mm.

Example 2

Two-component organosilicon polymer was used as starting materials: organosilicon compound KLT-75T, tin-based catalyst K-1 (TU 38.103691-89), and aluminum oxide powder (Al ₂ O ₃ ).

The technological sequence of operations is carried out analogously to example 1. The difference is, taken for example 2, the volume ratio of the initial components is 100:3:5, respectively, the organosilicon compound of the KLT-75T brand, the catalyst based on tin of the K-1 brand and the powder of aluminum oxide (Al ₂ O ₃ ).

The insulator obtained according to example 2 has the following performance characteristics: relative elongation at break 50%; tensile strength 2.5 MPa; hardness 25 Shore A; electrical strength of the material is 13.2 kV/mm.

The material of a solid state insulator is elastic, so:

-provides additional vibration protection of the x-ray tube during transportation and operation.

- allows not to take into account the thermal coefficients of expansion of the X-ray tube and the housing when designing the elements of fastening the tube to the housing.

In this case, as already mentioned, the insulators are not the main element of the heat sink for the anode of the tube, since the anode is additionally cooled through the anode radiator (11) by the forced liquid cooling system (12,13).

The invention will make it possible to manufacture a small-sized X-ray machine with improved fault tolerance, durability and safety, achieved through a rational choice of a method for manufacturing a solid-state insulator and ways of heat dissipation due to the proposed design of the emitter.

Claims (3)

1. A method for manufacturing a solid-state insulator for an X-ray machine, including preparing a mixture of a polymer with a ceramic filler powder and subsequent shaping of the product, characterized in that a two-component silicone polymer is used to prepare the polymer mixture: a compound, a tin-based catalyst and a ceramic filler - aluminum oxide powder ( Al ₂ O ₃ ), taken respectively in a volume ratio of 100/(3-5)/(5-7), and first, aluminum oxide powder (Al ₂ O ₃ ) is treated with high-energy activation in a planetary mixer at a speed of 1800 rpm ^-1 for 300 s, then its organosilicon polymer is introduced with a mixer at a speed of 120 rpm ^-1 for 60 minutes, a tin-based catalyst is added and the resulting mixture is mixed with a mixer at a speed of 300 rpm ^-1 for 2 minutes followed by evacuation to a residual pressure of 1.5⋅10 ^-3 Pa, the shaping of the product is carried out in stages, filling the injection mold in volumes of 150 ml with the resulting polymer mixture, followed by placing the polymer matrix on a vibrating stand for 10 minutes. 2. The method according to claim 1, characterized in that, after the high-energy activation treatment, the alumina powder particles have an average size of about 10 µm. 3. The method according to claim 1, characterized in that the x-ray machine consists of: an emitter, a power supply, a control panel interconnected by electric cables, while the emitter contains an x-ray tube, which is fed by two bipolar high-voltage multiplier blocks: cathode and anode, which are powered through isolation transformers from an alternating voltage driver; a high-potential heating block, a pump for circulating oil through the anode oil cooler; anode heatsink; liquid cooling radiator; fan block; device for compensating excess oil pressure when it is heated; at the same time, all internal elements of the emitter are mounted in a welded cylindrical housing, the inner surface of which is covered with electrical paper laid in several layers; the ends of the case are made as covers for access to the internal parts of the emitter, sealed connectors are installed on the outside of the covers; an oil-filling hole plugged with a plug is installed on the cover of the anode compartment; moreover, the high-voltage heating unit and the anode radiator are installed in solid-state insulators manufactured according to the claimed method.