RU167782U1 - Pipe Surface Cleaning Machine - Google Patents

Abstract

The utility model relates to the field of purification from contamination of metal products in vacuum at various stages of the technological process and can be used in pipe rolling, in the manufacture and repair of coated pipes to remove old coatings, scale, rust, technological lubricants and other contaminants from pipe surfaces. The plasma surface cleaning machine for pipes includes at least one external cleaning vacuum box equipped with means for loading and unloading pipes, solenoids, oscillators, welding rectifiers, chokes and a vacuum system. In the box for external cleaning, cooled electrodes are placed, which are installed from each other along the pipe at a distance that is a multiple of the length of the pipe, evenly placed around the perimeter of the pipe and grouped into clusters. The electrodes in the cluster are equipped with a means to maintain a gap between the working surface of each electrode and the surface of the pipe, the electrodes can be made of ferromagnetic or diamagnetic materials and have channels for cooling. Also in the box are blocks of reciprocating movement of the pipe and a roller table for moving the pipes at a distance equal to the distance between the electrode clusters. The machine contains at least one vacuum box for internal cleaning of the pipe surface, in which pipe moving blocks are placed and a coaxially cooled electrode is placed on the rod. Blocks of movement of the pipe are made with the possibility of rotation of the pipe around the longitudinal axis and the reverse movement of the pipe along the electrode. The rod with the electrode is equipped with devices for centering and

Description

The utility model relates to the field of purification from contamination of metal products in vacuum at various stages of the technological process and can be used in pipe rolling, in the manufacture and repair of coated pipes to remove old coatings, scale, rust, technological lubricants and other contaminants from pipe surfaces.

In the production of pipes, including seamless drawn by drawing method, the presence of oxides on the inner and outer surfaces of pipes is unacceptable, because they destroy the working tool (dies). Therefore, acid pickling is widely used for the cleaning of scale and rust in the production of such pipes, which is harmful to staff and the environment. This necessitates the development of environmentally friendly technologies and equipment for cleaning the surface of pipes.

Known devices for cleaning the outer surface of pipes, which are based on:

- exposure to an arc discharge on the workpiece surface at atmospheric pressure (ed. certificate of the USSR No. 476041, B08B 1/00, 1971; US patent No. 5143561, B21B 45/06, 1992; French patent No. 2664510, B21B 37/08, 1992 );

- exposure to an arc discharge on the workpiece surface in a protective gas environment (ed. certificate of the USSR No. 1272725, C22B 9/20, 1985; ed. certificate of the USSR No. 1770420, C22B 9/20, 1992; ed. certificate of the USSR No. 1812239 C23C 14/32, 1993);

- the impact of an arc discharge on the treated surface of products in a protective gas stream (ed. certificate of the USSR No. 171056, V23K 9/00, 1965; Maksimov L.Yu., Krivonos GA Ecological safe metal cleaning in the stream. - Heavy engineering, 1997, No. 5);

- exposure to an arc discharge on the workpiece surface in vacuum with the application of a constant magnetic field on the electric arc (ed. certificate of the USSR No. 719710, B08V 3/10, 1980; ed. certificate of the USSR No. 935141, B08B 3/10, 1982, ed certificate of the USSR No. 1749279, C22B 9/20, 1992; Paton B.E. et al. Plasma-arc remelting of the surface layer of ingots and billets. Steel, 1987, No. 1).

Known devices for cleaning pipes have significant disadvantages:

- acid and other chemical etching leads to undesirable hydrogenation of the metal, which reduces the strength of the pipes, and is also extremely harmful to the environment,

- low productivity when cleaning pipes.

The closest technical solution adopted for the prototype is a device for cleaning metal surfaces (RF patent No. 2139151, B08B 7/04, B08B 9/00, publ. 10.10.1999). The device is designed to carry out cleaning of the outer surface of pipes from scale, rust, process greases and other contaminants. The device comprises a vacuum chamber in which the pipes are cleaned, a vacuum system, pipe loading and unloading mechanisms, pipe reciprocating blocks and cooled electrodes. The outer surface of the pipes is cleaned in vacuum by electric arc discharges using electrodes as the anode, and the pipe being cleaned as the cathode.

The disadvantages of the device are low cleaning performance, because ring electrodes are not capable of fail-safe operation at high currents in discharges, and insufficient quality of surface cleaning.

The technical problem solved by the utility model is to create a machine for cleaning the surface of pipes from scale, rust, old coatings, process lubricants and other contaminants using environmentally friendly technology.

The technical result is to increase the productivity and quality of pipe cleaning.

This result is achieved due to the fact that in the machine for cleaning the surface of the pipes, containing at least one external box vacuum cleaning, equipped with a means for loading and unloading pipes, and a vacuum system, the reciprocating blocks of the pipe and cooled electrodes are placed in the box, placed from each other along the pipe at a distance multiple of the length of the pipe, according to a utility model, the machine contains at least one vacuum box for internal cleaning of the pipe surface, in which the blocks are placed emescheniya tube mounted coaxially and cooled electrode disposed on the rod, wherein the cleaning in the outer box electrodes are arranged uniformly over the tube circumference and are grouped into clusters. In addition, the electrodes in the cluster are equipped with a means for maintaining a gap between the working surface of each electrode and the surface of the pipe, the electrodes are made of ferromagnetic or diamagnetic materials and have channels for cooling. In the external cleaning box there is a roller table for moving the pipes at a distance equal to the distance between the electrode clusters, and in the internal cleaning box the pipe moving blocks are made with the possibility of ensuring the rotation of the pipe around the longitudinal axis and the reverse movement of the pipe along the electrode, while the rod with the electrode is equipped with devices for centering and connected to the power supply and cooling of the electrode.

According to the proposed utility model, the cleaning of the outer and inner surfaces of the pipe is carried out using electric discharges. At the same time, electrodes (anodes) are placed over the surface of the pipe to be cleaned, and the pipe is used as a cathode. Electric discharges between the anodes are ignited, and a group of cathode “spots” is formed on the pipe surface opposite each anode (I. G. Kesaev, ZhTF 34, 1482 (1964)).

The mechanism of surface cleaning in the cathode spot of the electric arc from oxides and any other contaminants consists in exposing the cathode surface to a stream of high-energy plasma ions generated by emission electrons in the cathode region of the arc. Energy flow with a density of the order of 10 ¹¹ W / m ² is transferred to the surface being cleaned by the flow of bombarding ions accelerated by the potential drop in the cathode spots. Moreover, according to the estimates of a number of researchers (Rakhovsky V.I. Physical basis for switching electric current in a vacuum. - M.: Nauka, 1970; Kesaev IG. Cathodic processes of an electric arc. - M .: Nauka, 1968), in the cathodic the spot temperature reaches (5-10) ⋅10 ³ K, and the vapor pressure of oxides and metal - 10 ⁷ -10 ⁸ PA. The mechanism for cleaning metals from oxides and other contaminants in the cathode spot can be represented in the freeze-frame mode as follows. Above the liquid metal surface there is a layer of dense metal metal, from the surface of which a jet of a gas mixture of a metal with dissociated oxides flows into the surrounding space at a supersonic speed. In this mixture, components with a low ionization potential (mainly metal atoms — according to the Saha equation (Finkelburg V., Mecker G. Electric arcs and thermal plasma. - M .: IL, 1961)) are in the plasma state. Cathode spots randomly or under the influence of their own or external magnetic fields move along the surface of the product being cleaned. Studies have shown that the speed of movement of cathode spots with a current density of about 10 ¹⁰ A / m ² depends on the thickness of the oxide layer (furnace and mill scale, rust, other contaminants), the saturated vapor pressure of the product material and pollutants on the surface, thermal conductivity, and the temperature of the cleaned products, configuration and surface topography, pressure and chemical composition of the environment (the speed of movement increases sharply with the addition of hydrogen).

In some cases, the cathode region of the arc discharge on the product being cleaned is a continuous filiform front at the interface between the purified metal and the oxide coating. The length or perimeter of the filiform front of the cathode region can reach hundreds of millimeters. This is the most productive regime of plasma-arc cleaning (ES Senokosov, AE Senokosov. Plasma electric arc cleaning of metal products, Metallurg, 2005, No. 4).

The highest productivity and high quality of plasma electric arc cleaning is achieved by lowering the pressure of the external medium relative to atmospheric to 1.3 × 10 ² - 1.33 Pa. In this pressure range, the electric arc is stable, the partial pressure of oxygen is below the dissociation elasticity of most metal oxides at temperatures realized in the cathode region of the vacuum arc, due to which the dissociation of oxides and other contaminants, their ionization and evaporation (sublimation) are intensively carried out on the surface being cleaned. Metals are mainly ionized, while ions are accelerated and returned to the surface of the product being cleaned under the influence of an electric field arising in the region of the cathodic potential drop. As a result, a layer of metal reduced from oxides forms on the surface of the product being cleaned. The energy consumption for cleaning 1 m ^{2 of the} surface, depending on the degree of contamination, is 0.3-2.0 kW⋅h.

In practice, it turned out that the performance of cleaning steel pipes from scale and rust also depends on the number of cathode spots on the surface being cleaned, which directly depends on the total discharge current. Attempts to increase the cleaning performance by increasing the discharge current through one ring anode ended with the fact that after 1000 amperes the strength of the intrinsic magnetic field of the arc began to prevail and pulled it into one cathode spot, which immediately led to the burning and fusion of the pipes.

Therefore, in the proposed utility model, instead of a single annular anode, several small-sized anode electrodes are used to clean the outer surface of the pipe, evenly spaced around the perimeter of the pipe and grouped into clusters. This allowed through each anode to increase the discharge current to 1000 amperes, i.e. to a dangerous level, when the cathode spots collapse into one spot and can burn through the pipe. Such a solution led to a significant increase in the total discharge current in the cluster cross section, and, consequently, to an increase in the cleaning efficiency.

To clean the inner surface of the pipe, the machine is equipped with at least one vacuum box, in which a cooled electrode is mounted on the rod along its axis and pipe moving blocks are placed. In the box, low pressure is set, with the help of displacement blocks, the pipe is reversed with the internal cavity along the electrode, the discharge is ignited and the inner surface is cleaned along its entire length. The cleaning performance is determined by the magnitude of the discharge current and the number of boxes of external and internal cleaning, which are placed in pairs in the machine — an external cleaning box and an internal cleaning box (steam).

In addition, in the proposed machine, the productivity of pipe cleaning is increased due to the fact that the cavity of the vacuum boxes of the external and internal pipe cleaning have the ability to communicate with each other through a pipeline with a valve (not shown conditionally in the drawings). Moreover, if in one box there is atmospheric air pressure (the pipe intended for cleaning has just been loaded into the box and sealed it), and in the other box is vacuum (the box has not been depressurized, but the cleaning has already been completed), then when the cavity of the boxes is informed, the pressure in them evens out. In this case, one of the boxes is half filled with air and until ready to remove the cleaned pipe, it is still necessary to supply atmospheric air, and the other box is half already pumped out and air is still required to be pumped out to operating pressure. Filling the boxes with atmospheric air is carried out quickly, no more than one second. Pumping to operating pressure is associated with a feature of the operation of vacuum pumps. The speed of vacuum pumps depends on the value of the initial (inlet pressure) in the working box (Vacuum technology. Handbook edited by ES Frolov and V.E. Minaichev, Moscow: Engineering, 1992. P. 321, Fig. 10.30) and initially several orders of magnitude less if the pumping starts from atmospheric pressure, compared with if the pumping starts from a previously pumped volume. Preliminary pumping of dense atmospheric air from the working box by several orders of magnitude increases the productivity of vacuum pumps, thereby significantly reducing the time for preparing the box for cleaning the pipe. In practice, pumping out the box, starting from atmospheric pressure to operating pressure, takes 10-15 minutes, and with preliminary pumping out, due to equalization of pressure in the boxes, does not exceed 2-3 minutes (with the time it takes to clean the pipe 4-6 minutes). In addition, the use of such a pumping scheme can significantly save on energy costs.

The utility model is illustrated by drawings, where in FIG. 1a shows a box for external cleaning of the surface of pipes, FIG. 1b shows a section aa in FIG. 1a, in FIG. 2 shows a box for internal cleaning of a pipe surface. External and internal cleaning boxes make up a pipe cleaning machine.

The list of items in FIG. one:

1 - box body external pipe cleaning;

2 - the entrance hatch of the box for external cleaning;

3 - exit hatch of the box for external cleaning;

4 - electrode;

5 - the body of the electrode cluster;

6 - device for maintaining the interelectrode gap;

7 - power supply and cooling of the electrode;

8 - cleaned pipe;

9 - blocks moving the pipe;

10 - drive roller table;

11 - box vacuum system;

12 - vacuum line.

The list of items in FIG. 2:

13 - box body of the internal pipe cleaning;

14 - entrance hatch of the box for internal cleaning;

15 - blocks moving the pipe;

16 - drive roller table;

17 - electrode;

18 is a device for centering the electrode at the entrance to the pipe;

19 - power supply and cooling of the electrode;

20 - rod;

21 is a device for centering the rod inside the pipe.

The proposed machine for cleaning the surface of the pipes is as follows. The pipe 8, designed to clean the outer surface, is loaded into the housing of the external cleaning box 1 through the entrance hatch 2 of the box. Inside the box 1, the pipe 8 is moved using the blocks of the reciprocating movement 9 and the drive roller table 10. After loading the pipe 8, the entrance hatch 2 is closed and the box 1 is sealed. At the first start of the cleaning machine, for example, at the beginning of the shift, the box 1 is evacuated using a vacuum system 11 through the vacuum line 12. During further work, as mentioned above, the primary pumping of the box is carried out by equalizing the pressure between boxes 1 and 13 after in the latter, the pipe was cleaned and still vacuum in it. Further vacuum evacuation to the operating value continues from the evacuation system 11. After reaching the operating vacuum in box 1, a positive potential is applied to each electrode 4 from the power supply and cooling units 7 (the diagram shows only one), the electrodes are cooled at the same time, and 8 from all power and cooling units supply negative potential.

After reaching the working pressure in the box 1 between each electrode (anode) 4 and the pipe 8 initiate an electrical discharge. Cathode spots are scanned on the surface of the pipe being cleaned by 8 magnetic fields (not shown in the diagram) or in another way, thereby cleaning the pipe surface from oxides and any other contaminants. The interelectrode gap between the electrodes (anodes) 4 and the outer surface of the pipe 8 is set and supported by the devices for maintaining the interelectrode gap 6, which ensures uniform pipe cleaning.

The pipe 8 in the cleaning process in the box 1 is moved using blocks 9 reciprocating to a length equal to the distance between the cases of the electrode clusters 5 in which the electrodes are placed 4. The number of electrodes in the cluster varies depending on the diameter of the pipe. Clusters 5 are placed from each other at a distance of 1, a multiple of the length of the pipe L: 1 = L / k, where k is the number of electrode clusters, k = 1, 2, 3 ... At the same time, in the process of cleaning the outer surface, it is enough to move the pipe 8 in a vacuum box only for a length of 1 and the entire pipe outside will be cleaned. This made it possible to significantly reduce the length of the entire machine and increase the productivity of external pipe cleaning by 2–3 times.

The experience in operating graphite electrodes showed their low efficiency due to rapid wear. In the proposed utility model, the electrodes can be made of a ferromagnetic material, when alternating traveling magnetic fields are used to move the cathode spots on the surface to be cleaned, and from diamagnetic material, when constant magnetic fields are used to scan the cathode spots on the surface to be cleaned. The electrodes have good electrical conductivity and can be made with channels for cooling.

After cleaning the outer surface of the pipe 8, the electric discharges are suppressed, the vacuum line 12 is shut off. The cavity of the external cleaning box body 1, which is still under vacuum, is reported through a pipeline (not shown conventionally in the drawings) with the internal cleaning box body cavity 13, the entrance hatch 14 of which is closed (the box at this point is ready to clean the pipe 8) and the vacuum line 12 (Fig. 2) is closed. This leads to almost instantaneous pressure equalization in the cavities of boxes 1 and 13.

After this, the cavity of the boxes is disconnected, atmospheric air is supplied to the box 1 and the cleaned pipe 8 is removed through the outlet hatch 3 of the external cleaning box, after which the hatch 3 is closed and the box is prepared for cleaning the next pipe. At the same time, the cavity of the box body 13 continues to be pumped out by the evacuation system 11 through the vacuum line 12 (Fig. 2).

In FIG. 2 shows schematically the second part of the machine - a vacuum box 13 for internal cleaning of the pipe surface. After cleaning the outer surface, the pipe 8 is loaded into the inner cleaning box 13 through the inlet hatch 14 using the transfer units 15 and the drive roller table 16. The inlet hatch 14 is closed, the box 13 is sealed and vacuumized using the vacuum system 11 through the vacuum line 12. If the cleaning machine pipe already worked, then the cavity of the box 13 communicate through the pipeline (not shown conventionally in the drawings) with the cavity of the box 1 and equalize the pressure. After equalizing the pressure, the cavities of the boxes 1 and 13 are disconnected and the working vacuum in the box 13 is created by a vacuum system 11 through the vacuum line 12 (Fig. 2). Using the moving blocks 15 and the drive roller table 16, the pipe 8 is rolled along the entire length along the electrode 17 onto the electrode 17, which is mounted on the rod 20 and centered along the axis of the pipe by the centering device 18. At the same time, a positive potential is applied to it from the power supply and cooling unit 19 of the electrode 17, and on the pipe 8 is a negative potential, while between the electrode 17 and the inner surface of the pipe 8, an electric arc discharge is ignited. Inside the pipe 8, the electrode 17 and the rod 20 are installed along the longitudinal axis and centered using the centering device 21. The pipe 8 in the cleaning process performs a reverse movement and can rotate around the longitudinal axis. Cleaning can be carried out due to several complete movements of the pipe 8 relative to the electrode 17 along the entire length of the pipe. After cleaning, the electric discharge between the electrode 17 and the inner surface of the pipe 8 is suppressed, the box evacuation system 11 is turned off, and the vacuum line 12 is closed (Fig. 2). The cavity of the box 13 is communicated with the cavity of the box 1, after equalization of the pressure, the cavity of the boxes is disconnected, atmospheric air is supplied to the box 13 and a cleaned pipe 8 is removed through the hatch 14.

The next pipe arrives for cleaning, and the machine continues to work according to the described cycle.

The number of boxes can be increased, but the principle of air bypass and the use of "exhausted" vacuum must be maintained, and for this the number of boxes of external and internal surface cleaning must be paired, i.e. add together the box of external and internal cleaning.

A prototype pipe cleaning machine was manufactured and tested at one of the pipe plants. To clean from contamination, in particular from scale, steel seamless pipes with a diameter of 33 to 159 mm were subjected. As a result of the tests, the cleaning performance increased by 2–3 times, the quality of cleaning the surface of the pipes increased, and the working life of metal electrodes increased, there are no comments on the ecology.

The proposed machine for cleaning pipes works using environmentally friendly technology, therefore, it is relevant and promising and can be used in enterprises for the manufacture and repair of pipes.

Claims (6)

1. Machine for cleaning the surface of the pipes, containing at least one vacuum box external cleaning, equipped with a means for loading and unloading pipes, and a vacuum system, in the box placed blocks reciprocating movement of the pipe and the cooled electrodes placed from each other along the pipe on a distance multiple of the length of the pipe, characterized in that the machine contains at least one vacuum box for internal cleaning of the surface of the pipe, in which the blocks for moving the pipe and mounted coaxially cooled electric ktrod disposed on the rod, wherein the cleaning in the outer box electrodes are arranged uniformly over the tube circumference and are grouped into clusters. 2. The machine according to claim 1, characterized in that the electrodes in the cluster are provided with means for maintaining a gap between the working surface of each electrode and the surface of the pipe. 3. The machine according to p. 1 or 2, characterized in that the electrodes are made of ferromagnetic material and have channels for cooling. 4. The machine according to claim 1 or 2, characterized in that the electrodes are made of diamagnetic material and have channels for cooling. 5. The machine according to claim 1, characterized in that a roller table is placed in the external cleaning box to move the pipes at a distance equal to the distance between the electrode clusters. 6. The machine according to claim 1, characterized in that in the internal cleaning box, the pipe moving blocks are arranged to allow the pipe to rotate around the longitudinal axis and reverse the pipe along the electrode, while the rod with the electrode is equipped with centering devices and is connected to the power supply unit and electrode cooling.

Images