Concern "Electromontazh"
Installation instructions for bus contact connections
between each other and with the terminals of electrical devices
UDC 621.315.68 (083.96)
Instead of VSN 164-82
This instruction has been developed to develop the basic provisions of GOST 10434-82, GOST 17441-84, the current Electrical Installation Rules (PUE) and building codes and rules (SNiP).
The instructions apply to dismountable and non-separable contact connections1 of busbars up to 152 mm thick, flexible busbars and profiles3 (channel, trough, “double T”, etc.) made of aluminum, solid aluminum alloy AD31T4, copper and steel, as well as connections of busbars with terminals electrical devices.
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- An explanation of the terms found in the instructions is given in Appendix 1
- Technical requirements for contact connections also apply to busbars with a thickness of more than 15 mm
- Hereinafter referred to as the tire
- Hereinafter referred to as aluminum alloy
- Hereinafter referred to as output
The instructions are intended for design, installation and operating organizations.
1. GENERAL REQUIREMENTS
1.1. Interconnection of busbars from homogeneous metals, branches from these busbars and connections of aluminum busbars and aluminum alloy busbars with terminals made of aluminum and aluminum alloys are made collapsible or non-dismountable. Connections of busbars made of dissimilar materials and in cases where operating conditions require periodic disassembly of the connections should, as a rule, be made collapsible.
1.2. Contact connections depending on technical requirements requirements for them according to GOST 10434-82*, are divided into classes 1, 2 and 3.
The class of contact connections depending on their area of application is given in table. 1.1.
Table 1.1.
| Application area | Recommended contact class |
| 1. Contact connections of circuits whose conductor cross-sections are selected according to permissible long-term current loads (power electrical circuits, power lines, etc.) | 1 |
| 2. Contact connections of circuits, the conductor cross-sections of which are selected for resistance to through currents, voltage loss and deviation, mechanical strength, and overload protection. Contact connections in circuits of grounding and protective conductors made of steel | 2 |
| 3. Contact connections of circuits with electrical devices, the operation of which is associated with the release of a large amount of heat (heating elements, resistors) | 3 |
Linear contact connections of power circuits must be of class 1.
1.3. Depending on the climatic version and the category of placement of electrical devices in accordance with GOST 15150-69*, contact connections in accordance with GOST 10434-82* are divided into groups A and B.
Group A includes contact connections of electrical devices of all designs located in rooms with air-conditioned or partially conditioned air (placement category 4.1), and electrical devices of designs U, HL and TS, located in enclosed spaces (metal with thermal insulation, stone, concrete, wood ) with natural ventilation without artificially controlled climatic conditions (location category 3), and in rooms with artificially controlled climatic conditions (location category 4) in an atmosphere of types I and II according to GOST 15150-69*.
Group B includes contact connections of electrical devices of other designs and placement categories in atmospheres of types I and II and electrical devices of all designs and placement categories in atmospheres of types III and IV.
1.4. Contact connections must be made in accordance with the requirements of GOST 10434-82*, GOST 17441-84, standards, technical specifications for specific types of electrical devices, SNiP 3.05.06-85, these instructions for working drawings approved in the prescribed manner.
1.5. Requirements for permanent connections
1.5.1. The surface of the seams of welded joints should be uniformly scaly without sagging. The seams should not have cracks, burns, lack of fusion longer than 10% of the seam length (but not more than 30 mm), unfused craters and undercuts with a depth of 0.1 of the tire thickness (but not more than 3 mm). Welded joints of expansion joints should not have undercuts or lack of penetration on the tapes of the main package.
1.5.2. Connections made by crimping should not have cracks in the tip shank, sleeve, or clamps at the crimping site; the holes must be located symmetrically and coaxially, the geometric dimensions of the pressed part of the connection must comply with the requirements of standards, specifications, and technological documents.
1.5.3. Welded and pressed connections that do not work in tension must withstand stresses arising from the influence of static axial loads of at least 30% of the temporary tensile strength of the entire flexible tire; tensile - at least 90% of the tensile strength of the entire flexible tire.
1.5.4. The ratio of the initial (after welding) resistance of the contact connections to the resistance of the control section of the bus with a length equal to the length of the contact connection should be: for class 1 - no more than 1 (unless otherwise specified in the standards and specifications for specific types of electrical devices); for class 2 - no more than 2; for class 3 - no more than 6.
In contact connections of buses of different conductivity, comparison should be made with a bus of lower conductivity.
1.5.5. The electrical resistance of welded joints that have passed the tests must remain unchanged; for connections made by crimping, electrical resistance after testing it should not exceed the initial value by more than 1.5 times.
1.5.6. When the rated current flows, the heating temperature of permanent contact connections (classes 1 and 2) should not exceed the values indicated in table. 1.2. The heating temperature of class 3 contact connections is established by standards and specifications for specific types of electrical devices.
1.5.7. The temperature of permanent contact connections when testing for resistance to through currents should be no more than 200°C for connections of busbars made of aluminum and its alloys, as well as for connections of these busbars with copper, and 300°C for connections of copper busbars. After testing for resistance to through currents, contact permanent connections should not have mechanical damage that would prevent their further operation.
1.5.8. Contact connections, in accordance with their design and placement category according to GOST 15150-69*, must withstand the effects of environmental climatic factors specified in this standard, as well as GOST 15543.1-89 E, GOST 16350-80, GOST 17412-72* or in standards and specifications for specific types of electrical devices.
Table 1.2
Heating temperature of contact connections
1.6. Requirements for dismountable connections
1.6.1. Collapsible tensile contact connections must withstand stresses arising from static axial loads of at least 90% of the tensile strength of the entire flexible busbar.
1.6.2. The ratio of the initial (after assembly) resistance of dismountable contact connections (except for connections with pin terminals) to the resistance of the control section of the bus with a length equal to the length of the contact connection must comply with the requirements of clause 1.5.4.
1.6.3. The initial resistance of class 1 contact connections with pin terminals should not exceed the values indicated in the table. 1.3. The resistance of contact connections of classes 2 and 3 is indicated in standards and specifications for specific types of electrical devices.
1.6.4. The electrical resistance of collapsible contact connections that have passed the tests should not exceed the initial resistance by more than 1.5 times.
Table 1.3.
Initial resistance of contact connections of busbars with pin terminals
1.6.5. When the rated current flows, the heating temperature of dismountable contact connections of classes 1 and 2 should not exceed the values indicated in table. 1.2. The heating temperature of class 3 contact connections is established in standards and specifications for specific types of electrical devices.
1.6.6. The temperature of dismountable contact connections and mechanical strength when testing for resistance to through currents must comply with the requirements of clause 1.5.7.
1.6.7. In collapsible contact connections, fasteners with a strength not lower than that indicated in the table should be used. 1.4.
Table 1.4.
Class and strength group of fasteners
Fasteners must have a protective metal coating in accordance with GOST 9303-84. For contact connections of group A, the use of blued steel bolts, nuts, and washers is allowed.
1.6.8. Collapsible contact connections of busbars with leads, as well as collapsible linear contact connections exposed to through short-circuit currents, vibration, and also located in explosive and fire hazardous areas, must be protected from self-unscrewing by locknuts, spring washers, disc springs or other methods. Spring washers should be used in connections with bolts up to M 8 inclusive.
1.6.9. Demountable contact connections must withstand the effects of environmental climatic factors in accordance with clause 1.5.8.
2. PERMANENT CONTACT CONNECTIONS
Structural elements and dimensions of welded contact connections of busbars should be selected in accordance with the recommendations of GOST 23792-79.
The main types of welded joints on busbars are: butt, corner, lap, T and end joints (Table 2.1).
Determination of types of welded joints - according to GOST 2601-84.
Methods for welding tires made of various materials are listed in table. 2.2.
When choosing a welding method, keep in mind:
1) For carbon electrode welding, no special welding equipment is required, while for welding in a shielding gas (argon) environment, it is necessary to purchase a special semi-automatic welding machine, or an installation for manual argon-arc welding.
2) Due to its characteristics, welding with a carbon electrode is possible only in the lower position; welding in argon (both manual and semi-automatic) can be performed in all spatial positions.
3) Manual argon-arc welding with a tungsten electrode is effective for tire thicknesses up to 6 mm. At large thicknesses, the productivity of this method decreases sharply, especially at low air temperatures, which leads to a sharp increase in energy costs for welding.
Table 2.1.
Main types of welded joints and tires
1 - tire; 2 - weld; 3 - package of flexible tapes; 4 - wire core (flexible bus).
4) Welding in argon (manual and semi-automatic) provides higher quality of welded joints compared to welding with a carbon electrode.
5) When welding with a carbon electrode, the main factors that have a harmful effect on the welder’s body and the environment are ultraviolet radiation and the release of large amounts of welding aerosol and dust consisting of metal vapor, its oxides and flux combustion products. These emissions must be removed directly from the welding site and filtered before being released into the environment.
6) When welding in argon, the basis of harmful emissions is ozone, which also must be removed from the welding site.
Table 2.2.
Tire welding methods
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1 Welding AD31 alloy with a carbon electrode is not recommended.
2.1. Welding of aluminum tires
Manual argon-arc welding with a tungsten electrode
2.1.1. For manual argon-arc welding with a tungsten electrode, stationary installations such as UDGU-301 and UDG-501-1, commercially produced by industry, are intended.
For this purpose, it is allowed to use a welding arc power source manufactured by the Rostov experimental plant NPO Montazhavtomatika, as well as a combined welding transformer of the TDK-315 type, manufactured by the Kharkov enterprise Prommontazhelektronika. The source must be equipped with a manual welding torch developed by LenPEI of the Elektromontazh concern (industrial torches require water cooling).
2.1.2. In the absence of the specified settings, the welding station should be assembled according to the diagram shown in Fig. 2.1., from the equipment specified in table. 2.3.
Rice. 2.1. Diagram of a post for manual argon-arc welding on “alternating current”
TS - welding transformer; OS - oscillator; RB - ballast rheostat; G - welding torch; R - gearbox; B - cylinder.
When choosing equipment, it should be borne in mind that for normal operation of UDG installations and EZR welding torches, cooling water is required.
Table 2.3.
Equipment for manual argon-arc welding of aluminum
| Name of equipment | Type, brand1 | GOST, TU | Purpose |
| 1. Welding transformer | TD-306 TDM-503 |
TU 16-517-973-77 TU 16-739-254-80 |
Welding power source |
| 2. Gas-electric burners | EZR | TU26-05-57-67 | Supplying welding current to the electrode; shielding gas supply |
| LenPEI designs | LE 12550 | ||
| 3. Arc exciter-stabilizer or welding oscillator | VSD-01 | TU 16-739.223-80 | Excitation and stabilization of arc combustion |
| OSPZ-2M | TU 1-612-68 | ||
| OSM-2 | |||
| 4. Ballast rheostat | RB-302 | Regulation of welding current, suppression of the DC component in the welding circuit | |
| 5. Balloon reducer | AR-40 | TU26-05-196-74 | Reducing argon pressure to operating value |
| DKP-1-65 | TU26-05-463-76 | ||
| 6. Balloon | 40-150 | GOST 949-73 | Transportation and storage of argon |
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1 Use any of the specified types
2.1.3. The list of materials required to perform manual argon-arc welding with a tungsten electrode is given in table. 2.4.
Table 2.4.
Materials for manual argon-arc welding of aluminum
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1 It is allowed to manufacture arc furnace electrodes or electrolyzer blocks from waste graphite electrodes
2.1.4. Preparation of tires for welding, in addition to straightening and cutting to size, should include:
- processing of welded edges depending on the thickness of the material to ensure the required groove dimensions in accordance with GOST 23792-79;
- drying the edges to be welded if they are covered with moisture;
- cleaning the edges to be welded after assembly with a steel wire brush and degreasing them with a solvent: gasoline or acetone;
- heating, if necessary, of the welded edges to 200-250°C, if welding is performed at an ambient temperature below 0°C.
For drying, as well as for heating the edges of tires and profiles, gas burners or flexible electric heaters (GEN), manufactured according to TU36-1837-75, can be used.
2.1.5. Welding wire preparation should include:
- degreasing and cleaning (mechanical or chemical) of the surface (see Appendix 2);
- cutting into bars of the required length.
2.1.6. When performing welding, the following technological recommendations must be observed:
- position the tungsten electrode from the burner nozzle no more than 5 mm;
- starting welding, excite the arc on the graphite plate, heat the tungsten electrode and then transfer the arc to the edges of the tires without touching them with the electrode;
- while welding, try not to touch the metal of the product with the tungsten electrode, as this leads to disruption of the stability of the welding process, contamination of the seam and rapid consumption of the electrode;
- maintain an arc no longer than 10 mm;
- When finishing welding, after the arc breaks, do not move the torch away from the end of the seam for several seconds, protecting the cooling metal with a jet of argon;
- when welding outdoors, protect the welding site from wind and precipitation with screens, awnings, etc., and also, if necessary, increase the argon flow rate enough to ensure effective protection of the molten metal.
2.1.7. At the beginning of welding, it is necessary to warm up the welded edges of the tires by moving the welding arc along them, then concentrate the arc at the beginning of the seam, melt the edges until a weld pool is formed, insert a filler rod into it and begin to move the arc evenly along the joint at the speed of melting of the edges. The welding diagram is shown in Fig. 2.2.
Modes and approximate consumption of materials during welding are given in table. 2.5.
Rice. 2.2. Manual argon-arc welding with a tungsten electrode
a) welding diagram; b) diagram of the movement of the electrode during welding;
1 - weld; 2 - burner; 3 - electrode; 4 - filler rod.
Table 2.5.
Modes of manual argon-arc welding of aluminum
| Tire thickness, mm | Welding* current, A | Electrode diameter, mm | Consumption per 100 mm seam | ||
| argon, l | additives, g | ||||
| 3 | 130-150 | 3 | 3 | 9 | 5,6 |
| 4 | 150-170 | 3 | 3 | 10 | 6 |
| 5 | 170-180 | 3 | 3 | 10 | 6,8 |
| 6 | 190-200 | 4 | 4 | 11,5 | 8,5 |
| 8 | 220-225 | 5 | 5 | 12 | 11-20 |
| 10 | 240-250 | 5 | 6 | 14 | 35 |
| 12 | 290-300 | 6 | 8 | 16 | 45 |
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* Variable.
2.1.8. When welding in vertical, horizontal and overhead positions, to prevent swelling of the metal and better formation of the seam, you should:
- reduce the welding current (by 10-20%);
- increase the argon consumption against the values indicated in the table. 2.5 to ensure effective seam protection;
- Welding should be performed with small cross-section beads and a short arc;
- when welding in vertical and horizontal positions, place the welding torch below the weld pool.
Semi-automatic argon-arc welding with consumable electrode
2.1.9. For semi-automatic welding of aluminum in argon, semi-automatic machines such as PDI-304 and PDI-401, produced by industry, are intended, as well as semi-automatic machine PRM-4, produced by the pilot plant of the Institute of Assembly Technology (NIKIMT)1, but supplied without a welding current source. As such, welding rectifiers VDU-505, VDU-506, VDG-303, etc. are used. To regulate the flow of argon during welding, a balloon reducer is used, see table. 2.3.
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1 Semi-automatic machine PRM-4, manufactured by NIKIMT, is included in the set of the product “Backpack assembly semi-automatic machine PRM-4 with attachment PV 400”, supplied by the Moscow Experimental Plant of Electrical Installation Equipment (MOZET).
- replace the steel spiral in the torch hose, which is the guide channel for the steel welding wire, with a tube made of fluoroplastic, Teflon or polyamide, i.e. made of materials that provide minimal friction when passing aluminum wire;
- perform mechanical processing of the burner parts, inside which the welding wire passes, in such a way as to eliminate sharp edges at the joints of the parts and sharp bends in the path;
- manufacture fluoroplastic bushings for inserting aluminum wire into the feed mechanism and into the torch hose, eliminating delays in wire feeding;
- replace (if necessary) the knurled feed rollers with smooth rollers.
2.1.11. The materials required for semi-automatic argon-arc welding are given in table. 2.4, however, instead of tungsten electrodes, it is necessary to use copper-graphite tips of the KTP-DGr9 grade according to TU 16-538.39-83, used in welding torches as an element that transmits welding current to the electrode wire.
Preparation of tires for welding - in accordance with clause 2.1.4.
2.1.12. Before use, the welding wire should be chemically cleaned (see Appendix 2) and, depending on the design of the semi-automatic machine, wound evenly, layer by layer, onto a reel or placed directly in a coil on the turntable of the feed mechanism.
2.1.13. During welding, the seams to be joined must be firmly secured with clamps or short (@30 mm) welds - tacks.
2.1.14. When welding, the torch should be driven at a uniform speed at an angle forward so that the argon stream is directed forward, ensuring reliable protection of the weld pool from air.
If it is necessary to obtain a larger seam width, it is also necessary to perform transverse vibrations with the torch. The welding diagram is shown in Fig. 2.3. The main welding modes are given in table. 2.6.
Table 2.6.
Modes of semi-automatic argon-arc welding of aluminum
Figure 2.3. Scheme for performing semi-automatic welding in various spatial positions
a) bottom; b) vertical; c) ceiling
1 - welding torch; 2 - weld.
2.1.15 When welding multilayer seams, if a dark coating appears on the surface of the seam, the latter should be removed with a rag moistened with gasoline or cleaned with a wire brush. Only after this can subsequent layers of sutures be applied.
2.1.16. When welding in vertical, horizontal and overhead positions, to prevent the molten metal from flowing down, it is necessary:
- reduce the welding current (by 10-20%);
- weld with a short arc, applying beads of small cross-section;
- when the metal overheats, which is visually expressed in its melting, take short breaks in work (to cool the metal).
2.1.17. Welding should be performed with an open arc DC straight polarity (minus the power source - on the carbon electrode). To protect the weld metal from oxidation, it is necessary to use fluxes. The method is characterized by a large volume of molten metal, so welding should be performed only in the lower position of the seam with careful shaping of the joint to prevent the flow of molten metal.
After welding, flux residues must be removed.
2.1.18. For manual arc welding with a carbon electrode, you should assemble a welding station according to the diagram in Fig. 2.4. from the equipment specified in table. 2.7.
Table 2.7
Equipment for manual welding aluminum carbon electrode
_________________
1 Use any of the specified types.
2.1.19. The materials required for welding are listed in table. 2.8.
Rice. 2.4. Diagram of a post for manual welding with a carbon electrode on direct current
IP - welding current source; E - carbon electrode; Ш - weldable tires.
Table 2.8.
Materials for manual welding of aluminum with carbon electrode
- It is allowed to produce rods by cutting from sheets or tires or by casting from tire metal.
- It is allowed to manufacture electric arc furnaces from electrodes (waste) (Appendix 4).
- It is allowed to manufacture graphite anodes, cathode blocks, and arc furnace electrodes from waste.
2.1.20. Preparing tires for welding involves cutting the edges to be welded at right angles. In this case, the edges are not beveled, but it is necessary to use devices with forming graphite pads that prevent the flow of molten metal.
2.1.21. Filler rods should be cleaned and degreased before welding.
Before welding, it is necessary to apply VAMI flux, diluted with water to a creamy mass, to the edges of the tires and to the filler rods, or pour it onto the edges in powder form.
2.1.22. At the beginning of welding, the welded edges should be heated by moving the extended welding arc along them, then concentrate the arc at the beginning of the seam, melt the edges of the tires until a weld pool is formed and begin moving the arc along the joined edges at the speed of their melting. It is necessary to insert a filler rod into the rear edge of the weld pool, which is used to smoothly and evenly mix the weld pool to remove oxides and slags.
2.1.23. When finishing the seam, you should allow the metal to harden, and if a shrinkage hole forms, excite the arc again and melt the crater.
2.1.24. At the end of welding, the seams must be thoroughly cleaned of slag, flux residues, and frozen drops of metal.
The welding diagram is shown in Fig. 2.5.
Rice. 2.5. Carbon electrode welding diagram
1 - tire; 2 - graphite lining; 3 - graphite block for shaping the end of the seam; 4 - filler rod; 5 - carbon electrode; 6 - weld pool; 7 - seam.
Table 2.9.
Modes for manual welding of aluminum with a carbon electrode
| Tire thickness, mm | Gap between tire edges, mm | Welding current1, A | Diameter of filler rod2, mm | Consumption per 100 mm seam, g | |
| additives | gumboil YOU | ||||
| 3 | - | 150 | 5 | 9 | 1-2 |
| 4 | - | 200 | 5 | 10 | 2-3 |
| 5 | - | 200 | 5 | 18 | 3-5 |
| 6 | - | 250 | 8 | 25 | 4-6 |
| 8 | - | 300 | 10 | 35 | 5-8 |
| 10 | - | 350 | 12 | 46 | 7-10 |
| 12 | - | 400 | 12 | 57 | 9-12 |
| 15 | - | 450 | 15 | 80 | 11-13 |
- The current is constant, the polarity is straight.
- Rods cut from tires or sheets must have a square cross-section with a side of the square equal to the diameter of the round rod indicated in the table.
Features of welding technology for aluminum conductors of various profiles
Rectangular tires
The main types of welded joints of rectangular busbars are presented in Fig. 2.6.
2.1.25. When welding in the installation area, portable assembly devices should be used to form seams, attached directly to the tires being welded (Fig. 2.7.).
2.1.26. When laying busbars individually, as a rule, butt connections should be made, and when installing busbar packages, overlap, end and corner connections should be made.
Rice. 2.6. Basic welded joints of rectangular busbars
a) butt joints of busbars; b) connections at an angle; c) welding the branch to the busbar; d) welding the branch to the busbar with an overlap; e) welding the compensator to the tires; c) T-joint of tires; g, h) welding of tires along the upper edges
1 - tire; 2 - weld; 3 - package of flexible tapes.
Rice. 2.7. Portable devices for welding tires during installation
a) for butt welding; b) for welding branches
1 - tire; 2 - clamp; 3 - graphite block; 4 - base of the device; 5 - folding clamp; 6 - branch.
2.1.27. Lap and end connections should be used for welding branches to single-lane and multi-lane busbars. In this case, the branches can also be multi-lane and have both smaller and equal thickness. Welding modes should be set for a tire of smaller thickness.
When welding, it is necessary to use special devices that prevent the leakage of aluminum and ensure the possibility of obtaining a weld of the required size (Fig. 2.8, 2.9).
Rice. 2.8. Welding tires along the upper edges with a semi-automatic machine in argon
1 - tires; 2 - clamp; 3 - semi-automatic burner; 4 - welding seam.
Rice. 2.9. Welding tire packages along the upper edges (carbon electrode)
1 - tires; 2 - assembly device; 3 - carbon forming inserts; 4 - additive; 5 - electrode.
2.1.28. When installing complete busbars (such as ShMA, for example), the main volume of work associated with the manufacture of enlarged sections should be carried out in the workshop of electrical installation workpieces, where the overlapping busbars of sections of standard length should be connected by welding along the upper and lower edges with edging of the assembled unit (see table 2.1, end connection) to increase its strength during transportation and installation. Busbar connections assembled at the design level should be welded only on one side accessible for welding.
Profiles and pipes
2.1.29. For the manufacture of conductors for various special purposes, in addition to rectangular busbars, pressed aluminum profiles and pipes in accordance with GOST 15176-89 E of the following types: channel, I-beam, oblique angle, round pipe, etc.
Examples of welded connections of tires from profiles and pipes are shown in Fig. 2.10 and 2.11.
2.1.30. Box-shaped busbars should be made by welding two channels, assembled with shelves inward, using clamps and gap clamps - pieces of aluminum plates (Fig. 2.12); the length of the welds is approximately 100 mm, the distance between the seams (step) is 1-2 m; seams must be made on both sides using semi-automatic argon-arc welding.
2.1.31. The technological process for manufacturing current conductors from profiles and pipes must be built on the principle of welding profile sections into a continuous thread, from which sections of the required length are cut off for the assembly of three-phase sections of the current conductor. The length of the conductor sections should be determined by the conditions of transportation and installation, and, as a rule, should be chosen as a multiple of the distance between supports or temperature compensators.
2.1.32. Areas for manufacturing conductors should be equipped with roller stands to facilitate the movement and alignment of profiles; mechanical rotators (tilters), ensuring welding is performed in a position convenient for work (Appendix 6): rotary saws, allowing cutting of a profile at a given angle, and other necessary mechanisms.
Rice. 2.10. Welded connections of conductors made of aluminum channels and I-beams
a, k) conductor sections with a welded liner; b, m) butt joints; c, d, o) T-joints; d, p) corner connections; f, g, h, p, s, t) branches with flat busbars; i, m) compensators; j) ending the profile with flat tires.
1 - channel; 2 - liner; 3 - seam; 4 - flat tire; 5 - compensator; 6 - flanged I-beam.
Rice. 2.11. Welded joints of tires from pipes
a) butt; b) angular; c) T-bar; d, e, f) with rectangular tires; g) a tip made by flattening the end of the pipe; h) tip with a welded copper-aluminum plate; i) a compensator made of wires, welded directly to the pipe; j) compensator made of wires welded to the flanges.
1 - pipe; 2 - weld; 3 - flat tire; 4 - copper-aluminum plate; 5 - wire compensator; 6 - flange.
Rice. 2.12. Welding a box bus from an aluminum channel
1 - channel; 2 - compression; 3 - semi-automatic welding torch; 4-connecting weld.
2.1.33. To facilitate the assembly, alignment and welding of busbars of abutting sections of current conductors, liners or backing rings made from aluminum strip 3-5 mm thick and 50-80 mm wide should be used. The insert (ring) should be attached with tacks to one of the ends of the profile and, during subsequent welding of the joined profiles, serve as a forming lining, preventing burns and leakage of molten metal.
2.1.34. When welding a “flanged I-beam” profile, the weld should be applied only along the outer perimeter of the profile. The joint between the inner walls of the profile may not be welded.
2.1.35. In channel and I-beam conductors, to compensate for temperature changes in length, as a rule, busbar compensators K52-K56 according to TU36-14-82 should be used. The designs of welded joints of expansion joints with profiles are shown in Fig. 2.10.
The cross-section of the compensator must be equal to the cross-section of the profile. Since the thickness of the compensator, welded only to two flanges of the profile, is greater than the thickness of its flanges, aluminum plates of the appropriate thickness should be pre-welded to them from the outside (Fig. 2.13).
Rice. 2.13. Welding expansion joints to the conductor
1 - conductor sections; 2 - compensators; 3 - strips; 4 - weld.
When welding T-joints of pipes, the end of the adjacent (branch) pipe must be processed so that it mates with the surface of the main pipe, or a hole should be drilled in the main pipe equal to the outer diameter of the branch pipe. The assembled assembly must be welded around the perimeter of the pipe interface. Welding modes must correspond to the welding modes of pipes with thinner wall thickness.
When welding branches, special devices should be used to fix the position of the pipes during welding (Fig. 2.14), or assembly should be done using tack welding tools. In this case, it is enough to press the rectangular tires with a clamp while welding (Fig. 2.15).
2.1.36. Compensators for tubular conductors must be made, as a rule, from bare aluminum wire grade A in accordance with GOST 839-80* E. To do this, depending on the diameter of the pipe, pieces of wires 300-600 mm long should be cut.
Structurally, expansion joints should be made by fusing the ends of the wires into a ring monolith (Fig. 2.11 i) or by welding the wires to the flanges (Fig. 2.11k) with rivet seams.
Rice. 2.14. Device for assembling pipe T-joints for welding
1 - rocker arm; 2 - folding bar; 3 - bracket; 4 - folding screw; 5 - heel; 6 - clamping screw.
Rice. 2.15. Assembly of a rectangular tire with a pipe for welding
1 - pipe; 2 - clamp; 3 - rectangular tire.
To do this, holes should be made in the flanges into which the welded wires are inserted. Flanges with welded wires must be welded to the pipes using fillet welds. It is also possible to weld the flanges to the pipes in advance, and then insert and weld the wires.
When manufacturing compensators without flanges, the treated wires should be assembled into a fixture (Fig. 2.16), consisting of an internal graphite mandrel and an outer clamping ring, in which the wires are welded into a ring monolith, intended for subsequent welding to pipes.
After welding, the expansion joint is bent into the required shape. Tire expansion joints made of aluminum strips can also be installed on tubular busbars. In this case, the ends of the pipes to which the flat compensator is welded are flattened. Welding should be carried out in modes corresponding to the welding modes of rectangular busbars.
Rice. 2.16. Device for fusing aluminum wires into a monolith
1 - internal graphite mandrel; 2 - hinge ring; 3 - hinge; 4 - aluminum wires; 5 - lamb.
Welding packages of tapes and wire cores
2.1.37. Busbar expansion joints should be made by fusing the ends of strip packs into a monolith using argon-arc welding with a consumable or non-consumable electrode; Carbon electrode welding is also possible.
2.1.38. Welding of the compensator in a special device is shown in Fig. 2.17.
The modes and techniques for welding the compensator and their welding to tires are similar to the modes for welding tires of the corresponding thickness (see Table 2.5, 2.6, 2.9). During the welding process, the mold must be filled to the top with molten metal. Before welding the tape, the package should be cleaned, degreased and dried.
Rice. 2.17. Welding compensator
1 - weld; 2 - graphite liner; 3 - semi-automatic burner; 4 - device for welding; 5 - package of tapes; 6 - welded monolith.
2.1.39. Wires to busbars should, as a rule, be welded using argon-arc welding. Carbon electrode welding is also allowed. Examples of welded connections between wires and busbars are shown in Fig. 2.18.
Welding of wires with aluminum busbars should be performed in the following order:
- remove insulation from the wires to a length of at least 60 mm;
- if necessary, degrease the ends of the wires with acetone or gasoline;
- Clean the busbar and wire strands with a steel wire brush;
- using the tools (Fig. 2.19, 2.20), assemble the unit to be welded so that the wires protrude above the bus by about 5 mm;
- carry out welding: with a wire cross-section from 16 to 95 mm2 with a current of 100-160 A, with a wire cross-section from 120 to 240 mm2 - 150-220 A; The welding technology is the same as for welding tires;
- after welding with carbon electrode welded joint thoroughly clean from slag and flux residues.
Rice. 2.18 Welded connections to busbars
a) end-to-end with a horizontal tire; b) electric rivet; c) overlap with a vertical tire arrangement; d) angular.
1 - bus, 2 - wire, 3 - weld, 4 - electric rivet
Rice. 2.19. Device for welding wires with a busbar mounted on a plane
1 - hinged frame; 2 - copper liner; 3 - bracket; 4 - clamp handle; 5 - carrying handle.
Rice. 2.20 Welding wires with a busbar mounted on an edge
1 - wires; 2 - tire; 3 - device; 4 - graphite liner; 5 - weld; 6 - semi-automatic welding torch; 7 - welding wire.
Termination of aluminum busbars with copper-aluminum plates
2.1.40. The modes and techniques for welding copper-aluminum plates with busbars up to 12 mm thick are similar to those given in table. 2.5, 2.6, 2.9. Cooling of a weld made by resistance welding is not required.
2.2. Welding copper bars
Manual carbon arc welding
2.2.1. For manual arc welding of copper with a carbon electrode, the same equipment should be used as for welding aluminum (see Table 2.7.).
2.2.2. For welding, the materials listed in table are required. 2.10.
Table 2.10.
Materials for manual carbon arc welding of copper
- It is allowed to use rods cut from copper bars or sheets.
- It is allowed to manufacture electric arc furnaces from electrodes (waste) (see Appendix 4).
2.2.3. When welding copper busbars, you should use the same fixtures and tools as when welding aluminum busbars. Due to the high fluidity of molten copper, it is necessary to form welded joints very carefully and securely to prevent metal leakage during welding. Welding of copper busbars and expansion joints must be done on carbon pads with a groove under the joint; Seal the ends of the seams with coal blocks.
2.2.4. Preparation of tires for welding (except for straightening and cutting to size) includes processing of welded edges depending on the thickness of the materials in accordance with GOST 23792-79, cleaning of welded edges in an area of at least 30 mm from their ends.
2.2.5. Before welding, filler rods should be cleaned of grease and dirt. If necessary, several filler rods are folded (twisted) together.
2.2.6. The tires prepared for welding must be laid and secured in the device, and a thin layer of flux must be poured onto the edges to be welded.
2.2.7. When starting welding, the edges to be welded should be heated with an arc, moving it along the joint until individual drops of molten copper appear in the arc zone; after heating the edges, concentrate the arc at the beginning of the seam until the edges melt and a weld pool appears; insert the filler rod into the rear edge of the weld pool (it should melt from its heat). It is not recommended to fuse the additive in drops by introducing it into the arc, as this leads to intense oxidation of the metal and the formation of cracks in the weld. Immerse the heated end of the rod in flux from time to time and introduce flux into the weld pool.
Immediately after welding, it is necessary to cool the seam sharply with water. Whenever possible, welding of copper bars should be done in one pass. Welding modes and material consumption are given in table. 2.11.
2.2.8. Lap and corner connections of copper busbars should be made in the same way as aluminum ones.
When welding fillet welds of these joints, the tires should be positioned in a “boat” position, if possible, because at the same time, due to the high fluidity of molten copper, the most favorable conditions to provide good quality welded joints (Fig. 2.21 a).
If it is impossible to perform boat welding, forced formation of the seam with coal bars should be used (Fig. 2.21b). In this case, in order to avoid lack of fusion of the edges of the busbars, the branches should be melted only after the busbar has melted.
Rice. 2.21. Welding of copper bars with overlap
a) tire arrangement “boat”; b) the tires are positioned “flat”.
1, 2 - tires; 3 - weld; 4 - coal block
The lap welding modes for tires correspond to those given in table. 2.11.
Table 2.11.
Modes of manual welding of copper with a carbon electrode
| Tire thickness, mm | Welding current, A1 | Carbon electrode diameter, mm | Diameter of filler rod, mm | Consumption per 100 mm seam, g | |
| additives | gumboil | ||||
| 3 | 150 | 12 | 4 | 29 | 1 |
| 4 | 180 | 12 | 4 | 35 | 2 |
| 5 | 220 | 12 | 6 | 65 | 3 |
| 6 | 260 | 15 | 6 | 105 | 4 |
| 8 | 320 | 15 | 8 | 150 | 5 |
| 10 | 400 | 20 | 8 | 210 | 7 |
| 12 | 500 | 20 | 10 | 290 | 9 |
| 20 | 1000 | 30 | 15 | 450 | 12 |
- Straight polarity (minus of the power source - on the carbon electrode).
Semi-automatic arc welding in shielding gas
2.2.9. This welding method is effective when connecting busbars up to 10 mm thick. When welding large thicknesses, preliminary and accompanying heating is necessary.
2.2.10. For semi-automatic welding of copper in shielding gas, as when welding aluminum, the equipment specified in paragraphs should be used. 2.1.9, 2.1.10.
2.2.11. When welding, the materials listed in table are required. 2.12.
2.2.12. When preparing tires for edge welding, they should be processed in accordance with the requirements of GOST 23792-79, cleaned and degreased to a width of at least 30 mm.
2.2.13. The electrode wire must be cleaned of grease and dirt and wound onto a semi-automatic cassette.
Table 2.12
Materials for semi-automatic argon-arc welding of copper
- It is allowed to manufacture graphite anodes and cathode blocks of electrolyzers, as well as electrodes of arc furnaces from waste.
2.2.14. After laying and securing the tires in the fixture, they should be welded using a technology similar to welding aluminum tires (see Fig. 2.22).
Rice. 2.22. Semi-automatic welding of copper busbars in shielding gas
1 - tire; 2 - graphite molding lining; 3 - burner nozzle; 4 - seam; 5 - welding wire
Before welding tires with a thickness of more than 10 mm, it is necessary to preheat the edges to a temperature of 600-800°C. For heating, use a propane-oxygen or acetylene-oxygen flame.
Immediately after welding is completed, the joint must be cooled with water.
Welding modes and approximate consumption of materials are given in table. 2.13.
2.2.15. Welding of single busbars in vertical and horizontal positions should be performed using electrode wire with a diameter of 1.2 mm. In this case, it is necessary to use a device for fixing and heating the tires. Tires up to 4 mm thick must be assembled for welding without cutting the edges; with a thickness of 5 mm or more, a one-sided bevel of the edges is required at an angle of 30° with a blunting of about 2 mm. The gap between the edges should not exceed 3 mm.
Before welding, tires should be heated to a temperature of 600°C. The first pass should be made with a “thread” seam; subsequent passes - with transverse vibrations of the burner.
Welding modes are given in Table 2.14.
After welding, the seam should be cooled with water.
Table 2.13
Modes of semi-automatic argon-arc welding of copper
| Tire thickness, mm | Welding wire diameter, mm | Welding current1, A | Arc voltage, V | Consumption per 100 mm seam | |
| electrode wire, g | argon, l | ||||
| 3 | 1,2-1,6 | 240-280 | 37-39 | 20 | 10 |
| 4 | 1,2-1,6 | 280-320 | 38-40 | 24 | 11 |
| 5 | 1,4-1,8 | 320-360 | 39-41 | 33 | 12 |
| 6 | 1,4-1,8 | 360-400 | 40-42 | 47 | 14 |
| 7 | 1,6-2,0 | 400-440 | 41-43 | 64 | 15 |
| 8 | 1,8-2,0 | 440-480 | 42-44 | 84 | 17 |
| 9 | 2,0-2,5 | 480-520 | 43-45 | 106 | 18 |
| 10 | 2,0-2,5 | 520-560 | 44-46 | 130 | 20 |
Table 2.14
Modes of vertical semi-automatic welding of copper busbars
- Direct current, reverse polarity.
Plasma welding
2.2.16. For plasma welding, installations of the type UPS-301, UPS-503, as well as URPS-3M should be used, including a power source, control panel, plasma torch and water cooling system (URPS installation, drawing LE 10942, LenPEO NPO Elektromontazh).
2.2.17. When welding, the materials specified in table should be used. 2.12.
2.2.18. Before plasma welding, the tires and filler rods to be welded should be prepared as in semi-automatic welding.
2.2.19. Welding of tires must be performed in devices that prevent leakage of molten metal, as when welding with a carbon electrode.
2.2.20. When starting welding, you should first light the auxiliary arc, which is necessary to ionize the interelectrode space, and thereby facilitate the initiation of the main arc.
When a torch with a lit auxiliary arc is brought to a distance of about 10 mm to the tires being welded, a main arc appears, which is used to melt the metal.
The plasma welding technique is similar to the technique of manual argon-arc welding with a tungsten electrode: heat the tires, melt the edges, introduce an additive and move the weld pool along the edges. The welding diagram is shown in Fig. 2.23.
Rice. 2.23. Manual plasma welding diagram
1 - filler rod; 2 - plasma torch; 3 - weldable tires.
Plasma welding modes are given in table. 2.15.
Table 2.15
Copper plasma welding modes
| Tire thickness, mm | Gap between tire edges, mm | Welding current, A | Arc voltage, V | Diameter of filler rod, mm |
| 4 | 2 | 350-400 | 37-40 | 4 |
| 6 | 4 | 380-440 | 37-40 | 6 |
| 10 | 4 | 440-450 | 40-45 | 8 |
| 12,5 | 4 | 450-500 | 40-45 | 10 |
| 20 | 5 | 800 | 40-45 | 15 |
Notes:
- The distance from the nozzle to the product is » 10 mm.
- Consumption of plasma-forming gas (argon) 3-6 l/min.
Features of welding copper expansion joints
2.2.21. To ensure complete penetration of the package over the entire thickness, the compensator tapes should be laid in steps. It is necessary to lay copper strips ≥ 50 mm wide from the same strip under the bottom and top strips to protect the outer strips from melting.
2.2.22. To protect the tapes from overheating, copper heat-removing plates 8-10 mm thick should be applied to their upper surface at a distance of 10 mm from the edge.
2.2.23. The welding modes for strip packs are similar to the welding modes for copper bars of the corresponding thickness. Welding must be performed similarly to butt welding of busbars, with the difference that the arc is directed primarily towards the busbar.
2.3. Welding of electrical installation products from dissimilar metals
2.3.1. Copper and aluminum should be welded in the manufacture of transitional copper-aluminum plates and tips by flash butt welding with impact upsetting on special contact butt machines.
Welding must be performed in electrical installation factories in accordance with manufacturing instructions.
Adapter copper-aluminum plates (MA and MAP) are intended for welding to aluminum busbars at the points of their connection to copper flat or rod terminals of electrical devices and machines.
In the same cases, adapter plates made of aluminum alloy AD31T1 type AP can be used.
2.3.2. Aluminum should be welded to steel by arc welding, for example, in the manufacture of steel-aluminum trolley strips and expansion joints; argon-arc semi-automatic or manual welding with a tungsten electrode (as well as manual welding with a carbon electrode) with preliminary hot aluminizing or galvanizing of the steel part.
Steel-aluminum parts (U1040 strips and U1008 trolley compensators, etc.) are intended for welding connections of aluminum conductors with steel ones, as well as steel conductors (trolleys) with each other. In this case, the steel part of the strips must be welded to the steel conductor using conventional electrodes for welding steel, and the aluminum part - to the aluminum conductor - in accordance with the requirements of these instructions.
3. DISMOUNTABLE CONTACT CONNECTIONS
3.1. Connection technology
3.1.1. Collapsible (bolted) contact connections, depending on the material of the connected tires and climatic factors of the external environment, are divided into connections:
- without means of stabilizing electrical resistance;
- with means of stabilizing electrical resistance.
3.1.2. Contact connections of busbars made from materials copper-copper, aluminum alloy - aluminum alloy, copper-steel, steel-steel for groups A and B, as well as from materials aluminum alloy - copper and aluminum alloy-steel for group A do not require the use of electrical stabilization means resistance. Connections are made directly using steel fasteners (Fig. 3.1 a).
Rice. 3.1. Dismountable contact connections
1 - bolt; 2 - nut; 3 - washer; 4 - tire (steel, copper, aluminum alloy); 5 - disc spring; 6 - washer made of color. metal; 7 - non-ferrous metal bolt; 8 - nut made of non-ferrous metal; 9 - aluminum tire; 10 - aluminum tire with metal coating; 11 - copper-aluminum transition plate; 12 - aluminum alloy plate.
3.1.3. Contact connections of busbars made of aluminum-aluminum materials, aluminum alloy-aluminum for groups A and B, as well as aluminum-copper and aluminum-steel materials for group A should be made using one of the means of resistance stabilization:
- disc springs according to GOST 3057-79* (Fig. 3.1b);
- fasteners made of copper or its alloy (Fig. 3.1c);
- protective metal coatings in accordance with GOST 9.306-85* applied to the working surfaces of tires1 (Fig. 3.1d) - Appendix 8;
_______________
* The use of electrically conductive lubricants or other electrically conductive materials is allowed if the possibility of their use is confirmed by test results in accordance with GOST 17441-84 and is indicated in the standards or technical conditions for specific types of electrical devices.
- transition copper-aluminum plates according to GOST 19357-81* (Fig. 3.1d);
- adapter plates made of aluminum alloy (Fig. 3.1e).
3.1.4. For group B, contact connections of busbars made of materials aluminum alloy-copper, aluminum alloy-steel should be made as shown in Fig. 3.1d, f; from materials aluminum-copper, aluminum-steel - as shown in Fig. 3.1b, c, d, f.
The working surfaces of tires and plates made of aluminum and aluminum alloy must have protective metal coatings.
3.1.5. Aluminum alloy plates and aluminum parts of copper-aluminum plates should be connected to aluminum busbars by welding. Demountable connections of adapter plates with copper busbars must be made using steel fasteners.
3.1.6. The location and diameter of holes for connecting busbars up to 120 mm wide are given in table. 3.1. The relationship between the diameter of the hole in the tires and the diameter of the tightening bolts is as follows:
3.1.7. The contact areas of tires with a width of 60 mm or more, having two holes in a transverse row, are recommended to be made with longitudinal cuts. The width of the incision depends on the method of making it and should be no more than 5 mm.
Table 3.1.
Dimensions, mm
| Compound | Branch | in³in1 | d |
 |
 |
||
| 15 | 6,6 | ||
| 20 | 9,0 | ||
| 25 | 11 | ||
| 30 | 11 | ||
| 40 | 14 | ||
| 50 | 18 | ||
 |
 |
||
| 60 | 11 | ||
| 80 | 14 | ||
| 100 | 18 | ||
| 120 | 18 | ||
 |
|||
| 80 | 14 | ||
| 100 | 18 | ||
| 120 | 18 | ||
3.2. Preparation and assembly of dismountable joints
3.2.1. Preparation of tires for dismountable connections consists of the following operations: making holes for bolts, processing contact surfaces and, if necessary, applying metal coating.
3.2.2. The location and dimensions of the holes for the bolts must correspond to those specified in clause 3.1.6.
3.2.3. When producing tires in bulk, it is recommended to cut holes using presses. For this purpose, the PRU-1 press should be used. Simultaneous cutting of several holes can be carried out using special devices. When cutting holes using a stop and jigs, markings should not be made.
3.2.4. The length of the bolts for connecting the tire package must be selected according to the table. 3.2. After assembling and tightening the connections, at least two threads of free thread must remain on the bolts.
Table 3.2.
| Thickness of tire package in connection, mm | Bolt length, mm | ||||||
| aluminum with aluminum | aluminum with copper or with aluminum alloy busbars | copper or steel | M6 | M8 | M10 | M12 | M16 |
| - | 4 | 4-6 | 16 | 20 | 20 | - | - |
| 4 | 6-7 | 7-10 | - | 20 | 25 | 30 | - |
| 5-10 | 8-10 | 11-15 | - | 25 | 30 | 35 | - |
| 11-12 | 12-15 | 16-20 | - | - | 35 | 40 | - |
| 13-17 | 16-20 | 21-25 | - | - | 40 | 45 | 50 |
| 18-22 | 21-25 | 26-30 | - | - | 45 | 50 | 55 |
| 23-27 | 26-30 | 31-35 | - | - | 50 | 55 | 60 |
| 28-32 | 31-35 | 36-40 | - | - | 55 | 60 | 65 |
| 33-37 | 36-40 | 41-45 | - | - | 60 | 65 | 70 |
| 38-42 | 41-45 | 46-50 | - | - | 65 | 70 | 75 |
| 43-47 | 46-50 | 51-55 | - | - | 70 | 75 | 80 |
| 48-52 | 51-55 | 56-60 | - | - | 75 | 80 | 85 |
| 53-57 | 56-60 | 61-65 | - | - | 80 | 85 | 90 |
| 58-62 | 61-65 | 66-70 | - | - | - | 90 | 95 |
| 63-67 | 66-70 | 71-75 | - | - | - | 95 | 100 |
| 68-72 | 71-75 | 76-81 | - | - | - | 100 | 105 |
3.2.5. The contact surfaces of tires must be treated in the following order: remove dirt and preservative grease with gasoline, acetone or white spirit; for heavily soiled tires, use flexible tires in addition to cleaning the outer layers after unwinding, clean the internal layers; straighten and process under a ruler on a tire milling machine (if there are dents, cavities and irregularities); remove foreign films with a steel brush, a disk with card tape or a hog file. It is recommended that stripping of tires in workshops for electrical installation workpieces be carried out using a ZSh-120 machine. When cleaning aluminum, grinding wheels are not allowed. Files and steel brushes should not be used to simultaneously process tires made of different materials.
3.2.6. To remove oxide films, working surfaces should be cleaned. After cleaning tires made of aluminum or aluminum alloy, it is necessary to apply a neutral lubricant to their surface (KVZ Vaseline in accordance with GOST 15975-70*, CIATIM-221 in accordance with GOST 9433-80*, CIATIM-201 in accordance with GOST 6267-74* or other lubricants with similar properties). The recommended time between cleaning and lubrication is no more than 1 hour.
3.2.7. Methods and technology for applying metal coatings to the contact surfaces of tires are given in Appendix 8.
3.2.8. In case of contamination, surfaces with protective metal coatings should be washed with organic solvents (gasoline, white spirit, etc.) before assembly.
Tinned copper grooves, intended for securing copper bars in loop clamps, must be washed with a solvent and coated with a layer of neutral lubricant (KVZ Vaseline in accordance with GOST 15975-70*, CIATIM-201 in accordance with GOST 6267-74*, CIATIM-221 in accordance with GOST 9433-80* or other lubricants with similar properties). Clean out such grooves sandpaper do not do it.
3.2.9. It is allowed to apply metal coatings to sections of tires (plates), which are then welded to the tires during installation. The length of the coated section of the tire (plate), depending on the cross-sectional length of this section, should be:
3.2.10. It is recommended to tighten the bolts of contact connections using indicator wrenches with a torque according to table. 3.3.
Table 3.3.
3.2.11. In the absence of torque wrenches, the bolts of the contact connections of copper, steel and aluminum alloy busbars should be tightened with wrenches with normal hand force (150-200 N). Connections of aluminum busbars must first be crimped by tightening bolts with a diameter of M12 and above with full hand force (about 400 N), then loosen the connections and re-tighten the bolts with normal force. For bolt diameters of 6-10 mm, crimping should not be done.
Connections with disc springs should be tightened in two stages. First, the bolt is tightened until the disc spring is completely compressed, then the connection is loosened by turning the key in the opposite direction 1/4 turn (90° angle) for bolts M6-M12 and 1/6 turn (60° angle) for the remaining bolts.
4. BUS CONNECTIONS TO TERMINALS
4.1. The terminals of electrical devices according to GOST 21242-75* can be flat or pin. The dimensions of the terminals are given in Appendix 9.
4.2. Welded connections of busbars with terminals made of homogeneous metals must be carried out in accordance with the instructions given in section 2.
The welded connection of busbars made of aluminum and its alloys with a copper terminal should be performed using a copper-aluminum adapter plate.
4.3. Demountable connections of busbars with flat terminals, depending on the material of the terminals, busbars and climatic factors of the external environment, must be carried out using one of the methods specified in paragraphs. 3.1.2-3.1.7.
4.4. For group A, contact connections of busbars with pin terminals, depending on the busbar material and the value of the rated output current, should be made:
- for busbars made of copper, steel and aluminum alloy - directly with steel nuts1 (Fig. 4.1,a);
_________________
1 In all cases, thrust nuts of copper or brass must be used.
- for aluminum busbars with output for rated current up to 630 A - directly with nuts made of copper and its alloys in accordance with GOST 5916-70* (Fig. 4.1, b); for rated current above 630 A - directly with steel or copper nuts with a protective metal coating on the working surface of the bus (Fig. 4.1, c) or using adapter copper-aluminum plates according to GOST 19357-81* (Fig. 4.1, d), or adapter plates made of aluminum alloy (Fig. 4.1, d).
4.5. For group B, contact connections of busbars with pin terminals, depending on the material of the busbars, should be made:
- busbars made of copper - directly with steel nuts (Fig. 4.1, a);
- tires made of aluminum and aluminum alloy - using adapter copper-aluminum plates in accordance with GOST 19357-81* (Fig. 4.1, d) or adapter plates made of aluminum alloy (Fig. 4.1, e), while the adapter plates made of aluminum alloy must have protective metal coating.
4.6. The dimensions of the holes in the tires must correspond to the diameter of the pin:
| Pin diameter, mm | 6 | 8 | 10 | 12 | 16 | 20 | 24 | 30 | 36 | 42 | 48 | 56 |
| Tire hole size, mm | 6,6 | 9 | 11 | 14 | 18 | 22 | 26 | 33 | 39 | 45 | 52 | 62 |
Rice. 4.1. Pin Connection
1 - pin terminal (copper, brass); 2 - nut (st); 3 - tire (copper, steel, aluminum alloy); 4 - nut (copper, brass); 5 - tire (aluminum alloy); 6 - tire with metal coating; 7 - copper-aluminum transition plate; 8 - copper-aluminum transition plate; 8 - aluminum alloy plate.
5. CONNECTIONS OF FLEXIBLE BUSBARS BETWEEN THEM AND WITH TERMINALS IN OPEN DISTRIBUTION DEVICES
5.1. Connections and branches on copper, steel, aluminum and steel-aluminum flexible busbars of open switchgears should be made by crimping, crimping, using loop or branch bolt clamps. Branches of aluminum and steel-aluminum busbars should preferably be performed by propane-oxygen welding. Terminations should be made using hardware clamps connected to the flexible busbar by crimping, bolting or welding. The technology for making pressed and welded connections of flexible tires is given in the instructions.
5.2. Bolt loop and branch clamps must be made for aluminum and steel-aluminum busbars - from aluminum alloys, for copper - from brass, for steel - from steel (Fig. 5.1, 5.2).
Bolt loop clamps intended for connecting copper busbars to aluminum must have tinned copper grooves soldered into them at the manufacturer's factory.
5.3. Bolted hardware clamps are designed for tightening tires using dies (Fig. 5.3). For copper busbars they should be made of brass, for aluminum busbars - from aluminum alloys.
Rice. 5.1. Loop clamp
1 - clamping strip; 2 - clamp; 3 - bolt; 4 - nut; 5 - spring washer.
Rice. 5.2. Branch clamp
1 - base; 2 - clamp; 3 - bolt; 4 - nut; 5 - spring washer.
Rice. 5.3. Hardware Bolt Clamps
a - for connection to a rod terminal and a flat one having one hole. b, c - for connection to flat terminals with two and four holes.
The design of hardware clamps intended for aluminum busbars includes adapter copper plates secured to the clamp body by soldering or welding. These plates provide better contact when connecting an aluminum hardware clamp to a copper terminal on a device or to a copper-clad or copper-reinforced aluminum terminal.
If the aluminum hardware clamp is connected to the aluminum terminal by bolting or welding, the copper plates should be removed.
Hardware clamps have one, two or four holes for connection to device terminals or buses.
5.4. Hardware clamps that have one hole in the claw with a diameter of 14.5 mm can be drilled to the diameter of the pin terminal, but not more than 30 mm.
5.5. The bars should be secured in the clamp in the following order:
- place the busbar in the corresponding grooves of the clamp (when installing adapter clamps from copper to aluminum, the copper busbar should be in contact with the tinned copper groove, and the aluminum busbar with the aluminum one);
- install dies;
- coat the cut part of the bolts with AMC-1 grease, avoiding its contact with the contact surface;
- tighten the bolts.
The bolts must be tightened with nuts so that all parts of the clamp experience equal pressure along the length of the contact. After the bolts are fully tightened, there should be a gap of 3-4 mm between the dies. The proximity of the dies closely indicates that the dimensions of the grooves do not correspond to the given tire and the required pressure in the contact is not provided. Such clamps must be replaced.
5.6. The termination of flexible busbars with hardware clamps for connection to flat terminals of devices should be done in accordance with the design of the terminal.
5.7. Connections of flexible busbars terminated with hardware clamps to flat terminals of devices must be made directly.
5.8. Connections of flexible busbars terminated with hardware clamps to the pin terminals of devices should be made:
- copper, terminated with a hardware clamp with one hole, with a terminal diameter of up to 28 mm - directly; for output diameters over 28 mm - through copper strips;
- copper, terminated with hardware clamps with two and four holes - through copper strips;
- aluminum and steel-aluminium, terminated with hardware clamps - through copper strips.
6. QUALITY CONTROL OF CONTACT CONNECTIONS
6.1. Acceptance rules
6.1.1. Connections should be checked during qualification, standard, periodic and acceptance tests of electrical devices in accordance with the requirements of GOST 17441-84.
6.1.2. All types of checks and sample size during qualification tests are given in table. 6.1.
6.1.3. Connections that fail the test according to one of paragraphs. 1-7 tables 6.1, it is necessary to re-test this item on a double number of samples, and the results of repeated tests are final.
6.1.4. The types of inspections and sample size during type testing should be sufficient to verify those characteristics of connections that may change due to changes in design, material or manufacturing technology.
6.1.5. During periodic testing, checks according to paragraphs. 1, 4, 5 tables. 6.1. Periodic testing should generally be carried out once every two years.
6.1.6. During acceptance tests, checks according to paragraphs. Tables 1 and 4 6.1. The sample size should be established in the standards or technical specifications for specific types of electrical devices; in the absence of such instructions, the sample size should be 0.5% (but not less than 3 pieces) of connections of the same standard size, presented simultaneously according to one document. The selection of compounds for the sample should be carried out in accordance with GOST 18321-73*.
Table 6.1.
| Name of checks | Items | Number of samples, not less | Note | |
| technical requirements | test methods | |||
| of this instruction | ||||
| 1. Verification of compliance with design requirements | 1.4; 1.5.1; 1.5.2; 1.6.7; 1.6.8 | 6.2.1...6.2.4 | 16 | When checking according to paragraphs 1-7 |
| 2. Test for the influence of environmental climatic factors | 1.5.8 1.6.9 |
6.2.5 | 3 | After checking according to point 1 |
| 3. Static axial load test | 1.5.3 1.6.1 |
6.2.6 | 3 | After checking according to point 1 |
| 4. Determination of initial electrical resistance | 1.5.4, 1.6.2, 1.6.3 |
6.2.7 | 10 | After checking according to point 1 |
| 5. Heating test with rated (long-term permissible) current | 1.5.6 1.6.5 |
6.2.8 | 10 | After checking according to point 4 |
| 6. Accelerated heat cycling test | 1.5.5 1.6.4 |
6.2.9 | 7 | After checking according to point 5 |
| 7. Test for resistance to through currents | 1.5.5, 1.6.4, 1.5.7, 1.6.6 | 6.2.10 | 3 | After checking according to point 5 |
6.2. Test methods
6.2.1. When installing contact connections for testing, their compliance with the requirements of GOST 10434-82*, TU for specific types of electrical devices or the requirements of this instruction should be monitored.
6.2.2. For flat dismountable joints, it is necessary to control the tightness of the contact surfaces. Connections can be considered to have passed the test if a probe 0.03 mm thick does not enter the mating groove of live parts beyond the zone limited by the perimeter of the washer or nut (Fig. 6.1). If there are washers of different diameters, this zone should be determined by the diameter of the smaller washer. For compression joints, the total length of the sections where a 0.03 mm thick probe enters the joint between the mating planes of the conductors should not exceed 25% of the overlap perimeter.
Rice. 6.1. Monitoring the tightness of contact surfaces
The permissible insertion depth of a probe with a thickness of 0.03 mm is equal to
6.2.3. For permanent connections made by crimping, it is necessary to control the geometric dimensions of the crimped part for compliance with the requirements of clause 1.5.2. (Fig. 6.2).
Rice. 6.2. Controlled elements of pressed connections
6.2.4. Welded or soldered joints should be checked for the absence of cracks, undercuts, unfused craters and compliance of the welds with the requirements of clause 1.5.1.
6.2.5. Testing for the influence of environmental climatic factors must be carried out for compliance with the requirements of clause 1.5.8. Connections can be considered to have passed the test if, upon visual inspection, no foci of corrosion are found on their contact surfaces that would impede operation, and if the increase in electrical resistance after the test does not exceed the values established in paragraphs. 1.5.5, 1.6.4.
6.2.6. Axial load testing for welded joints should be carried out in accordance with GOST 6996-66* on standard samples or joints; testing of soldered, crimped and dismountable connections - according to GOST 1497-84*.
The strength of the connection should be assessed by comparing the static axle loads that destroy the connection and the entire tire.
Connections can be considered to have passed the test if they can withstand the static axial loads specified in paragraphs. 1.5.3, 1.6.1.
6.2.7. The electrical resistance of the connection should be measured in the area between the points shown in Fig. 6.3.
The conductor resistance must be measured at the reference resistance (a whole section of conductor equal to the conventional length of 1 connection).
Measurement should be carried out using probes with sharp needles that destroy the oxide film. The resistance (voltage drop) of the connections must be measured using a DC voltmeter-ammeter method, a microohmmeter or a double bridge using electrical measuring instruments with an accuracy class of at least 0.5.
The resistance of flexible busbar connections should only be measured using the voltmeter-ammeter method.
Rice. 6.3. Resistance measurement points
a - bolted connection of tires; b - branch from the busbars (bolted connection); c - bus connection with a flat terminal; g - welded joint (branch from tires); d - welded joint; e - connection of flexible busbars; g - branch from a flexible bus; h - termination of the flexible bus; and - connection of the bus with a flexible terminal.
Measurements must be made at an ambient temperature of 20°±10°C.
When determining resistance using the voltmeter-ammeter method, it is recommended to take the measuring current no more than 0.3 of the rated current of the conductor. Connections can be considered to have passed the test if the average value of the sample resistance satisfies the requirements of paragraphs. 1.5.4, 1.6.2 and 1.6.3.
6.2.8. The rated current heating test should be carried out on connections that have passed the test in accordance with clause 6.2.7. Heating is carried out using direct or alternating current. If there is no rated current value in the standards and technical specifications for specific types of electrical devices, tests should be carried out at the test current, the values of which are given in GOST 17441-84.
Test methods - according to GOST 2933-83*. Linear contact connections are assembled into a series circuit. The length of the busbars connecting the contact connections must be at least:
with a cross-sectional area up to 120 mm2 inclusive - 2 m, with a cross-sectional area over 120 mm2 - 3 m.
Connections can be considered to have passed the tests if their temperature, taking into account the upper operating value of the ambient air temperature according to GOST 15543-70* (measured temperature rise over the air temperature during testing plus the upper operating value of the ambient air temperature) is not higher than the values specified in paragraphs. 1.5.6, 1.6.5.
6.2.9. Accelerated testing in the cyclic heating mode should be carried out on mock-ups of contact connections that have been tested according to clause 6.2.8. The length of the mock-up bus sections should be 250-300 mm. Accelerated testing consists of alternating (cyclic) heating of connections with current to 120±5°C, followed by cooling to a temperature of 25±10°C. The value of the test current must be established experimentally based on the heating time of the connections of 3-10 minutes. To speed up testing, cooling of the connections by blowing is allowed.
The number of heating-cooling cycles must be at least 500.
During testing, the electrical resistance of the connections should be measured periodically every 100 cycles in accordance with clause 6.2.7. and determine the average sample resistance value.
The connections can be considered to have passed the test if the average value of the sample resistance after each experiment of 100 cycles in comparison with the average value of the sample resistance obtained before the start of the tests meets the requirements of paragraphs. 1.5.5, 1.6.4.
6.2.10. Connections that have passed the tests according to clause 6.2.8 should be tested for resistance to through currents. Test methods for connections are in accordance with GOST 2933-83* and GOST 687-78* E. Connections can be considered to have passed the test if they meet the requirements of paragraphs. 1.5.5, 1.6.4, 1.5.7 and 1.6.6 for electrical resistance of the connection and heating temperature with through current.
7. SAFETY
7.1. When installing contact connections, the requirements of SNiP III-4-80 must be met. Contact connections in terms of safety requirements must comply with GOST 12.2.007.0-75* and ensure the operating conditions established by the “Rules for the technical operation of consumer installations” and “Safety rules for the operation of consumer electrical installations”, approved by Gosenergonadzor on December 21, 1984.
Annex 1
Table A1.1
Terms mentioned in the Instructions
| Term | Document establishing the term | Definition |
| Electrical device | GOST 18311-80* | A device in which, when operating in accordance with its intended purpose, electrical energy is produced, converted, transmitted, distributed or consumed. |
| Contact connection | GOST 14312-79 | Contact unit forming a non-breaking contact |
| Demountable contact connection | Same | A contact connection that can be opened without destroying it. For example, screw, bolt, etc. |
| Permanent contact connection | Same | A contact connection that cannot be opened without destroying it. For example, welded, soldered, riveted, etc. |
| Linear contact connection | Same | Contact connection of two or more conductors of current conductors, cables, overhead power lines, external control circuits, alarms, protection, etc. |
| Initial electrical resistance of the contact connection | Same | Contact resistance measured immediately after assembly (before testing) |
| Solid aluminum alloy | Same | Aluminum alloy with a tensile strength of at least 130 MPa (13 kgf/mm2) |
| Adapter plate | GOST 19357-81* | A current-carrying part intended for connecting current-carrying busbars made of dissimilar materials and connecting current-carrying busbars from one material to the terminals of electrical devices made of another material |
| Copper-aluminum plate | Same | Adapter plate consisting of copper and aluminum parts |
| Aluminum alloy plate | Same | Hard Aluminum Alloy Adapter Plate |
| Grounding conductor | PUE-86 | Conductor connecting the grounded parts to the ground electrode |
| Neutral protective conductor | Same | Conductor connecting the neutral parts to the neutral of the electrical installation |
| Abrasive tinning | GOST 17325-79* | A method of tinning with simultaneous removal of an oxide film from a metal surface by friction with solid metal or non-metallic particles |
| Tinning by immersion in molten solder | Same | - |
| Piece electrode (coated electrode) | GOST 2601-84* | An electrode coated with a mixture of substances applied to the electrode to enhance ionization, protect against harmful environmental influences and metallurgically treat the weld pool |
| Homogeneous materials | Same | Materials whose nominal electrochemical potentials are close in value |
| Dissimilar materials | Same | Materials with different nominal electrochemical potentials |
Appendix 2
Chemical treatment of welding wire made of aluminum and its alloys
To degrease and remove the oxide film, the wire should be placed for 0.5-1 minutes for etching in a bath with a 5% solution of caustic soda technical brand And according to GOST 2263-79*. Solution temperature 60-70°C.
After etching, the wire must be rinsed in hot running water for 30-40 s. The washed wire is clarified by immersion for 30-40 s in a 15% solution of nitric acid according to GOST 701-89E at room temperature (16-25°C).
The brightened wire should be washed in running water for 30-40 s and dried in a cabinet at a temperature of 100-150°C.
The treated wire must be stored in a hermetically sealed container in a dry place.
Wire with a chemically treated surface is wound onto reels mechanically in rows without kinks or gaps.
Wire spools should be placed in a plastic bag along with a control package of dehydrated silica gel indicator powder (GOST 8984-75*), which is sealed at a relative ambient humidity of less than 20% for 30 minutes after treatment.
Premises in which chemical processing of welding wire is regularly carried out must comply with the requirements of the All-Union Standards for Technological Design of Mechanical Engineering, Instrument Making and Metalworking Enterprises. Metal coating workshop", ONTP 05-86, approved by the Ministry of Automotive Industry on 03/05/86 in agreement with the State Committee for Science and Technology of the USSR and the State Construction Committee of the USSR dated 12/30/85, 45-1246.
Appendix 3
Electrode holder for carbon electrode
- carbon electrode;
- protective screen;
- dielectric handle;
- welding cable.
Appendix 4
Graphite carbon electrodes
Appendix 5
Welding fluxes
Note.
Fluxes are contained in hermetically sealed glass containers.
Appendix 6
Rotator for three-phase sections of conductors
- split rim;
- rollers;
- roller axes;
- racks;
- base;
- shelves with clamps.
Copper and its alloys (brass, bronze, etc.) are widely used in various industries (especially in electrical engineering and pipe manufacturing) as structural materials.
Copper is widely used in industry due to the fact that it is a good conductor of heat and current.
Copper conducts electricity and heat well, resists corrosion well, and has high ductility and aesthetics. Anyone who frequently works with metals should know how to weld copper.
Features of copper welding
The process of working with copper products largely depends on the presence of various impurities in its composition (lead, sulfur, etc.). The lower the percentage of such impurities contained in the metal, the better it will be welded. When working with copper, the following features must be taken into account:
- Increased oxidation. When this metal is heat treated with oxygen, cracks and brittle zones appear in the near-weld zone.
- The absorption of gases in the molten state of copper leads to the formation of a poor-quality weld. For example, hydrogen, combining with oxygen during metal crystallization, forms water vapor, as a result of which cracks and pores appear in the heat treatment zone, reducing the reliability of the weld.
- Great thermal conductivity. This property of copper leads to the fact that its welding must be carried out using a heating source of increased power and with a high concentration of thermal energy in the area of the weld. Due to the rapid loss of heat, the quality of seam formation decreases and the possibility of formation of beads, undercuts, etc. in it increases.
- A large coefficient of linear expansion causes significant shrinkage of the metal during solidification, as a result of which hot cracks can form.
- As the temperature increases above 190°C, the strength and ductility of copper decreases. In other metals, with increasing temperature, a decrease in strength occurs with a simultaneous increase in ductility. At temperatures from 240 to 540°C, the ductility of copper reaches its lowest value, as a result of which cracks can form on its surface.
- High fluidity makes it impossible to carry out high-quality one-sided welding by weight. To do this, you need to additionally use gaskets on the reverse side.
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The influence of impurities on the weldability of copper
Impurities found in copper have different effects on its weldability and performance characteristics. Some substances can facilitate the welding process and improve the quality of the weld, while others can reduce it. For the production of various copper products, the most popular is copper sheet grades M1, M2, M3, which contain sulfur, lead, oxygen, etc. in a certain amount.
O2 has the greatest negative impact on the welding process: the more it is, the more difficult it will be to achieve a high-quality weld. In copper sheets M2 and M3, an O2 concentration of no more than 0.1% is allowed.
A small concentration of lead at normal temperatures does not have a negative effect on the characteristics of the metal. As the temperature increases, the presence of lead in the same amount causes red brittleness.
Bismuth (Bi) is practically insoluble in solid metal. It covers the copper grains with a brittle shell, as a result of which the weld becomes brittle in both hot and cold states. Therefore, the bismuth content should be no more than 0.003%.
The most harmful impurity after oxygen is sulfur, because it forms sulfide, which, being at the grain boundaries, significantly reduces the performance characteristics of copper and makes it red-brittle. When copper with a high concentration of sulfur is heat treated, it enters into a chemical reaction, which leads to the appearance of sulfur gas, which, when cooled, makes the weld porous.
Phosphorus is considered one of the best deoxidizing agents. Its content in the copper billet not only does not reduce the strength characteristics of the weld, but also improves them. However, its content should not exceed 0.1%, because otherwise the copper becomes brittle. This should be taken into account when choosing filler material. Phosphorus also reduces the ability of copper to absorb gases and increases its fluidity, and this can increase the speed of welding work.
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Copper can be welded in various ways, the most popular of which are:
- gas welding;
- automatic submerged;
- argon arc;
- manual welding.
Whatever method is chosen, before starting work it is necessary to properly prepare the surfaces to be welded. Before welding copper, bronze, brass and other alloys, the welded edges and filler wire must be cleaned of dirt and oxidation to a metallic shine, and then degreased. The edges are cleaned using metal brushes or sandpaper. However, it is not recommended to use coarse sandpaper.
Etching edges and wires can be carried out in an acid solution:
- sulfur - 100 cm 3 per 1 liter of water;
- nitrogen - 75 cm 3 per 1 liter of water;
- salt - 1 cm 3 per 1 liter of water.
After the etching procedure, the workpieces are washed in water and alkali, followed by drying with hot air. If the thickness of the workpiece is more than 1 cm, then it should first be heated with a gas flame, arc or other method. Joints for welding are connected using tacks. The gap between the joined elements must be the same throughout the entire area.
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Gas welding of copper products
By welding copper with gas welding and following the technology for performing the work, you can get a high-quality seam with good performance characteristics. In this case, the maximum strength of the joint will be about 22 kgf/mm 2.
Due to the fact that copper has high thermal conductivity, the following gas flow rate must be used for welding:
- 150 l/h with a product thickness of no more than 10 mm;
- 200 l/h with a thickness of more than 10 mm.
To reduce the formation of cuprous oxide and protect the product from hot cracks, welding should be carried out as quickly as possible and without interruptions. Wire made of electrical copper or copper containing silicon (no more than 0.3%) and phosphorus (no more than 0.2%) is used as an additive. The diameter of the wire should be approximately 0.6 times the thickness of the sheets being welded. In this case, the maximum permissible diameter is 8 mm.
When welding, it is necessary to distribute heat so that the filler material melts slightly before the workpiece.
To deoxidize the metal and clean it from slag, fluxes are used, which are introduced into the weld pool. They also process the ends of the wire and the edges of the plates being welded on both sides. To refine the grains of the deposited metal and increase the strength of the weld, it is forged after completion of the work. If the thickness of the workpiece is no more than 5 mm, forging is carried out in a cold state, and with a thickness of more than 5 mm - at a temperature of about 250°C. After forging, the seams are annealed at a temperature of 520-540°C with rapid cooling with water.
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Automatic submerged arc welding
This welding method is performed using a conventional welding machine using direct current of reverse polarity. If you use ceramic flux, you can also work on alternating current. To weld copper no more than 1 cm thick, you can use conventional fluxes. If the thickness is more than 1 cm, then you need to use dry granulation fluxes.
In most cases, all work is carried out in 1 pass, using technical copper wire. If the seam should not have high thermophysical properties, then to increase its strength, the connection of bronze and copper is carried out with bronze electrodes. To prevent the molten metal from spreading and forming a seam on the back side of the workpiece, flux pads and graphite pads are used.
Welding of brass is carried out under low voltage, because with a decrease in arc strength, the likelihood of zinc evaporation will decrease. Bronze welding is carried out using direct current of reverse polarity. The height of the flux is limited or a coarse granulation flux (up to 3 mm) is used.
Welding of copper bars can be done efficiently if argon is used. You need to apply for a job with a professional in your field. It is worth coming to the workshop of specialists to get excellent work. Thanks to the use of the best and newest equipment and the experience of the craftsmen, any flaws in the work are excluded. The result will please all customers.
Welding copper bars, what are its advantages?
Argon welding has many advantages over other types of similar work. Special equipment and protective gas argon are used. Welding copper bars is quite simple, but a lot depends on the grade of copper itself. It is worth remembering that if you use certain brands, the seams may not be sealed.
If the quality of the copper bars is not very good, then the work will be more difficult to carry out. Welding with argon allows you to get wonderful results. Much also depends on the quality of work; professionals need to pay maximum attention when working, otherwise careless movements can cause holes.
Features of argon welding
The technology for welding copper busbars is practically no different from working with stainless steel. Therefore the price will not be high. To get the best result:
- the surface of the copper bars must be perfectly clean,
- a specific current mode is used,
- the protection applied must be provided at the highest level.
Copper welding has found wide application in both electronics and chemical engineering in the manufacture of devices for use in conditions where high corrosion resistance is required. Therefore, the technology of copper welding, as well as the technology of welding non-ferrous metals and alloys, in general, is constantly being improved, despite the desire to save them. Before describing how to weld copper, it is necessary to clarify that in most cases, sheet copper parts and pipes are used for welding.
We also note that there are no special types welding for copper products. And all known methods can be used for welding them, with the exception of resistance welding, which is used to a limited extent.
Manual arc welding of copper with metal electrodes
The feasibility of using consumable electrode arc welding instead of gas welding of copper is dictated by technical and economic advantages, as well as when welding steels. First of all, this method is highly productive. The speed of consumable metal arc welding is much higher than that of other welding methods. Copper arc welding can be done manually, automatically under submerged arc or under shielding gases. Copper welding using semi-automatic and automatic machines is described below in the text. Now let's look at manual arc welding of copper.
Preparing the welding site
If the thickness of the welded copper is 6-12mm, then it is recommended to perform a V-shaped groove with a total opening angle of 60-70°. If a back weld is provided on the reverse side, the angle can be reduced to 50°.
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Before welding, it is necessary to move the copper sheets or strips apart at an angle to each other, with a gap of 2-2.5% of the length of the seam, see the figure on the right. If welding is carried out without first moving the sheets apart, it is recommended to pre-tack them with short seams about 30mm long at a distance of approximately 300mm from each other. Tacks are made with an electrode of smaller diameter and provide a gap between the edges of 2-4 mm. If there is no gap, the likelihood of metal overheating increases. When making tacks, it should be taken into account that repeated heating of copper leads to the appearance of pores in the metal, therefore, as you approach the tacks, they must be cut out and cleaned. This will not take much time, because... tacks are made to a shallow depth.
When the metal thickness is more than 12 mm, an X-shaped cutting of the edges is recommended, which will require double-sided welding. If it is not possible to perform an X-shaped cutting, then perform a V-shaped one. At the same time, the consumption of electrodes and welding time increase by almost one and a half times. In X-shaped edge preparation, the tack is made on the back side of the first seam and removed before starting the second seam.
Welding of a butt joint without edge preparation or with a V-shaped groove is performed on pads that are pressed close to the joint, or on a flux pad. Steel, copper or graphite pads with a width of 40-50mm are used with a forming groove.
Before welding, it is recommended to preheat the edges. Heating can be local, general or auxiliary, depending on the dimensions of the product and the thickness of the copper being welded. Typically the heating temperature is 300-400°C.
Electrodes for arc welding of copper and coatings for them
Coated electrodes are used for copper arc welding. The use of an electrode without a protective coating leads to oxidation of the seam, unstable arc burning and the appearance of defects in the weld seam (porosity). Electrode rods are used in the form of copper wire (which can be alloyed with silicon and manganese), bronze of the Br.KMts 3-1 brand or bronze of the Br.OF 4-03 and BR.FO 9-03 brands.
Electrode rods of this composition alloy the weld metal with silicon, manganese, phosphorus (sometimes tin) and have a deoxidizing effect. Protective coatings are selected with a composition that ensures arc stability, metal deoxidation and slag formation. All this contributes to good seam formation and improved welding quality.
Modes of manual arc welding of copper
Welding is performed with direct current of reverse polarity. The use of alternating current often does not provide the required arc stability. It is possible to weld with alternating current only if iron is present in the protective coating. In this case, it is necessary to increase the current strength by approximately 40-50%. But it should be borne in mind that the use of alternating current can lead to spattering of the electrode metal. Approximate welding modes are shown in the table below.
Modes of manual arc butt welding of copper sheets with copper electrodes using direct current:
Welding speed is 15-18 m/hour. If bronze electrodes are used, the welding speed increases, because a bronze electrode melts faster than a copper one.
When welding copper with a thickness of more than 10-12mm with an electrode diameter of 6-8mm, the welding current is increased to 500A.
When welding T-joints, the welding modes are approximately the same as for welding butt joints. In this case, it is necessary to install the welded joint “in a boat”.
Manual copper arc welding technique
Welding of large thickness copper is welded in several layers. Each previous layer is thoroughly cleaned before surfacing the next one. But it is better to weld small and medium thicknesses of copper in one pass.
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Welding is performed with reverse-stepped seams, with a section length of 200-300mm. The entire length of the welded section is divided into two sections: 2/3 of the length of the seam and on the other side 1/3 of the length. First, the long section is brewed towards the small one, and then the short section. The diagram of this welding is shown in the figure on the left. This welding technique significantly reduces the risk of cracks in the metal.
Welding is performed in a lower position, or slightly inclined, and it is performed at a “forward angle”, i.e. the electrode should be tilted in the direction opposite to welding at an angle of 15-20°. When welding, “swelling” of the welded edges may occur as the gap between them decreases. In this case, the seam must be periodically corrected with a hammer or sledgehammer. It should be borne in mind that if welding is performed on a graphite backing, it may crack. Therefore, steel pads or copper pads are preferable.
Quality hand welded copper
Pure borax or with the addition of other components works well as a flux. Read more about fluxes for gas welding of copper.
Contact welding of copper
When welding copper, the most common type of resistance welding is butt welding. It is used for welding copper rods, wires, tapes, and pipes. But this type of welding is more suitable for welding copper alloys. Spot and seam welding are not widely used in practice. We talked in more detail about contact welding of copper products and the modes for them on the page: "".
Video: general information about copper welding, its history
The video contains a brief history of copper and its processing from ancient times to the present. The video contains general recommendations for welding copper using various methods.
For copper busbars, as well as for aluminum ones, there is a fairly large selection of welding methods, practically covering all the needs of electrical installation production. These include: carbon arc welding, tungsten arc welding and semi-automatic, semi-automatic and automatic submerged arc welding, plasma and gas welding.
Welding copper is more complex than welding aluminum, due to the characteristics of copper as a material. One of the main complications associated with copper welding is the need for preliminary or concomitant heating of the tires when the metal thickness is already more than 10-12 mm. This is due to the high thermal conductivity of copper. In addition, due to the fluidity of copper, making vertical and horizontal seams is difficult, and ceiling seams are almost impossible.
However, it should be noted that some very highly qualified welders also achieve ceiling welding, in particular welding fixed joints of tubular busbars, which is a great art. It is necessary to literally “feel” the metal and regulate the welding process so that the weld pool is of minimal size and individual drops of metal harden without having time to roll off. In this case, it is necessary to additionally heat the heat-affected areas of the tires to red heat using extraneous heat sources. Very
It is also advisable to use semi-automatic pulsed argon arc welding.
When choosing certain methods of welding tires for specific conditions, it is useful to take into account the following features.
The best quality of connections in terms of ductility, density and appearance of the seams is provided by semi-automatic argon arc welding. It is used for metal thicknesses up to 12 mm and makes it easier to make vertical, horizontal and ceiling seams when using an impulse attachment.
Manual tungsten arc welding also produces good joints, but can only be used in the down position.
Approximately equivalent to argon arc welding in terms of the quality of seams is semi-automatic submerged arc welding, which is used in the lower position with tire thicknesses up to 14 mm. It is less convenient in installation conditions due to the somewhat more bulky equipment (flux feeders), the need for compressed air at the work site to supply flux, and the lack of visual control over the formation of the seam (the seam is covered with a layer of flux).
Automatic welding under a layer of flux is advisable only for making extended seams for large volumes of work. Such seams are found when preparing heavy busbars in electrolysis plants. Carrying out short seams using automatic1 welding, such as occur when connecting busbars end-to-end, is not justified, since the time required to install the machine at the beginning of the seam and for the final operations is relatively long.
The most widespread in electrical installation practice is DC welding with a carbon electrode, which allows the connection of copper busbars with a thickness of 30 mm or more with a completely satisfactory quality of the seams. Independence from the presence of argon at the work site makes it the most accessible. The ability to pass higher currents through the electrodes than when welding by other methods, and thereby obtaining greater welding energy input, makes it possible to avoid additional heating of tires with a metal thickness of up to 20-25 mm. This is a great advantage of carbon electrode welding, as it simplifies the technology and organization of welding work.
The desire to completely abandon additional heating when welding copper busbars has led to attempts to use plasma welding for this purpose, in which a high concentration of thermal energy is achieved.
As a result of the developments carried out by LenPEO VNIIPEM, it is possible to use plasma welding to connect copper busbars with a thickness of only up to 10-12 mm. Its advantages, along with the ability to avoid additional heating, also include savings in filler material, such as
8 R. E. Evseev, V. R. Evseev 22 £>-
how welding is done without a gap between the edges; more beautiful appearance seams (low seam reinforcement) and some reduction in the time required for welding. The disadvantages include the need for water cooling of the torch (plasma torch), the relative complexity of the plasma torch and its large mass (about 2 kg). The latter leads to increased fatigue of the welder during long-term work. In addition, welding requires two argon cylinders, which complicates and burdens the installation.
Assessing these features of plasma welding, the authors believe that this method will be more appropriate in electrical installation practice after the development and mastery of technology for connecting thick busbars. At present, it can be used in workshops for electrical installation workpieces and should be considered as being in the stage of production testing.
Gas welding of copper busbars is an auxiliary method due to lower productivity compared to electric welding and the low prevalence of gas welding equipment in electrical installation organizations. Using gas welding, connections can be made to busbars with a thickness of up to 30 mm, although in the practice of electrical installation work there are cases of gas welding of busbars of greater thickness. It is most advisable to use gas welding for connecting tubular water-cooled busbars, as well as for welding parts for terminations and fittings of the water-cooling system to such busbars.
For welding copper, due to its high thermal conductivity, only acetylene is used, since acetylene substitutes (propane butane, etc.) do not provide a sufficiently high flame power.