The rapid development of the power industry, especially the long-distance transmission of electrical energy and the widespread use of high voltage, large cross-section and large length power cables in urban grids, has greatly driven the development of overhead lines and power cables. Stranding is a basic process in the production of conductive wire cores for overhead lines and power cables, and is one of the main links in quality control. Stranding equipment in the wire and cable enterprises a large proportion of the fixed asset investment, is the basic equipment of the cable industry. This article mainly introduces overhead transmission lines and power cable conductors used in the production of stranding equipment.
1. Stranding machine selection
Stranding machine for multiple single line in accordance with certain requirements stranded together into a whole wire or core, the main role is to improve the bending ability of the wire and the stability of the structure. Depending on whether the individual wires are arranged according to a certain
The stranded wire is divided into regular stranded and non-regular stranded (bundled wire).
Depending on the structure of the stranding machine, the stranding machines are usually divided into cage stranding machines, flat stranding machines, fork stranding machines, frame stranding machines as well as tube stranding machines and bow stranding machines. All of these machines can strand copper and aluminium conductors and cable cores of regular construction.
Due to the small number of tube stranding machines and bow stranding machines, usually 1+6 or 12 discs, they are only suitable for small cross-sectional wire cores as well as for stranding steel cores in steel-core aluminium stranded wires. These two types of equipment have a low rotational inertia and a high speed and are called high-speed stranding machines.
Cage stranding machine is the wire and cable industry and the wire rope industry in the longest history of stranding equipment, its biggest feature is to be able to back twist, especially for commercial strength hard-drawn round wire stranding and OPGW, submarine optical cable without twisting stranding, bundle stranding core of the re-sanding, in addition to the cable can also be used for wire armouring, so the elimination of the cage stranding machine is inaccurate.
At the same time, the biggest weakness of the cage stranding machine also lies in the retreat twist, the complex structure of the retreat twist device seriously limits the cage stranding machine's rotation
The complex rewind mechanism severely limits the speed increase and the implementation of automatic up and down trays.
In the 1960s, the European cable industry confirmed that most wires and cores could also be stranded without twisting, so the development of non-twisting rigid stranding machines, such as fork stranding machines, frame stranding machines and other types of rigid stranding machines, increased production speed exponentially, coupled with the use of centralised loading and unloading devices, the saving of auxiliary time, increased automation, the productivity of the stranding machine, the output per unit area of the workshop The working conditions and environmental conditions have also been improved.
To date, the rigid stranding machine without back-twisting is not only widely used for stranding overhead lines, meshed and sector-shaped copper and aluminium (aluminium alloy) wire cores, but also for cable actinides.
It can also be used for cable actinide shielding and soft wire armouring.
Early use of non-return twist stranding machine for the plane stranding machine for low-voltage paper insulated cable core stranding and paper wrapping, simple structure, low efficiency, is rarely used. Efficient mainly fork stranding machine and frame stranding machine. Fork stranding machine turning radius is small, high speed, coupled with a simple structure, low cost, once widely used. However, in terms of spindle force analysis, the spindle of the fork strander can be regarded as a simple beam bearing a concentrated load at multiple points, which is not as rigid as the frame structure of the frame strander, and at the same time the frame strander is structurally easy to achieve centralised loading and unloading and increased automation, so since the mid-1990s the frame strander has been more widely accepted by users.
The choice of the stranding machine is not only based on the structural requirements of the conductor (e.g. wire material, single wire diameter, number of roots, stranding
direction], pitch range, maximum conductor length, etc.) to determine the form of the stranding machine, the number of stranding cage sections, the size of the pay-off tray, the maximum
traction force and the size of the take-up tray, etc. The corresponding components should also be selected according to the wire production process. For example, the production of overhead lines
to prevent the wire from being loose and set up when the "lantern", the stranding machine needs to be equipped with a "pre-deformation device" to eliminate the wire in the
internal stress. To reduce the diameter of the conductor and save insulating material when producing cable cores, a "compression device" is required. Production
For the production of cable cores with a cross section of more than 800 mm2, a pre-twisting system for the production of split conductors is required.
Stranding quality and stranding equipment structure of the rationality, equipment manufacturing quality and reliability has a very close relationship
The stranding cage and other rotating parts in particular should run smoothly, safely and reliably: wire tension control to be uniform; breakage parking
Should be rapid and timely, action - consistent: wire channel should be smooth.
Stranding machine centralised up and down the tray is to reduce auxiliary time, improve labour productivity of effective measures. Up and down the tray in a variety of forms, should be selected according to the actual situation in the factory, while the stranding machine automation and safety interlocking devices should also be adapted to it.
Bunching machines are usually used for small cross-section, soft cores of irregular stranding, due to the high speed of the bunching machine, occupying the ground
Less floor space, investment, after adding some process measures, its use has become more and more widespread. Many foreign factories use large east
Wire machine stranding 7, 19 steel, aluminum wire and tight pressure core and small wear surface rubber insulation line into the cable, and even for electric
Cable wire armouring.
2. The structural characteristics of the stranding machine
Stranding machine structure despite the variety of forms, but the main components of the functional principle, structure is similar. Nearly
In the past twenty years, the frame stranding machine in the use of new structures than other stranding equipment, the following frame stranding machine as an example to be introduced:
1. Drive
Multi-stage stranding machine, each section of the stranding cage drive has long been used ground shaft drive, with the delicacy of electrical transmission precision and reliability, the cost of
With the improvement of the precision and reliability of the electrical transmission, the cost reduction, many equipment manufacturers have adopted a separate drive for each section of the cage, electrical synchronisation
The drive mode of the cage, the ground shaft has been cancelled, simplifying the structure, and the production site is also smooth.
2. Cage
(I) Thimbles
In addition to the older stranding equipment also using the mandrel, the bobbin in the cradle frame fixed basically: the use of the thimble structure, that is, one end fixed, the other end of the thimble can be moved. With the gradual promotion of the upper and lower plates of the machine maple, the moving thimble has been transitioned from a single plate manually to an external gas (electric) source gas (electric) dynamic, the development to a direct supply of gas source in rows of centralized pneumatic.
Stranding machine rotary air joints and sealing devices are used to good effect.
After the active ejector pinches the bobbin in the stranding cage, there is a mechanical locking device and an electrical interlock, which prevents the machine from starting when the ejector is not tightened, and prevents accidents due to compressed air breakage.
In order to reduce the concentration of the time to change the disc, the frame twisting machine thimble mouth to a cylindrical type, the use of the thimble and the friction of the end surface of the bobbin to replace the thimble structure in the carrying pin.
(2) Braking and tension control of the pay-off reel
The tension of the traditional stranding machine is installed in the fixed thimble on the friction wheel and friction belt to achieve, from the full plate to the empty plate of the release process, the release tension can not be adjusted, the single line tension is not uniform, the release tension on each release plate is not consistent, easy to cause a single line pull thin or "jumping", "lantern "and other phenomena, seriously affecting the quality of stranded wire. Some of the improved stranding machines use mechanical feedback control of the tension device, some use pneumatic control.
Frame stranding machine more than the use of pneumatic control, compressed air through the rotation of the air to connect the U.S. people into the stranding cage, each payload plate fixed thimble
A set of pneumatic tensioning device is installed on each payoff plate, which consists of a short-stroke cylinder, friction tensioning block and friction tensioning plate, in each.
A set of tension control levers is installed in each row of each gibbet or gibbet cage, which adjusts the compressed air pressure according to the diameter of the wire in the payoff tray.
The pressure of the compressed air can be adjusted according to the diameter of the pay-off reel, so that the tension of the single line pay-off remains uniform. The air pressure can also be adjusted in steps according to the length of the pay-off.
The air pressure is automatically adjusted during operation.
(3) Wire break stop and cage brake
With the increase in speed of the stranding machine, it is required that the command of the wire break stopping device is agile and the cage braking is rapid and smooth to avoid the break
Wire end into the parallel die, otherwise it will cost a lot of time to repair, so the front of the cage alone by the broken wire stop ring is
Therefore, the broken wire stop ring at the front of the cage alone is not sufficient, not to mention that the broken wire does not necessarily touch the stop ring under centrifugal force.
The new frame stranding machine has a wire break monitor on the fixed thimble of each payoff plate.
When a wire break occurs or when the wire is discharged, the wire disc stops rotating and the pulse signal is suspended.
When a wire break occurs or the wire is discharged, the bobbin stops rotating, the pulse signal is suspended and the stranding machine is ordered to stop, while the position of the broken bobbin is indicated.
Stranding machine each cage are equipped with braking devices, frame stranding machine speed, high rotational inertia, short braking time, so the traditional electromagnetic brake has been overwhelmed, now more pneumatic or gas-hydraulic disc brake, can be completed in 5 ~ 6 seconds emergency braking. The impact and damage to equipment caused by emergency braking is also very serious and should be minimised. So many equipment braking is divided into emergency braking and normal braking, the normal braking time is much longer, generally about 15 seconds.
3. Traction device
Stranding machine using the traction device is mainly single-wheeled and double-wheeled, belay traction use less. Two-wheeled traction
There are many structures, such as single small wheel, double groove wheel, single active, double active, should be based on the stranded products of the most
The choice should be based on the maximum traction force of the stranded product.
Avoiding abrasion of the stranded conductor on the traction wheel should be given sufficient attention.
For single traction wheels an endless nylon cord can be placed between the wound conductors to avoid any contact between the two turns. The "double active traction device" is a combination of two traction
The spindles of the two towing wheels are staggered at an angle so that the stranded conductor naturally transitions between the two towing wheels from one slot to the next along the towing wheel betel.
The transition from one groove to the next is natural.
4. Centralised loading and unloading device
In order to reduce auxiliary time, reduce labour intensity and increase labour productivity, more and more mills are opting for a centralised loading and unloading device with.
A centralised up and down tray device (Fig. 6) is being used for frame winches. Commonly available are top lifting, side 45° pushing, bottom top lifting and our forms of ground level tilting. The factory can choose according to the actual situation.
Top lifting requires complex spreaders and expensive lifting equipment. Neither the side 45" push nor the bottom top lift can be operated continuously.
The bottom lift cannot be operated continuously. The unloading of the empty plate from the operating platform is followed by a full plate, which takes a long time; the mechanism is installed
The mechanism is installed underground and uses a hydraulic system, which makes maintenance difficult. The ground level tilting centralised loading and unloading mechanism is simple, reliable and can be operated without a
Reliable, no mechanical foundation, and can use the machine working time to carry out handling work, so the time to change the plate is short, but the plate stacking
The area is slightly larger. The centralised plate loading and unloading mechanism used on frame winders is mostly of the bottom top type and the floor level tilting type.
5. Pre-deformation devices
Frame stranding machine can not back twist, in the stranding of high-strength hard round wire, single line internal stress, resulting in wire stranding
Not tight, easy to loose strands, bringing problems to the construction. In the production of overhead conductors, pre-deformation devices are installed in front of the stranding cage to eliminate
This is why, during the production of overhead conductors, a pre-deformation device is installed in front of the stranding cage to relieve the internal stress of the single wire.
6. Core compression devices
In order to reduce the diameter of the conductive core and save material, power cables, especially cross-linked cables, are usually tightly pressed cores, with a tight compression factor of approximately 0.85 to 0.90.
The process varies from plant to plant and can be moulded or rolled. In order to facilitate the layering process, each section of the cage is equipped with a pressing device in front of each section. Due to the different pressing cross-sections of each section of the cage, the corresponding number of pairs of rollers
The adjacent pressing wheels are arranged perpendicularly to each other, so that the core is evenly deformed. The distance between each pair of rollers can be the surface of the core should be smooth and should not have "edges" or "corners". There should also be no metal emblems to avoid inducing.
The surface of the inner shield should be smooth, without "edges" or "corners".
7. Pre-twisting device
Cable cores with cross-sections greater than 800 mm2 should be split to reduce the skin effect of the cable. Pre-twisting devices can be configured to suit the needs of the user. Conventional stranding machines have an additional pre-twist variable speed system to drive the pre-twist device and to adjust the "pre-twist pitch". The rotation of the pre-twist head and the movement of the wire core form the pre-twist pitch, which should be the same as the pitch of the split wire after it has been stranded. The speed of the pre-twist head is therefore intrinsically linked to the speed and pitch of the stranding cage. Traditional pre-twisting variable speed systems for stranding machines are complex and are driven by ground shafts. The new stranding machine uses a separate motor-driven pre-twisting device with stepless adjustment of the pre-twisting pitch and a high-precision electrical synchronisation technology to automatically track changes in the wire speed and ensure a stable pre-twisting pitch.
8. Traveling winding and pay-off device
In order to improve the quality of the stranding line, lighten the labour intensity and shorten the length of the stranding machine, the frame stranding machine has been generally fruitful to use the walking type wire collecting and discharging device.