Wooden support line: photo, dimensions, weight. Installation and repair of wooden supports

The condition of the transmission line is significantly influenced by the type of supports used. For 100 years the wooden support remained one of the main structures of overhead lines (overhead lines).

Only in the 60s of the last century it began to be done with protective impregnation. Then, instructions were given on the use of antiseptics, but they were poorly executed, which led to decay of the supports. The ubiquitous transition to reinforced concrete poles did not solve all the problems, because they found shortcomings that were not inherent in wood products:

• Brittle impact;
• Small bending strength;
• Significant weight;
• Presence of leakage currents.

Benefits

Wooden support will never be written off due to the following advantages:

1. Low cost.
2. Light weight.
3. When the wooden support falls, the weight of which is 3 times less than the reinforced concrete, it hangs on the wires without the "domino" effect, which is characteristic of heavy poles.
4. Indispensable in areas with increased seismic activity.
5. Better withstand wind loads.
6. High dielectric characteristics.
7. Long service life with proper manufacturing (up to 40 years).
8. Do not require special maintenance.

disadvantages

Along with the advantages of wooden support has disadvantages.

1. Impregnating compositions may contain harmful substances that are in the air of the working zone (fuel oil, kerosene, creosote, etc.). Especially harmful are oil based antiseptics. In addition, they have increased fire hazard.
2. Logs must be made with the necessary diameters and taper.
3. High-quality products are obtained during winter felling and drying under a canopy for 6 months. Here it is necessary to treat logs with an antiseptic so that they do not rot.

Materials

The support of the power transmission line is made of coniferous trees, where the resin is a natural preservative and antiseptic. The greatest demand is for the northern pine, which has high strength and elasticity. The problems that ferro-concrete pillars have due to their fragility never create wooden supports (photo below - loading of finished products).

For impregnation, slate or creosote oil, as well as mixtures containing copper, chromium, and arsenic are used. In addition, antiseptic supports are treated with fire-fighting agents (flame retardants). This allows you to dig in the pillars directly into the ground, without concrete stepchildren, which increases the service life.

The highest absorbency is available in pine products. If sprues and larch are used for supports, it is much more difficult to impregnate them.

Impregnation allows you to instill the poles directly into the ground. Only here it is necessary to additionally protect the ends with a protective paste or lids. It is important to dry the wooden support before impregnating it for up to 3 months. The attachment to the stepsons of reinforced concrete leads to the splitting of the wood under the bandages from the wire rod.

Important! For the production of poles, use the lower part of the tree (pile), where there are fewer branches and a more uniform structure.

Dimensions and Strength

The length of the supports is 3.5-13 m. Depending on the diameters in the upper (d) and lower (D) parts, they are as follows:

• Light: d = 140 mm; D = 160-220 mm;
• Average: d = 160 mm; D = 180-235 mm;
• Strong: d = 195-210 mm; D = 210-260 mm.

An important indicator is the strength at the bottom of the rack. For a log diameter of 190 mm, the maximum bending moment is 55 kNm, and for 240 mm, 95 kNm.

Criteria for choosing a wooden support

1. The northern pine of winter fellings is used as the material.
2. At the top of the column, the thickness is not less than 16 cm.
3. As an impregnation, an aqueous solution of CCA is used.
4. The whole support or the lower part is impregnated in the factory at a pressure of 12-14 atm.
5. Technological holes are made before impregnation.
6. Depth of impregnation is 85% of the outer layer of wood - sapwood (up to 40 mm).
7. The impregnation process is finished, if the color of the support is gray-green. If it is brown or brown, this means that the reaction did not end up to the end. The boundary should be visible on the log edge.
8. Supports are sold in classes C ₁ and C ₃ with a size fit.

Features of impregnation of supports

In the ground, the pillars are installed without stepchildren. The ends are impregnated more than the side surface. In operation, up to 90% of the protective composition is washed out of them. To prevent this, the top is covered with a galvanized roof of 250x250 mm, and the bottom is covered with a flat material that does not allow moisture.

In accordance with GOST 20022.0-93, the wood under the supports is impregnated with the protective agent XM-11 in terms of dry salt in an amount of 13-15 kg / m ³ . Buying logs for poles, it is necessary to find out, under what conditions they were made, since in some specifications this quantity is understated by 2 times. Not all manufacturers correctly withstand the technology of manufacturing products. It requires the organization of quality control, although a specialist can determine it visually.

Technology of production of supports

The process involves 4 important steps.

1. Debarking

On a specialized machine, the bark with the bast is removed. Only after this the trunk begins to dry. Zabolonovaya wood should be affected to a minimum, because it is well impregnated with antiseptic. If the entire top layer is stuck, the longevity of the support will be much reduced due to the fact that it will be more susceptible to decay. Then the wooden support, the dimensions of which meet the requirements, is sorted according to the purpose. Some manufacturers produce drying without removing the bast, which makes it possible to prevent the cracking of wood. Then the bast is removed, as it will interfere with the impregnation process.

2. Drying

Removal of moisture is a long and energy-intensive process on which the quality of impregnation depends. Dried wood can not be impregnated. Its moisture content should be reached to a level of 28%. Drying is done naturally in stacks (2-5 months) or warm air in drying chambers, which is circulated by fans (7-10 days).

3. Impregnation in an autoclave

A vacuum is created in the chamber, which draws out excess moisture. Then the logs are closed with an aqueous solution of antiseptic, after which the pressure in the chamber rises to 14 atm. After the solution is drained, a vacuum is created there again. The best impregnating composition is the antiseptic of SAS of Finnish origin. Domestic analogues are made from industrial waste and contain impurities that reduce the depth of processing and contribute to the elution of the composition of wood.

4. Fixation

The impregnating composition contains harmful substances. Logs lie awhile. This leads to the formation of insoluble antiseptic compounds in the structure of the wood. The temperature of the medium must be positive. To accelerate the process, the supports are treated in an autoclave with superheated steam. Canadian manufacturers treat logs with special compounds, thereby increasing the durability of products.

Supports of overhead lines

The installation of wooden poles is carried out on the HVL of the 3rd class, where the rated operating voltage is 1 kV or less. The most common intermediate supports that serve to support the wires. In addition, they perceive wind loads, as well as the weight of the armature and its own. Independently, they can not withstand the forces arising along the line, if there is a breakage. This load is perceived by the anchor supports with the arrangement of additional struts along the axis of the overhead line. Basically, they serve to create the tension of the wire section. To perceive lateral loads, use anchor supports with the arrangement of struts or "legs" in a perpendicular direction.

There are also angular supports that perceive longitudinal and lateral loads. They are installed to rotate the lines.

Installation of wooden supports is made with an accurate marking of places, and assembly - with a tight fit of parts.

The clearance, where the cutting is done, should not be more than 4 mm. The mating points are tightly fitted. The holes are drilled.

Maintenance and repair of wooden supports

The support of the power transmission line is subject to periodic inspections and repairs. In the summer, at a depth of 30-50 cm, the depth of decay of the wood is checked. If the diameter of the log is 25 cm and the decay is more than 3 cm, it is considered unfit and should be replaced.

Major overhaul of the lines, where most of the wooden supports are installed, is done no less than 6 years from now. The rest of the repair work is carried out within the timeframe, depending on the available resources.

The fire hazard of wooden supports requires labor-intensive operations to reduce it. In the presence of wooden prefixes a ditch with a depth of 0.4 m is pulled out and a grass is removed with a bush.

Details from the supports are changed to new ones with the line running. Here it is necessary to take into account that on the parts of the structure the loads can exceed the calculated ones.

If the poles deviate from the vertical by an unacceptable amount, additional loads can cause a change in position and clashing of the wires or touching the parts. Displacements occur because of the weakening of the foundation or the foundation of the foundation, the displacement of the ground, the weakening of the joints.

The bearing is made with steel cables reinforced on the rack. The base is dug to a depth of 1.5 m and the traction mechanism straightens the support. Then the pit is buried and rammed.

When the stand is skewed due to the weakening of the connection with the bandage, it is straightened, not displacing the stepchildren.

On the decayed rack establish a bandage. Before this, the rot is removed and the column is covered with antiseptic paste.

Damaged parts reinforce the temporary lining of wood or metal, using half-hammers, bolts and a shroud wire.

The details before going to the track are checked for compliance with the design parameters.

To extend the life of the racks, they should be additionally impregnated in the process of operation by the diffusion method. Antiseptic bandages are installed on the underground and aboveground parts of the support and at the junction points. In the cracks and on the tops of racks with attachments, an antiseptic paste is applied.

Due to the fact that the mass of the wooden support is small, in the repair rarely requires heavy equipment.

The support that can not be repaired is released from all loads and replaced with a new one using special equipment.

Conclusion

Wooden support with impregnation is not worse than reinforced concrete, and in some cases even better, due to the mass of merits. In order for them to be used more actively in practice, an industry standard is needed. This will allow to establish uniform requirements for all manufacturers, so that quality is guaranteed.