Each of us, when we mention the expression “sewage system”, we see a system of collectors and pipelines through which storm drains and household waste move. However, these are not the only communications that can be laid underground. Another option for the underground sewer network is cable sewage.
Description
The described system is an underground network of containers and channels into which telephone and electric cables are laid. Such a system may include pipes as well as wells. The former are used for laying wires, while the latter are needed for inspection, replacement, repair and increase power.
Cables can be laid in an open way, while pipelines are not used, they are replaced by basements of buildings, tunnels and collectors. The lines in this case are strengthened with the help of special devices.
Purpose of cable duct
Cable drainage is necessary to protect wires from atmospheric phenomena and the load of soil and pavement. It is used for possible repair, replacement, and also branching of telephone and electric networks, while there is no need to open the soil and destroy the roadway.
Varieties of cable sewage systems
The most common classification of cable ducts is that based on the method of laying pipelines. Pipe installation is carried out in pre-dug trenches. However, laying can also be trenchless, while the cable is above the ground, and the soil surface is not disturbed. Such installation is carried out using horizontal drilling technology.
Such systems may vary in cross-sectional size and the shape of the wells, the pipes themselves and the materials used in the manufacture of the elements. Wells can be plastic, brick and reinforced concrete. For such systems, pipes from:
- asbestos;
- concrete;
- plastic;
- fiberglass;
- pitch fiber.
The most popular are plastic and asbestos. In some cases, instead of pipes, plastic blocks are used that have several sections called multi-channels.
Cable duct
Cable ducts are recessed channels that are at a depth depending on where the material is laid in the base of the pipes. Depth can vary from 40 to 200 cm. If we are talking about concrete pipes, they can be laid even deeper, but plastic should be located at the smallest depth. The pipelines that are located under the tram tracks are deepened to the maximum, but minimally under the pedestrian zones. Under the roads, the elements are at medium depth.
Pipes have a slope of 4 mm per meter, this allows for a natural flow of water that can enter the channels. The cable and pipes between the wells should be in a straight line, but a slight displacement is still allowed, it should not be more than 10 mm per meter of pipe. Inspection wells are located every 25-150 m, the final value depends on the cable laying scheme. Inside large collectors and basements of buildings, cable laying in pipes is not carried out, since the wires here extend along the consoles.
Cable ducts can include several pipes in one trench, while the voltage of the wires should be the smallest in those that are closer to the surface of the earth. The most suitable diameter is considered to be 100 mm, but previously 15-cm pipes were used, in which it is more difficult to lay the cable. In one bundle should not be telephone and electrical cables.
Inspection wells
Inspection chambers for cable-type sewers are mounted using the same technology as conventional sewage chambers. They are containers with a bottom, the upper part of which is closed by a hatch, a neck is installed between it and the well. In the side walls there are special openings for the exit and entry of the pipe with cables. Most of these containers have a double system of hatches, the inside of which has a secret lock, only the owner of the well has a key to it.
Depending on where the cable network is located, wells can be:
- walk-through;
- substation;
- separating.
The first variety is installed in straight sections or in those places where the deviation from the straight line does not exceed 30 °. As for the substation and rotary wells, they should be located near buildings or in places where the network is bent, respectively. Separation wells are located at the outlet or approach points of several channels.
What else you need to know about viewing wells
The construction of cable ducts may include the installation of wells of different sizes, they must be spacious so that they have the opportunity to work with the cable and install equipment. Well tanks are made of different materials, but recently plastic products with stiffeners have been increasingly used. This is especially true for conditions where the load is not so great. For example, in cable ducts of the private sector, one can find well models of the KKT-2 type, its diameter is 136 cm, equipment can be installed in it.
Work on cable ducts: the use of cable with copper conductors
The laying of cable ducts in which the cable with copper conductors will be used requires the installation of a galvanic steel stocking on the sealed end of the cable. A wire rod will be fixed for it. Cable laying is carried out according to a certain technology, it provides for fixing the drum with a cable on devices like jacks or trolleys.
These works are carried out by the receiving well. The cable is fed at the top of the drum, and at the entrance to the channel should be polyethylene bushings or cable elbows. In the receiving well, the wire billet with the cable begins to be pulled, while at the feeding well the tension from the cable reel is constantly monitored. When the gasket in the span ends, the ends are checked for leaks and laid on consoles. Cable laying in cable ducts in winter can be carried out at a temperature of at least 10 ° C, whereas if a sheath of lead is used, the ambient temperature can be -20 ° C.
Features of double-walled pipes
Double-walled cable ducts have high ring stiffness, they are able to withstand impressive mechanical loads, which is especially true for corrugated products. Pipes have good flexibility, with the help of them you can bypass obstacles along the route.
They can be operated at a wide range of temperatures, and the presence of special accessories allows you to create tracks of any complexity. Such pipes for cable ducts can have a length of 35 to 150 m, they are delivered in bays and have a nylon thread. Even at low temperatures, they retain elasticity, and the minimum bending radius is 8 diameters.
Conclusion
If necessary, mount the well in the pedestrian zone, you should take into account the estimated load on the tank, which is 10 tons. As for the carriageway, this parameter increases to 80 tons.