In accordance with the requirements of fire safety, when laying any communications, cable penetrations must be constructed - products, prefabricated structures that are designed to pass cables, pipelines, communication lines through walls and partitions. Their main purpose is to prevent the spread of fire in neighboring rooms on flammable materials. They are arranged on the basis of SP 2.13130.2009 and GOST R 53310-2009. Their installation is mandatory and is regulated by Federal Laws.
Fire compartments and cable penetrations
According to the requirements of fire safety , during the construction of residential buildings, they are divided into fire compartments, which block fire and smoke on their territory, and prevent them from spreading outside the compartment. However, engineering lines pass through any room, which violate the integrity and integrity of the fire section. In order to preserve the fire resistance of the structure and mount cable penetrations.
A striking example that proves the need to install such structures is the fire at the Ostankino TV tower in 2000. Here, telecommunication lines were placed in a vertical shaft, without breaking it into fire compartments and laying protective passages. As a result, the fire quickly spread throughout the building.
Cable entry design
The simplest cable penetration is a metal sleeve embedded in a wall or partition. A cable passes through the sleeve, a pipeline, the outer diameter of which is slightly smaller than the diameter of the fire fighting structure. The gap between the communication line and the inner wall of the sleeve is filled with tow, thoroughly saturated with fat. That is why the simplest cable penetrations are also called oil seals. Also, asbestos, rubberized rings, special gaskets can be used together or instead of tow.
At industrial facilities and power plants, several other structures are arranged. They are two metal strips, the ends of which are connected by sleeves. To close the gap between the communications and the inner walls, special diaphragms and washers are used. One such cable penetration serves to pass several engineering lines.
Sealing Materials
To create the possibility of laying an additional or replacing the old engineering line, all wires, cables and other communications pass through the walls in boxes or scraps of metal pipes (sleeves). Therefore, termination of cable penetrations should be made of refractory, water-, gas-tight material, which is easy to remove.
At the same time, the ability to resist fire at the seal should not be lower than the refractory abilities of the wall.
In SNiP 3.05.06-85, specific mixtures are indicated with which it is allowed to fill the gap between the cable and the penetration:
- cement-sand mixture in a ratio of 1:10;
- composition of clay and sand with a ratio of materials 1: 3;
- sealing mass of clay, sand and cement (1.5: 11: 1);
- gypsum and expanded perlite, taken in a ratio of 2: 1;
- other materials that meet fire safety requirements.
It is also allowed to patch cable penetrations with construction foam if it is certified in accordance with the requirements of GOST R 53310-2009. The gaps in the walls can not be filled if the partitions are not fire barriers.
Modular penetrations
In modern construction, modular penetrations are used to isolate fire compartments. They are steel or plastic frames that are equipped with blank inserts or modules with holes. To protect against electromagnetic radiation, copper gaskets are installed. Tightness is created by tensioning bolts.
In general, modular fire penetrations are a complex structure assembled in situ from prefabricated sealing inserts from a polymer that is difficult to burn. As fasteners, elements of galvanized stainless steel are used.
In such a penetration, the cable is placed in a special sealing module and crimped with an adapter for increased tightness. By tightening the tensioning bolts, the sealing inserts are compressed, tightly crimp the cable and provide gas and water tightness of the penetration.
Features of installation of cable penetrations
Installation of penetrations has its own characteristics, which depend on the type of material of the supporting structure. So, laying cable systems in monolithic concrete buildings, fire-retardant structures are laid directly in the formwork before pouring the concrete mixture. When constructing prefabricated monolithic type buildings, penetrations are laid in blocks at the factory during their manufacture.
In brick houses for laying cable systems are placed in special channels - gates. In finished monolithic buildings, small holes are drilled with a diamond drill. The penetration diameter is calculated separately. During the construction or temporary operation of the building, penetrations are made from special fire-retardant pillows.
Cable penetration test
Depending on the place of use, cable penetrations must meet specified requirements. So, when they are laid in nuclear power plants, they should be tested for the ability to absorb, isolate or reflect radiation.
On ordinary construction sites, universal cable penetration is tested by heating, force impact (mainly on bending resistance), as well as fire resistance, water and gas insulation properties.