Introduction to cable tunnel fire prevention
With the rapid development of China's economy, electricity load grows year by year power transmission channel tension, therefore, in the future, multi-loop, high-capacity tunnels are increasingly used, the safety of the cables running in the tunnel is also highly valued, because the tunnel itself is hidden and concentrated, cable fire accidents often can not be found in time, resulting in large-scale cable fires, resulting in economic losses and safety accidents.
Cable tunnel fire analysis
Cable tunnels are suitable for large distances, multi-loop cable transmission, its fires occur mainly in the following categories: the tunnel has combustible materials (including combustible gases, insulating oils, etc.), the presence of combustible materials led to the arc, sparks or external sources of ignition under the induction of fire; cable body or joint failure breakdown led to their own combustion and burned around the cable thus leading to fire.
Tunnel power cable channel fires mainly show the following characteristics:
(1) the tunnel is a fully enclosed structure, heat is not easy to disperse, the temperature inside the tunnel rises, resulting in rapid fire development.
(2) the channel is long and narrow, a large amount of smoke is difficult to discharge, threatening the safety of life, evacuation difficulties, firefighters difficult to approach, unable to timely fire;
(3) fire outage losses, cable tunnel cable is relatively dense, if a fire, will affect multiple lines, resulting in widespread power outages, and post-disaster repair difficulties.
2.Civilized City Initiative
Fire prevention in cable tunnels should be based on prevention, while improving fire control measures and fire extinguishing measures. To achieve the principle of "prevention-oriented, combined with fire prevention".
According to the importance of cable tunnels combined with economic and reasonable factors, it is appropriate to use one or more security measures: 1) cable in the selection of fire-retardant cable and minimize the number of joints:
(1) the cable in the selection of flame retardant cable, and minimize the number of joints
The probability of failure of the cable at the attachment is much greater than other locations, cable failure is very likely to cause a fire, so from the design point of view in the cable selection and tray length design should be as far as possible to reduce the number of cable attachments is an effective measure of active fire prevention.
According to the power design specifications, AC single-core cable metal sheath or shield on any point of the normal induced voltage at non-contact, in the case of taking effective measures to prevent personnel from arbitrarily contacting the metal layer of security measures, shall not be greater than 300V. In order to meet the specifications of the technical construction of the integrated corridor laying conditions and transportation conditions reasonably increase the length of the tray.
(2) cable joints at both ends of 2-3 meters and adjacent cables painted fireproof paint, fire-resistant tape around the package, fire blanket
Three kinds of materials for local fire prevention requirements of high effect. Among them, fireproof coating and fireproof tape can achieve a better fireproof effect at a lower cost. In practice, often used in the power cable joints on both sides and adjacent cable 2 ~ 3m long section of the application of fireproof paint or fire tape, can achieve good fire protection requirements, winding fire blanket on the basis of the above fire protection measures on the cable joints to add a layer of protection, reduce the impact of cable joints on adjacent cables when a breakdown accident occurs, but the cost is higher according to the cable importance level of discretionary installation.
(4) the tunnel according to the fire partition set fire walls and fire doors, the cable and slot box perforation location for fire blocking
Fire blocking materials selection Fire blocking, is the use of fire blocking materials in the cable penetration holes and electrical holes to do partition, its role is to prevent the spontaneous combustion of the cable itself due to heat or external open flame to spread the fire, to protect the safety of personnel and equipment purposes.
At present, the tunnel within the consideration of the long-term cable laying requirements (convenient demolition), the use of fire-resistant package as the base material, fire panels and organic plugging combination of firewall, in the cable tunnel, according to the size of the site, make and fix the fire partition door, between the fire panel with fire retardant package filling, and organic plugging embedded between the gaps in the cable, and finally the use of fire-resistant paint to coat both sides of the cable.
3.suggestions
(1) the tunnel is located in a humid underground environment, cable through the wall position blocking for a long time in a humid environment is easy to fall off, can not play a role in isolating the fire, it is recommended that the initial blocking is completed and then the outside of the waterproof coating, reduce the fire blocking materials directly in contact with the humid air off.
(2) the use of fire walls in the tunnel for the same period of construction of the tunnel, the late laying of new cables in the process of laying a certain amount of damage to the fire package, a certain impact on the tunnel fire, and in the repair process to produce construction waste, it is recommended that according to the important level of the tunnel and the number of cable circuit planning in the long term can be used metal fire panels, the material has a good firestopping effect, can replace the traditional organic fire partition and fire package combination form Firewall, more conducive to the long-term cable laying. The market price of this material is much higher than the traditional firestopping materials, and can be considered according to the actual engineering situation.
3) It is recommended that the cable body fiber optic temperature measurement and fire alarm in the tunnel be linked to achieve multifaceted monitoring, so that early detection and early treatment.
4、Closing remarks
Tunnel fire prevention is a whole system, should be done from the source, establish the "prevention-oriented, fire prevention combined" concept, using a combination of multiple means of the form of fire hazards in the nascent stage of elimination, to minimize the possibility of cable fire and extended combustion, solid fire safety "firestop wall ".
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