1、summary

Transportation tunnels mainly refer to highway tunnels, railway tunnels, subway tunnels, cable tunnels, etc. As one of the three-dimensional transportation modes, traffic tunnels can not only alleviate urban traffic pressure and solve the limitations of transportation trunk lines crossing rivers, seas, and mountains, but also shorten the route mileage, reduce the impact on the surrounding environment and people's production and life。

 With the increasing role and wider application of transportation tunnels in people's production and life, their potential disasters are gradually receiving more attention. Among various tunnel accidents that have occurred, tunnel fires are the most serious, causing the greatest casualties and material damage. Due to the enclosed environment of traffic tunnels, when a fire occurs, the exhaust and heat dissipation conditions are poor, and the temperature is high, which quickly generates high concentrations of toxic smoke. Fires not only cause paralysis of the entire line of transportation, but also greatly affect the normal production and daily life, leading to social and economic losses, especially for various long-distance tunnels. Once a traffic fire accident occurs, the consequences are more dangerous and serious than other accidents. Therefore, it is particularly important to adopt online fire monitoring for traffic tunnels. Traffic tunnel fire monitoring has received increasing attention。

Linear thermal detectors are recommended tunnel fire detectors according to standards such as JT/T 610-2004 Technical Conditions for Fire Alarm Systems in Highway Tunnels, JTG/T D71-2004 Design Specification for Traffic Engineering in Highway Tunnels, and GB 50116-98 Design Specification for Automatic Fire Alarm Systems. Linear thermal detectors include temperature sensing cables, distributed fiber optic fire detectors, and fiber optic grating linear thermal fire detectors, which detect anomalies in the temperature field around the fire location to determine the fire situation.

The linear temperature detectors independently developed and produced by Nanjing Zhunzhi Sensing Technology Co., Ltd. include distributed fiber optic linear temperature fire detectors and fiber optic grating linear temperature fire detectors, with a protection level of IP68。

Distributed fiber optic linear temperature fire detectors and fiber optic grating linear temperature fire detectors, using modern sensor technology, network communication technology, and data processing technology, are a comprehensive monitoring system for tunnel environmental temperature monitoring, data processing, and information analysis. The system monitors multiple key factors in the tunnel and environment in real time, providing effective basis for tunnel use, management, and maintenance, thereby maximizing the safety of traffic tunnels。

Installation method of linear temperature sensing fire alarm detector

Urban road tunnels, extra long bidirectional highway tunnels, and underwater tunnels in roads should use both linear fiber optic thermal fire detectors and point type infrared flame detectors (or image type fire detectors) simultaneously; Other highway tunnels should use linear fiber optic temperature fire detectors or point type infrared flame detectors。

   Distributed fiber optic linear thermal fire detectors (or fiber optic grating linear thermal fire detectors) should be installed at the top of the lane at a distance of 100mm~200mm from the ceiling, and the grating spacing of fiber optic grating linear thermal fire detectors should not exceed 10m; The number of protective lanes for each distributed fiber optic linear temperature fire detector and fiber optic grating linear temperature fire detector should not exceed 2; The detection range requires the entire tunnel to be fully covered without any detection blind spots。

    Fiber optic grating linear temperature sensing optical cables can be fixed on steel strands using cable hooks with a spacing of 300mm. The steel strands are fixed with brackets with a spacing of 30 meters.

   The installation method of fire monitoring for urban roads and highway tunnels is shown in the following figure：

  Linear temperature fire detectors should be installed along the cables in the tunnel, and their effectiveness should be ensured in heating parts such as cable joints and terminals; The linear temperature sensitive fire detectors installed in the tunnel can be connected to electrical fire monitors. Cable tunnels without external fire sources should have linear temperature sensitive fire detectors installed on the surface of the cable layer; Cable tunnels with active access should be equipped with linear thermal fire detectors on both the surface of the cable layer and the top of the tunnel. The linear thermal fire detector adopts an "S" - shaped layout or may have external fire sources entering the cable tunnel, and can respond to linear thermal fire detectors with a flame size of no more than 100mm.

一根线型感温火灾探测器可以保护多层电缆

The linear thermal fire detector should adopt a contact laying method to detect all power cables inside the tunnel; When laying distributed linear fiber optic temperature fire detectors in heating parts such as cable joints and terminals, the extension length of the temperature sensing optical cable should not be less than 1.5 times the length of the detection unit. Scheme II should be adopted at the cable joints; The fiber optic grating linear temperature fire detector should be equipped with temperature sensing grating units in the heating parts such as cable joints and terminals, and only the methods of Scheme I and III should be used。