Overview of solutions
Because the highway tunnel is of closed space, heavy traffic and poor escape and rescue conditions, the consequence will be extremely serious in the event of fire. Therefore, the fire prevention work of highway tunnel has been highly valued early. In recent decades, the automatic fire alarm system has obtained great development. In our country, with the development of transportation construction, the automatic fire alarm system of highway tunnel has been more and more applied. In recent years, the newly-built expressway tunnel has been provided with the automatic fire alarm system which can play a certain role in safe operation of expressway tunnel.
Different from general housing construction, the highway tunnel has many features which can obviously affect the accuracy of fire alarm. There are the following five basic features for tunnel and its fire:
(1) Open flame is the manifestation of most fire in highway tunnel;
(2) The wind speed is often very high in highway tunnel;
(3) There will be often dense smoke in the event of fire;
(4) Fire is mobile burning vehicle;
Selection of solutions
Based on the intelligent distribution of fire alarm system and dual-wavelength infrared flame detector and the essential features of highway tunnel, in order to quicken the accurate determination of fire location, we propose the tunnel fire alarm solutions for the tunnel safety modification: We adopt the fire alarm system composed of point-type flame detector and manual alarm button for quick response and accurate identification of burning vehicle flame signal. According to site conditions, our selection plan is as follows:
1. Adopt the wall-mounted intelligent bus fire controller FP9000 in control center and connect it with fire control graphic display unit through network interface to display the fire alarm equipment operating condition and alarm state of highway tunnel on CRT.
2. Select the dual-wavelength infrared flame detector or three-wavelength infrared flame detector as open lame detector, quickly respond gasoline or diesel fire, ensure stale and reliable detection.
3. Provide an integrated fire panel which contains manual alarm button and supporting waterproof box at the original manual button part, place one input module in the integrated panel to return the alarm signal of flame detector to control center via two-bus; the integrated fire panel includes two indicator lamps, power indicator and alarm indicator of flame detector. The integrated panel is of waterproof structure.
4. In the central control panel of tunnel, there are four power supply boxes as zonal power supply to flame detector and every 10~15 flame detectors are supplied from one power supply box.
Features of solutions
This system is a centralized bus fire alarm system of centralized control and management. In the adjacent field management center, the controller is connected with the integrated fire panel via bus and reset power line. The integrated panel is installed on tunnel wall at 1.5m above ground for the convenience of manual operation of manual alarm button. The flame detector is installed on the side wall of tunnel at about 2.5m above ground, facing the forward direction of vehicle. The power supply of all flame detectors are sourced from the local zonal power supply box, and the zonal power supply box adopts 220V power supply and includes the built-in DC power supply and standby battery to convert AC220V external power supply to DC 24V and at the same time charge the standby battery. In fire alarm controller, there are DC power supply and standby battery to convert AC220V external power supply to DC 24V and supply power to the manual alarm button and input module in the integrated fire panel.
The bus and relevant power line run in the wire duct below tunnel and are connected by jacketed cable. The bus, reset power line and flame detector power line are advisable to adopt 2.5mm2 twisted shielded pair without joint in local wire duct. All connections are conducted in the integrated panel.
The graphic display unit software is installed on the computer in management center and, behind conversion interface, is connected with the fire alarm controller in local equipment room via optical fiber to display the information of fire alarm controller.