Fire in a tunnel is unquestionably the most feared risk which could happen to a tunnel operator, not only in terms of the potential for catastrophic damage, but in terms of the risk of life. As illogical as it may seem, traveling in a tunnel conjures up in ones mind primal fears about entering an abyss of the unknown. Popular opinion has it that at least 15 % of an educated public would avoid using a tunnel if an alternate route would be available. Should a disaster occur, there are very few options for escape compared to a surface disaster. This is why architects of tunnel structures should go to almost inordinate lengths to put safety and prevention of disasters at the forefront of tunnel design. There is a lot of equipment, procedures, attention and resources to look after a few kilometers of roadway which on the surface, does not rate much attention.
Fire protection in vehicular tunnels must be achieved through a composite of facility design, operating equipment, hardware, software, subsystems and procedures integrated to provide the requirements for the protection of life and property from the results of fire. The level of fire detection and protection required for the entire facility should be accomplished by integrating the requirements developed through proven methodologies whose operating parameters have been tested, applied, and have successfully proven their primary purpose of detection of overheat and fire.
Studies of fire protection for tunnels indicate that there are three interdependent factors to be considered:
- The early detection of overheat or fire and the rapid transmission of alarms to the proper authorities.
- The response of appropriate fire fighting personnel with minimal delay.
- A matter of rescue operations followed by extinguisher and control.
Where life is endangered by fire, effective rescue operations decreases rapidly with any delay. Unless an effective means of early warning and communication is established, the reporting of fire and other emergencies, coincident with ventilation control, may be of little value in terms of lives saved.
Of the available fire and heat detection devices for industrial uses, including smoke detection, optical detection, incident detection, the most promising method of providing the early warning and annunciation of overheat of fire in a tunnel is with linear heat detection technology.Protectowire linear heat detectors are reliable, cost effective, impervious to tunnel environments including CO, dirt, dust, EMI, and periodic tunnel washings and are able to monitor long lengths of a tunnel with an infinite number of alarm points along its length.
Protectowire is typically used where other types of detectors would be unsuitable which has made its use in tunnel environments more acceptable. Since the introduction of linear heat detection technology by The Protectowire Company over 60 years ago, linear heat detection has replaced other means of fire protection for many hazards. Major applications for Protectowire includes conveyor systems, cable trays, dust collectors, cooling towers, pipelines, fuel distribution terminals, mines, off shore platforms, tank farms, refrigerated storage, a wide variety of industrial and power plant systems, and more recently, vehicular tunnels. The distinct advantage of Protectowire is the ability to place the detector in direct contact with or in close proximity to the area or equipment being protected, or to monitor long lengths of areas in a single detection zone.
Automatic fire detection should be provided within all tunnel roadways, ramps, and tunnel cross passages by the installation of listed components of an early warning linear heat detection system described below. The zoning of the system should correspond to the tunnel ventilation zones. When ventilation zones are not required to coincide with detection zones, a maximum of 3,500 feet (1,066 m) should be monitored in a single detection zone. Protectowire is installed at the apex and both sides of the tunnel when 2 or more lanes wide, or at both sides when single lane operation is required.
Install Protectowire linear heat detection cable using messenger wire supporting the detector with stainless steel turnbuckles located between every 250 feet (76 m) of messenger cable. A standoff with rubber grommet is placed at 55 foot (17 m) intervals to additionally support the linear heat detector/messenger cable. Terminate each detection zone with an end-of-line resistor housed in a NEMA-4X enclosure with compression strain relief. Unwrap the Protectowire from messenger far enough to form a loop in the messenger wire. Clamp the loop with a U-bolt and slip the loop over the turnbuckle until the messenger wire has only a small amount of sag. Provide additional support at 50 foot (15m) intervals using beam clamp #BC-2.
Each detection zone is monitored at the linear heat detection control panel and displayed on a digital point location meter to facilitate pinpointing the exact location of an overheat or fire along the length of the detection loop.
Detection zones should be configured to coincide with tunnel ventilation zones where possible to provide fan control in the event of fire. Where long copper feed cable lengths are required to the start of the detection zone, do not exceed 100 Ohms of feed cable resistance.
Recent fires and the increasing construction of vehicle tunnels around the world have shown the need for greater documentation of fire detection requirements and technologies for roadway tunnels.
While every country that has a vehicle tunnel has some sort of standard or criteria to conform to for these special applications, it would be difficult to document a single requirement for a tunnel having different environments with the various fire detection devices available that could be utilized.
Currently around the world are many projects in the design or construction stage with an increasing number of tunnels being planned for retrofit and refurbishing of structural improvements. These projects will enhance safety for both normal operational environment and emergency situations, with particular emphasis on safety.
Partial List of Protectowire installed tunnel systems
- AFC Tunnel – Atlanta, Georgia – USA
- Parkway Tunnel – Univ. of Wisconsin, Madison, Wisconsin, USA
- McCarron Airport Tunnel – Las Vegas, Nevada – USA
- Denver International Airport Tunnel – Colorado – USA
- Muni-Metro Tunnel – San Francisco, California – USA
- Tuneles del Negron (Asturias) – Northern Spain
- Tuneles de la Autovia de Mataro – Cataluna, Spain
- Berry Street Tunnels – Pittsburgh, Pennsylvania – USA
- Acapulco Tunnel – Acapulco, Mexico
- Shanghai Yan An East Road Tunnel – Shanghai, China
- MAI Naftuh Tunnels – Tel Aviv, Israel
- Steve Wynn Tunnel – Atlantic City, New Jersey
- Selatin Tunnel – Ismir, Turkey
- Alanya Tunnels – Turkey
- Hannekleiv Tunnel – Norway
- 1st Avenue – New York City, NY
- Park Avenue – New York City, NY
- Battery Park Tunnels – New York City, NY
- Kirkeheia Tunnel – Norway
- Barranco de La Balliena Tunnel – Barcelona, Spain
- SpainSomport Tunnel – Pyrenees Mountains, Spain
- Guadarrama Tunnel – Madrid, Spain
- Pardornello Tunnel – Galicia, Spain
- Cadi Tunnel – Catalonia, Spain
- Baladino Tunnel – Madrid, Spain
- Gagarinski Tunnels – Moscow, Russia