Cable tunnels represent a challenge to the fire protection industry due to their length and the location of cable trays acting as obstructions to the fire extinguishing medium. Additionally, the types of fires which are found in this environment are often deep seated within the cable bundles. The impact of a high volume of water being discharged into these tunnels when they are protected with traditional fire fighting methods, such as sprinklers or deluge, can be very costly due to the clean up required, in sometimes hard to access tunnel sections.
SECURIPLEX FIRE-SCOPE® 2000 water mist system offers the advantage of rapid fire control, reduced water requirement and reduced water damage. All of this, coupled with a sharp reduction in fire propagation, translates into a reduction of downtime, clean up costs and loss of production.
Cable tunnels can be of unlimited length. When protecting them with a water mist system, long tunnels are subdivided into tunnel sections and treated independently in order to reduce the water requirements and limit water damage. A tunnel section would typically not exceed 1,640 feet.
Nozzles are installed every 6 feet on the ceiling of the tunnel and tied in from a main water header over the entire tunnel section. Tunnel sections can be subdivided into fire zones (discharge zones). Discharge will occur only in the zone where detector(s) are activated. Fire zone activation is controlled by an electrically actuated valve.
Nozzles are single fluid operating at a pressure of 175 psig and a flow rate between 1.8 gpm to 5.5 gpm, depending on the tunnel and tray configuration.
The water is supplied either by a reservoir or the city main and pressure is boosted with a pump which provides a continuous discharge for a minimum of 30 minutes or until the local fire department arrives.
Detection is achieved using smoke detectors installed along the ceiling of the tunnel and/or linear heat detectors installed in the cable tray(s).