Whilst TUNNELS (road / rail) themselves may only present owners and operators with a nominal risk of fire, a much greater risk comes from items which pass through the tunnel. A typical example of this being the recent fire (January 2015) within the Channel Tunnel where smoke from a vehicle fire onboard a train located approximately 33% of the way between the UK and FRANCE - and deep beneath the English Channel - created a situation whereby all travel through the tunnel was temporarily suspended and a grave risk to human life and capital investment was highlighted!! We were also reminded of the limited escape options available to those trapped beneath ground in a tunnel as a result of a fire occuring.
Many personnel consider specification of a very expensive and proven unreliable detection concept who's limited experience has resulted in a number of failures to detect an adverse tunnel condition or the system has generated false alarms .....FIBRE OPTICS LINEAR DETECTION. In many cases the false alarms have been the result of either accidently induced sharp bends in the fibre cable during installation - which has prevented uninterrupted performance of the laser light within the cable during non alarm conditions - or from nominal levels of local vibration. Another condition which can adversely affect the laser light under non alarm conditions. PROLINE F.M. approved, UL /cUL listed, NFPA72 & EN54-28 linear detection dedicated standard conformity type TH "digital" linear detection provides a more economic and reliable solution to rapid detection of overheat or incipent fire conditions by continuously monitoring for abnormal temperature conditions at point of risk along the entire length of the installed sensor cable. Whilst Proline may recommend a minimum bend radius for the sensor cable, the potential for false alarm signals from anyone not adhering to manufacturer recommendations is not as harsh for Proline as it is for a fibre optics linear detection system. The Proline linear sensor is NOT affected by RFI or EMI /EMC , is classified as a "simple electrical apparatus" because of its extremely low monitoring current ( milli-amps) and when used together with a Proline supplied ZI interface unit, can provide indication of the location of the alarm condition along an associated length of TH sensor cable of up to 10,000 metres in length!!! Full in situ site testing is also possible without having to repair or replace the linear sensor cable. Additionally, the ZI interface unit can be conveniently located within a security office or control room with interconnecting cable installed between the risk area installed sensor cable and "remote" interface. Maximum length of interconnecting cable can be in excess of 2,000 metres!!
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