NEWSHEET8

Road & Rail Tunnel Fire Protection

"History has an unfortunate habit of repeating itself" a statement applicable to many aspects of life, but never more feared than when related to loss of life and capital investment from a major FIRE.

The investigations, reports and legislative improvements that follow a public sector fire, are all intended to ensure that "such a disaster will never happen again"! Regrettably however, as time passes and the knowledge gained from such investigations is lost - as decision-making personnel reach the end of their working careers - the next disaster, frighteningly similar to the one before, looms ever closer!

The fear of being trapped by fire - underground, is possibly one of the worst you could imagine. With escape options severely restricted in comparison to similar surface located fires.

Statistics indicate that in excess of 20% of the human population would avoid using a tunnel if an alternative route were available. It is therefore one fear that operators of underground transportation systems (whether road or rail) strive to reduce, by ensuring they are able to advertise that their facilities are protected by the most modern and safe fire protection systems or so one would imagine !

FIRE DETECTION in multi-carriageway road tunnels, rail tunnels and stations and associated areas, present architects, consultants, engineers and operators with a unique series of problems and considerations - not likely to be experienced with many (or any) other Commercial or Industrial risk areas. Just a few such considerations are listed below:

• Multi - Level constructions with a labyrinth of passages, shafts and tunnels
• A large number of people within concentrated areas
• Grossly restricted escape and recovery routes
• Limited ventilation options - reducing potential survival times
• A dramatically increased potential rate of spread of toxic flame and smoke
• Multiple fire risk considerations.

Of ALL the fire and heat sensing devices available on the International markets for Industrial use, one of the most effective method of providing the early detection and signalling of a fire condition within tunnel risks, and potentially the PREVENTION of the fire by detection of the pre-combustion overheat condition that precedes many fires, has been repeatedly proven to be LINEAR HEAT DETECTION

Why Digital Linear Heat Detection?

The answer to that is simple . show me another detection concept that offers a cable and detector combined (and the cost benefits offered by this to the end user ), that can be installed at the EXACT point of risk (therefore not reliant upon favourable airflows to provide rapid detection and signalling of adverse temperature rises - not necessarily dependant upon the presence of flame), will operate continuously without high levels of maintenance and repair within dirty/dusty/damp and corrosive environments, and within areas of limited access and surveillance, that can monitor detect and signal an alarm at pre-combustion levels and that can remotely indicate the EXACT location of the alarm along the heat sensor cable that forms the basis of the detection system !

Add to this, the flexibility offered by linear detection when integrating with Central Fire Alarm or Building Management Control systems and its already proven installation record throughout road And rail tunnel complexes around the world (USA, Mexico, U.K., Spain, France, Scandinavia, Turkey, Middle East, Malaysia, Philippines, Russia, China, Taiwan, Korea) and I think you understand why the comment and specification ?

Many fire system specifiers still themselves employ a "tunnel" philosophy - this time restricted to vision - restricting the specification of linear detection to cable trays and electrical cabinets. These are the original (1970's) "traditional" applications for linear detection. Still regularly used in such areas, but system features are more widely recognised and broadly adapted to a diverse range of applications - to the ultimate benefit of all concerned with the SAFE operation of the tunnel.

For protection of the risk area/s under consideration, there are the obvious applications of roof installation within the tunnels - a single run of sensor cable installed above each rail line or road carriageway. The Linear detection zones should be configured to coincide with tunnel ventilation and/or automatic Extinguishing zones to maximise fan control and fire control.

A typical detection zoning arrangement is illustrated below:

Road Tunnel installations, provide a number of additional risk areas which could be more effectively protected by LINEAR HEAT DETECTION than most other detection devices. These include electrical supply cables (where insulation breakdown or overloading present the primary risks), Electrical control rooms - with the electrical cabinets also utilising the linear temperature monitoring capability - and tunnel ventilation ducts.

Rail Tunnel complexes include many more areas where linear detection already has a proven performance record. These include:- escalators, under platform edge (where passenger rubbish, food cartons, cigarettes- even where prohibited, we all know limited smoking still occurs and with it the risk of fire from discarded ends - remain undetected and at risk of ignition from rolling stock catenary arcing, electrical system short or from the largest risk - the arsonist!), concession areas, ticket offices, electrical rooms and power, communication and instrumentation cabling!

The maximum distance between parallel runs of Proline "TH" sensor cable across the roof/ceiling of a tunnel should not exceed 10.6m/35feet -UL listed -all alarm temperature ratings, or 9.0m/30feet (TH68 &TH88) or 7.5m/25 feet (TH105)- F.M. Approved.

It is not the intention of this publication to explore in detail the most effective installation locations and fixing methods for linear heat sensor cable associated with each risk area mentioned above. Nor is it meant to investigate the most effective linear heat detection system to specify.

Linear Heat Detection has a proven installation record throughout Road AND Rail Tunnel Complexes around the world, that can be verified by major International end users.