Increasing Fire Safety of Cologne Main Station by High Pressure Water Mist- In recent years the focus for water mist application has progressed from industrial applications towards ordinary hazard risk protection.
It should not be forgotten that water mist offers a number of benefits over conventional fire fighting technologies in industrial application fields.
Water Mist remains a viable solution to industrial fire protection challenges.
Case Study Cologne Main Station
-Cologne Main Station was constructed in 1900.
-After being heavily damaged in World War II it was reconstructed in 1953.
-From the year 2000 a number of refurbishment works have been initiated, whereby improvement of fire safety has been a major aim.
-Cologne Main Station is a major intercity rail traffic intersection point for Germany and Europe.
-On 11 rail tracks, 1200 trains and 280,000 passengers pass through every day.
-Traffic discontinuance would lead to severe infrastructural and economic problems.
Fire Protection Measures
-All public areas within the main station, including shops, have been protected by a conventional sprinkler system.
-The extensive tunnel network under the rail tracks within the stations contain large amounts of power and data cables which required an improvement of fire protection.
-A fire within these cable tunnels would lead to risk for passengers, but also to interruption of operability of the station, thus direct and indirect losses.
Fire Risk Assessment
-A fire consultant firm was assigned to carry out a risk assessment and to develop a holistic fire protection concept.
-The underground cable tunnel network consists of one fire zone with a total length of 1600m.
-The concept should include all measures including evacuation, fire detection, fire fighting, smoke extraction and last not least overall cost evaluation including life cycle costs (LCC).
Fire Fighting System Assessment
-Different fire fighting technologies were evaluated for the protection of cable tunnels, among these conventional deluge systems and water mist.
-High pressure water mist technology was selected to be most favourable due to:
-Fire test proof of extinguishing effect
-Best cooling abilities with smallest water amounts (lowest damage potential)
-Lowest impact on electric components
-Most tolerance for continuous modification of cable tray arrangement
Fire Protection Concept
-Protection concept based on a deluge high pressure water mist system for all cable tunnels was developed in co-operation with:
-Client (Deutsche Bahn (DB))
-Rail authority (Eisenbahnbundesamt)
-DB, as operator of the train station, requested an early activation of the fire fighting system to reduce fire damages to the cables and to the cable tunnel structure.
-Early activation by a smoke aspirating system has been part of the fire test scenarios for cable tunnels up to 4 m height.
System Testing and Acceptance Process
-Fire tests were defined based on CEN TS 14972 cable tunnel fire test scenario concerning:
-Arrangement of fire load
Fire Tests for Cable Tunnels
Fire Test Arrangement and Scenarios
-Test tunnel of 3 m width and 21 m length with an adjustable ceiling between 3 m and 4 m height.
-Longitudinal ventilation with 1 m/s air velocity.
-Fire tests with 3 m and 4 m ceiling height.
-250 kW ignition source for 5 minutes.
-Water mist system release after 5 minutes of pre-burn.
-Water mist discharge for 15 minutes.
-Fuel package from CEN TS 14972 with Polypropylene (PP) and Polyethylene (PE) cables.
-Cable trays with a width of 700 mm being arranged in 200 mm vertical distance.
-Temperature in 100 mm distance underneath the ceiling in 2,5 m horizontal intervals.
-Temperature on top of the cables within the second cable tray in 2,5 m horizontal intervals.
-Air velocity along the cable tunnel.
-After 5 minutes from start of water mist discharge all temperatures shall be below 100°C.
-After a duration of water mist discharge of 15 minutes and system shut off no visible flames and no smouldering fires are allowed.
-No re-ignition is allowed.
-0,5 m of cables shall be unaffected by the fire at both ends.
Fire Test Results
Achieved Results according to CEN TS 14972
-All temperatures in the test cable tunnel have been reduced below 100°C within 5 minutes of water mist system discharge.
-No visible flames or smouldering fires after 15 minutes of system discharge and system shut off.
-Fire damage on cable limited to the extent caused during pre- burn time before water mist system discharge.
-Nozzle layout based on full scale fire test results up to 4 m cable tunnel height.
-Definition of 21 virtual fire zones within the cable tunnels (each ca. 70 m long), being supplied by water mist via 21 section valves.
-Safety concept foresees up to two adjacent sections to be activated simultaneously.
-Fire detection by smoke aspirating system.
-Temperature monitoring within the cable tunnels with linear optical heat detection.
-Small bore stainless steel pipework can ideally be integrated into the congested cable tunnels.
-Jockey pump to prefill main pipe from pump unit to decentralized section valves.
-Centrally located independent diesel driven 500 l /min water mist system pump unit.
-Water mist system supplied by fresh water via 4000 l break tanks.
-Total space requirement in the pump room 15 m2.
-1st alarm by smoke aspirating system is raising a pre-alarm in main control station.
-2nd alarm by smoke aspirating system is activating the high pressure water mist pump unit and opens the respective section valve to discharge water mist.
-System is activated for 30 minutes. After this time, fire brigade verifies temperatures in cable tunnels by linear optical heat detection cable (Fire brigade will not access cable tunnels).
-In case of heat increase, fire brigade can manually activate the water mist system for further 30 minutes.
High pressure water mist offers numerous benefits over conventional fire fighting technologies for a number of industrial applications.
After thorough evaluation of different technologies Deutsche Bahn has decided to implement water mist in their cable tunnels as a cost efficient measure to increase fire safety to Cologne Main Station.
Presented by Rüdiger Kopp, FOGTEC Fire Protection at an International Watermist Conference.
Published with the kind premission of IWMA