Guadarrama Tunnel gets Crowcon gas protection

Crowcon's gas monitoring systems have been installed in the world's fourth longest rail tunnel to detect flammable and toxic gases before they reach hazardous levels.

The 28km-long Guadarrama Tunnel in Spain and the 8.5km San Pedro Tunnel form part of the recently-opened Madrid-Valladolid high speed rail link.

The Guadarrama Tunnel comprises two parallel tunnels connected by cross-passages every 250 metres, as well as a 500 metre-long emergency room, located equidistant from both tunnel entrances.

The San Pedro Tunnel, which also comprises parallel tunnels, is connected by cross passages every 400 metres.

More than 500 Crowcon detectors are installed throughout the tunnels, including Xgard detectors (validated to IEC61508 SIL2/3) for detecting carbon monoxide (CO), nitrous dioxide (NO2) and oxygen (O2) levels, and flameproof (Exd) infra-red Nimbus units for detecting methane (CH4) levels.

Signals from these detectors are processed by more than 70 Vortex rack-mounted controllers, which are connected to PLCs via RS485 and provide operators with all gas readings and alarm/fault information.

If the detectors register dangerous levels of gas, ventilation and exhaust systems are automatically triggered by the Vortex control panels, which also pinpoint which detector is in alarm mode.

They then immediately transmit this information via PLC to a Scada system that transmits the information to control rooms in Madrid and Segovia.

Internal combustion engines emit exhaust fumes that contain significant quantities of CO and NO2 (both highly toxic).

If a tunnel is inadequately ventilated, these gases can accumulate to dangerous concentrations.

Oxygen depletion is also a risk where a fresh-air supply is limited.

In the absence of adequate ventilation, oxygen levels can be quickly depleted by breathing, combustion and dilution by other gases such as carbon dioxide (also a toxic gas), nitrogen, argon or helium and chemical absorption by corrosion processes.

Under EU regulations, fire and gas safety systems are obligatory in tunnels longer than 500M.

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