But kilometre long railway tunnels require specific measures for the environmental control, especially if diesel engines share these tunnels with passenger trains.
Environmental control purpose
- Normal operation with emissions from Diesel engines
- Incidences due to explosive/toxic gas accumulations or fire inside the tunnel
Among other security concerns the environmental control system has to ensure visibility conditions inside, allowing a normal railway service, and monitor toxic gas levels. Those two conditions will determine the air management inside tunnel.
The most important parameters are:
- Carbon Monoxide (CO) (measurement range from 0 to 300 ppm CO)
- Visibility/Opacity (measurement range from 0 to 15x10-3/m (extinction))
The main purpose is to get a fast response against high level of explosive/combustible gases and assure an early fire detection inside the tunnel. In those cases important parameters change to:
- Carbon Dioxide (CO2) (measurement range from 0 to 5000 ppm CO2)
- Explosive/Combustible gases (range from 0 to 100% LEL)
- Ambience temperature
- Relative humidity
- Fire with smoke production
According to tunnel specific conditions and difference between transported goods, monitoring could include also:
- Nitrogen dioxide (NO2) (measurement range from 0 to 20 ppm NO2)
- Oxygen (lack of O2) (measurement range from 0 to 25% O2)
Sensor system equipment
To ensure a reliable and stable control sensor of the best quality and reliability have been developed for each specific analysis.
SENS BG-IR family sensor has been developed with the newest infrared technologies ensuring an advanced and long-standing electronic device.
Toxic gases and air quality
Other toxic gases and air quality
When O2 concentration drops below 19 % Oxygen sensor warns of possible problems due to lack of oxygen.
Carbon dioxide CO2
Fire in an initial stage could cause high level of smoke emissions previous to reach high power capacity. We can compare between the engine’s emissions (5x10-3/m) to fire emissions (17x10-3 /m or higher)
Several studies confirmed the difference between situations, as shown in the table
|Tunnel Closure||> 0,008/m|
|Initial Fire||0,018 to 0,023/m|
For railway tunnels there is no data available relating fire or engine emissions, but according to our broad experience in monitoring we know that normal values are always below 0,003 /m with temporary episodes resulting of humidity, dust, etc. With diesel engines values grow up to 0,004 or 0,006 /m.
Anyway the measuring device has to be efficient ensuring an effective margin form 0 to 0,015 /m to discern acceptable visibility from zero visibility under emergency conditions.
The VisGuard type opacimeter manufactured by Sigrist Photometer, a renown company with more than 50 years experience in the market, is a compact device working according to the principle of light dispersion offering a measuring range of 0 to 0,0015 /m and less.
These devices provide a highly stable measurement because of implemented self calibrating features which compensate aging of components.
Temperature and relative humidity
According to Law 15/1999 of December 13 Protection of Personal Data (Act), personal data supplied by you will be emailed ORTRAT staff to adequately provide the requested service. Your personal data will be collected through this form. In any case the data will be transferred to third parties. In compliance with the LOPD, the user may exercise their rights of access, rectification, cancellation and opposition by contacting ORTRAT.
|Transmisor ExSens CO2-5000-IR|
|Transmisor ExSens CO-300-EC|
|Transmisor Sens BG-IR4|
|Opacímetro VisGuard - Elemento detector de opacidad|
|Ubicación del transmisor - La leyenda de los gases ligeros y pesados|