Visibility and gas monitoring are used to control the tunnel ventilation at normal operation. If, and with how much power, artificial ventilation by jet fans is operated depends on the measured visibility.
The extractive monitoring system extracts air from the tunnel through an intake system and feeds it into the visibility sensor and gas analyser.
The electrochemical CO gas analyser measures the concentration of CO gas in the inducted air and periodically performs an automatic calibration with zero and reference gas to ensure long term stability and accuracy.
The visibility sensor measures the intensity of light scattered at an angle of 30° by the inducted air and sets it into relation with the light passing through. The scattered light intensity is then multiplied by a factor to obtain the extinction coefficient.
System Set-up
- Electrochemical gas analyser with automatic calibration
- Visibility sensor based on scattered light method
- Operating unit
- Zero and reference gas
- Intake fan
- All components above installed in an enclosure ready for operation
- Intake system consisting of intake point to be mounted in the tunnel and intake tube system to connect with the monitoring system
Features
Extraction of air to be analysed from the tunnel’s driving area through an intake system
Sensor located in an enclosure outside the driving area, e.g. in a niche, a crosscut, an operating room inside or outside the tunnel
Control and evaluation unit to display measured values and with signal outputs to the tunnel control system
Electrochemical gas analyser with automatic calibration of zero and reference value
Visibility measurement using scattered light method with integrated fog compensation
Intake tube length up to 400 m
Monitoring of up to 4 measuring points through one monitoring system
Delivered in an enclosure with all wiring, pumps and tubes ready for operation incl. zero and reference gas
Advantages
- Specifically designed for application in tunnels
- Highest availability of tunnel as all important components of the monitoring system are located in accessible rooms (no need to close the tunnel for traffic)
- No electronic components in the tunnel’s driving area
- Robust, corrosion-free intake cowls with protection against ingress of water
- Automatic calibration and high accuracy of measurement
- Flexible integration into the tunnel control system
