In road tunnels, dampers are mainly used for a) fan isolation, b) supply of fresh air and removal of exhaust fumes during normal operation and c) concentrated smoke exhaust during emergency operation.
During normal operation the Tunnel Ceiling Dampers (TCD) ensure even removal of vehicle exhaust fumes along the length of the tunnel. In case of emergency, most dampers in the tunnel ceiling will be closed. However the dampers in the vicinity of the fire will be opened so that concentrated smoke exhaust from the tunnel is established. A smoke free tunnel improves the chances of escape for commuters and improves access for emergency workers due to better visibility and less chance of intoxication.
Ceiling Dampers are typically installed together with an installation frame and are inserted in the openings in the tunnel ceiling to minimize flow resistance in the ventilation duct.The actuator is usually installed in a thermal enclosure to maintain full functionality up to 400°C for 2 hours. The thermal enclosures are fitted with aerodynamic nose and tail in order to minimize the flow resistance in the ventilation duct.
In metro / train tunnels, dampers are mainly used for a) fan isolation, b) bypass of air pressure caused by passing trains, c) supply of fresh air and removal of exhaust fumes during normal operation via track and tunnel isolation dampers, d) removal of smoke from platform and tunnel areas during fire scenario and e) fire separation.
Strict testing and certification for high temperature operation and structural integrity during fire scenario are mandatory for most projects that these types of dampers are applied for.