A Question of Pressure
Finally, considering pressure transversals in mass transit rail systems is extremely important when applying TVCDs. Dampers in tunnels can be subjected to rapid pressure spikes created from high-speed trains passing in front of them. Depending on train speed, tunnel tolerances and damper location, pressures as high as 24-in, of water gage may be created as trains approach and travel away.
Over time, this aggressive movement has adverse effects on damper construction if this harsh impact wasn't considered during designing. Manufacturers should possess this data showing actual testing for these conditions and modifications should be made when needed.
Ventilation dampers play important roles in today's modern tunnel ventilation and emergency systems. When properly selected and applied, they can provide trouble-free service for many years. Today's TVCDs aren't just airflow devices but an integral part of the tunnel ventilation and emergency system function.