Giant Plug May Help Stop Mass Transit Disasters
The Department of Homeland Security has combined concepts behind bathtub drain stoppers and space suits to prevent disasters in underground transit systems.
The DHS Science and Technology Directorate earlier this year successfully tested its resilient tunnel plug, a giant inflatable stopper that can be used to keep gushing water or chemical and biological agents from spreading throughout transit tunnels.
“No one’s ever done this before,” S&T Project Manager John Fortune said. “It’s a completely novel technology.”
The plug was developed with the help of Pacific Northwest National Laboratory, West Virginia University and ILC Dover, which makes spacesuits for NASA. It can be filled with water or air in minutes to seal off a section of tunnel and keep flooding under control. It inflates to about 32 feet long and 16 feet wide. It can hold 35,000 gallons, about the same amount as a backyard swimming pool. The plug consists of three layers — a thick webbing made of a liquid-crystal polymer fiber called Vectran, a non-webbed Vectran and polyurethane.
“We used the same design and manufacturing techniques we use in spacesuits and inflatable space habitats,” said Dave Cadogan, engineering director at ILC Dover. “The webbings and underlying layers form a tough barrier that is strong and resilient to change.”
Using commercially available fabrics kept development costs down and will make the plugs more affordable for mass transit operators, officials said.
The experiment in January took place in a specially built Morgantown, W.Va. test bed modeled after a tunnel in a major city. Researchers filled the plug with low-pressure air as it was inflated to the tunnel’s shape. Then they added water to replace that air. Finally, they flooded the tunnel.
Despite the intense pressure, the plug held.
The plug is made to have a larger circumference than the tunnel. This way, it can fit itself around irregularities such as pipes, vents, lights, tracks and platforms. When not being used, it shrinks down to a small enough size that it can be stored in a tunnel where it can be remotely inflated at a moment’s notice.