Blast valve
Encyclopedia
A blast valve is used to protect a shelter, such as a fallout shelter
or bunker
, from the effects of sudden outside air pressure changes. A nuclear weapon
creates a shock wave, which may produce sudden pressure changes of more than an atmosphere (about 15 pounds per square inch) even several miles or kilometers from the detonation point. After the shock wave passes, a sudden negative pressure follows.
If such pressure waves enter a shelter, they will likely do substantial harm to occupants and equipment. A blast valve is placed in air intake/exhaust pipes, that remains open normally, but automatically closes when strong pressure is applied in either direction.
A typical blast valve has entries of 6-12" diameter (150–300 mm), and a larger center section. Within the center section is a disk mounted on an axle, with weak springs that keep it centered, away from both entries. Pressure displaces the disk along the axle, until it plugs one entry or the other. After the blast, the springs return the disk to the center, re-opening the valve.
Another type of blast valve employs rounded metal tubes held in place by springs. As pressure rises it pushes the tubes against the frame of the valve closing the opening. These valves are typically unidirectional in airflow and are employed in large wall structures where large amounts of airflow is required.
Fallout shelter
A fallout shelter is an enclosed space specially designed to protect occupants from radioactive debris or fallout resulting from a nuclear explosion. Many such shelters were constructed as civil defense measures during the Cold War....
or bunker
Bunker
A military bunker is a hardened shelter, often buried partly or fully underground, designed to protect the inhabitants from falling bombs or other attacks...
, from the effects of sudden outside air pressure changes. A nuclear weapon
Nuclear weapon
A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission or a combination of fission and fusion. Both reactions release vast quantities of energy from relatively small amounts of matter. The first fission bomb test released the same amount...
creates a shock wave, which may produce sudden pressure changes of more than an atmosphere (about 15 pounds per square inch) even several miles or kilometers from the detonation point. After the shock wave passes, a sudden negative pressure follows.
If such pressure waves enter a shelter, they will likely do substantial harm to occupants and equipment. A blast valve is placed in air intake/exhaust pipes, that remains open normally, but automatically closes when strong pressure is applied in either direction.
A typical blast valve has entries of 6-12" diameter (150–300 mm), and a larger center section. Within the center section is a disk mounted on an axle, with weak springs that keep it centered, away from both entries. Pressure displaces the disk along the axle, until it plugs one entry or the other. After the blast, the springs return the disk to the center, re-opening the valve.
Another type of blast valve employs rounded metal tubes held in place by springs. As pressure rises it pushes the tubes against the frame of the valve closing the opening. These valves are typically unidirectional in airflow and are employed in large wall structures where large amounts of airflow is required.