For
design of blast resistant buildings, it is important to apply the right blast
resistant products, like blast valves, blast dampers and blast doors. The
selection for blast doors could be easy, as they are assumed to be closed to
stand blast waves when accidents happen. However, for blast valves and blast
dampers, this is obviously a different story.
Blast valves and
blast dampers are protective equipment of HVAC systems.
In normal conditions, blast valves and blast dampers work at ventilation
position and they are supposed to be closed by overpressure to block the blast
waves. It is very tricky for product engineers to handle the contradictory
design targets, like strong structure but light weight, with the ability to
close fast but with high air flow rate. Hence there are actually multiple
options available in market for different applications. For example, if the
designed blast duration is very short, like a couple of milliseconds, then
strong structure of blast valves or blast dampers might not be needed.
When
blast waves hit the blast protective equipment, the amount of passing through
impulse is depending on many facts, like the size of ventilation area, mass of
closing blades, as well as complications of air path, peak pressure of blast
waves, duration of blast waves and rising time of peak pressure, etc. No matter
what the situation is, there is one factor that could be considered as the
useful consideration to design of a blast resistant HVAC system, that is, the
impulse block rate of blast protective equipment like blast valves and blast
dampers. Impulse block rate = 1-Impulse passing through / Impulse reflected. The protective equipment, like blast valves and blast dampers, could
mitigate the incident impulse, like what you saw from the movie, HONEY, I
SHRUNK the KIDS. If you see the incident impulse as a dangerous Tyrannosaurus,
then the high performance blast valves and blast dampers could transform them
into the size of a mouse. The rate of mitigation, here referred as impulse
block rate, depends on various product solutions.
