3-6
3.6
Precautions for connecting the ducts
Caution
Ensure not to apply the weight of the duct on the fan.
Otherwise, failure, breakage, or vibration may be caused.
(1) Use an expansion joint not only to prevent the vibration and noise from being transmitted
outside during test run but also to absorb the thermal expansion of the duct in case of fire
and to prevent the weight of the duct from being applied on the fan.
The expansion joint should be the one certified by the Minister of Land, Infrastructure,
Transport and Tourism.
(2) Support the duct using appropriate supporting fixtures to prevent the weight of the duct from
being directly applied on the smoke ventilation fan.
(3) Smoke exhaust duct should be made of noncombustible material and is usually not
heat-insulated as a rule.
(4) Connect the duct of discharge side to the smoke vent.
(5) Before connecting the ducts, check inside the ducts and fan, and remove any foreign matter,
such as waste cloth and tools.
(6) If an inactive (not running) fan is exposed to air in the reverse direction, it rotates in reverse.
Avoid exposure to such air because it takes longer to start a fan that is rotating in reverse.
(7) In general, unexpected pressure loss may occur due to the connection to (a) ducts that are
much smaller than the port diameter of the fan, (b) ducts with a series of bends, or (c) ducts
with bends just before or after the connection to the fan.
(8) If the intake air is swirling, install guide vanes or increase the radius of the bends.