Dampers
Dampers
Dampers
SANKET ABHANG
An air damper is a device that uses valves or plates to stop or regulate the flow of air within a
duct, chimney, variable-air-volume (VAV) box, air-handling unit or other similar pieces of
equipment. Dampers are also used to stop airflow into unoccupied or unused rooms where air
conditioning is not required. In addition, dampers can also be used as protection measures
against smoke or fire.
An air damper is a complex mechanism with many moving elements. Their main components are
the blades, which adjust their position to control airflow. In addition, dampers include frames,
linkages, axles, bearings, seals, blade pins, actuating motors, flanging, jackshafts, and sleeves,
among other components.
Manual dampers are adjusted manually depending on the required airflow, as implied by
their name.
Dampers can also be classified based on their application, and the following are some of the
main types:
The main locations where air dampers are required to meet code are the following: stair
enclosures, elevator shafts, common corridors, mechanical rooms, fire-rated walls, exterior
building walls, shaft enclosures, horizontal assemblies, and duct and transfer openings.
Air Dampers in Fire Protection Applications
The three main types of dampers used in fire protection applications are fire dampers, smoker
dampers and combined fire/smoke dampers. This section provides an overview of each type and
its applications.
Fire Dampers
Fire dampers interrupt airflow through the duct automatically, restricting the passage of flames.
To accomplish their function, these dampers are installed in ducts that cross fire-rated assemblies
or fire-rated walls. They can be installed in both horizontal and vertical ductwork, and can be of
both curtain type and multi-blade type.
A fire damper has the following components:
1. Sleeve
2. Curtain blade
3. Break-away joints
4. Fusible link
5. Access door to inspect the fire damper
All fire dampers are installed in the open position, with a fusible link. When the temperature in
the ductwork exceeds a specified value, the fusible link melts and the damper gets shut off, either
by gravity or by a spring. To guarantee they accomplish their function, fire dampers need to pass
various tests.
Fire damper selection is based on three main factors: fire resistance rating, temperature and
operation range. Fire rating depends on the time span for which a damper will withstand the heat
associated with a fire. For walls, partitions and barriers with fire resistance rating of less than 3
hours, 1.5-hour fire dampers are used. For fire barriers rated for 3 hours or more, 3-hour fire
dampers are used. This procedure ensures building code compliance, which require that the fire
resistance rating be maintained across the full area of walls, partitions and floors.
The exceptions for the use of fire dampers are parking garages, kitchen exhaust ductwork, and
dryer exhaust ductwork.
Smoke Dampers
Smoke dampers prevent smoke from spreading in HVAC systems that are designed to shut down
automatically in case of fire, and they only have two positions: open and closed. These dampers
are installed in a slotted duct section - they are installed whenever a duct penetrates a smoke
partition or smoke barrier inside the building. They can be applied in passive smoke control
systems, or as part of an engineered smoke control solution.
In passive systems, smoke dampers close and prevent the circulation of air and smoke through
ducts or ventilation openings that cross a smoke barrier. On the other hand, in engineered smoke
control systems, the spread of smoke is controlled by the building HVAC system or by dedicated
fans that create pressure differences. Smoke dampers may be controlled by heat sensors, smoke
sensors, fire alarms, or any other method that meets the design intent.
A smoke damper has the following components:
1. Sleeve
2. Smoke blades (parallel)
3. Break-away joints
4. Duct-mounted smoke detector
5. Damper actuator
6. Access door
It is important to decide which ratings are required for UL Listed fire dampers. They are
summarized in the following table:
SMOKE DAMPER
DESCRIPTION
RATING
UL555S requires each smoke damper, with its installed actuator, to be rated for ope
specific pressure differential (inch wg) and to close against a specific velocity or air
3) Velocity and pressure
Dampers should be selected to operate at the pressures and velocities they will enco
application, with a minimum of 4 inch wg (1 kPa) and 2000 fpm (10.2 m/s)
4) Electric and pneumatic Electric and pneumatic actuators that have been UL tested and approved with the da
actuators matched set are factory-assembled.
The SD-1320 and SD-1330 smoke dampers are UL/cUL leakage rated dampers, listed
under the latest UL 555S standard.
SD-1620 smoke dampers meet UL Class II. Leakage is less than 20 cfm per square foot
at 4 inch w.g. and at 350°F (177°C).
SD-1630 smoke dampers meet UL Class I. Leakage is less than 8 cfm per square foot at 4
inch w.g. and at 350°F (177°C).
1 4 8
I 4 8 11
II 10 20 28
III 40 80 112
Conclusion
Air dampers have a wide range of applications, ranging from airflow modulation in normal
operating conditions, to providing a reliable barrier against smoke or fire during emergencies.
However, code compliance is an important aspect to consider regardless of the application, so
working with qualified HVAC professionals is highly recommended.