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DAMPERS & DUCTWORK

General

There are several type of dampers used depending on the required function. The two broad functions are flow control/isolation, and fire isolation (fire dampers). This sections discusses the flow control/isolation dampers, while the fire dampers are discussed in detail in the NFPA standards.

Following are the major types of flow control/isolation dampers -

• Multiblade dampers with opposed blades - used for small to large size applications for flow control/modulation.
• Multiblade dampers with parallel blades - used for small to large size applications for flow isolation, i.e. two position open/shut dampers.
• Single blade or butterfly dampers - used for small to medium size applications for flow isolation or control/modulation.
• Gravity operated backdraft dampers - used as a back flow preventer for small to medium size applications .

These dampers can be manually operated or provided with actuators for automatic operation. Following are the various types of actuators that can be used -

• Pneumatic (diaphram or piston type) - fail in open or closed position
• Electric motor - fail as is (cannot provide fail open or closed position)
• Electro hydraulic - fail in open or closed position

All of the above actuators can provide flow isolation (open/shut) or flow control (modulation) function. The variation is mainly in the power source and the capability of providing the desired fail position.

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Last modified:11/16/2008