7/28/2019 Jehar - Damper Design & Selection

http://slidepdf.com/reader/full/jehar-damper-design-selection 1/2

Page8_5 Frame Page 1 of 2

http://www.hrsgdesign.com/page8_5.htm 5/19/02

Dampers, Louvers, & Diverters

In HRSG systems, many different types of dampers and louvers are employed. The type andconstruction used is dependent on the purpose it is used for. Dampers and louvers can generally be broken down by the following types.

Butterfly Damper: 

Parallel Blade Louver: 

Opposed Blade Louver: 

l Butterfly Damper 

l Parallel Blade Louver  l Opposed Blade Louver 

l Double Louvers l Diverter Dampers

l Slide Gate(Guillotine) l Swing Gate

Butterfly dampers are single blade, low leakage or minimum leakage dampersutilizing a round, square or rectangular blade. Butterfly dampers are well suited for on/off service or flow control balancing. Electric, pneumatic, hydraulic and manual

gear actuators with pneumatic or electrical positioners can be used.

The parallel design is used primarily for isolation. The use of blade edge and jambseals achieves minimal leakage past the closed damper. These dampers are usedmostly in air preheat and heat recovery systems. They would be used where a tightshut off is required, such as isolating one unit from another in a multiple unitsystem. Electric, pneumatic, hydraulic and manual gear actuators with pneumatic or electrical positioners can be used.

The opposed design exhibits the best flow control characteristics with moderateleakage past the closed damper. This type damper would be necessary if theaccuracy of the flow amount is required or if the flow pattern must be maintained,such as when entering a burner zone. Electric, pneumatic, hydraulic and manualgear actuators with pneumatic or electrical positioners can be used.

7/28/2019 Jehar - Damper Design & Selection

http://slidepdf.com/reader/full/jehar-damper-design-selection 2/2

Page8_5 Frame Page 2 of 2

http://www.hrsgdesign.com/page8_5.htm 5/19/02

Double Louvers: 

Slide Gate(Guillotine): 

Flow Diverter Dampers: 

The double louver design utilizes two banks of blades. Zero flue gas leakageis achieved by pressuring the area between two closed banks of blades with

seal air. The parallel/opposed configuration provides zero leakage yet retainsgood flow control characteristics. These dampers can be found inapplications where fast bypass capability is required during an upsetcondition. Double louvers can also be found where overhead space is notavailable to install a slide gate damper.

Slide gate isolation dampers are available in low leakage and zero leakage designsutilizing either machine screws or chain drives. Slide gate dampers can befurnished with electrical actuators, air actuators or hydraulic actuators.

Flow diverter dampers are utilized on many process andheat recovery systems to direct the flow in one or twodirections. In a heat recovery system, the diverter damper would normally direct the gas to a waste heat recoverysystem or in a bypass mode through a silencer and stack.The diverter damper can also be furnished with a singleend pivoted blade to direct the gas flow into one of the twooutlets. The metallurgy of the damper is based on thedesign temperature and pressure of the system.