Multi Louver Damper

Listing ID #3939023

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Preferred Buyer Location India only

Multi Louver Damper The louver type of damper consists of several blades mounted parallel across a duct, with centrally pivoted shafts extending out through a frame and driven by a linkage. Louver....

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Multi Louver Damper

The louver type of damper consists of several blades mounted parallel across a duct, with centrally pivoted shafts extending out through a frame and driven by a linkage. Louver dampers are versatile, able in theory to handle any application in the power plant.

Some of their advantages:

Fit anywhere in ducting, at any altitude.
Compact, no bonnet, little external clearance needed.
Lightweight
Drive and linkage more readily accessible
Control function simple with opposed blades.
Thin metal blade construction gives quick response to thermal transients.
Fast opening and closing.
Low leakage to outside environment.
Good modulation and control characteristics.
Actuation power requirements are low.
Normally does not require a support structure.

Louver dampers have basic disadvantages, however. Here's a partial list:

Large leakage perimeter.
Leakage through seals goes downstream inside the duct.
Comparatively high pressure drop because of blade and seal obstruction of flow.
Obstructions such as seals, shafts, stops, and fasteners tend to catch ash and scrubber slop.
Inherent flimsiness of long thin blades tends to promote flutter.
Blades and seals, always in the flow, tend to corrode and erode more.
Blades can buckle and wrap, causing leakage and lockup.
Bearing troubles are possible.
Inadequate drive power and blade strength to crush through concretions and force a seal.
Larger flange-to-flange required to contain blade(s) in full open position.
Sealing problems in dirty applications.
More moving parts and thus increased maintenance

The drive for a louver are simple, needing only 90° of motion. The torque requirement can vary widely over damper life, if corrosion and thermal effects are severe. Electric motors, air cylinders, and oil cylinders are able to actuate louver dampers with little difficulty.

Louver dampers are best applied to balance or control flow. The normal leak path of 0.7% of duct area produces a three to five percent leak rate in average applications.

As a general rule, a damper should be used in the middle third of the control range for best results. This gives equal percentage in either direction should the need arise.

A variety of options are available. Metallic spring seals, sealed (dust tight) blade ends, shear seals, and many materials are available.

Leakage performance of a louver depends on ratio of flowing to shutoff pressure, design temperature, number of blades, and blade edge treatment. Since the first two are system related, the last two are the usual areas of improvement. Reduction of number of blades reduces leak path to the limit that a single blade has only perimeter leakage.

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