How to Select Dampers and Louvers
Dampers and louvers are used to control the flow of air in a process system or enclosed area. Dampers are usually motorized or manually-adjustable for flow control. Louvers are often fixed for a constant flow rate. There are many different types of products. Dampers are designated as industrial control, backdraft, counterbalanced, bubble tight, isolation, or discharge products. They are made of metal and usually square, circular, or rectangular in shape. Some industrial dampers are designed for pressure relief, or recommended for use within specific HVAC systems. Like dampers, louvers are usually made of aluminum or steel. Louvers may be adjustable, or suitable for applications that require noise control.
There are many different types of industrial dampers. Examples include industrial control dampers, backdraft dampers, and counterbalanced backdraft dampers. Industrial control dampers are flange-mounted devices that are equipped with linkages out of the air stream. They vary in terms of size and shape and are rated for either medium-duty or heavy-duty applications.
Backdraft dampers have a galvanized steel frame and extruded aluminum airfoil blades. These vanes provide improved strength with reduced noise and static pressure. Counterbalanced backdraft dampers are usually made of galvanized steel. They are designed to meet application requirements based on temperature, pressure, or velocity.
Industrial dampers include bubble tight dampers, round isolation dampers, and round discharge dampers. Bubble tight dampers are used in applications that require shut-off capabilities under extreme conditions. They may be qualified for use in nuclear power plants and tested according to ASTM and ASME standards. Round isolation dampers are made of carbon steel and have a butterfly blade. They provide extremely low leakage in both HVAC and process systems. Round discharge dampers are also made of galvanized steel, but are designed for use on the discharge side of an axial flow fan. These dampers prevent fan shutdown and can withstand pressures and velocities in multi-fan applications.
There are four basic types of industrial louvers: stationary, adjustable, combination, and air measuring. Stationary louvers are equipped with angled or airfoil-style blades that may provide weather protection and sound attenuation. Adjustable louvers with airfoil blades are also commonly available. Combination louvers have blades that begin to open at one level of static pressure and become fully open at another. They may have backdraft damper blades and feature an all-aluminum construction for corrosion resistance. Air measuring louvers have closely-spaced vertical blades that prevent ingress of water.