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.

Opposed Blades Louver Dampers

are the most effective type of damper for controlling the flow of gases with the least disturbance to flow in ducts. Each pair of blades is carefully fitted to ensure precise operation in opposing directions, and thus creating highly controllable passages for the gas.

The frame is made from a formed or fabricated channel and is designed to withstand any system upset conditions. The blades are designed to adequately handle all loads, up to and including upset conditions with a maximum center span deflection determined by the engineering department so as to ensure smooth and trouble free operation. The drive shafts are supported in maintenance-free bearings. An adjustable floating packing gland seals the shaft passage through the damper frame. A special non-binding, fully adjustable external linkage is used to operate the damper. A wide variety of operators can be specified -electric, pneumatic, hydraulic or manual.

Double Louver Dampers:

The Double Louver Damper is used to combine flow control with the capability of 100% isolation.

The damper is configured with two rows of blades in a common frame. 100% isolation is achieved by closing the blades and pressurizing the space between the two rows with clean air from ambient at a pressure greater than the upstream pressure in the duct. The clean air barrier prevents leakage of flue gas into the isolated area and also ventilates the downstream area with clean air.

Tandem Louver Dampers:

Where a double louver damper forms a seal air barrier between seperate rows/banks of blades, a tandem damper has only on row of blades and the air chamber is formed between the upstream and downstream section of each blade.

The single set of shafts allows the number of blades to be minimized. Even wide blades can be contained within the minimum duct space required by a double louver.

In addition to eliminating the need for a second set of shafts, the wider blades allowed can reduce the number of blades in the damper. The smaller number of shafts substantially reduces the bearing and packing maintenance and operating torque.

This compact structure allows much more freedom of duct design than a conventional double louver.

Parallel Blade Dampers

We offer our clients with a wide gamut of qualitative Parallel Blade Dampers. These products are manufactured by making use of high-grade material, procured form the established vendors of the industry. Further, to cater to the diversified demands of the clients, we offer these dampers in different sizes and specifications.

Other information:

  • Efficient performance
  • Longer service life
  • Robust construction
  • Smooth finish
  • Able to meet applications where hidden linkages provide service problems Ask for Price

Opposed Blade Dampers

Our valued customers are presented with a qualitative Opposed Blade Dampers. These precisely designed opposed blade dampers allow unlimited airflow adjustment facility from any airflow panel. The offered products provide additional airflow than compared to other slide dampers. Moreover, we also provided these opposed blade dampers as per the clients requirements at a cost effective manner.

  • Made of high-grade stainless steel and mild steel
  • Anti abrasive finish
  • Optimal mechanical strength
  • Dimensional accuracy

When To Use Opposed Blade Vs Parallel Blade:

Parallel Blade- Parallel blade dampers are usually selected for volume control from wide open to 75% of wide open. A relatively large control arm swing provides sensitive control through a relatively small change in air volume. Parallel blade dampers also offer the best first-cost selection for simple open-closed damper requirements.

Opposed Blade- Opposed blade dampers are selected for applications requiring volume control over a broad range, from wide open to 25% of wide open, as the control arm swing is more proportional to the damper effect.

Motorized Multi Louver Dampers

These are Motorized Multi Louver Dampers with Direct Mounted Actuator which operate in unison to offer a smooth flow control of Blower Air. These are typically suitable for Industrial applications and mounted in ducts. These units are with a sturdy sheet metal construction suitable to handle large quantities of Air and are mounted at the Suction or delivery side of combustion air blowers. The operating actuators are directly coupled to the Damper shaft. This eliminates the linkage arrangement and thus the relatively tedious linkage settings. The end limits can be set by means of adjustable limit switches inside the actuator.

Features :

  • Sturdy Sheet Metal body. Louvers are provided with pressed ribs to provide adequate stiffness. The shafts of all the Multi Louvers are supported between Ball Bearing at both the ends.
  • This reduces the frictional torque required to be overcome by the actuators and ensures a smooth operation.
  • The Ball bearings are enclosed type and ensure that no lubrication is required during its lifetime.
  • Actuators with suitable torque and Operating time is provided as an actuator for achieving the desired control over 0 to 90 degree travel of the motor.
  • Actuator is provided with either 4-20mA, 2-10V dc or SPDT floating control input Actuator is available in 230 or 110 VAC power supply Actuator is directly mounted on the Multi louver damper shaft. Actuators have an IP-65 degree protection hence suitable for weather proof applications.
  • Position Feedback available in 4-20mAor 2-10Vdc (field configurable) for the models with 4-20mAor 2-10Vdc control input.
  • Auto declutchable Manual Hand wheel is provided for operating the damper by in event of power failure. Visual indicator provided on the actuator to indicate FULL OPEN/ FULL CLOSE position.
  • Dampers in SS construction available on request.

Specifications :

  • Type: Rectangular Multi louver
  • Service: Air Handling
  • Sizes: As per user specifications
  • Flange Drilling: To be done by the user else to be specified prior to ordering
  • Max ambient temperature: 60CC
  • Max working Pressure: 1000 mmWC
  • Leakage efficiency:99%
  • Body & Flange:Carbon Steel
  • Louvers:Carbon Steel
  • Shaft:EN-8
  • Painting: Aluminum paint

Collar Damper / Volume Control Damper / HVAC DAMPER

Installed behind grilles and diffusers, opposed blade volume control dampers help in adjusting air volumes to suit the requirements of the space as per the consultants design. The vertical louvers at 25 mm spacing facilitate even air distribution of the supply grille.


  • Aluminum construction
  • Nylon bushing for friction free operation
  • Manufactured in High Quality Mild Steel or Galvanized Iron.
  • Designed to control air volume in all handling Accessories like grilles and diffusers.
  • Opening Mechanism like Screw or handle types are available.
  • Standard Finish: Natural anodized & Powder coated.