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Butterfly Dampers
Design Sheet
Butterfly Dampers
Flextech Industries’ butterfly dampers are available for a wide variety of applications in round ductwork, where low-leakage isolation, flow control, or a combination of the two is desired. Flow characteristics are close to that of a single-blade louver. Varying degrees of isolation can be obtained from 90 to 99.9% depending on the seal arrangement.
Flextech Industries’ shaft seals provide a low-cost, heavy-duty design that is suitable for applications with clean, corrosive, dirty, and/or dry environments. Our design can be utilized for applications up to 2,000°F gas temperature. Flextech butterfly dampers are equipped with a standard outboard bearing and a frame-mounted shaft seal arrangement. This categorization allows for packing replacement without bearing removal.
Flextech offers four seal designs for butterfly dampers:
Swing-through Seal
Swing-through seals are used in extremely dirty applications where tight shut-off is not required. The gap around the blade can be increased or decreased to suit the customer’s individual need. This design can be used in applications up to 2,000°F.
Step Seat
The step seat is standard for butterfly dampers and is recommended for relatively clean flue gas applications, with up to 98% sealing efficiency. This design can be used in applications up to 2,000°F. This design utilizes a rolled bar that is welded to butterfly housing at the blade-closed position.
Tadpole Seal
A tadpole seal is also recommended for relatively clean applications, when tighter leakage rates are required. The tadpole seal is constructed of a woven high-temperature silica cover with a silica rope bulb. This design can be used in applications up to 2,000°F and provides up to 99.5% sealing efficiency.
Step Seat with Perimeter Seal
A step seat with perimeter seal is recommended for clean applications. It is similar to the step seat, with the addition of an elastomeric perimeter seal bolted onto the blade. Sealing efficiencies rival those of the tadpole seal. The maximum design temperature is 400°F.
Advantages of Flextech Industries, Ltd. Butterfly Dampers:
- Excellent for isolation
- Fast operating speeds
- Little or no outside space required for support structure
- No leakage to ambient
- All blade seals are internal to the frame and shaft seals are externally mounted for easy access.
- Lower cost
- Easily maintained
Warrior Series
Warrior Series butterfly dampers are custom-engineered and manufactured in many configurations depending on the application. Performance dampers consist of a housing or frame with or without flanges, a flat plate and shaft assembly, shaft packing glands to prevent leakage to ambient, and outboard mounted maintenance-free bearings.
Hvac / Light Duty Series
Flextech offers a standard line of butterfly dampers featuring low-cost and quick deliveries. This design offers carbon or stainless steel construction, a metal step seat seal, and a manual quadrant actuator. These dampers are designed for temperatures up to 200°F as a standard (with excursions to 400°F, under certain circumstances).
Single Plate Disc
The single plate disc is the standard blade for all round dampers. It is utilized for high-temperature and low-pressure flue gas applications. It is available in continuous shaft and stub shaft configurations.
Reinforced Single Plate Disc
The reinforced single plate disc is suitable for higher-pressure applications. Structural reinforcements are applied to the face of the disc in an aerodynamic shape to minimize flowing pressure losses and maintain good control characteristics.
Blades
Single blade discs are the standard design. When modulation or flow control is required, a second plate disc design is available.
Actuator Systems
The following actuator options are available with Flextech butterfly dampers:
- Manual - Locking hand lever or quarter-turn gearbox types
- Pneumatic - Cylindrical or quarter-turn types
- Hydraulic - Cylindrical or quarter-turn types
- Electrical – Quarter-turn types only
Butterfly Damper MaterialsFrame and Blade Materials:
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