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Stack Dampers

Forney supplies a complete line of high quality stack dampers to utility and heavy industrial customers.

Standard sized stack dampers from Forney utilize a flat flange for welding the damper to the stack. The flat flange allows the damper to fit stacks from 12 to 26 feet in diameter, in 2-foot increments. The stack wall will be welded to the flat flange of the damper instead of an edge-to-edge type connection. The flange gives the installer flexibility for out-of-tolerance stacks, which speeds up installation, reduces misalignments, and meets STS1 code.

Utilizing a standard size stack damper is most economical but not for all applications. Forney provides custom designed dampers for sizes outside our standards.

Proper functioning dampers are vital to the operation of your plant, so we put our design emphasis on areas critical to the effectiveness and life of the damper. Forney’s stack damper can automatically open when excess pressure builds up in the boiler preventing internal damage.

Durable Construction
• Standard material used is ASTM A36 carbon steel; however other material such as ASTM A588 Cor- Ten, A516 or 304 stainless steel can be used.
• A rain trough with drain directs water through the frame by a threaded pipe which can be added to for a more desirable location.
• Four (4) lifting lugs are evenly spaced around the frame for crane pickup.


Reliable Operation
• Redundant limit switches are provided on the non-drive shaft.
• The actuator is equipped with a 4-20ma feedback positioner to track precisely where the blades are during cycling.


Simplified Maintenance
• Two 6” diameter view ports are mounted 180 degrees apart.
• Blades can be designed for 500 lbs point load with mechanical lockouts on each blade to support maintenance personnel for internal service.
• All Forney stack dampers have OHSA approved linkage guards to protection personnel around the stack damper.

These items combine to make the difference between an adequate damper and one that is truly reliable, durable and economical to maintain.


Size Standard sizes available from 12 – 26 feet in 2-foot increments
Custom sizes available up to 30 feet (9.14 m)
Temperature Range: up to 500°F (260°C)
Pressure: up to 30” w.c. (75 mbar)
Frame Materials: Standard: ASTM A36 carbon steel;
Optional: ASTM A588 Cor-Ten, A516 or 304 stainless steel
Shaft Material: 316 Stainless steel
Blade stops: Open position and Closed position with trough
Linkage: Adjustable
Actuation: Electric, pneumatic, or hydraulic
Insulation: External upon request
Blade design: Reinforced Airfoil
Two blade, four blade or multi-blade louver damper
Blade Material: Standard: ASTM A36 carbon steel;
Optional: ASTM A588 Cor-Ten, A516 or 304 stainless steel
Damper position indicator: Mechanical, limit switches, or position transmitter
Leakage: Less than 0.5%
Pressure Drop: Below 0.1” w.c. at full open
Seals: Between blade tips – Hastelloy C-276

Stack Damper Spec Sheet
Publication #404007-06