Honeywell AUTOMATIC CONTROL Engineering Manual page 465

Fig. 5. Snap-On Blade Edge Seal.
Fig. 6. Over-Center Compression Blade Edge Seal.
PRESSURE
INFLATES
SEAL
HIGH HIGH
PRESSURE PRESSURE
SIDE SIDE
Fig. 7. Inflatable Blade Edge Seal.
Blade side seals minimize leakage between the ends of the
blades and the frame (Fig. 8). One type of side seal is a stainless
steel or coated spring steel spring. Other types of side seals
(e.g., molded rubber parts riveted to the frame) conform to the
blade cross-section profile when the damper is closed. Blade
edge seals that interfere with blades closing completely could
increase leakage at blade side seals.
The twisting load on damper blades and/or their physical size
may necessitate heavy-duty or double linkage between blades to
minimize torsional bending. Bending of damper blades reduces
the effectiveness of blade edge seals by lowering compression
forces or by preventing complete contact between blades.
BLADE
EDGE
SNAP-ON SEAL WORKS
WITH COMPRESSION
AND/OR AIR PRESSURE
C2387
SNAP-ON SEAL WORKS
WITH OVER-CENTER
COMPRESSION
C2388
DAMPER
BLADE
LOW
PRESSURE
SIDE
DAMPER
BLADE
C2386
DAMPER SELECTION AND SIZING
AXLE
BEARING
DAMPER
FRAME
Fig. 8. Continuous Spring,
Stainless Steel Blade Side Seals.
In addition, damper blades can include a reinforcing element
to limit blade torsion or twist (Fig. 9). Depending on the damper
size and sealing requirement, this reinforcement can be on the
drive blade only or on multiple blades. The design of air foil blades
usually increases their torsional stiffness, much like reinforced
standard blades (Fig. 10). Air foil blades also reduce noise and
provide lower, full open airflow resistance at higher velocities.
Fig. 9. Reinforced Standard Damper Blade.
Fig. 10. Air Foil Type Blade
455 ENGINEERING MANUAL OF AUTOMATIC CONTROL
THRUST
WASHER
BLADE
SIDE
SEAL
C2389
REINFORCER
C2396
C2397