Products » Dampers


Isolation Applications

Round

  • Sealing efficiencies for butterflies are 99.50% to 99.85% without seal air and 100% with seal air.
  • Guillotines, although more costly, provide the least static pressure loss and assurance of 100% sealing efficiency or "man-safe" isolation with a solid plate blade.
  • Sealing efficiency for a guillotine damper ranges from 99.75% to 100%.
  • Closing times are faster with poppet valves (1/2 to 1 sec) versus butterflies (1 sec) and guillotines (10 sec min - size dependant)
  • Poppets do not seal as well as butterfly or guillotine dampers with sealing efficiencies to 99.75%.
  • Poppets do not survive system upsets and fires as well as butterfly and guillotine dampers.
Damper Sealing Efficiency
(Percent)		 Pressure Loss
(in WC)		 Size & Weight Operating Time
(Seconds)		 Cost

Butterfly 		99.75 to 100% 0.1 to 0.3 # > 1 $

Guillotine 		99.75 to 100% 0.0 ### > 10 $$$

Poppet 		> 99.75 0.5 to 2.0 ## < 1 $$
 

Rectangular

  • Sealing efficiencies for rectangular butterfly dampers range from 99.00% to 99.75% and 100% with seal air.
  • Multi-blade louver dampers offer sealing efficiencies from 98.00% to 99.50% and 100% in double louver configurations (w/seal air).
  • Guillotine dampers provide sealing efficiencies from 99.75% without seal air and 100% with seal air.
  • Operating times range from 1/2 to 1 sec. for louvers, 1 sec. for butterflies, and 10 sec min and are size dependant for guillotines.
  • Louver dampers are more costly than butterflies but less than guillotines.
  • Static pressure loss is minimal with guillotine dampers and greatest with louver dampers.
  • Louver dampers are available in parallel or opposed blade configurations for improved flow control where sealing efficiency is important but improved control is also desired.
Damper Sealing Efficiency
(Percent)		 Pressure Loss
(in WC)		 Size & Weight Operating Time
(Seconds)		 Cost

Butterfly 		99% to 100% 0.1 to 0.3 # > 1 $

Guillotine 		99.75 to 100% 0.0 ### > 10 $$$

Louver 		98% to 99.5% 0.5 to 1.0 ## > 1 $$

Control Applications

Damper Control, Vol. & Press. Pressure Loss
(in WC)		 Size & Weight Cost

Butterfly 		Better 0.1 to 0.3 # $

Multi-Blade Butterfly 		Best 0.5 to 1.5 ## $$

Radial Vane 		Best 0.5 to 1.5 ## $$

Flap Diverter 		Good 0.2 to 2.0 ### $$$

Round

  • Flow Control of gas in round ducts is best accomplished with round opposed-blade and radial vane blades.
  • Butterfly dampers provide excellent control of static pressure and volume in mid-range, but less than adequate low-flow control when compared to opposed-blade louvers.
  • Radial vane dampers are preferred for control of gas entering centrifugal or radial fans.
  • Flap diverter dampers are designed to control flow during startup of waste heat equipment.
  • Positioning devices with analog or digital inputs are available to maintain reliable flow control on most damper configurations.
  • Feedback instrumentation is available to provide exact positioning data.
 
Damper Control Vol. & Press.
(in WC)		 Pressure Loss
(in WC)		 Size & Weight Cost

Louver 		0.5 to 1.0 0.5 to 1.0 ## $$

Butterfly 		0.1 to 0.3 0.1 to 0.3 # $

Flap Diverter 		0.2 to 2.0 0.2 to 2.0 ### $$$

Rectangular

  • Opposed-blade louver dampers provide superior control of static pressure and volume for rectangular duct applications.
  • Increasing the number of opposed-blades between 2 through 6 generally improves flow control characteristics.
  • Parallel-blade dampers installed on centrifugal fan inlets divert gas thus reducing fan horse power and electrical power input.
  • Flap diverter dampers are designed to control flow during startup of waste heat equipment.
  • Positioning devices with analog or digital inputs are available to maintain reliable flow control on most damper configurations.
  • Feedback instrumentation is available to provide exact positioning data.

Options and Accessories

Dampers can be provided with a wide array of options and accessories designed to improve performance, automate operation, provide system feedback, increase safety or create redundancy for critical applications. The following is a sampling of devices to consider when specifying or purchasing equipment:

Materials of Construction

Dampers can be manufactured of many materials including carbon steel, stainless steel or nickel alloys such as Inconel, Hastelloy, Monel, fiberglass, etc. Matching the adjacent ductwork is the preferred approach. In some instances, internal refractory lining is incorporated in our scope of supply.

Drives

Dampers can be operated utilizing manual handwheels or actuator chain falls. Automated actuators include electric, pneumatic and hydraulic. Electric actuators can be supplied in all customary voltage requirements. Pneumatic and hydraulic actuators can be supplied with the necessary solenoids and accumulators. Damper control systems are designed to assume the closed, open or last position upon loss of source power or signal.

Positioners and Positioner Feedback

Control dampers require an input signal to position the blade(s) correctly. Signals are either electric (4-20 mA), pneumatic (3-15 psi or 3-30 psi) or digital. Positioners are a required accessory for controlling the location of the blades beyond full, open or close. Refer to the Engineering Design Data, Curves & Specifications on pages 15 & 16 for additional information on blade orientation versus flow or pressure drop.

Linkage

The styles of linkages are fixed and adjustable. Fixed linkage employs hardened steel pivots with thin-film PTFE (Teflon®) bushings. Linkage has lever arms pinned to the blade shafts. Adjustable linkages utilize turnbuckles to allow field re-adjustment of blades at operation temperature or over time.

Bearings

Bearings can be standard ball bearings, high-cycle ball bearings or adjustable UHMW (Ultra High Molecular Weight) and graphite sleeve bearings. Ball bearings are typically used when process temperatures do not exceed 500°F. Graphite sleeve bearings are ideal for 90 degree rotation and temperatures exceeding 500°F.

Packing

Packing glands are mounted separately from bearings to allow maintenance of shaft packings and eliminate improper loads on bearings or packing. The number of compressive bolts and packing gland material is dependant on the operating conditions. Other accessories to consider:

  • Limit or proximity switches
  • Position transmitters
  • Access doors
  • Electric enclosures
  • Conduit trim
  • Personnel guards
  • Lock-outs
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