Frequently Asked Questions

What is the control range for a control damper?
The effective control range for a volume control damper is between 20 degrees to 70 degrees. A damper does not control flow well as it approaches the full closed position and the full open position.

Can stuffing boxes (shaft seals) be added to a counterbalance or pressure relief damper?No. Stuffing boxes add a great amount of friction torque to a damper. The high torque requires high pressure to open the damper. Once the damper is open, it will not shut again unless counterweights are added to close the damper. The added weights increase the amount of pressure required to open the damper, which further decreases the performance. It's best to use a motorized damper when stuffing boxes are required.

Can counterweights be placed on the blades?
This is done on the BD-40 and BD-41 dampers, but cannot be done on our dampers with end pivoted blades. This question generally comes up because of space restrictions. There are a number of creative ways to counterbalance a damper to get around most space restriction problems without putting weights on the blades. Discuss your application with the factory for the best method.

Can the rotation of an inlet vane be changed in the field by turning the vane over?
No. Flipping an inlet vane over does not change the rotation of the air as it leaves the vane. Inlet vanes are built for either CW or CCW fan rotation at the shop. Once the vanes are built, the rotation can only be changed by rebuilding the vanes.

Can seals be added to an inlet vane?
Seals can be added to an inlet vane, but leakage is only reduced to approximately 7 to 10% of typical flow rates. An inlet vane is designed to pre-spin the air entering a fan and is not intended for isolation. If low leakage is required, an isolation damper should be added to the system.

What standard seals are available for AWV products?

What is a figure 5.2, 5.3, 5.4, and 5.5 curve?
The curve numbers refer to AMCA Standard 500-D-98 test set-ups.

-Figure 5.2 is for a test with the damper mounted on the exhaust end of a duct. The pressure drop shown on a curve for a damper tested per figure 5.2 includes the damper loss and an exit loss.
-Figure 5.3 is for a test for a duct mounted damper (duct work on both sides of the damper). The pressure drop shown on a curve for a damper tested per figure 5.3 is the damper loss only.
-Figures 5.4 (intake) and 5.5 (exhaust) are for plenum-mounted dampers. Since no ductwork is involved, pressure drop curves for dampers tested per these figures include an entrance loss, damper loss, and an exit loss.

Can we provide a pressure drop curve for an inlet vane?
No performance curves are available for inlet vanes. Inlet vanes are used to pre-spin the air entering the fan inlet. The pre-spin reduces the amount of horsepower required by the fan to move a given volume of air. The same size inlet vane will perform differently on different fans. This makes it impractical for us to provide a performance curve for an inlet vane, as each vane would have to be tested on the fan for which it would be used.

Does an airfoil blade have less pressure drop than a single thickness blade?
At high velocities an airfoil blade has lower pressure drop than a single thickness blade. At low velocities (1000 fpm or less) the difference in pressure drop between the two blade styles is slight.

Can AWV make bubble tight dampers?
We can make bubble tight dampers. These dampers are for two-position applications only and the air must be free of particulate.

What are some of the different leakage classifications and the allowable leakage for each classification?
The leakage rates for various standards are given in the tables below. When specifying a leakage class, we need to know which specification is being used (i.e. UL555S, ASME N509-1989, etc.). Specify the highest leakage class that is acceptable for the application in order to keep costs low.

What Nema ratings are available on actuators?
Nema ratings apply only to electrical equipment. Pneumatic actuators do not have Nema ratings. Electrical actuators are available in Nema 1 (General Purpose - Indoor), Nema 2 (Drip-proof - Indoor), Nema 4 (weather-resistant - Outdoor) and Nema 7 (explosion proof). These are the most common housing ratings for electrical actuators. Other Nema ratings are available from some actuator manufacturers, but these are typically only available as an option and for a higher cost.