In the optimal application, your inlet duct will have a long, straight pathway into the fan. The recommended length is as much as five to eight times the diameter of your duct. In the real world, it often is simply not practical or even possible. Fortunately, there is a next best option to create the runway the air needs on its way into your centrifugal fan – an inlet box.
The Best Way to Do a “Bad Thing”
An inlet box allows for a 90-degree turn close to the fan inlet to pull the air from any direction. This becomes necessary in many instances where space is tight and access is constrained. Considerations include facility size and layout, other equipment and machinery, need for access, and positioning of ductwork.
If you determine that an inlet box is necessary, you still have some additional choices to make. Which direction will the air be coming from? You can rotate the inlet box in basically any direction. Choose the most direct route for the air to enter the 90-degree turn into the box. You may also use an inlet box that contains a diverter to evenly distribute the air as it goes into the fan to minimize the impact of the quick turn on the performance of the fan.
Demonstration Video: When to Use an Inlet Box with your Centrifugal Fan
Senior Application Engineer Chet White recently shared how to determine the need for an Inlet Box in your industrial fan application via AirPro’s YouTube Channel. You can watch the 1½ minute video here.