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Selecting the correct industrial fan for your pneumatic system is critical to success. The more complex the air system, the more difficult selecting the correct industrial fan becomes. Add in the variable of multiple operators on a given pneumatic conveying system, and it becomes apparent that a safety factor for the fan efficiency to generate sufficient airflow is preferred. So how is this accomplished?
There are generally three methods to control your industrial fan’s volume output. Each has its advantage, however when thinking in terms of pure energy efficiency, there is a clear pecking order.
The First Method to Fan Efficiency
The first and typically cheapest to implement is an outlet damper, actuated manually, electrically, or pneumatically. While this usually represents the lowest capital cost of air volume control, it is also least efficient. That said, there are cases where outlet damper control is necessary for optimal system performance, regardless of fan efficiency.
The Second Method to Fan Efficiency
The second method involves the use of a damper on the intake side of the industrial fan. This can be done directly on the intake opening with an internal or external variable inlet vane (VIV) designed to pre-spin the air in the direction of wheel rotation, or through the use of an inlet box where a damper is mounted to the intake of this box with vanes set to pre-spin the air similarly to the VIV. These can also be actuated manually, electrically, or pneumatically. While this method has greater capital cost as compared to the discharge damper, the advantages include better system control and lower energy costs.
The Third Method to Fan Efficiency
The third method of volume control – operate the industrial fan motor with a variable frequency drive (VFD). With the cost of VFD’s becoming more reasonable, return on investment has improved. This method is the most energy efficient way to control your fan’s volume. It gives you full control of your fan’s potential.