The Inlet guide vanes regulate the flow of centrifugal fans in order to adapt the same to different operating conditions of the plant. The management of the flow by a simple damper is an inexpensive method but rather ineffective about the energy consumption. The inlet guide vanes are much more effective because the correct conformation of the adjustable vanes reduce the load losses and, accordingly, the impact on the air flow characteristics of the fan in the inlet to the impeller. As previously mentioned, these must be installed at the inlet and to reduce the load loss is recommended the installation of a nozzle in a protected entry. Alternatively, the direction of the pre-whirl must always be positioned in the direction of rotation of the fan.
Comparing the dampers regulators, the first result in improved control. Depending on the position of the blades, the controller generates a pre-whirl with changes in the performance of the fan curves. The power required by the fan can be adjusted by varying the angle of inclination of the blades. The direction of the pre-whirl must always be the same of the direction of rotation of the fan.