Understanding Fan Vibration and Imbalance

Posted by eliteinternet on February 10th, 2020

The issue lies with imbalance. Imbalance forms a potentially dangerous condition and can easily result in costly plant shutdowns. Engineers need to understand what it is and how to detect the problems so they can be better prevented. Detecting imbalance can save you a great deal of money and it is vital to clarify differences lying between imbalance and fan vibration. 

Difference between vibration and imbalance:

A fan rotor comprises of a riveted, welded or cast fan impeller, as constructed on the shaft. Even if the manufacturer takes care to locate the blades and weighing parts, the center of the weight is separated from the axis of rotation. This difference taking place between the rotational axis and weight center is stated as an imbalance.

The imbalance must not be stated as a function of rotational speed. So, you can assess and measure it when the fan is not operating. You can better detect the imbalance by multiplying the fan rotor’s weight by the radial distance between the axis of rotation and weight center. 

The time when vibration occurs:

Vibrations take place when the fan is operating and might have multiple causes such as imbalance. Some of the other causes behind fan vibration will be coupling misalignment, mechanical looseness, defective bearings, and even rotor cracks. 

Fan vibrations will further take place due to insufficient flatness of the surface region of bearing mounts, driver vibration, and even V-belt slippage. To determine the vibration in a fan rotor, some companies might even use a vibration signal box. 

Buildup on the blades:

Imbalances can begin because of operating conditions or the manufacturing process. Most of the fan rotors are widely used on wet scrubber systems, where the sticky and wet particulate matter passes through and adheres to the surface of the fan impeller. 

• Most of the time, this buildup is distributed evenly over surfaces which results in minimal imbalance. 
• If any piece of that built-up material flies off because of the centrifugal force, then a significant imbalance might take place.

During some instances, backward-curved fan blades have proved to be effectivein controlling the buildup, mainly on the preheater ID fans in the cement industry. The current backward-curved fan design needs to be selected carefully. If the blades come with too much curvature, then buildup might develop in the hollow pockets on the backside. These curved fan designs can be procured with steeply sloped blades to prevent this buildup.

To learn more about fan blades and vibration signal box, feel free to visit https://www.stiweb.com/.