How To Balance An Industrial Fan

For the most part, industrial fan balancing is an important and standardized production step. It involves adding or subtracting mass in a plane or planes on a rotor or impeller to bring the center of gravity closer to the axis of rotation. This procedure reduces fan noise and vibration during operation, which can lead to reduced motor life, bearing or belt wear, and power waste. 

The vibration may result in the full failure of the fan or other related systems in severe circumstances. This suggests that proper fan balance is critical for fan performance, safety, and maintenance. As the twenty-first century has progressed, and technology has advanced, the demand for industrial fans has increased, and the dynamic balancing of industrial fans has evolved. 

However, it is critical to first comprehend what an industrial fan is, along with the impacts and causes of an imbalanced fan, before we finally dive into how to balance an industrial fan.

What Is An Industrial Fan

An industrial fan is a piece of universal mechanical equipment that rotates several blades attached to a hub and shaft and is operated by a motor or turbine to provide and accommodate a huge flow of air or gas. Industrial fans are useful in various industrial processes and span across different industries. 

Industrial fans are mostly used in mining, underground engineering, power plant ventilation, workshop ventilation, boiler ventilation, air intake, atomic protection equipment, and chemical plant high-temperature corrosive gas emission. Fans are frequently employed to aid incomplete combustion, ventilation, and transportation, and they affect practically every sector of the economy.

What Causes Imbalances on an Industrial Fan?

If a fan was built correctly and ran nicely for a long time before suddenly displaying signs of being unbalanced, the cause could be something other than simple unbalance. It is important to examine for structural welds, worn bearings, or dirt caught in the fan’s crevices. Rain or a nearby water source can sometimes cause moisture to reach the fan, resulting in muck clinging to the blades. The following are some reasons behind the industrial fan’s imbalance:

1. Oxidation Of the Impeller

The surface of the impeller is quickly oxidized at high temperatures, resulting in a thick oxide coating. Because the bonding force between these coatings and the impeller’s surface is uneven, certain coats will break off due to vibration or centrifugal force. This is also a contributing factor to impeller imbalance.

2. Accumulation of Dust on the Impeller

Fans with hollowed-out blades can rust from the inside out. Unusual vibration in a fan might also be caused by loose fasteners or damaged welding. The most vulnerable are fan impellers used in mines, dusty workshops, and boilers. Particles in the air, such as dust, will adhere to the impeller blades over time, and these specks of dust are unlikely to adhere uniformly to the impeller, resulting in impeller unbalance. As a result, it’s critical to keep the impeller clean as much as possible. The impeller blade should be brushed and dusted regularly.

3. Wear & Tear of the Impeller 

Due to the high temperature and high speed of the flue gas, certain large dust particles and small particles will travel through the fan impeller, causing the impeller to wear out over time. As a result, the blade will wear and scratch as it exits the blade. The impeller must be balanced or changed at this time.

However, to address some of these issues, the fan must be dismantled and checked. If feasible, remove the rust or replace the blades. Drill microscopic holes in the blade tips to allow moisture to drain away from the body. Finally, multiplane dynamic balancing is used.

How to Manage the Industrial Fan Balancing

Multiplane balancing in the assembled form can enhance the imbalance and vibrational behavior of multiple bearing rotor systems. Weight modifications may usually be accomplished with the rotor in its original housing. In-place balancing is the process of balancing apart without removing it from the machine. This method avoids the need for time-consuming and costly disassembly. 

It also eliminates the risk of the rotor being damaged during removal, transportation to and from the balancing machine, and reinstallation in the machine. The fan can be balanced in several ways, including the following:

• Balance Mandrel
• Precision Shafting
• In-plane balancing (single and multiple plane dynamic balancing)

For the sake of this tutorial on how to balance an industrial fan, we’ll concentrate on Two-Plane Dynamic Balancing due to its numerous advantages. After completing the fan assembly, running it up to full speed, and trimming the balance, a two-plane balancing method offers better results.

What is Two-Plane Dynamic Balancing?

Two-plane balancing involves employing a pair of trial weights during the third run to find the effective static couple solution, assuming that the left correction weight is interpreted as the quasi-static correction weight located in the left balancing plane in addition to the right correction weight.

This means that a fan wheel is secured to a shaft hanging between two supports, bearings, an amplitude reader port on either side of the wheel, and an optical tachometer to determine the phases where the impact is highest during the two-plane balancing system. 

Once you have the data, you can determine where and how much to modify the weight to get the desired balance. How to balance an industrial fan involves three steps;

1. Measure the Amplitude.

The first step in balancing an industrial fan is to determine the imbalance using vibration amplitude. The two amplitude reader ports are used for this, one on the rear of each plane on each side of the fan wheel, and the other on the back of each plane on either side of the fan wheel. The ports detect vibrations as indicators of unbalance while the wheel turns.

2. Measure the Phase

The second step in balancing an industrial fan is to determine which phase or phases have the most substantial imbalance. This is accomplished by positioning a tachometer (tach reader) where it can be read using a laser along the fan shaft, with a tach strip marking the “zero degrees spot” on the 360-degree plane, and picking up the tach each time it crosses the corresponding zero degrees spot on the fan wheel’s outer rim of the wheel.

3. Determine the Needed Adjustments

The third step is to determine the adjustment. The readings are taken after each run after the amplitude reader ports, tachometer, and tach strip have been installed. Three initial runs are usually taken. The initial run is carried out with no weight on each side of the wheel. On the second run, a weight is attached to the left plane’s “zero degrees place,” and on the third run, the same weight is moved to the right plane’s “zero degrees spot.” 

The information collected from these three initial runs is now used by the balancing equipment to tell us where and how large the imbalance is. As a result, where to make modifications to restore balance is determined by either welding weight on or welding weight off (or grinding weight away 180 degrees across). And that’s how to balance an industrial fan in the shop in advance of assembly and field balancing.

Conclusion

The answer to the question of how to balance an industrial fan can be found in two-plane dynamic balancing. It not only makes it simple and affordable, but it also ensures accuracy and efficiency.