DSS247: Understanding Fans and Blowers for Industrial Applications with Chet White

In today’s episode of the Dust Safety Science podcast, we’re discussing fans and blowers for industrial applications. Joining us is Chet White, the Sales and Marketing Manager from AirPro Fan and Blower Company. Chet, who operates from Cody, Wyoming, brings a wealth of knowledge about fans, boasting extensive experience in the field. He has a background in engineering, systems testing, and application engineering and has dedicated over 12 years to his work with AirPro Fan and Blower.

Intro to Fans and Blowers in Industrial Settings

“We have three plants in Rhinelander, Wisconsin, and so we have our own dust collection line and our fans [are] the source of the energy to move that air,” Chet explained. “So in a basic sense, we’ve got 30 to 50 weld stations set up in our factory. We have lines that come down. As our welders are welding, they need that fume that’s coming off of their welders sucked away, so they have hoods that come down. Our fan is basically providing the energy to suck all these fumes from all these various ports or points.”

He said that the reason for choosing a centrifugal fan over the more commonly known axial fans, like those in windows or on ceilings, is due to its unique functionality. Axial fans move air in a linear path, where air enters and exits in the same direction. In contrast, a centrifugal fan alters the air’s direction, making it a more potent machine.

This capability is crucial in certain applications, particularly when evacuating gas from various sources. These setups often involve extensive ductwork with numerous pick-up points, bends, and dust collection systems, creating significant pressure challenges. A centrifugal fan, with its higher power, is adept at handling these additional pressures, something a typical household fan is not equipped to do.

Pneumatic conveying systems operate at pressures even higher than those in standard baghouse applications. Consequently, the fans used in these systems are typically larger in diameter but narrower in width. While they don’t move a large volume of air, they must push air through very tight pipes, which requires significant pressure to convey even a small amount of air.

“At AirPro, we often refer to the fan as the “heartbeat” of the system, a metaphor everyone can understand since everyone has a heart,” Chet said. “Just as no part of the body can function without blood being pumped to it, the fan plays a crucial role in these systems. While there may be other more expensive components in the system, none of them can operate effectively without the gas being conveyed by the fan. This makes the fan an essential and central part of the system’s functionality.”

What is the Difference Between a Fan and a Blower?

Essentially, the terms ‘fan’ and ‘blower’ can be used interchangeably. However, for clarity, a fan is typically viewed as a device primarily used for moving air. On the other hand, a blower is more often associated with creating and handling higher pressures, particularly in transporting gas through environments with substantial pressure.

A blower is usually connected at the outlet of a fan, which aligns with the concept of a blower exerting energy outward. In most cases, blowers are designed to draw in fresh air and equipped with filters or silencers at their inlet to mitigate noise. The high-pressure aspect is handled at the outlet.

This design serves two main purposes. Firstly, having the fan blow into a high-pressure system, rather than drawing from it, is more efficient. Secondly, this approach reduces stress on the bearings. When a fan is set up to suck from a high-pressure system, there is a significant force trying to dislodge the wheel from its shaft. Therefore, placing blowers on the forced draft side of a system, where they blow into a high-pressure environment, is more effective and mechanically sound.

What Should Be Considered When Choosing a Fan for a System?

In dust collection applications, the static pressure isn’t typically extremely high. Generally speaking, these systems have a static pressure ranging from 5 to 20 inches, with 40 inches being on the higher end for dust collection. These setups often require a larger volume of air since they draw from multiple ports. Therefore, selecting a high-efficiency fan is crucial due to the energy costs involved.

Placing the fan within the system, particularly before it reaches the baghouse, means it won’t be handling clean gas. From the perspective of fan placement, it’s important to consider a location where the fan will only move clean gas to achieve the highest efficiency. If the fan is situated in-process, where it encounters unclean gas, its maximum static efficiency tends to range between 65 to 70%. Conversely, positioning the fan on the clean side, where it only deals with clean gas, can increase its static efficiency to between 75 and 81%. This difference in efficiency can lead to significant electrical savings.

Will Fans Experience More Wear and Tear If They’re Not on the Clean Side?

“Depending on the abrasive properties of the dust that’s moving through, if you run material through a product, you will wear it out faster,” Chet said. “So we see fans that were manufactured in 1960, 1970 that are still in operation on the clean side today. I personally have never seen a fan that’s conveying material last longer than about 20 years. I mean, guess it could if you really build up the blades with abrasive resistant properties, but that’s very expensive as well.”

What About Design Requirements?

Particle size plays a crucial role in fan systems, especially when handling long, stringy materials that can easily jam. To prevent this, it’s often necessary to use a reducer, such as a shredder, to limit the size of materials entering the fan. This is particularly important in systems with higher pressures and lower volumes, where there isn’t much space between the fan blades. Large particles can get wedged in the blades, causing imbalance and potentially leading to severe malfunctions.

Another consideration is the abrasive nature of the materials being processed. The impact on the fan blades varies depending on the size and type of material. For instance, processing large chunks of material, like two-inch squares of aluminum from car manufacturing lines, requires robust fan blades, often made three-quarters of an inch thick and reinforced with materials like chromium carbide. This preparation is essential for withstanding high-impact scenarios. In contrast, continuously moving fine abrasive materials, such as sand in a blast booth, can cause faster wear due to the constant erosion spread across the blade surface.

When designing or selecting fans for these applications, identifying and reinforcing high-wear areas is vital. This includes using abrasion-resistant materials for the blades, either manufacturing them entirely from these materials or applying a protective liner. Additionally, the fan housing itself should be examined for wear points, which can also be fortified with wear-resistant liners to enhance durability and longevity.

What Are Key Maintenance Considerations for Fans?

To extend the lifespan of your fan to twice its standard duration, it’s essential to closely monitor two aspects: temperature and vibration. There are various temperature detection devices available, which primarily focus on the bearings of the fan. These bearings are crucial indicators of the fan’s overall health as they hold the wheel in place. You’ll find bearings either on the motor or on the fan shaft, particularly if the motor is connected through a drive assembly distant from the fan. Monitoring temperature is crucial. If the bearing temperature exceeds the grease’s rated temperature or deviates significantly (by about 20 to 50°F) from the normal range, it’s a sign of potential issues that need immediate attention to prevent premature and catastrophic failures.

Vibration is the second key factor. Fans operating within the vibration specifications set by the manufacturer tend to have a longer lifespan. Constant operation at or near the shutdown point on the vibration tolerance chart can accelerate fan failure. Different types of vibrations indicate specific problems: vertical vibrations suggest issues with the connection to the floor, necessitating a check of foundational bolts. Horizontal vibrations often point to an unbalanced wheel, requiring balancing. Axial vibrations along the fan shaft could indicate insufficient foundational support.

Regularly monitoring both vibration and temperature provides valuable insights into the fan’s condition, indicating areas needing maintenance or improvement to enhance its longevity. These measures are particularly crucial in material handling applications. While clean air applications might require less frequent visual inspections, barring unexpected incidents like foreign objects passing through the system, material handling applications demand more regular checks. Periodic inspections every few months, including checking the blades, noting any wear patterns or cracks, and ensuring the wheel’s integrity, are vital to prevent severe damage or breakdown.

What Other Features Should Be Included in Fan System Designed?

The fan is a critical point in any system, especially regarding the potential for ferrous materials to come into contact. Inlet cones, which are placed at the entrance of every fan, are a prime example. We recently inspected a site and observed the gap between the inlet cone and the wheel, typically about a quarter inch. If both the cone and the wheel are made of carbon steel, there’s a risk of them rubbing together. This is a concern particularly when handling highly combustible dust, as friction between ferrous materials can create sparks and potentially cause an explosion.

While a properly installed fan with all bolts securely tightened greatly reduces this risk, it’s not entirely eliminated. In environments with combustible dust, it’s advisable to use fans rated for spark resistance. In the United States, these ratings include AMCA C, AMCA B, and AMCA A. Internationally, there are other specific ratings. AMCA B and AMCA A relate to the gas moving through the fan, different from explosion-proof ratings for external components like motors or other instruments attached to the fan. Explosion-proof ratings are based on the fan’s external environment, while internal ratings like AMCA B and AMCA A consider the fan’s source and destination of airflow.

In terms of these ratings, AMCA C is the basic level where non-rotating components close to the rotating wheel, like the inlet cone, must be made of non-ferrous materials. This includes a rubber ring inside the backplate of the housing and non-ferrous materials for shaft seal holders. AMCA B requires the rotating part, the wheel, to be made of non-ferrous material. Finally, AMCA A stipulates that the entire gas stream path must be composed of non-ferrous materials. These ratings are designed to minimize the risk of ferrous materials coming into contact and generating sparks that could lead to an explosion.

Conclusion

It’s clear that fans and blowers are more than just simple air-moving devices; they are vital elements in industrial processes and require careful consideration and expertise in their implementation and upkeep. Thanks to Chet White’s extensive knowledge and experience, listeners can now have a deeper understanding of an often-overlooked yet fundamental aspect of industrial safety and efficiency.

If you would like to discuss further, leave your thoughts in the comments section below. You can also reach Chet White directly:

Email: [email protected]
LinkedIn: https://www.linkedin.com/in/chet-white-41877b46/
Website: https://airprofan.com/

If you have questions about the contents of this or any other podcast episode, you can go to our ‘Questions from the Community’ page and submit a text message or video recording. We will then bring someone on to answer these questions in a future episode.