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This article takes an in depth look at industrial fans and their uses.
You will learn:
An industrial fan is a highly efficient, heavy duty air flow device that is constructed from exceptionally durable materials and components to withstand stringent environments and operate longer to provide constant air flow and pressure. The strength of industrial fans is due to the materials used to manufacture them, which include ball or roller bearings, enclosed motor housing, continuous welds, and housings made of cast aluminum and stainless steel.
There is a wide range of uses of industrial fans, from cooling large commercial buildings to providing cooling for technical assembly operations. Regardless of the size of the workspace, air flow and circulation are critical to the health of workers and the efficiency of an application.
There are several types of industrial fans that vary in the amount of air to be moved, their motor, area to be cooled, and a variety of other factors. Though there is an endless number of fans, they break down into two categories, which are centrifugal and axial.
A centrifugal fan is like a blower and is an enclosed unit that functions like a pump. It pulls air in using a rapidly rotating impeller then pushes it out at a 90° angle.
An axial fan pulls and blows air parallel to its axis, causing the air to transfer axially outward. The amount of air flow and the fan design is determined by the fan’s blades, casing, and suction nozzle.
An air foil fan has flat standard blades and is used in cooling towers, engine cooling, and refrigeration. They can be set up for blowing or sucking with blades that can be set at different pitch angles to adjust air flow. Air foil fans consume little energy and produce very little noise.
Backward curved fans have a single thickness and curved plate blades that prevent dust build up and expansion along the blades‘ passages. The blades curve backwards from the inner edge to the outer edge relative to the direction of the rotation. The air flow is in a radial direction due to the impeller developing static pressure because of the longer blades. Backward curved fans have exceptional efficiency and are suitable for high pressure applications.
Backward inclined fans have simple flat backward inclined blades that do not interfere with the air flow. The blade design has a lower noise level and is energy efficient. They are designed for use in clean air and high temperature applications.
Radial blade fans have six to twelve flat blades that extend radially from the hub of the fan. The blades are narrow, heavy, and deep; this enables the avoidance of the accumulation of dust or sticky material on the blades. Since a radial blade fan does not accumulate dust or dirt, it is ideal for high pressure dust loading applications. Impellers for a radial blade fan can be paddle wheel, open wheel, backplate wheel, or steel plate designs, and they produce medium air flow.
Radial tipped fans deliver static efficiency without material build up on the impeller due to the rapid movement of particulate matter and dust. They have a rugged design, which makes them suitable for high volume air flow at moderate to high pressure. They are normally used with baghouse dust collectors, scrubbers, and cyclones.
Paddle wheel fans are a multipurpose type of fan that is used for high temperature applications and material handling. They have heavy, deep radial blades and a compact housing able to meet the needs of high pressure applications with satisfactory efficiency. The blades are equally spaced and extend perpendicularly to the rotation of the wheel.
Forward curved fans are referred to as squirrel cage fans and are used for residential and light commercial HVAC equipment as well as low to medium static applications. The housing of a forward curved impeller converts high velocity air, leaving the tips of the impeller blade with a lower velocity static force to direct the air flow to the outlet. It can have a housing type that is referred to as scroll, volute, or sirocco. A forward curved impeller installed in a scroll housing is called a forward curved blower.
High temperature axial fans are designed to operate in conditions where the temperature reaches 100° C (212° F). They are specially engineered for applications that operate at significantly high temperatures, and they have a thermal protected external rotor capacitor induction motor. The definition of a high temperature fan requires that it be able to operate at temperatures that are 30% higher than the standard fan. They are used to circulate air in ovens, machinery, and enclosed equipment.
A tube axial fan has a disk type impeller contained in a cylindrical enclosure. The impellers are made of cast aluminum, steel, or stainless steel, materials that are capable of withstanding high temperatures. The blades are welded to a hub at angles varying between 30o and 50o and are precision balanced to ensure smooth operation. The performance of an axial fan depends on the design of the impeller and the housing; this is true of most industrial fans.
A vane axial fan is a disk type fan in a cylinder with air guide vanes positioned before or after the impeller. They are capable of operating for long periods of time even when exhausting smoke and have a high temperature motor and motor cooling system. Their blades are made of steel with balanced corrections and a control box for remote control. Vane axial fans have high temperature resistance, a balanced flow, and little to no vibration.
Variable pitch industrial fans are axial fans with adjustable impeller blades that are built to operate in a variety of fan applications. The design of the fan allows for the changing of the blade angle while the rotor is in motion. Variable pitch fans come in single and double stage varieties with single stage fans having one propeller and double stage fans having two propellers. The change of pitch in a variable pitch fan is accomplished by the hub spring, diaphragm, blade shafts, rotary air joint, and valve positioner.
Wind tunnel fans are designed to move huge volumes of air in a wind tunnel. They are made of stainless steel, steel, and coated carbon steel. The purpose of wind tunnel fans is for industrial and scientific testing of a product's endurance. They are designed such that they can be adjusted to provide low air flow at high velocity or high air flow at low velocity.
Though the traditional use of wind tunnel fans is for testing purposes, they are also used for recreational applications like indoor skydiving.
Industrial cooling fans are made of heavier and more durable materials. They are designed to cool people and equipment in industrial operations. The main concern and reason for the use of cooling fans is to reduce the potential stress on workers that are exposed to high temperature conditions. They are an axial type of fan capable of moving large volumes of air for spot or general cooling at construction projects, warehouses, and assembly operations. Industrial cooling fans work on the principle of high air volume and low speed to deliver a continuous amount of cool air.
Of the two forms of duct fans, inline duct fans are the more powerful and are designed to remove heat and humidity from grow tents and rooms. They are designed to cool and vent large areas and volumes of space. Inline duct fans are used with flexible tubing, silencers, and carbon filters and require an Electrically Commutated (EC) motor to achieve the greatest efficiency. Their mixed flow impeller helps to reduce noise and allows them to operate in high static pressure areas. For assistance to an air conditioning system, they are installed near the end of a long stretch of duct.
Every industry requires some form of air flow system to ensure the health and welfare of its workers. The designs and varieties of industrial fans provide the opportunity to select a fan that perfectly fits the conditions where air flow is required for comfort and safety.
Industrial fans move and push air in enclosed spaces, replacing stale, contaminated, and stagnant air with fresh, comfortable air. The size of an industrial fan depends on the environment where it will be used and its Air Movement and Control Association (AMCA) classification.
Exhaust industrial fans, also referred to as blowers, are designed to create air flow using blades, a hub and shaft, and motor. They are capable of reaching flow rates of 200 cubic feet to 2 million feet per minute. The defining factors for industrial exhaust fans are their construction, materials, and different gauges. Industrial exhaust fans can be used to create suction, pressurization, cooling, combustion air, forced ventilation, and exhaust ventilation.
A specialized type of exhaust fan is a UL 793 smoke and heat vent fan that are used as part of smoke control systems. These specialty fans can be blast power roof ventilators or hooded exhausts and come in a variety of configurations. UL 793 smoke and heat exhaust fans are used in restaurants for grease exhaust.
In-line duct fans have small airflow capacity and are non fire rated. They are used where air flow is too low for a centrifugal fan and too high for a propeller fan. In-line duct fans have a flow rate of up to 2000 m3 per hour. The impeller and casing for in-line duct fans are made of lightweight plastic, which makes them easy to install and do maintenance. They are a round long cylinder with an operating temperature of 40o C and a diameter of 300 mm or less.
Industrial fans are widely used in the agricultural industry as a method for creating airflow in livestock barns, dairy farms, and greenhouses. They provide condensation in stale areas as a means of decreasing the effects of birds and insects.
In greenhouses, industrial fans help the blooming of flowers by modifying the temperature and humidity as well as creating a suitable climate for growing. They are capable of moving high volumes of air with low pressure to equalize temperature. In the summer, industrial fans reduce the amount of condensation in greenhouses while in winter they help keep crops warm with heat exchangers.
Fresh air is a critical part of cattle breeding and animal enclosures. Industrial fans remove pungent odors and exhalations improving the environment for cattle, and help in increasing production and reducing the potential of diseases.
Cement making requires a variety of processing fans that have resistance to abrasion and dust build up and are capable of operating in high temperature applications. Fans for the cement industry include pre-heater exhaust, kiln induced draught, raw mill exhaust, cooler, forced draught, and mill exhaust fans.
Fans for the auto industry must be durable, easily maintained, and exceptionally reliable. In January 2003, legislation was passed requiring that workers be protected from explosions in their workspace. Workers in the auto industry have an increased chance of exposure to such conditions. Fans for the industry are designed to operate safely in hazardous and explosive atmospheres.
Operations in the chemical industry involve the handling and use of hazardous and flammable substances and materials that require proper and safe storage. An essential part of their storage is sufficient and adequate ventilation that is provided by specially designed industrial fans. The correct placement of industrial fans keeps chemicals cooled and avoids the buildup of hazardous fumes.
Industrial fans for the oil and gas industry are designed to perform in the harshest and most severe conditions. They are made of exceptionally durable materials with welded flanges and components that provide resistance to weathering, abrasion, moisture, and other potentially harmful atmospheric elements. For extra protection, fans for the oil and gas industry undergo a coating process.
The power generation industry uses forced draft, induced draft, and dust control fans that are required to operate at extremely high temperatures. The construction of power generation industry fans includes the application of heat resistant paints and coatings and the inclusion of specially designed bearings. Due to the particulate content in the air stream from power generation facilities, fans are designed with self cleaning impellers.
Industrial fans for a gymnasium are wall mounted, which gives them greater flexibility and the ability to adapt to the gym layout. They are strategically placed to offer sufficient circulation to the available space. Most gyms have limited floor space since equipment or floors are used for physical activity. It is for this reason that gym fans are wall mounted; this also keeps athletes from being uncomfortable. A major factor considered when installing an industrial fan in a gym is the size of the room. In most cases, multiple small volume fans are the best option.
Industrial fans are used in conveying systems to move cereal, grains, wood chips, and powdered materials. The process of pneumatic conveying is used by the food, mineral, plastics, coffee, and pharmaceutical industries. All bulk materials can be pneumatically conveyed using an abrasion resistant fan. Pneumatic conveying systems require that industrial fans be made of durable alloys that have special linings and coatings for protection and safety.
The industries listed here are only a few of the many that rely on high quality and reliable industrial fans as a part of their operation.
The many types of industrial fans require specific components to fit the application for which they are going to be used. Essential to fan construction is durability and the capability of withstanding use in demanding stressful conditions. Designers and engineers carefully select the proper materials to perfectly fit the conditions for which a fan is made.
Industrial fans are designed to circulate air in warehouses, factories, large open buildings, and other applications that would become stagnant or stale without air movement.
The motor of an industrial fan can be direct drive and connected to the impeller or be indirect where the impeller is belt driven. Motors for industrial fans are typically alternating current (AC) and include windings, bearings, and other components. The frame for the motor is designed to contain and protect the internal parts of the motor and dissipate heat. For hazardous and potentially explosive conditions, the motor may be designed to be explosion proof.
In direct drive industrial fans, the impeller that holds the fan blades is connected directly to the motor. In the case of a centrifugal fan, the impeller can be driven by a belt or direct drive and is enclosed in a housing or drum. The impeller is the most important part of an industrial fan since it holds the blades.
The fan blades are a crucial component of the fan and determine the fan's effectiveness. Blade profiles can be forward, backward, radial inclined, curved, and tipped. Depending on the application and design of the blades, they can rotate forward or backward. The blades pull the air in and push it out as they spin. The blade profile determines the efficiency of the air flow and the volume air the fan can move.
The housing contains the impeller and the fan blades and is the part of the fan through which the air flow will pass. When air enters the housing, its structure compresses the air; this increases the air‘s speed. Two factors, the housing and impeller, are the essential factors in determining the performance of an industrial fan.
There is a wide variety of mounts for industrial fans that vary according to how the fan will be used, the volume of air to be moved, and several other factors. Common mounts are floor and wall; floor mounted fans can sit directly on the floor on metal legs or can be on a post or pole. Wall mounted industrial fans can hang from the ceiling, off the side of a wall, or be secured in a corner. The placement and type of mount depends a great deal on where the fan needs to be positioned for its purpose.
Duct, conveyor, and material moving fans are located where they will be most efficient and effective for the process. Fans that are part of enhancing air movement in a dust system or are part of the movement of raw materials have a unique design and are engineered into the application.
Belts and pulleys are included in indirect drive fan motors and are part of the transmission. They are a critical part of the operation of the fan and have to be carefully chosen to meet fan standards. The motor is mounted on the housing and the belt or pulley extends from it to the impeller pulley.
It may seem that industrial fans and industrial blowers are the same since they are both designed to move air. In reality, there is a distinct difference between them, which includes how they move air, where the air is directed, and the pressure they create.
The first distinction is how a fan and blower move air. A fan uses a rotor and blades to move the air around it, such as in a warehouse or other open space, to increase flow and air movement. A blower is a directional air movement tool that is pointed in a single direction and creates a flow of air in that one direction.
The next difference is their construction. A fan is axial and uses its blades, rotor, and motor to move air along its axis in multiple directions. A blower is radial and uses a centrifugal powered unit with impellers to move air radially. Additionally, fans are much smaller and use less energy than blowers.
In regards to air pressure, a fan has an air pressure ratio of 1.11 between the pressure at which air enters and leaves the fan. The ratio for a blower is between 1.11 and 1.20 with a pressure rise between 1136 to 2066. The pressure rise for a fan is 1136.
The key factor in the construction of an industrial fan is the type of metals and materials used to produce them. The choice of materials affects the weight, cost, sanitation, durability, maintenance, and appearance of the fan. The factor that determines the types of materials is the application for which the fan is designed.
Caustic conditions, high operating temperature, and explosive environments all play a part in the selection process. The common types of metals include various grades of steel, stainless steel, nickel alloys, titanium, monel, and aluminum.
Aluminum is used for the manufacture of the critical components of fans such as the housing and wheel. Spark resistant construction (SRC) is a standard of the Air Movement and Control Association (AMCA) when dust, fibers, gases, vapors, or liquids are present and may cause explosions. Aluminum falls under the classification as a SRC material.
The characteristics and properties of stainless steel make it ideal for fan manufacturing. Austenitic stainless steel grades 304 and 316 are the most used in industrial fan construction. With the addition of molybdenum and titanium, stainless steel‘s resistance to corrosion and high temperature applications is enhanced.
Added to stainless steel‘s corrosion and high temperature resistance are its ductility, strength, hardness, low maintenance, and exceptional appearance.
The Air Movement and Control Association (AMCA) is an organization that originated in 1955 with the combination of the National Association of Fan Manufacturers (NAFM), the Power Fan Manufacturers Association (PFMA), and the Industrial Unit Heater Association (IUHA). The goal of the association is to develop standardized methods for the certifying and classifying of heating, ventilation, and air conditioning equipment.
The AMCA is a not for profit organization whose membership is voluntary. The majority of reputable fan manufacturers belong to the association and adhere to its standards. An AMCA certification can be achieved by testing a fan following the approved methods of the AMCA. Once the test standards are met, an AMCA certification label can be placed on a fan.
In the area of Spark Resistant Construction (SRC), the AMCA has three standards:
This is a small sampling of the standards that the AMCA publishes. They have a wide variety of publications, testing requirements, and other methods for determining the class of a fan. All manufacturers are aware of the standards and use them as a means of determining the correct fan for an application.