Heavy Duty Centrifugal Fans Used in Industries

In many large scale industries centrifugal fans of high capacity provide optimal and cost effective solutions to deliver high pressures of airflow for various process applications. Generally, to get the desired high pressure and volume outputs, industries install two or more centrifugal fans in the series or parallel combinations. Sometimes, the option of multiple fans in the industries, may not be feasible due to limited availability of space in the working area. Hence to meet the demands of large scale applications in industries, a single heavy duty centrifugal fan can be used with high power rating. There are mainly two types of heavy duty fans that are widely used in industries, namely double inlet centrifugal fan and multistage centrifugal fan.

Double inlet centrifugal fans

The primary function of double inlet centrifugal fan is to provide large movement of airflow in the industrial process. These are custom made heavy duty fans that can sustain extreme operating conditions and handle different types of gases in any process plant.

• Working

Double inlet centrifugal fans have two separate inlets and one common outlet. These type of fans are used for high volume outputs. The air/gas to be handled by the fan enters through two inlet boxes that are flange mounted to fan inlet side or directly welded to the volute casing. Inlet boxes are also provided with dampers to control the downstream of the air coming into it. Then the air/gas flows to the impeller mounted between bearings inside the volute casing, where both the air streams join together and come out through the common outlet.

These type of fans are usually large in size than the standard regular fans, but deliver good results in terms of output.

• Applications

> Cement industry: In cement industry double inlet fans are used to obtain flow rates of above 10,00,000 m3/h. Some of the process fans like raw mill fans, mill fans, filter fans that are used in the cement industry use double inlet centrifugal fans. The reason behind using a single double inlet fan to handle the entire process in cement industry is to reduce the power consumption, which is more when two individual fans are used.

> Power plant industry: In power plant industry burning coal requires high amount of air/gas. For a large capacity plant, the demand for the supply of air/gas quantity will be more. To ensure proper running of various processes in power plant industry, double inlet is used in forced draft fans.

Multistage centrifugal fans

Many industries have high pressure requirements for process and they use two single stage centrifugal fans to get the desired output. Even increasing the diameter of impeller blades of these individual fans will impact only 10 to 20% on the pressure. So for high pressure airflow requirements, many large scale industries use multistage centrifugal fans.

• Working

Multistage centrifugal fans use two impellers on a single shaft. These two impellers are joined by a tube, which helps in air/gas to flow from first impeller to second impeller. At first, the airflow enters the first impeller, gains some pressure and this again gets redirected to the second stage of impeller where it gains some more pressure and leaves the system radially. Multistage centrifugal fans give approximately 50% extra pressure up to 1.7 bar pressure than the regular fans.

• Applications

> Chemical Industry: Multistage centrifugal fans with high energy air/gas output are widely used in chemical industries as high pressures are required to evaporate fluid or water content in chemical substances. Apart from this, these fans also find applications in other high pressure process requirement industries like cement, power plant, wood & paper etc.

Most of the heavy duty centrifugal fans are custom designed in various sizes using high strength materials, to withstand corrosive gases, abrasive elements and high temperatures in diverse industrial applications.

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