Mr. Prasad Rao Kotagiri, Managing Director, Reitz India Limited attended FL Smidth Suppliers' Conference held in Copenhagen, Denmark during November, 2015.Monday, 30 November 2015 07:55 Written by Neel Rao
You would have come across many fans like Pressure Blower, FD fans, ID fans, Raw Mill fans, Flue Gas Recirculation Fans etc. They are all technically centrifugal fans having different names and serving different purpose in the industry.
Centrifugal fans displace air radially, thus diverting the direction of air by 90 degree. At a constant speed of fan, centrifugal fan will move constant volume of air and not constant mass of air. Hence it is called as constant volume fan. This can be achieved from centrifugal fans with different construction and design.
Depending on the industrial requirements of airflow rate, volume, and pressure centrifugal fans have been customised to serve industry. Centrifugal fans are named as per the function served by them. They are often referred with different names based on the industrial process they support. While the technical functionality of these fans is same, the design element is changed to support several industrial processes.
An Industrial building is often a closed building. We want an environment inside the building to be comfortable. There are various types of industrial processes going inside the industrial building. These different processes can make the temperature inside the building higher. This extra heat has to be vented out of the building using an external equipments like fans, louvres, gravity vents, heaters.
When a centrifugal fan is to be installed for any industrial process, the airflow requirement has to be determined before considering different fan arrangements to accomplish the desired performance. Fans typically work better when they have optimal size that fits ideally in the designated area, placed in the right location to withstand the operational conditions and have proper drive method to modulate the speed. When considering different centrifugal fan arrangements, the motor will have various placement settings with respect to the drive side of the fan. The fan can use different drive methods, depending on whether the motor is independent of the fan as in belt drive arrangement or motor connected directly to the fan axle or shaft as in direct drive configuration.
The size of the industrial fan is often overlooked when selecting a fan system for a new or replacement industrial application. Generally, industries use oversized fans to accommodate for uncertainties of future requirements. While some moderate oversizing is typically acceptable, choosing an excessively large equipment than the actual system requirement should be avoided. The size of the centrifugal fan should be optimal to the anticipated normal demand where it can operate at maximum efficiency for a given volume of air. Proper sizing of the fans involve determining all aspects of fan efficiency including airflow requirement and system effects at the fan inlet and discharge.
Excessive noise of a fan system can be a serious concern in industries. Higher noise levels caused by the fan systems can disrupt the productivity and cause nuisance to the working environment. The noise generated could be due to the turbulence effect at the fan blades or rotation of the fan shaft or motor. Typically, the noise produced by a centrifugal fan system is dependent on various factors including the fan size, airflow rate and pressure. Fan systems that work at optimum efficiency produce lower noise levels than the fans with inefficient operation. Using over sized fans for industrial applications or operating fans at higher speed produce vibrations, causing higher noise levels. The sources of noise in a centrifugal fan could be due to airborne or structure borne vibration levels. To identify where the issue is being produced and suggest solutions for specific noise issues, it is essential to understand the sources causing the problems.