Fan Inlet Air Velocity Profile and the Need for Carefully Designed Ductwork Systems


George Gamble, Consultant

The inlet air velocity profile of any surface installed mine ventilation fan is one of the most important factors to consider when designing the connecting ductwork from the mine shaft collar to the fan. Oftentimes deficient fan performance can be traced to poorly designed ductwork that adds unnecessary pressure loss and/or adversely influences the fan inlet air conditions (velocity profile). Such designs may lead to added power requirement, excessive vibration and noise, and reduced fan performance. Understanding the need for optimized inlet air conditions begins with discussing the process utilized when factory testing takes place during the development of the fan performance curve. Additional discussions include design considerations for the shaft collar connection, the connecting ductwork, and fan inlet. Illustrations of cost savings and pressure losses will be included for audience consideration. The design of ductwork for parallel fan installations on the surface is another issue that requires consideration. A preferred method will be illustrated. The selection of accessory components, such as self-closing doors, can also add to the potential for reduced fan performance. Several components will be discussed. An elementary presentation of the Air Movement and Control Association (AMCA) Standard 201 ‘Fans and Systems’ will be included to provide background for those audience members that want additional technical explanations of the need for a uniform inlet air velocity profile at the fan inlet.