Centrifugal fans and fan systems used in industrial HVAC applications can fail in many ways. To fix failures it’s useful to know what causes them. Engineering manager Marcel Kamutzki from fan and blower manufacturer Daltec Canadian Buffalo Manufacturing Ltd. in Guelph, Ont. detailed five malfunctions and their symptoms during a workshop for maintenance pros in Hamilton. 1. Fan is too noisy. When an impeller hits the inlet or housing, it’s likely not centred; the inlet or housing is damaged; the impeller is crooked or damaged; there’s a loose shaft or loose bearing; a shaft is bent; or there’s a misaligned shaft and bearing. If the impeller is hitting the cut-off, the cut-off is not secure in the housing, it’s improperly positioned, or it’s damaged. There are numerous causes if the problem is the belt drive: the sheave is not tight on the shaft; the belts are hitting the belt tube; belts are too loose or too tight; belts have the wrong cross section; belts are not matched in length on multi-belt drives; variable pitch sheaves are not adjusted so each groove has the same pitch diameter; the sheaves are misaligned or the belts are worn; the motor anchoring, base or fan is not secur...