Analysis of fan impeller backplate detachment accident
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This fan is the main exhaust fan for our company’s RTO system; it has an air handling capacity of 15,000 m3/h, and its Siemens motor has a power rating of 110 kW. It has been in operation for about 1.5 years. Last night, the fan started making severe noise. Upon inspection, it was found that the front bearing housing was broken, and the impeller at the inspection access point on the fan’s casing had fallen off. After disassembling the fan, it was determined that the front bearing housing and bearings were damaged, and the impeller had separated from the main shaft – the separated part was located on the back of the impeller. The breakage site was not at the welded area; from the photos, it seems to indicate signs of twisting, but mechanical analysis suggests that twisting was unlikely to be the cause. Please help analyze what might have caused this issue
Such analysis should determine whether the failure was caused by the bearing deteriorating and affecting the impeller, or by the impeller being damaged and affecting the bearing. I think the first possibility is more likely. If the impeller fails first, the bearings need not be damaged to such an extent. The bearing damage occurred first, causing the impeller to vibrate violently due to imbalance; in addition, there may have been physical impacts that led to damage to the impeller as well. The bearings for a rotor rotating at such high speeds should be sliding bearings (bushings). This is one possibility; another possibility is that, due to scaling on the impeller, scale fragments break off, resulting in an imbalance in the rotor’s dynamic balance ? ? However, this should probably be capable of chain stopping or manual emergency stop, and it’s not necessarily inevitable that such a phenomenon will occur. So I think it’s more likely that the bearing will fail first. The remaining issues that merit careful consideration are those related to the automated security systems on site, as well as the issue of operators. It’s damaged to such an extent that it’s hard to understand.
If the bearing fails first, there should be some signs, right? How could it fail all of a sudden?