Discussion on severe vibration in the flue gas duct at the exhaust fan outlet
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Dear experts: Hello! ! There’s a rather tricky situation at the moment; I hope I can get some help. Thank you! ! ! We have a ultra-low emission retrofit project; for the exhaust fan, only the casing, impeller, and main shaft were replaced, while the motor of the exhaust fan was not changed. After the induced draft fan started operating, at low load levels (when the opening degree of the inlet damper is within 30%), the exhaust flue and the maintenance platform for the exhaust flue experienced severe vibration, but the vibration of the induced draft fan remained within normal limits. This phenomenon does not occur under high load conditions (when the inlet damper opening is above 30%). Dear experts, how can this vibration be eliminated? Are there any good methods? Thank you! ! !
Is there any way to deal with this? ?
The fan itself vibrates normally; if the inlet and outlet pipelines also do not vibrate, check whether the foot pads of the fan base are appropriate
Can this be resolved by increasing the number of supports for the inlet and outlet pipes or by changing their location? Suspecting pipeline and platform resonance?
The fan itself vibrates normally, but the exhaust flue vibrates severely
Now the exhaust flue and the platform are resonating
It seems there are two possibilities: either the fan selected is too large, as indicated by the inlet valve opening being less than 30%, or the fan’s foundation is not proper, with a relatively thin base
When the damper opening is 30%, the curve falls within the fan’s surge zone, and it is very difficult to resolve the issues associated with this surge zone; unless a non-overload operation curve is used. If this opening level is not to be used on a permanent basis, then it can be ignored
The motor can be controlled using an inverter, with frequency hopping to avoid resonance points