We are having a medium capacity blower and there is a churning action in the fan casing?

We are having medium capicity blower with new bearings and requisite quantity of grease.FAN SHAFT IS LEVELLED.No rubbing action inside it.Temperature inside the casing(65 degree centigrade) is more than the bearing temperature.Application is simply drawing air from atmosphere and feed to the burner.Despite all parameter are well within control there is a churning effect inside it and make the operation noisy.Balancing of fan assembly is also ok.It is mounted on vibration isolators. What are the probable causes?

We are having a medium capacity blower and there is a churning action in the fan casing?
The air temperature within the casing being higher than the shaft bearings is a result of compression of the air in addition to the heat generated by turbulence. You are also paying for the energy to heat this air, hence the more efficient the blower, the cheaper it is to run.





You don't mention what type of blower you are using. Assuming you are using a 'squirrel cage' type blower, some turbulence, with it's associated noise and heat, can be eliminated by adjusting the gap between the squirrel cage and the entrance to the blower's discharge opening. The smaller this gap, the more air is discharged, instead of tumbling back into the blower housing.





I have had luck with some books written by Dave Gingery, primarily the one titled "How to design and build centrifugal fans". I've listed the website below.





Hope this helps





Ouzinki