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Join Date: Feb 2010
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Centrifugal Blower Noise

06/03/2010 2:22 AM

We have a centrifugal inclined blade fan that runs at about 1500RPM,

we are having issues with the noise levels around the fan. The maximum noise that is recorded around the eye of the fan or the suction of the fan is recorded to be around 115 dB.

Any suggestions on what to look into to reduce the noise?

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#1

Re: Centrifugal Blower Noise

06/03/2010 5:27 AM

Really difficult to say with such little info but we had one once which was in a salt air environment. Salt had built up with time and was rubbing. Cleaned it up and it was fine.

Another one we had went bad because of corroded fan blades. After rubbing down, resetting and a little engineers blue to make sure everything was nice that one went fine too.

If it's a new blower then I'd try some sort of baffle but can't really say more than that.

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#2

Re: Centrifugal Blower Noise

06/03/2010 6:54 AM

Infact it is a new one too, but since its work in pretty dusty environment we can look into the building up of dust deposits.

I can provide you with more info, just let me know of what you require to provide a good suggestion.

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Guru

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#3

Re: Centrifugal Blower Noise

06/03/2010 8:34 AM

Place box around fan housing allow in air flow from a clean supply ie out side or via a tube away from the working area.

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#4
In reply to #3

Re: Centrifugal Blower Noise

06/03/2010 6:39 PM

Good answer, in addition, lining the duct with sound deadening material and offsetting the inlet works surprisingly well.

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#5

Re: Centrifugal Blower Noise

06/03/2010 7:04 PM

Sometimes just restrictions to the intake or output on a fan can cause unwanted noise.

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#6

Re: Centrifugal Blower Noise

06/03/2010 11:38 PM

@unredundant

is it safe offsetting the inlet of a centrifugal blower or a fan?

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#7
In reply to #6

Re: Centrifugal Blower Noise

06/04/2010 1:46 AM

An intake duct, lined with acoustic damping, and an a duct inlet that is not in direct line with the blower inlet, will dramatically lower the noise level.

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#8

Re: Centrifugal Blower Noise

06/04/2010 8:36 AM

Also, Check the direction of rotation of the fan blades!

If you are not familiar with this sort of equipment (Centrifugal Fans with inclined blades) you might have tought that the blades should be turning forward. Most centrifugal fans with inclined blades will have their blades turning backward. Check if there is an arrow indicating the direction of rotation.

Turning the wrong way for these fans will generate more noise and will be less efficient (against intuition...).

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#10
In reply to #8

Re: Centrifugal Blower Noise

06/04/2010 10:00 AM

And a further thought along that line would be since it is a new installation that the electrician reversed two phases and the motor is running in the wrong direction (assuming a 3 phase installation). As you state you will get output but maybe not the output that the process was designed for or requires and not the output the fan was purchased for.

Reverse rotation would probably be a lot noisier than the correct rotation. Also it is hard to believe that a manufacturer would sell a design that operates at such a high noise level. OSHA in the US would be all over such an installation and the plant manager to reduce that down to a safe level (80-85 db) by some means.

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#9

Re: Centrifugal Blower Noise

06/04/2010 9:21 AM

If it is possible, you can replace this fan with a larger one (i.e. with larger blades). In this way, you can decrease the operating speed of the fan -hence reducing its noise- while retaining the same CFM (i.e. airflow).

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#11

Re: Centrifugal Blower Noise

06/04/2010 11:59 AM

There are many factors that influence the performance of a centrifugal fan. The most critical is the selection of the right fan for the conditions of service, ie, cubic feet per minute (CFM) of air required and total static pressure pressure against which it will deliver that air. Selecting a fan nearest its sweet spot on the efficiency curve and with an outlet velocity below 1,800 feet per minute will generally result in reasonable sound level. The design of the ducts on the inlet and discharge side have a significant effect on both the fan performance and noise generation. I suggest you retain a professional, such as a test and balance firm, who is well versed in fan application review the installation, measure the CFM and static pressures, and make the necessary adjustments. If you're lucky, he might find it's delivering far more air than is required. If so, the fan RPM can be reduced accordingly which may well solve the noise problem. If he determines the duct design at the inlet, outlet, or both are incorrect you'll have a whole different and maybe expensive ballgame on your hands. Be certain you get a well qualified professional and resist the temptation to go cheap! Good luck. Lou Bindner

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#12

Re: Centrifugal Blower Noise

07/02/2010 6:10 AM

Hey ppl,

thanks for everybodys suggestion.

We experimented on the acoustic insulation of the fan and we brought it down to 93 dB which previously was around 111dB.

:)

This drastic lowering in noise has created a great impact on the surrounding.

For anybody who is interested, can request for a small report that I wrote regarding this issue. Might be useful in future.

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Anonymous Poster
#13
In reply to #12

Re: Centrifugal Blower Noise

09/02/2010 4:25 PM

Hi Ali can you please email me your noise report I am having similar type of problem.

my email is sam_aero@hotmail.com

Thanks

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Anonymous Poster
#14
In reply to #12

Re: Centrifugal Blower Noise

12/15/2010 3:42 PM

Hi Ali,

I have same problen in multi stage blower (4 stages), can you please forward this report to me.

Regards, Imran

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Active Contributor

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#15
In reply to #14

Re: Centrifugal Blower Noise

05/19/2011 3:31 AM

@imran

Sure thing,

Where to send to it?

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Anonymous Poster #1
#16
In reply to #12

Re: Centrifugal Blower Noise

08/02/2012 12:09 PM

Hey Can you email me the report at tanu1029@yahoo.com

Thanks

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Participant

Join Date: Oct 2012
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#17
In reply to #12

Re: Centrifugal Blower Noise

10/15/2012 11:49 AM

Hello Ali,

I am having same kind of problem. Would you please help by sending your report to my mail.

I am waiting for your reply.

Thank you.

Asib

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Active Contributor

Join Date: Feb 2010
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#18
In reply to #17

Re: Centrifugal Blower Noise

12/28/2012 12:36 AM
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Active Contributor

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#19

Re: Centrifugal Blower Noise

12/28/2012 12:37 AM
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Participant

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#20
In reply to #19

Re: Centrifugal Blower Noise

02/03/2014 2:47 AM

hey can you email your report to binto911@gmail.com

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Users who posted comments:

ali_shujah (6); Anonymous Poster (3); asib (1); binto616 (1); farmatt (1); G.K. (1); LAA_Lucke (1); Lou Bindner (1); MACA (1); peterg7lyq (1); Spinco (1); Unredundant (2)

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