How to reduce noise and vibration??? 1

[component]

I have a Power Equipment Test Facility designed for testing generators at speeds up to 15000 rpm and with a mechanical power rating up to 75 kW. It bascially consists of a dc motor, speed increasing gearbox and a torque transducer.These 3 devices are coupled together by shaft couplings.
Everytime during the operations, there will be alot of noise and vibrations created. May i know how do i go about it to reduce these 2 problems especially the noise .

 

[dharni]

Hi,

First thing you should do is to find out which component is producing larger noice, how it is connected to other components and if noice making component is connected to any kind of support then what is the fixure type i.e. how it is connected.

Is it producing noise the moment you start your equipment or at some specific low/high speed?

Is it producing noise with or without specimen?

 

[component]

Let me explain what i mean again. Thanks for your reply.
Firstly the is used to test the whether the generator will pass or fail the test.
The Power Equipment Test Facility consists of a dc motor, speed increasing gearbox and a torque transducer.
This is how it is connected:
The dc motor is linked to one end of the speed increasing gearbox by a shaft coupling.
Then the other end of the speed increasing gearbox is linked to the transducer by another shaft coupling.
Finally the transducer is connected to the generator which is to be tested.
All the components are mounted onto a square block of metal.
This test is carried out at high speeds only and create alot of noise when in use.Im not sure whether which component are making these noises because it is very loud during the testing.
May i know what are the possible ways to reduce the noise and vibrations.

Thank you very much.

 

[jabonet]

Hello.

My experience is that these speed increasing gearboxes are noisy, specially if something starts going bad inside, usually the bearings.

The Rest of the components are not particulary noisy, any unbalance should produce a humm of some 250 Hz. but the gearbox can multiply several time making it a hellish noise.

Another thing is that you have the unit conected by driveshafts, if you could run the equipment at full speed and sudenly reduce torque to minimun, is the noise still there? if it is NOT, then the noise is NOT coming from any unbalance, and will be most likely the gearbox.

You can also get closer to the source of the noise by knowing it frequency and what componets of the machinery can generate that.

BTW how does the gearbox work, two shafts full of teeth? in that case what kind of teeth?

You ask for ways of reducing noise AND vibration, which unit is vibrating? all of them, or just one or two.

To reduce noise in any effective way it is importan to know what frequency it is. and what kind of sowrounding do you have, concrete, for example.

Can you run the DC motor alone, then the DC and gearbox and finally with a generator that you know is working quietly? if so what are the results?

Hope this helps

 

[MachineryWatch]

I agree with jabonet. You need to do some test runs while acquiring some sound and vibration spectral data using accelerometers and microphones. First you need to find out if the noise is caused by mechanical defects including support structure cracks, etc. If it is, correcting the defects may considerably reduce the noise. If the vibration source is not from a machine defect, then you can start addressing the use of sound reduction treatments once you know the frequencies involved.

Skip Hartman

http://www.machinerywatch.com

 

[component]

Thanks everyone for giving suggestions.At least now i know how and where to start.
Thanks again

 

[plasgears]

Mount the motor in flexible mountings. I assume flex couplings, preferably rubber. The flex mounted gearbox should feature plain bushings rather than ball bearings. Further, consider the use of a urethane pinion gear in the gearbox. Next, design for helical gears and bent washer spring spacers. Backlash should be sufficient, not excessive, BL = .040"/P. The gearbox should be form fitting around the gears so that you don't produce panel vibrations. In addition, the form fitting minimizes the grease fill amount and keeps the grease in circulation. The gear tooth form should allow for tip relief to minimize approach impact and maximize recess action. See ABA-PGT tooth form from the company of the same name in CT. Finally, design the pinion for extended addendum, a' = 1.2 x a. The larger gear would have a' = 0.8 x a. WD = 2.35/P. Extended addendum pinions run quieter than std.