Vibration spectrum analysis

[PJMechanicalEng]

Hello good evening, I have doubts about indicating the harmonics or bands in this spectrum that is from a reduction box, to try to identify if there is an imbalance or misalignment or other problem. Can anyone help? Thank you.

 

[GregLocock]

Not without a much better description of the gearbox, input rpm, number of teeth on each gear etc.

 

[PJMechanicalEng]

Accessible three-way straight cut bevel gearbox with 1.5:1 ratio (20 gear input).
1689 rpm. My doubt is identify 1xrpm 2 xrpm etc. Thanks

 

[GregLocock]

1689 rpm is 28.15 Hz. You may have some 2nd order at twice that

Something doesn't add up, you'd expect to see at least some content at tooth mesh frequency.

 

[NovaStark]

Where your peaks are most likely the gear mesh frequencies. Around the main peak, you can check to see if you have sidebands that match the running speed of either the input/output gear.

Comparing to previous measurements may help you to determine if there is increased wear.

As PJMechanicalEng has already said, 1689 rpm = 28.15 Hz = where the marker is on the far left. What software are you using for the spectrum analysis ? Most have cursors such as harmonic, side band, bearing frequency, etc. that you can enter the running speed (and other details) to help identify where 1X, 2X, 3XRPM (or otherwise) are located.

 

[dtimberlake]

Where was the vibration measured?

Radially Directly on a bearing housing?​

Axially on the main housing or on an end cap close to a bearing?​

The middle of an inspection cover?​

etc etc ?​

Is this in search of a noise complaint?

As a follow up to an oil analysis that triggered an alarm?

 

[PJMechanicalEng]

Where was the vibration measured?

Was measured vertically with a sensor end cap close to a bearing.​

I want to identify on the spectrum 1xrpm 2 x rpm 3 x rpm to find a possible an answer to an yellow alarm that give on acelaration on g.

 

[GregLocock]

1st order is 28 hz, 2nd at 56, 3rd at 84 hz

Now see if you can work out 4th order