Calcn. of Displacement, Velocity & acceleration 2

[kashyap]

I just want to know, if acceleration displayed on vibration analyzer can be directly divided by angular velocity of the shaft in order to obtain the value of veloity(mm/sec)and similarly for displacement(velocity/angular velocity of the shaft).

 

[sms]

Yes, but only at a single frequency this does not hold for a complex wave. For a sine wave, the conversions in metric units:

g=0.641*V*f
and
V= pi*f*D

where V is velocity in meters/second

and D is displacement in meters pk-pk

and f is the frequency of the sine wave in Hz

I'll leave it to you to convert from meters to mm or microns.

 

[dgallagher]

For conversion formulas and application note on comparing readings:

http://www.reliabilitydirect.com/appnotes/cvr.html

 

[kverspoor]

Check out this downloadable conversion calculator also!

http://www.wilcoxon.com/know_calculator.html

Regards.. kv

 

[kashyap]

Dear dgallagher,

thanks for the information, but i have a small suggestion to make. Foll. is the formulas displayed in u'r website,
I think wherever 103 is displayed it's 10E+03, which otherwise could be misleading.

But for the rest thank you,

sicerely,

Kashyap.

D = Displacement, P-P, Mils.
V = Velocity, 0-P, in/sec.
A = Acceleration, 0-P, g's.

D = 19.10 x 103 x (V/CPM)
D = 70.4 x 106 x (A/CPM2)

V = 52.36 x 10-6 x D x CPM
V = 3.87 x 103 x (A/CPM)

A = 14.2 x 10-9 x D x CPM2
A = 0.27 x 10-3 x V x CPM

 

[electricpete]

The original question involved converting between acceleration, velocity, and displacement based upon the shaft angular velocity (rpm or rpm/60).

The first response correctly pointed out that any such conversion only holds for a single frequency (the conversion is frequency-dependent).

Subsequent formula's would be correct by substituting f=shaft angular velocity IF AND ONLY IF the acceleration is due soley to vibration at 1x running speed. Such vibration is common, but sometimes the predominant vibration may be 2x, 3x running speed etc (for misalignment, blade pass, gear mesh etc)or even a non-syncronous multiple of running speed (for bearing problem).

 

[dgallagher]

kashyap - thanks for pointing out the typo in the formula - must not have translated properly when it was imported into the website.

 

[Rob45]

Kash:
Judging from the questions you've been asking, you might want to invest in a text on the subject.

 

[kashyap]

Dear Rob,

good observation & analysis,


keep - it - up!!!!!!!!!!

cheers,

kashyap

 

[TrickyDick]

Hi,

Also try out the freeby download at

http://www.mpiuk.co.uk/vibsliderule.htm

Enjoy!