Skip to main content

Replies sorted oldest to newest

[Edit: added the link address]


The sensitivity is a vector (amplitude and angle). The amplitude is given as

S = weight/vibration.

You could have different values for different planes and directions etc. So, to be consistent, you need to mention the context such as the balancing speed, weight placement radius, etc.

Regards- Ali M. Al-Shurafa

Last edited by Registered Member

The choice of wording, β€œsensitivity of rotor balancing system with rotor” makes me wonder if the OP is referring to the β€œResidual Unbalance Test” in many API specifications, as Appendix G.  In this test, while the rotor is in the balancing machine, a known weight is added at six positions and the results are plotted.  I believe the procedure is discussed at length in API RP 684 as well

As per 612, 7th Edition, details are explained and the i have done this exercise many times with rotors.

I am manually drawing the circle, Is any one using excel programmed/spread sheet for this to get the result accurate with circle.

In other OEMS, like Toshiba, japan, after completion of High speed balancing, They will also do Sensitivity check by putting a known mass at known angle and check the response of the weight on the both planes.(only one run per plane).

Based on this data I was asking about sensitivity check in this forum.


I have used Excel for polar plots of balancing, dial indicator and ultrasound data. I found that using the Radar plot with at least 8 data values is visually suitable. John's reference link looks handy for this method. I have found two "tricks" on occasion that helped.

1) Rescale the data, as needed for visual appearance
2) Overlay a circle (I use Bluebeam Revu) to find circle center of data and variation from mean value.

There are sources on Internet for Excel add-on for Polar Plots.

Regarding the OP question, balance sensitivity is determined by the Trial Weight method for field and shop balancing. The sensitivity would be (weight x radius) divided by (vibration level at 1xSS). Some folks use the reciprocal of that value, but either way the relation between balance weight and vibration level can be calculated.


Add Reply

Link copied to your clipboard.