Description

This balancing machine app determines the location and amount of unbalanced masses on a rotor based on given inputs and readings.

APPENDIX

Units of Measurement

Displacement:

1 Mil= 25.4 microns

Velocity:

1 in/sec= 25.4 mm/ sec

Unit Abbreviations

in/s: inch per second

mm/s: millimeter per second

μm: micrometer

pk: peak (zero-to-peak)

rpm: revolution per minute

Equations:

(5- 10 %) M x g = Mu x Ru x Ω2

Where:

M: Rotor Mass, Kg

g: Gravity, 9.8 m/ sec2

Mu: Calibration Mass

Ru: Raduis of Calibration Weight

Ω2: Angular Speed, 2πN/60

N: Rotor Speed, RPM

C= (O+C)-O

Influence Vector H=C/Wcal

Correction Weight Wcorr=N/C x Wcal = -O/C x Wcal

Where:

O: Original Unbalance Vector

O+C: Response to the original unbalance plus the unbalance caused by the calibration weight

GLOSSARY

Balancing:

Adjusting the radial mass distribution of a rotor so that the mass centerline (principal inertia axis) approaches the geometric centerline resulting in a reduction in1X lateral vibration.

Calibration Weight Wc:

Used in rotor balancing. A weight of known magnitude that is attached to (or removed from) the rotor at a known physical location. When operating the machine under repeatable conditions, the resulting change in 1X vibration response vectors may be attributed to the calibration weight for a linear mechanical system. This procedure calibrates the rotor system for its susceptibility to mass unbalance. This weight is often called a trial weight.

Critical Speed(s):

Any shaft rotative speed associated with high vibration amplitudes. Often, the speed corresponds to a rotor lateral mode resonance frequency excited by rotor unbalance (also known as balance resonance speed).

Influence Vector H:

Used in balancing, the resulting 1X vibration vector (amplitude and phase) due to a calibration weight divided by the calibration weight vector, at a particular shaft rotative speed. The measured vibration vector divided by the unbalance force vector represents the rotors unbalance transfer function. Also known as an influence coefficient.

Peak-to-Peak Value:

The difference between positive and negative extreme values of an electronic signal or dynamic motion.

Root Mean Square (RMS):

Square root of the arithmetic mean of a set of squared instantaneous values. Used as a measure of amplitude; RMS equals 0.707 x peak (sine wave only).

Unbalance:

Unequal radial weight distribution in a rotor. A condition where the mass centerline (principal inertia axis) does not coincide with the geometric centerline of the rotor. Eccentricity of the local center of gravity from the undisturbed axis of rotation.. Also, the effective mass responsible for the rotor lateral synchronous vibration. Sometimes expressed in terms of eccentricity alone, e.g., in mils of eccentricity.

Unbalance Response:

Vibration amplitude and phase of rotor synchronous precession at a given speed, caused by dynamic forcing action of rotating mass unbalance.

Zero-to-Peak Value:

One-half of the peak-to-peak value.