Diagnosing Preloads
Orbit shows high eccentricity, Highly elliptical 1X orbits
Caused by gravity, fluidic forces, seals, misalignment, and effects of pipe strain on machine
Diagnosing Unbalance
The orbit will retain the elliptical shape. And tends to be circular.
Diagnosing Misalignment
The orbit shape will be flatter. The ratio will be greater than 5:1
Diagnosing Oil Whirl
Spectrum Analysis of Oil Whirl
There will be a peak in the range of approximately 0.38X to 0.48X. The height of that peak can become quite high
Orbit Analysis of Oil Whirl
Oil Whirl will generate a characteristic source of vibration in the range of approximately 0.38X to 0.48X
Because it is lower than 0.5X we will witness two dots in the live orbit
Diagnosing Oil Whip
It occurs when the speed of the machine is over twice the critical speed; therefore, the critical speed is close to the oil whirl frequency
The 1x peak is more than two times the resonant frequency
Diagnosing Shaft Rubs
- Spectrum Analysis of Shaft Rubs
- large number of 1X harmonics
- sub-order peaks and harmonics (e.g. 1⁄2X, 1⁄4X, etc.)
- The noise floor may lift
- Orbit Analysis of Shaft Rubs -> The direct orbit will have multiple loops