Diagnosing Journal Bearings common fault conditions - The Informative Brief
● 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
(a) large number of 1X harmonics
(b) sub-order peaks and harmonics (e.g. ?X, ?X, etc.)
(c) The noise floor may lift
- Orbit Analysis of Shaft Rubs -> The direct orbit will have multiple loops
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NSW State Manager at Conditon Monitoring Australia
11 个月Thanks for sharing but wouldnt you see truncation in the waveform/waveforms when rubbing occurs??
Team Lead- Testing
11 个月Thanks Aly Attia for this. For air lubricated bearings (similar to oil journal bearings), what diagnosis we can have for the following orbit. Does it show rubs?
VA CAT III, MLA II, CMRP- Rotating Equipment Vibration & Condition Monitoring & Reliability Engineer Kuwait Oil Company
11 个月Nice animation. Can you please include orbit v/s full spectrum relationship animation also..