MDI Guest Blog: Diagnosing Common Faults in Journal Bearings
This blog was created in conjunction with CTC's educational partner, Machinery Diagnostics Institute (MDI)
Diagnosing common faults in journal bearings is of paramount importance for engineers and maintenance professionals to ensure the continued reliability and optimal operation of machinery.
Recognizing the early signs of bearing faults enables timely interventions, preventing catastrophic failures, costly repairs, and extended downtime. Here are the warning signs the experts at Machinery Diagnostics Institute (MDI) look for in detecting these common faults:
Diagnosing Preloads
In diagnosing preloads that may be caused by gravity, fluidic forces, seals, misalignment, and effects of pipe strain on machine, warning signs include:
- Orbit that shows a high eccentricity
- Highly elliptical 1x orbits
Diagnosing Unbalance
Orbit will retain the elliptical shape and tends to be circular.
Diagnosing Misalignment
Orbit will be flatter in shape. The ratio will be greater than 5:1.
Diagnosing Oil Whirl
In the Spectrum Analysis of Oil Whirl, there will be a peak in the range of approximately 0.28x to 0.48x. The height of the peak can become quite high.
Orbit Analysis of Oil Whirl
Oil Whirl generates 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
Oil Whip 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 may be more than two times the resonant frequency.
Diagnosing Shaft Rubs
The Spectrum Analysis of Shaft Rubs may show:
- A large number of 1x harmonics
- Sub-order peaks and harmonics (e.g. 1/2x, 1/4x, etc.)
- The noise floor may lift
The Orbit Analysis of Shaft Rubs may show that the direct orbit will have multiple loops
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