This document discusses vibration from journal bearings. It begins by defining vibration and journal bearings. It then discusses the main types of vibration that can occur from journal bearings: oil whirl and oil whip. It explains the characteristics of each type, such as typical frequency and orbit patterns. It then lists and describes three main causes of vibration in journal bearings: the type of lubricant used, misalignment during assembly, and unbalanced mass of the rotating component. The document concludes by discussing how the vibration orbit signature can be analyzed to determine operating conditions and references several papers on related topics.
2. Vibration From Journal Bearing
• Vibration is a mechanical phenomenon whereby oscillations occur
about an equilibrium point. The oscillations may be periodic or
random.
• Journal Bearing is a comprehensive kind of bearing that contains a
journal or shaft that freely rotates in a support with a shell or metal
sleeve.
4. Types of Vibration From Journal Bearing
• Oil whirl is probably the most common cause of subsynchronous instability
in hydrodynamic journal bearings. Typically, the oil film itself flows around
the journal to lubricate and cool the bearing. This develops an average
speed slightly less than 50 percent of the journal surface speed.
• Spectrum: Strong peak at between 0.38X and 0.48X. The amplitude can be
quite high
• Orbit:Because of the strong sub-synchronous vibration there will be two
dots on the Orbit: and there may be an internal loop. Watching a live
Orbit: will show that the inner-loop will rotate around the Orbit: in the
direction of rotation.
6. Types of Vibration From Journal Bearing
• Oil whip occurs on those machines subject to oil whirl when the oil
whirl frequency coincides with and becomes locked into a system's
natural frequency (often a rotor balance or critical speed frequency).
When a shaft goes into oil whip, its dominant dynamic factors
become mass and stiffness in particular; and its amplitude is limited
only by the bearing clearance. Left uncorrected, oil whip may cause
destructive vibration resulting catastrophic failure – often in a
relatively short period of time.
8. What Makes Journal Bearing Have Vibration?
1. Types of Lubricant
2. Misalignment when Assemblying
3. Unbalance Mass
9. 1. Types of Lubricant
• Vibration on Journal Bearing depend on the types of Lubricant that
we used on the journal bearing. Lubricant can reduce the level of
vibration on journal bearing, because lubricant have function not only
to lubricate, but also as a vibration absorber on Journal Bearing. Also,
every lubricant have different viscosity. Today, there are a lot of
Lubricant that can we used for journal bearing. There are a lot of
paper that studying about it.
10. 2. Misalignment When Assemblying
• Misalignment is difference of position of height when assemblying
the Journal Bearing with shaft and the source of vibration.
• When there is misalignment when assemblying the Bearing, it can
make a great vibration.
11. 3. Unbalance Mass
• When the center of rotation is not equal with the center of gravity, it
can make the shaft rotates unbalance.
• Unbalance rotation of shaft makes vibration at the journal bearing.
12. Spectrum Of Journal Bearing’s Vibration
• The orbit signature of the center of the journal is then qualitatively
analyzed to investigate system operating condition.
• Lee and Han proposed the directional Wigner distribution to
effectively determine the procession parameters of the planar
motion both in time-frequency domain and in order-frequency
domain.
13. Spectrum Of Journal Bearing’s Vibration
• The orbit signature of the center of the
journal is then qualitatively analyzed to
investigate system operating condition.
15. References
• Eddy, Noor, dkk. 2014. Analisis Getaran pada Bantalan Luncur yang
Diakibatkan oleh Pengaruh Kekentalan Pelumasan. Prosiding Seminar
Nasional Aplikasi Sains & Teknologi (SNAST) 2014, Yogyakarta. ISSN: 1979-
911X.
• Faisal Rahmani, J.K.Dutt, R.K.Pandey. Dynamic Characteristics of a Finite-
Width Journal Bearing Lubricated with Powders.
• Alexey Kornaev, Leonid Savin,Elena Kornaeva, Alex Fetisov. Influence of the
ultrafine oil additives on friction and vibration in journal bearings.
• Narendiranath Babu T., Himamshu H.S., Prabin Kumar N., Rama Prabha D.,
Nishant C. Journal Bearing Fault Detection Based on Daubechies Wavelet.
2017. School of Electrical Engineering, VIT University Vellore, Tamil Nadu,
India.
