Vibration from journal bearings can provide information about shaft misalignment and other machine problems. Journal bearings consist of a rotating shaft within a metal sleeve or shell, without rolling elements. Different vibration signal characteristics from probes in the journal bearing can indicate issues like unbalance, radial preload, or natural frequency. Heavy preload may cause an orbit shape with a height to width ratio over 4:1, identifying unbalance. The spectrum from one test showed maximum displacement of 60-65μm at 10-20Hz, the machine's natural frequency.

1. VIBRATION FROM JOURNAL BEARING
SANI BRILLIAN FAHMI (15/385259/TK/43921)
SONY C. H. Napitupulu (15/385260/TK/43922)
WIANDRA ALIF AUDI (15/385263/TK/43925)

2. CONTENTS
• Vibration from a journal bearing
• Types
• Characteristics and Causes
• Spectrum

3. Vibration from a journal bearing
• What is journal bearing
• Journal or plain bearings consist of a shaft or journal which rotates freely in a
supporting metal sleeve or shell. There are no rolling elements in these
bearings.
• Journal bearings are often used in turbines, generators, compressors, motors,
pumps, etc. They are also used to analyze the misalignments experienced by
the shaft.

4. Types of Journal Bearing

5. Characteristic and Causes
• Journal bearing can identify the problem in the shaft by receiving
signal from the probe that already installed in the journal bearing,
this probe is usually placed in the horizontal in vertical axis from the
centerline. Different signal characteristic can lead to different cause
or the problem from the machine.

6. Example of Good Machine Characteristic

7. Example of Preloaded Machine Orbit

8. Radial Preload can caused by gravity, fluid forces, abnormal
bearing loads, seals, and misalignment which the probe from the
journal bearing will send a signal which will be displayed as orbit of
the shaft.

9. • Light Preload
• HeavyPreload

10. • We can diagnose the unbalance by identifying the orbit from the
shape and Height to Width ratio
• If the machine is unbalanced due to heavy preload, the orbit size will
increase and the height to width ratio will be as much as 4 : 1

11. Spectrum
The spectrum shown below is produced using shaft in the journal bearing of a Rotorkit device, product of Bentley
Nevada

12. From this spectrum it is shown that the biggest displacement which is in the range of 60-65µm happened in the
frequency of 10-20Hz. We can conclude that this value is the natural frequency of the machine that is used in the
experiment.