Hello everyone, I encountered reverse precession in the 1X orbit of the NDE bearing in my 3400 kW motor. During coast-down from 2700 rpm to 1000 rpm, the orbit initially shows reverse precession but then transitions to forward precession. The steady state condition consistently exhibits forward precession.
If you are wondering whether this unconventional orbit is suitable, please let me address your concerns. Best regards, Ali M. Al-Shurafa.
I appreciate Mr. Shurafa's prompt response. The phenomenon of Steady State forward precession is consistently observed, while coast-down forward and reverse precession 1X orbit is only sporadically observed. Despite vibration amplitudes being within acceptable limits, I am interested in understanding the underlying causes for this unpredictable behavior. What are the potential reasons for this issue?
In order to receive insightful feedback from forum members, it is essential to provide thorough details. Without sufficient information, you may only receive generic comments and speculative guesses. From my perspective, this behavior may be considered typical. Best regards, Ali M. Al-Shurafa.
That's an interesting observation you've made. Reverse precession could potentially be a consequence of an imbalance in the rotor dynamic system, showing up during the coasting down phase. When the motor stabilizes at a lower speed, it might be able to balance this asymmetry, hence showing forward precession. The cause could be mechanical (like a shaft misalignment or eccentricity) or even related to bearing characteristics. I'd suggest checking for a soft foot condition or coupling imbalance. Keep records of your observations, they will be highly useful for troubleshooting and improving the machine's performance.
Hi there, interesting observation! When you're seeing reverse precession at startup or coast-down, it could be indicative of a transient event or imbalance that's only active under these conditions. It might be helpful to explore aspects such as shaft alignment, unbalance or inherent machine properties like bearing stiffness. As you know, the direction of precession depends on the relationship between the phase lag of the vibration and the rotating vector. Bear in mind that steady state usually reveals inherent machine characteristics more accurately than transient states, so the forward precession at steady state is likely the true behavior. Hope this helps!
Hello, this is indeed an interesting observation. Considering the scenario, I believe a potential cause could be the natural frequency of the system being excited as the motor coasts down. It 'dwells' in this phase momentarily, causing the reverse precession. This can be exacerbated by any looseness in the system or bearing defects. Also, lubrication could play a role in this as well. Depending upon the type of your bearing (e.g., rolling element vs. fluid film) and the condition of lubrication, the precession pattern can change temporarily. It could be quite insightful to perform a vibration analysis right throughout the coast-down process to better understand this behavior. Also, check for any aligning discrepancies or bearing faults that might be leading to this odd precession shift.
That's really interesting! Reverse precession can be a puzzling phenomenon, especially in high-power motors like yours. It’s likely due to transient conditions during the coast-down, where the changes in load and speed can cause such irregularities in the vibration patterns. It sounds like your system stabilizes well once it reaches that steady state. Have you noticed any specific patterns or variables that seem to influence the transition from reverse to forward precession?
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Answer: 1. What is reverse precession in the context of NDE bearing orbit during motor coast down? - Reverse precession refers to the movement of the orbit in the opposite direction of rotation during coast down, as observed in the 1X orbit of the NDE bearing in the motor.
Answer: - The reverse precession observed during the initial phase of coast down could be due to specific operating conditions or dynamic factors affecting the bearing behavior at lower speeds.
Answer: - The transition from reverse to forward precession in the NDE bearing orbit during coast down could be influenced by changes in the system dynamics, loading conditions, or other operational variables as the motor slows down.
Answer: - The consistent forward precession observed in the steady state condition of the NDE bearing orbit could be a result of the stabilized operating parameters and system behavior once the motor reaches a certain lower speed range.
Answer: - The presence of reverse and forward precession in the NDE bearing orbits can provide insights into the dynamic behavior of the motor system, helping to identify potential issues such as misalignment, unbalance, or other mechanical anomalies affecting the
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