​Rotating Machinery Vibration - From Analysis to Troubleshooting

​Rotating Machinery Vibration - From Analysis to Troubleshooting

If you are interested in troubleshooting rotating machinery vibration problems, this article will help you do that. It will go over the causes and possible solutions for these problems, including Bearing faults, Alignment issues, and Gear failures. This article will help you get started on troubleshooting your vibration problems and get back to work as soon as possible. The information you will gain here will help you make an informed decision about how to proceed.

Loose parts in the rotor assembly

The frequency of the vibration caused by loose parts in the rotor assembly varies depending on the clearance between the shaft and the loose part. The surface friction and tangential drag coefficient of the loose part play an important role in determining the frequency. Fluid drag on the rotor may either drive the loose part at a high frequency or slow it down. These forces are antagonistic and may balance out at steady state. A characteristic beat pattern is generated when the loose part's speed is low.
A common rotor malfunction is caused by a loose pedestal. This causes unbalanced forces on the rotating rotor, which can exceed the forces applied by gravity and other external forces. In such cases, periodic lifting of the pedestal causes cyclic variability and impacting in the system. A simplified model can be used to simulate periodic softening. This model typically excludes axial displacement.

In addition to loose parts, internal fluids can also cause specific types of vibration in rotating machinery. These vibrations often occur at an irregular frequency relative to the rotor speed. The components of the rotating machinery may also cause the vibrations, and this can be an indication of early degradation of parts. While vibration analysis techniques can alert to these early symptoms, visual inspection is necessary. This can help in the diagnosis of rotating machinery vibration and subsequently reduce the frequency and intensity of the problem.

A simple oversized bearing malfunction model reflects the rotor-to-stator rubbing situation, but with different parameters. It produces rotor vibration that is unbalance-related and self-excited. It can also produce oscillations due to the coupling between transverse and axial motion in a stationary member. Finally, there is torsional vibration of the rotor assembly that is important on certain machineries. While it is not as critical as torsional vibration, it can cause significant trouble in variable-speed machinery trains.

Bearing faults

A common cause of bearing failure in rotating machinery is a faulty motor bearing. Bearing vibration signals are very difficult to detect with conventional methods, due to their high noise content. To detect faults in bearings, researchers have developed various methods. These include envelope demodulation, spectral kurtosis analysis, and the maximum overlap discrete wavelet packet transform. The following article summarizes some of these methods. In addition to the standard techniques, these methods are effective in diagnosing incipient faults in rotating machinery.

The process of vibration diagnosis includes the preparation of data obtained from the vibration data and the analysis of it. Modern technology has improved the capabilities of CM in rotary machines, allowing it to identify and diagnose faults earlier, before they cause severe damage. It can also measure the current, lubricant properties, temperature, and humidity, as well as vibration. This technique can also detect if there are slacks in the lubricant.

An unsupervised SAE multiclassification model is a promising method for bearing fault diagnosis. Using the filtered signal, this method extracts in-depth features, improving fault classification accuracy. The proposed model was validated using a test set and engineering experiments, and its accuracy has been confirmed in various cases. It is also useful for detecting structural faults of rotating machinery, since it can recognize both types of bearing faults.

Early detection of bearing faults is essential for preventing unscheduled machine failure. Bearing fault detection early can minimize unscheduled downtime and prevent catastrophic accidents. Identifying bearing faults and repairing them can save time and money, and improve productivity. If detected and repaired in a timely manner, it will prevent catastrophic failures. It will also prevent unscheduled machine downtime and costly maintenance costs. And it's all good for your bottom line.

Alignment problems

Rotating machinery vibration is a common symptom of improper functioning. Unstable equipment cannot reach its full lifespan and will cause downtime. It also presents a safety risk. Here's how to recognize the symptoms and prevent costly machine failures. Vibration is the best indicator of alignment problems. High axial and radial vibration levels are a sure sign of misalignment. These vibration levels typically occur at 1X or 2X of the machine's speed.
In order to detect alignment problems, it is necessary to collect and review all machine history files. Review operator complaints, repair work orders, and inspection reports, and document vibration frequency data. Using recommended procedures will ensure a proper alignment. Also, make sure to record any bracket or bar sags found in the machine. The report should include this information and be filed with the machinery maintenance history. Once you've determined the cause of alignment problems, you can focus on preventing them from happening again.

Misalignment can cause a wide range of problems, from unsteady rotation to mechanical breakdown. There are numerous causes of misalignment, but one of the most common is overhung load. This is when a force is exerted at an angle to a shaft's support point, causing misalignment. In addition, the stress put on the supporting housing will cause the shaft to heat up, which will also affect the alignment.

When a co-generation plant needed realignment every six months, it needed to shimm its turbines by 0.05mm. Its foundation was a mixture of fill dirt and land recovered from the San Francisco Bay. Vibration analysis revealed the misalignment and the underlying cause. This information can be vital in determining the cause of misalignment and finding effective solutions for it.

Gear failures

In order to detect gear failures in rotating machinery, you must first determine the exact cause of the machine's vibration. A common indication of gear damage is a kurtosis of the vibration signal, which changes with the frequency. The frequency of this signal is the inverse of the ratio of the gears' mesh lengths. However, a more complex model is necessary to distinguish the failure from the normal noise.

Time-synchronous averaging is another technique for fault detection. Time-synchronous averaging can remove noise associated with zero-mean random noise by averaging the amplitude and phase information of the signal. It also identifies transients, impulsive signals, and beats. It is an excellent tool for analyzing rotating machinery vibrations. If you are unable to locate a cause in a vibration signal, you can use time-domain averaging to make the necessary analysis.

The spectrum of BPFI-induced harmonics is the most common signal produced by a failed bearing. The spectral features of this signal are modulated by the impact frequency, which indicates that a faulty bearing is the cause of the vibration. This frequency spectrum is also indicative of a damaged bearing. However, the spectra of the signal of a healthy bearing are not distinguishable from those of a damaged bearing.

Another common cause of vibration in rotating machinery is mass unbalance. These are caused by fatigue and mass unbalance. The presence of a crack within the shaft causes vibration. The amplitude of the vibration depends on the depth of the crack and its position within the shaft's mode shape. Crack detection should be conducted as soon as possible, otherwise you may be causing unnecessary damage to the machine. And if you have observed a crack, it is critical to correct it before the damage gets worse.

Shaft seals

Shaft seals for rotating machinery are designed to isolate the rotating shaft from the stationary housing. Using a combination of elastomers and special seal materials, these components prevent leakage. A good shaft seal will reduce vibration in your machine and prevent damage to your machine. Here are some tips to help you choose the right shaft seal. To get the right shaft seal, learn about their characteristics and how they work.

Shaft seals are used to minimize a rotating machinery's vibration. They work to seal the rotating shaft from contaminants and dirt. They protect other components in the application and reduce the overall vibration that can be caused by the wear and tear of the parts. A shaft seal is vital for high-speed motion. These products will not only protect your machine, but the entire application as well. So, what should you look for when selecting a rotary shaft seal?

The RMS analysis is the most commonly used method of signal processing. It measures the average effective energy of a signal. Figure 4 displays the vibration energy curves of different types of seals. The ordinate represents the root mean square of the vibration acceleration in each experiment. The abscissa shows the full flow of each experiment. To find out which type of seal is most effective, you must understand the various vibration properties of the seal.

The balance diameter polymer seal is intrinsically tolerant of radial vibration. The faces of the seal are separated by a film of gas. A non-contacting face seal absorbs little energy and damps only small vibrations. The stiffness of the fluid film and the responsiveness of the seal design provide the necessary stability. The shaft seal assembly must absorb the axial vibration caused by the shaft. The shaft seal assembly must also accommodate the rotational forces.

Written by: Onur Uludag
Onur has worked in the industry for many years, especially interested in the maintenance of heavy machinery and trained himself in this field.