Vibration Analysis and Vibration Monitoring
Vibration Analysis is a predictive maintenance method which allows early problem detection in rotating machinery, such as: Turbines, generators, mills, gearboxes, fans, shafts, motors, compressors, pumps, mixers and driers – in fact, almost any type of rotate and active machinery.
We are having the most reputed Vibration Analysis experts in the team. We have ISO Level-III Vibration Analyst from Mobius Institute– one of the very few in the country – heading the Vibration Analysis services for Auricle.
Vibration analysis is a process of looking for anomalies and monitoring change from the established vibration signature of a system. The vibration of any object in motion is characterized by variations of amplitude, intensity, and frequency. These can correlate to physical phenomena, making it possible to use vibration data to gain insights into the health of equipment. Vibration analysis can be used to
- Find a developing problem that can be repaired to increase machine lifetime
- Detect and monitor a chronic problem that cannot be repaired and will only get worse
- Establish acceptance testing criteria to ensure that installation/repairs are properly conducted
Convert to Frequency Space
The next step is to perform a fast-Fourier transform (FFT) algorithm to convert the time waveform into a vibration frequency spectrum. The scope of the frequency spectrum depends upon the accelerometers and the analog-to-digital converter (ADC) used. As discussed above, much of the insight delivered by vibration analysis is based upon correlating frequency spikes to physical characteristics of the system.
Look at Harmonics
The correlation process starts with looking at so-called synchronous peaks – peaks that are harmonics of the fundamental rotational frequency of the shaft. Consider an 1500 RPM, 25 Hz motor that is driven by a 480 V, 50 Hz electrical input. The fundamental frequency would be 25Hz. Any synchronous beats – peaks at 2X, 3X, 4X, etc. – provide insights about issues directly related to the rotation of the motor shaft.
Consider a six-vane pump. A pump with six vanes, for example, will have a vibration spike at 6X, or six times the fundamental frequency. If that peak triples or quadruples, it indicates some sort of problem with the vanes.
Time-waveform analysis can enhance vibration analysis. It should not be considered a primary tool but rather as a tool to provide additional insights. It can be useful for low-speed applications because it reveals the way the machine is moving. Time-waveform analysis is frequently used for analyzing gears, for example. There is a crossover point at around 100 RPM – below that speed, time-waveform analysis provides better results and frequency analysis is not effective.
The other tool that complements frequency and time-waveform analysis is phase analysis. This is an analysis of the heavy spot of the analysis in relation to some trigger. This might be vibration introduced by anything that correlates with the shaft rotation frequency, such as a bearing defect. Phase analysis makes it possible to determine where the shaft vibration occurs in relation to the shaft.
Vibration Data Analysis
The features in vibration spectra can be separated into steady-state signals, which repeat continuously and transient signals, which occur as a result of specific events. Signal characteristics can be further subdivided into synchronous, asynchronous, and sub synchronous features as follows:
Synchronous Vibration Peaks
In rotating equipment, the vibration spectrum will feature a spike at the fundamental rotation frequency of the shaft. This is true for any system, not just one with flaws. The system typically will also display spikes at multiples of the fundamental frequency, referred to as 2X, 3X, etc. These are known as synchronous peaks. They are frequently tied to physical characteristics of the system. A gear with 32 teeth will introduce a vibration spike at 32X, or 32 times the fundamental frequency, for example.
Non synchronous Vibration Peaks
Not all features in a vibration spectrum are synchronous. The system may suffer periodic shocks or impacts that will generate spikes. Non synchronous frequency spikes also can be generated by features like a gearbox with multiple stages, a pump suffering from cavitations, etc. These non synchronous peaks can provide useful diagnostic information.
Vibration spectra can exhibit a third type of feature known as sub synchronous peaks. These are basically harmonics of the fundamental frequency. They are caused by any physical element of the system that operates at a frequency below that of the main shaft. A loose belt on an axis rotating at 30 Hz, for example, might slip enough to move at just 29.19 Hz. This will create a frequency spike immediately next to the fundamental spike at 30 Hz. Other examples include cage defects in ball bearings, turbulence, etc.
Benefits of Continuous Vibration Monitoring
The tools and methods described above can be applied to quantitatively assess the condition and performance of equipment. Vibration data can reveal when equipment has broken welds or bolts, whether the rotor bars in a motor are intact, if the air gap between rotor and stator in the motor is non-concentric, etc. Vibration data can alert maintenance teams to structural or rotating looseness or the presence of resonance.
Vibration analysis can be used to determine whether bearings have been properly installed. In a taper bearing, for example, the inner race has to be expanded to take up the clearance between the rotating element and the outer race. If that clearance is not removed, the bearing may wind up crooked or wobbling. This will introduce non-periodic features into the vibration signal. Phase analysis also can be used to check bearing concentricity.
Vibration analysis also can be used to determine how well a machine is assembled. It can detect misalignment in a pump, for example, determining whether the rotating elements are binding, if the base is uneven, or if torsion exists between motor and pump.
Auricle Provide the possible services areas for rotating machines:
- Field Vibration Diagnostics
- Field Vibration Data Collection
- On-site Vibration Monitoring Contracts
- Turbine Vibration Analysis & Balancing.
- Annual Condition Monitoring Contracts.
- In-situ Field Balancing Services.
- Slow Speed Machinery Analysis.
- Variable Speed Machinery Vibration Analysis
- Multistage Gearbox Analysis
- Temporary continuous monitoring
- Remote Monitoring Services.
- And many more complex Vibration Solution