Gears are critical components of industrial gearbox but they are also the fundamental components for making the machine work. It is very important that they work perfectly, as intended or your entire operation could come to a halt. Gearboxes, while tough, are sensitive machines prone to failure if not properly maintained. These machines are often subjected to extreme stress and high temperatures. As a result, even the smallest misalignment could be deleterious, so it is recommended to prevent breakdowns through continuous monitoring.
Gear vibration analysis
Vibration analysis has grown in importance recently when it comes to industrial gearboxes. This type of maintenance is one of the most widely used gear fault analysis techniques. It aids in early fault detection, enabling users to prevent breakdowns.
Vibration analysis involves listening to the vibration in the gearbox. An industrial gearbox is composed of a variety of components, and each of them vibrates on a unique frequency. If your gearbox has suffered damage, the noise patterns will change. The sound you hear can help you diagnose the type of the damage, and even it’s source. Keeping a record of all maintenance can help you pinpoint when a problem began and what caused it.
Common vibration analysis methods
Gear failure can be caused by manufacturing errors, improper design, application errors, lubrication problems (for more information see the article How to manage gearbox lubrication) or a variety of other causes. While industrial gearboxes are designed to withstand heat and pressure, if there is an error in the manufacturing process, it could result in serious damage. Inferior materials, insufficient lubrication, and incorrect materials or gear geometry are all design flaws that can result in damage. Improper mounting or installation, cooling, and maintenance are application errors that may cause damage to your gearbox as well. Many technicians will use these techniques to detect flaws. If you aren’t sure how to perform these tests, contacting an expert can be beneficial.
Bearings and gearbox vibration are fundamental issues for rotating machines, which are an indispensable component in many industrial applications.
Bearings are critical components and, as such, any failure can prove expensive in both repair cost and down-time. Because of this condition monitoring has become increasingly important over the years, usually centred around vibration measurement taken at critical locations, either continuously (online) or as part of a monitoring schedule. Vibration monitoring has become an integral part of most maintenance regimes and relies on the detection of various well-known frequency characteristics associated with this type of component. Detailed knowledge of design of the bearing or gearbox allows characteristic vibration frequencies to be calculated. However these frequencies are often masked by vibration from nearby components or by noise, sometimes making diagnosis difficult. Vibration time signatures are also often subject to both amplitude and frequency modulation which affect the resultant frequency spectra. Here we are going to look at the causes and effect of amplitude modulation in particular and how it is manifested in the frequency domain.
- Resonance analysis takes the natural frequencies and vibrations in the gearbox and analyzes them. Resonance tests can be conducted with a coast-down curve, impact tests, run-ups, and measurements of bending lines on the shafts.
- Time domain analysis evaluates the vibration time, signal, and amplitude to ascertain if there are faults in the gear-rotor bearing system. This method alerts technicians if there are impulse signals that arise from gears or bearings.
- Frequency domain analysis utilizes three different techniques: the Hilbert transform method, power cepstrum analysis, and fast Fourier transform. Each of these techniques measures the difference between the spectral density to identify any parts that may be faulty. These techniques are used to identify misalignments, unbalance, and other similar issues.
- Envelope analysis evaluates the roller bearings and gear mesh for roughness or damage. Phase measurement analysis (PMT) is often paired with frequency domain analysis to identify loose parts, unbalance, and misalignments.
- Order analysis is used to test rotating or reciprocating machines such as turbines, compressors, and pumps, by reviewing noise and vibration signals. Orbit analysis is used specifically to inspect shaft vibrations.