Cavitation describes the process where a liquid is vaporized due to fluid flow effects to form “cavities” or vapor bubbles; these bubbles rapidly implode and generate immense forces. A sudden drop in pressure of a liquid, below its vapour pressure, causes it to vapourize. This…
read moreIn the field of rotordynamics, critical speed is a common term used to describe the speed which excites the natural frequency of a rotor such as shaft-fan system, shaft-propeller system, etc. As the rotational speed approaches the rotor’s natural frequency, the system starts to resonate.…
read moreSprings and dampers are key components in many vibration isolation, and dissipation systems; examples include springs and shock absorbers (dampers) used in cars, and in washing machines. Figure 1. A spring (left) and shock absorber (right) attached to a washing machine tub to dampen vibrations to the…
read moreGear mesh frequency, which is also called tooth mesh frequency, is the frequency at which gear teeth mate together in a gearbox. There are three important frequencies involved in gearboxes: input speed, gear mesh frequency, and output speed. Gearboxes will always have a strong vibration…
read moreOne of the first steps in vibration analysis is identifying the operating or running speed of a machine. Knowing this value is important because details about the state of the machine are usually linked to this particular frequency, as explained in a previous posting. Identifying…
read moreIt is important to recognize sidebands phenomenon in machinery analysis. Sidebands are caused by amplitude modulation between two signals. They can be found in machines which have gearbox, rolling element bearing, and other certain fault conditions. Sidebands can be recognized by carefully examining evenly spaced…
read moreStatic balancing was the primary method for balancing before more sophisticated machines became available that could dynamically measure imbalance in rotating parts. Static balancing can be accomplished by placing a part on knife edges; the part will usually rotate until the heaviest side rests at…
read moreHave you ever walked in a plant and heard a sound from pumps or motors to be alternatively soft and loud? If you have, you experienced a phenomenon, which is called “beating”. The same phenomenon occurs in vibration. If two or more machines run close…
read moreIdeally a vibration signal will be free of any noise or interference that would hinder analysis. Unfortunately, this is never the case in the real world; there are always constant and uncontrollable changes to the vibration in a machine that add noise to the signal.…
read moreWe can measure vibration of a machine and generate a time waveform (time domain). Fast Fourier Transform (FFT) can then be performed to produce a spectrum (frequency domain). One thing to consider is FFT is performed on a block of samples, which are called the…
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