Vibration Analysis

Vibration analysis is a technique that uses the noise or vibration created by rotating mechanical equipment to determine its actual condition. Monitoring the vibration from plant machinery can provide a direct correlation between the mechanical condition and recorded vibration data of each machine in the plant. If applied properly, vibration analysis can identify specific degrading machine components before serious failures occur.

Most vibration-based predictive maintenance programs rely on one or more monitoring techniques. These include broadband trending, narrowband trending, or signature analysis. Periodic vibration analysis of rotating equipment can minimize machine failure due to faulty bearings, misalignment, bent shafts, mechanical looseness, gear wear, unbalance, resonance and many other machine faults. InfraRed Imaging Solutions Inc. uses the DLI Watchman “DCX”, a superior, high performance, four channel, portable data collector. This system also analyses motor current and plane balancing, and is suited for demanding environments that require fast, accurate, data collection.

In simplest form, vibration can be considered to be the oscillation or repetitive motion of an object around an equilibrium position. The equilibrium position is the position the object will attain when the force acting on it is zero. This type of vibration is called “whole body motion”, meaning that all the parts of the body are moving together in the same direction at any point in time.

The vibratory motion of a whole body can be described as a combination of six separate motions: the three orthogonal directions x, y, and z, and rotation around the x, y, and z axes. Any complex motion of a body can be broken down into a combination of these six motions. Such a body is therefore said to possess six degrees of freedom. The vibration of an object is always caused by an excitation force.

The excitation force may be externally applied to the object, or it may originate inside the object. It will be seen that the rate (frequency) and magnitude of the vibration of an object is completely determined by the excitation force, direction, and frequency. This is the reason why vibration analysis can determine the excitation forces at work in a machine.

These forces are dependent upon the machine’s condition, and knowledge of its characteristics and interactions allows the IRIS inspectors to diagnose a machine’s problem.