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Vibration in Machinery – Their Causes and Identification

written by: kkaarthic • edited by: Lamar Stonecypher • updated: 9/23/2008

This article briefly describes the various causes of vibration in machines that we come across in life. This article may help you learn more about identifying the causes and help you to tackle them.

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    Causes of Vibration

    identifying of the root cause of any problem helps us to tackle the same with great ease. This applies to vibration also. Most of the machines we use in our day to day life like the Mixer, Washing Machine, Vacuum Cleaner, etc. tend to indicate if something is wrong in them by means of vibration and noise (a major by-product caused by vibration).

    Even a novice is able to judge that the machine has a problem based on the sound that he or she hears from it.

    This article can provide you with at least some of the major contributors, which cause the change in vibration level of a machine. Let me discuss these now in detail.

    1. Unbalance: This is basically in reference to the rotating bodies. The uneven distribution of mass in a rotating body contributes to the unbalance. A good example of unbalance related vibration would be the “vibrating alert” in our mobile phones. Here a small amount of unbalanced weight is rotated by a motor causing the vibration which makes the mobile phone to vibrate. You would have experienced the same sort of vibration occurring in your front loaded washing machines that tend to vibrate during the “spinning” mode.
    2. Misalignment: This is an other major cause of vibration particularly in machines that are driven by motors or any other prime movers. A small figure is attached herewith to let you know about the types of misalignment. They are
    3. Bent Shaft: A rotating shaft that is bent also produces the the vibrating effect since it losses it rotation capability about its center.
    4. Gears in the machine: The gears in the machine always tend to produce vibration, mainly due to their meshing. Though this may be controlled to some extent, any problem in the gearbox tends to get enhanced with ease. The major things that tend to cause excessive vibration in gears are
        1. Misalignment of the gear axis
        2. Gear teeth running out of contact
        3. Wear and breakage of gear tooth.
    5. Loose Foundations: This is a simple area where we fail to look into in any machine that vibrates. The improper mounting of the machine without holding it rigidly to the ground causes the machine to vibrate. The next time your water pump at home vibrates be sure to check out the foundation bolts of the motor before you proceed with further analysis.
    6. Bearings: Last but not the least, here is a major contributor for vibration. In majority of the cases every initial problem starts in the bearings and propagates to the rest of the members of the machine. A bearing devoid of lubrication tends to wear out fast and fails quickly, but before this is noticed it damages the remaining components in the machine and an initial look would seem as if something had gone wrong with the other components leading to the bearing failure. Such is the criticality of the bearings in any machinery.