Abstract
Vibrations in rotating machinery are commonly the result of mechanical faults including mass unbalance, coupling misalignment, mechanical looseness etc. Rotating machinery with overhung rotors is very common in industries. Unbalanced rotor and misaligned shafts usually cause excessive machine vibration, generates large forces on bearings and thus reduces the machine life span and may lead to property loss and even loss of human life. Two-plane balancing of overhung rotors is one of the most challenging problem that maintenance engineers may encounter. As a prerequisite, successful diagnosis of unbalanced overhung rotor system must be performed. The vibration signatures of unbalanced overhung rotors with unknown initial conditions are different from those of the systems with centre hung rotors that has been studied in the present work. Experiments were carried out on a Machinery Fault Simulator-Lite (MFS-Lite) for both balanced and unbalanced rotor systems. The data were analysed using the Balance Quest software and efforts were focused on identifying the system characteristic signatures. Further, the results were verified through analytical methods and the results were found to be satisfactory.
Highlights
A small amount of unbalance weight in rotating system may have devastating effects as the system is operating with high speed or running near the critical speed
We have compared these results for two planes (Centerhung) from Analytical Results which is calculated from Influence Coefficient Method and has been shown in Table
The Experimental Results for Single Plane and Two Plane Centerhung and Overhung rotor conditions were carried out with different operation speed, different unbalance type and different unbalance weight. This has been shown by Analytical Method i.e. (Influence Coefficient Method) in order to check the correctness of the results
Summary
A small amount of unbalance weight in rotating system may have devastating effects as the system is operating with high speed or running near the critical speed. Srinivasan [3] has done comprehensive experimental studies in the rotating machinery for the faults like misalignment (parallel misalignment from 0.025 mm to 0.65 mm, angular misalignment from 0.02 degree to 0.6 degree), unbalance (105.06 gm-cm to 491.98 gm-cm), mechanical looseness, rotor rub, bearing clearance (from 0.02 to 0.08 mm) and crack (transverse cracks of width 0.75 mm and depth ranging from 1.02 to 4.02 mm at the mid span of the shaft). Vyas and Satish [5] have carried out experimental studies to generate data and discussed the development of neural network simulator for prediction of faults like mass unbalance, bearing cap looseness, play in spider coupling and rotor with both mass unbalance and misalignment and health machine network. Fault simulated were: Mass unbalance, Loose Bearing cap & Misalignment and both mass unbalance & misalignment
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