STUDY OF IDENTICAL FREQUENCY RELATED FAULT DIAGNOSIS THROUGH VIBRATION SIGNATURE ANALYSIS IN A RIGID ROTOR

Abstract

Due to the presence of competitive environment, high productivity with quality production has become necessary requirement of the industries today. Proper and timely maintenance of the machines is most important to achieve this goal. Early fault detection in a machine is a key element of effective maintenance, because of its importance; the diagnosis of machine faults at an early stage has become necessary requirement of maintenance strategy. There are many standard fault diagnosis techniques available today. Vibration signature analysis is one of them. The present work is related to the same field. . An attempt has been made to develop a method to detect some pre-selected possible faults in any rigid rotor of a machine. Being a most critical component of any rotary machine, a rotor has been chosen for study in the present work. Broadly a fault diagnosis through Vibration Signature Analysis techniques involves capturing of vibration signal at key points of the machine element followed by an extensive analysis of it. A vibration signal incorporates lot of hidden information about various faults in a machine. The basic task is to explore hidden information in signal and use it for fault diagnosis of various components of the machine. The process is not simple and straightforward. A signal needs to be first electronically conditioned before sending it for mathematical analysis to explore valuable information. Study of vibration signals in frequency domain is very popular. This is so because most of the machine faults are related to some known frequency. There are standard charts which give information about possible faults in machine and their associated frequency. A continuous increase in amplitude of vibration at any frequency indicates presence of fault in the machine associated with this frequency. But problem is faced when more than "one fault is associated with same frequencies. Variation in amplitude at these frequencies indicates the presence of faults but fails to tell exactly the types of faults. Such a situation iv arises in the case of rigid rotor when it is prone to three faults namely (1) Rotor imbalance (2) Rotor axis offsetting (3) Combination of imbalance and misalignment.. Both of the faults correspond to frequency, which is same as rotational frequency and its first to harmonics. Aim of the project is to study the variation pattern of amplitude so as to differentiate the two. A test rig is designed and fabricated to simulate the fault of known level. Experiments were conducted to take vibration signals under various fault levels. The signals are processed in MAT LAB environment to explore valuable information. Results obtained are as per the expectation. V