Vibration Diagnostic Guide

®

SKF Reliability Systems

Vibration Diagnostic Guide

CM5003

Vibration Diagnostic Guide

Table of Contents
Part 1
Overview …………………………………………………... 1 How To Use This Guide …………………………………… 1 Detection vs. Analysis ……………………………………... 1 Vibration (Amplitude vs. Frequency) ……………………... 1 “Overall” Vibration ………………………………………... 2 Time Waveform Analysis ………………………………….. 5 FFT Spectrum Analysis……………………………………. 5 Envelope Detection ………………………………………... 6

SEE Technology …………………………………………... 7
Phase Measurement ………………………………………... 7 High Frequency Detection (HFD) ………………………..... 7 Other Sensor Resonant Technologies …………………….... 7

Part 2
Spectrum Analysis Techniques …………………………... 13 Misalignment …………………………………………….. 14 Imbalance ………………………………………………… 16 Looseness ………………………………………………… 18 BentShaft ………………………………………………… 19 Bearing Cocked on a Shaft ………………………………. 19 Bearing Defect …………………………………………… 20 Multi-Parameter Monitoring ……………………………... 24

Appendix A
Understanding Phase ……………………………………... 25

Glossary
Glossary ………………………………………………….. 27

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Overview / How To Use This Guide / Detection vs. Analysis / Vibration (Amplitude vs. Frequency)

Vibration Diagnostic Guide Part 1OVERVIEW
This guide is designed to introduce machinery maintenance workers to condition monitoring analysis methods used for detecting and analyzing machine component failures. This document was created by field experienced SKF application engineers using measurements obtained with SKF Condition Monitoring equipment. This guide is a “Living Document” and will continuously grow as application andexperience information becomes available. It is important to note that this guide is not intended to make the reader an analysis expert. It merely informs the reader about “typical” methods of analysis and how machinery problems “typically” show themselves when using these methods of analysis. It is intended to lay the foundation for understanding machinery analysis concepts and to show the readerwhat is needed to perform an actual analysis on specific machinery. Rule 1 Know what you know and don’t pretend to know what you don’t know! Often, a situation arises where the answer is not obvious or not contained within the analysis data. At this point “I don’t know” is the best answer. A wrong diagnosis can cost greatly and can rapidly diminish the credibility of the machinery maintenanceworker. Analysis of the problem by a vibration specialist is required.

DETECTION VS. ANALYSIS
CAUSE AND EFFECT
There is a big difference between detecting a machinery problem and analyzing the cause of a machinery problem. Swapping out a bearing that is showing wear by vibrating heavily may or may not solve your problem. Usually, some other machinery problem is causing the bearing to wearprematurely. To solve the bearing problem you must solve the cause of the bearing problem (i.e. misalignment, looseness, imbalance). If not, you are not running a condition monitoring program, you’re running a bearing exchange program. It is essential that machinery problems be detected early enough to plan repair actions and to minimize machine downtime. Once detected, a cause and effect approach mustbe used to take further steps toward analyzing what caused the detected problem. Only then will you keep the problem from becoming a repeat problem.

VIBRATION (AMPLITUDE VS. FREQUENCY)
Vibration is the behavior of a machine’s mechanical components as they react to internal or external forces. Since most rotating machinery problems show themselves as excessive vibration, we use vibrationsignals as an indication of a machine’s mechanical condition. Also, each mechanical problem or defect generates vibration in its own unique way. We therefore analyze the “type” of vibration to identify its cause and take appropriate repair action. When analyzing vibration we look at two components of the vibration signal, its amplitude and its frequency. • Frequency is the number of times an event...