Vibration Diagnostics - Basic Information; Introduction; Basic Rules - Adash 4900 Vibrio III Manual

ADASH Ltd. Adash 4900 – Vibrio III

Vibration Diagnostics - Basic Information

Introduction

What is it the vibration diagnostics? This chapter explains the basic steps and you will be able to begin
practical measurements. More information you can find in the literature.
If we are talking about the vibration diagnostics, we mean regular measurements (usually every
2-4 weeks), whose objectives primarily are:
1. Finding of change of vibration level, it means change of machine operational condition.
2. Determining reason for this change.
3. Recommending maintenance (repair, adjustment, lubrication etc.).
4. Checking of maintenance success (including revision of dismantled part to confirm the
analysis).
The machine vibration diagnostics solves two basic tasks:
1. Diagnostics of machine mechanical failure (imbalance, misalignment, mechanical
loosenes etc.).
2. Diagnostics of rolling bearing condition.

Basic Rules

1. If the measured value of vibration increases in time, it is a change indicator - worsening of
the machine condition.
2. If the measured values do not change, the machine works in stable operation condition.
This does not necessarily mean that this state is good. For example if a bearing was installed
incorrectly, then there would be a high signal value immediately. This value will remain stable for some
time (the bearing will be able to withstand it), but then there will be a fast increase and destruction of
the bearing. This short bearing life can take hours, days, weeks or even months.
3. Reliability of the diagnostics will never be 100%.
There will always be defects, which develop in time shorter than regular measurements. The defects
that are caused by material fatigue can develop in several seconds only (cracks, breaks). The proof of
the diagnostic performance is primarily a decrease in maintenance costs (not to absolute zero) and a
significant decrease in unexpected breakdowns (not their complete elimination).
4. Using of standards is possible only with special machines, for which the special standards
exist.
It is not possible to simply define limit vibration values in general for a wide range of machines.
However, it is possible to create the standards for special machines (e.g. turbines), and these
standards are a strong diagnostic tool. General standards have a character of recommendation on
how to define the limit values. The way how to find the good condition values is to use measured
values of new or repaired machine. Also you can ask the machine producer for them.
5. Shortening of an interval between measurements means more successful prevention of
unexpected failures.
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