Vibration Diagnostics - Basic Information; Introduction; Basic Rules - Adash A4900 - Vibrio M User Manual

Adash 4900 – Vibrio M

Vibration Diagnostics - Basic Information

Introduction

What is vibration diagnostics? This chapter explains the basic steps you will need to be able to begin
practical measurements.
When we are talking about vibration diagnostics, we mean routine measurements (usually
every 2-4 weeks), whose primary objectives are:
1. Finding changes in vibration, which in turn means a change of machine operational condition.
2. Determining the reason for this change.
3. Recommending maintenance (repair, adjustment, lubrication etc.).
4. Checking 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 looseness etc.).
2. Diagnostics of rolling bearing condition.

Basic Rules

1. If the measured value of vibration increases in time, it is an indicator of a degrading machine
condition.
2. If the measured values do not change, the machine is in stable operating condition.
However, this doesn't necessarily mean ideal condition. For example, if a bearing was installed
incorrectly, then there will be 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 can develop quickly in between routine measurements and thus
are not caught by the analysis. The defects caused by material fatigue can develop in seconds
(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 standards is only possible for 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 standards for special machines (e.g. turbines), and these
standards are a strong diagnostic tool.
General standards should be determined by comparing a unit with similar machines as well as
asking the machine manufacturer for any suggested vibration guidelines they have created for
their specific models. Once baseline data is established (several consecutive readings), it will
become easier to identify unusual spikes in vibration level and patterns.
5. Shortening the interval between measurements means more successful prevention of
unexpected failures.
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