Vibration Diagnostics - What is it all about?
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What is vibration diagnostics?
Vibration diagnostics is a major part of predictive machine maintenance programs. Over the years, vibration diagnostics has proven to be the most effective method for checking “machinery health“. Vibration diagnostics tools are here to help us to predict machine failures. When predictive maintenance is applied and the machines are checked regularly, machine faults can be discovered at an early stage and appropriate action can be taken. By doing so you can avoid unexpected machine shutdowns and you can avoid replacing parts which are still in good condition. Adash supplies a full range of vibration diagnostics equipment, from simple data collectors to advanced vibration analyzers and on-line monitoring systems. The data from the devices can be transferred to Adash software for further analysis.
How does it work?
Running machines generate vibrations, which contain a lot of information about their condition. A vibration meter or analyzer is used to measure this vibration. The sensor needs to be mounted on an appropriate point on the machine (e.g. bearing housing). The instrument measures the vibration signal, tells you the severity of the vibrations and also possible machine faults. The most frequent faults are bearings faults, unbalance, misalignment and looseness.
2 Predictive Maintenance, Machine Condition Monitoring, Vibration Diagnostics - What are these terms?
Vibrations and Vibration Diagnostics
Let’s explain briefly what the vibrations, which we are focusing on, really are. Electric motors vibrate when running and you can hear a sound (a noise) because noise is in fact vibration. We guess there is no need to explain that when you speak your vocal cords generate vibrations which are transmitted through the air to other person’s ear. You cannot see these vibrations, but you can hear them. Imagine the bass speaker while playing some music. Can you see the movement of the speaker membrane? Yes, you can. But can you see the movement of the motor while it is running? Not really. To ‘see’ a motor’s vibrations we’ve got some excellent helpers today: an acceleration sensor and vibration meter or analyser.
Talking about the speaker again, can you separate each noise which comes from the speaker while playing some music? You can easily separate basses (low frequencies) from trebles (high frequencies) with an equalizer. Why we are still talking about speakers? Because it is very similar to the vibrations on the machine. On the machine we also want to separate those ‘bass and treble’ noises but here we are talking about separating machine faults, such as overall machine condition related to shaft speed (low frequency) and bearing / gearbox faults (higher frequency).
To separate these faults we use the vibration meters and analysers mentioned above. While performing Vibration Diagnostics we want to distinguish two important things which we get from the signal: overall machine condition and bearing condition, (as each of them is diagnosed from different parts of the vibration signal.)
Vibration Diagnostics is more sophisticated of course and later on you will find out that you need to separate more vibration sources which are generated by a running machine (for example loose foundation bolts, unbalance, misalignment, fan blade faults, gear mesh faults and many more.) But for now let’s just talk about those two basic things for easier explanation.
Machine Condition Monitoring
There are more methods for evaluating a machine’s condition and its faults. Besides Vibration Diagnostics you may have heard about Ultrasonic detection, Thermography, Non-destructive Testing etc. and all these methods are part of Machine Condition Monitoring. Each method has its pros and cons; it is up to your maintenance program which methods you select (or combine them) and which methods are the best for your particular machines. However, during the last few decades it has been found and proven that Vibration Diagnostics is the most efficient and reliable method for most rotating machinery.
3 How should I start my Predictive Maintenance Program?
Which machines should I measure and when?
You need to consider which machines are critical for your factory’s production. These critical machines should have the biggest priority over the other machinery and you should also consider how much time you can spend to measure them regularly. It is ideal to measure the machines every week, but we are not living in an ideal world. Despite that, try to schedule measurement of those particular machines at least once per month.
Note: If you plan to measure your machinery every half a year, please close this document and throw your vibration meter / analyser into the trash. It does not make any sense to measure with such a huge time span. It would not be predictive maintenance but the run to failure method. Imagine how many things can happen during this half a year…
To separate these faults we use the vibration meters and analysers mentioned above. While performing Vibration Diagnostics we want to distinguish two important things which we get from the signal: overall machine condition and bearing condition, (as each of them is diagnosed from different parts of the vibration signal.)
Vibration Diagnostics is more sophisticated of course and later on you will find out that you need to separate more vibration sources which are generated by a running machine (for example loose foundation bolts, unbalance, misalignment, fan blade faults, gear mesh faults and many more.) But for now let’s just talk about those two basic things for easier explanation.
Machine Condition Monitoring
There are more methods for evaluating a machine’s condition and its faults. Besides Vibration Diagnostics you may have heard about Ultrasonic detection, Thermography, Non-destructive Testing etc. and all these methods are part of Machine Condition Monitoring. Each method has its pros and cons; it is up to your maintenance program which methods you select (or combine them) and which methods are the best for your particular machines. However, during the last few decades it has been found and proven that Vibration Diagnostics is the most efficient and reliable method for most rotating machinery.