We often hear about how to correct unbalance in rotating machinery, but to correct unbalance, it is first necessary to accurately diagnose what type of unbalance your machine is experiencing so that you can take the proper action to correct the problem.
In this post, we will go over the three types of unbalance you may come across. In a follow-up post we will address more details of unbalance: its causes, how to fix it, and other problems often incorrectly diagnosed as unbalance.
The three common types of unbalance are:
Each type of unbalance will reveal itself in the machine’s vibration amplitude and phase angles.
Now let’s break down what each of these types of unbalance looks like in your machinery.
First, static unbalance.
Static unbalance occurs when the unbalance is at the center of gravity. The vibration amplitude will be the same on both bearings and the phase angles will also be the same.
Next, couple unbalance.
Couple unbalance occurs when the principal inertia axis is displaced from the rotational axis, and the axes intersect at the center of gravity. The vibration amplitude will be the same on both bearings as with static unbalance, but the phase angles will be 180 degrees different.
Lastly, dynamic unbalance.
Dynamic unbalance is a mix between static and couple unbalance and occurs when the principal inertia axis is displaced from the rotational axis and does not intersect at the center of gravity. Both the vibration amplitude and the phase angles will be different.
To learn more about unbalance read our follow up post here.
Also, to purchase products which will help you diagnose unbalance in your machinery, visit VibrAlign’s online store, where we stock products that do everything from helping you diagnose the details of unbalance and what steps you should take to correct it to the tools you need—such as balancing weights and clamps—so that you can take action to correct unbalance and excess vibration and get your machinery back to an optimal functioning level.
Photo courtesy: iStock/ivandan