Single vs. multi-axis measurement

The primary function of vibration monitoring is detecting maintenance issues and faults on rotating equipment. The most important point to consider when applying vibration monitoring for Real-time Maintenance (RtM) is the specific failure mode to target on your equipment.

The forces on a rotating device, such as a motor armature or a bearing, are predominately found radially to the direction of rotation. Failure modes like unbalance, misalignment and bearing damage are first detected in the radial direction. Therefore, measuring a single axis in the radial direction is the most common and effective method for applying RtM.

Some applications, such as when thrust bearings are used, involve high axial forces. Although the initial bearing fault frequencies are detected axially, they quickly become a component of the radial forces.

The second primary consideration in applying RtM technology is simplifying measurements. Ideally, making multiple-axis measurements provides the most visibility to machine health. However, reducing the number of axes measured to the most significant simplifies measurement interpretation, data management, and network bandwidth traffic. 

In summary, optimizing vibration measurements on rotating equipment to a single radial axis provides the best overall results for RtM monitoring.