Understanding Bearing Position Numbering & Orientation


This article will help guide you to the nomenclature used to define vibration test locations in the ALERT vibration analysis software.  This article covers the location on the machine where a sensor is connected to collect vibration data and the relative orientation for triaxial measurements.  These principles apply regardless of the type of acquisition hardware used and sensor type including single channel sensor usage.

Bearing Position Number (Location Number)

A bearing position number defines measurement locations in the data collector and ALERT database. The examples below illustrate how the bearings are commonly sequenced beginning with the free end of the prime mover and following the flow of energy through the machine train. 

This numbering scheme is only a convention and not a rigid rule that must be followed.  As long as the digits within the “pickup codes” (MID) agree with the “bearing position numbers” (in the Location), the Expert System will work just fine.  The bearing position numbers must be between 1 and 99.


The Expert Automated Diagnostic System (EADS) does not require all bearing positions to monitored to perform vibration analysis on a machine and thus the bearing number should allow a user to easily be able to reference the software applications relative to the machine position of interest.  For example, if directed to collect data on bearing position number 2, a user should be able to understand this position is the drive end of the prime mover (e.g., motor). 

Best engineering practice, however, defines the number of positions desired based on distance between bearings, HP rating, frame size, and flow or other disturbances.


SymphonyAI Industrial programs use two different nomenclatures to define orientation based on how the machine shafting is oriented with respect to its foundation and considers two cases:  1) Machines mounted with horizontal shaft centerline; and 2) Machines mounted with vertical shaft centerline.  Below are typical examples of each type.


Orthogonal Axes

The three orthogonal axes of a machine relate to the three, simultaneous directions of data capture from the acquisition device, such as TRIO (portable), Watchman AIR (wireless), SPRITE (online).  Even if a single axis sensor is used, the nomenclature is still defined to associate the input channel to the sensor position.

When installing a wireless sensor or mounting/attachment pad, it is important to recognize the associated channels as they will relate to the orientation once installed.

The wireless sensor as a label at the top which illustrates the position of channels 1, 2, and 3.

A mounting pad has a thread connection, either a hole/screw or relative mount as well as a notch or alignment pin.  Channel 1 always references towards the in-line mounting position (into the capture screw hole).  Channel 2 is always in the direction with the notch or alignment pin.  For wireless, channel 2 is in the relative position of the power button.  Channel 3 is perpendicular to channel 2.

When referencing the orientation in the ALERT software, including the data collectors and mobile application, a 3-letter code is always used.  These three letters refer to the direction related to the three capture channels.  The nomenclature used is determined by how the machine is physically oriented.


Horizontal Machines

The preferred nomenclature for horizontal machines is Vertical, Horizontal, and Axial where the horizontal axis is in the direction of vibration in horizontal plane, vertical axis is vibration in the vertical plane, and axial is vibration in line with the shaft's axis.


Vertical Machines

Given a vertical machine would have two horizontal planes, the preferred nomenclature for vertical machines is Radial, Tangential, and Axial where the radial axis is in the direction radial to the circumference of the asset, tangential axis is tangent to the circumference of the asset, and axial is vibration in line with the shaft's axis.  



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