Vibration Monitoring: Sensor Placement Tips

Two critical elements of reliable vibration data collection are the location and installation of the sensors. The data collection point, or reading point, is where on the machine the vibration sensor will be placed. The sensor should be placed in one or more orientations or directions.

Selecting Data Collection Points

For both manual and automated vibration data collection, the selection of the collection point is critical for accurate, repeatable, and safe measurement. The following are some tips for selecting where to place vibration sensors:

• Ensure that data collection points are as close as possible to the bearings supporting the shaft.
• Avoid collecting data from areas of weak support, such as a motor cowling, as resonance can amplify readings from such locations.  Instead opt for the motor fin or other locations with rigid support.
• Confirm that the machine can be accessed in a safe manner.  Stay clear and keep hands away from rotating parts (couplings, shafts, belts, pulleys, etc.).  Avoid loose clothing and cablings from vibration data collectors getting entangled with rotating parts.
• Make sure the collection point has an adequate surface area to mount the sensor.

Nomenclature of Data Collection Points

We begin noting data collection points starting at the Non Drive End (NDE) of the Driver and walk our way towards the NDE of the Driven.  For each collection point, two orientations should be taken radial to the shaft (horizontal/vertical) and one axial. A good way to label data collection points is to use numbers to represent the position and letters to represent the direction. As shown below, if we have a motor driving a pump, our first data collection point would be 1V.  “1” stands for the Non-Drive End (NDE) of the Driver (Motor). “V” stands for vertical direction. There can be also another point designated as 2H where “2” stands for Drive End (DE) of the Driver (Motor), “H” stands for horizontal direction. 

Horizontal versus Vertically Mounted Machines

The philosophy for data collection points is the same for both horizontally and vertically mounted machines (Figures 2 and 3). Vertical and horizontal directions are usually at an angle approximately 90 degrees apart.  Axial direction is parallel to rotating shaft as shown below. 

To ensure vibration data is collected consistently from the same location, finish off by marking these locations with Steel ID Tags (for manual data collection technique). For automated data collection method, mount fixed accelerometers with the right sensitivities on the designated data collection points as noted above.

To learn more about incorporating vibration monitoring into your overall equipment maintenance and reliability strategy, contact a Reliability specialist at Fluid Life today.