SEE Technology

What is SEE?

SEE Technology is a new type of bearing fault detection method which breaks away from the traditional approaches to the problem by using high frequency, acoustic emission detection in the frequency range of 250,000 Hz to 350, 000 Hz. This technique has characteristics that set it apart from normal vibration analysis at 0 to 20 kHz and other enveloping techniques at 5 kHz to 60 kHz. SEE provides an excellent way of monitoring problems with bearings that other current techniques cannot provide. Some of these advantages are detection of: early bearing defects, lubrication problems which stem from contamination and fretting.

An acoustic emissions transducer is sensitive to metal-to-metal contact that occurs when bearing elements roll over a bearing race without an intervening lubricating layer. The transducer emits a high-frequency, pulsed voltage that gives evidence of the defective event.

A higher than normal SEE reading, based on a statistical mean and standard deviation, would suggest either insufficient lubrication or the beginnings of a bearing defect. If the readings were to return to normal after the application of additional lubricant, you can assume that the proper corrective action was taken.

Any Questions? Take a look at the SEE FAQ

Taking SEE Measurements

Low frequency vibration is measured by firmly placing a sensor close to the part of the machine being measured. The more securely the sensor is placed, the better the reading is. This is not true with SEE readings. Secure placement does not mean better readings. A vibration probe actually moves with the machine it is resting on. The machine's vibration is transferred to the probe which has a crystal inside which shakes with the probe. The crystal converts the mechanical motion into electrical signals.

The SEE sensor is, for all practical purposes, a microphone. It does not have to be held firmly to the machine to get a good reading. The SEE sensor is listening for acoustic signals to be transmitted from the surface under it. Since these acoustic signals attenuate very easily, and air is an excellent attenuator for acoustic signals, they will not reach the SEE sensor if the transducer is held against the machine.

The secret is in the coupling between the machine and the sensor. The coupling most widely used is grease. Grease fills the air gap between the sensor and the surface of the machine resulting in the acoustic signals travelling from the machine, through the grease to the SEE sensor.

The following tables show some probable correlations between normal vibration and SEE enveloping readings.

For advanced Spectral Analysis using SEE Technology please refer to "Identifying the stages of bearing damage" in the Case Studies section

Although care has been taken to ensure the accuracy of the data compiled on these pages, the aptGroup does not assume any liability for error or omissions. SEE Technology is a trademark of SKF Condition Monitoring

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