Simply stated, increased vibration levels-above a certain threshold-are used to initiate shutdown to enable the causes to be investigated. Many turbines are equipped with sensors for monitoring tower or blade vibrations using this method. Slightly more sophisticated techniques are needed for gear boxes.
Although vibrations would rise if a bearing failed or a tooth broke, the aim is to detect problems at an earlier stage by monitoring the details of the vibration spectrum. The key to success is in the software used for analysis of the signals, rather than in the actual sensors.
The most common problems are excessive tooth wear and, at a later stage, cracked or missing teeth. In each of these cases small but significant changes to the vibrations spectrum occur, which can be detected by the technique developed by PCH, says the company. The equipment is calibrated by measuring and recording the vibration spectrum over an initial period, but once this has been done, claims PCH, the settings can be adjusted to whatever level of sensitivity is required.