On-line Surveillance Monitoring of Gearboxes

Successful on-line surveillance based condition monitoring and evaluation of intricate industrial machinery, such as gearboxes, relies on the ability to successfully compartmentalize signals from multiple sources that are all presenting themselves simultaneously to the measurement transducer. Most industrial machines are relatively simple to monitor, as transducers are easily placed to monitor direct vibration transmission paths from the moving elements. This is true for most common machines, such as direct motor driven pumps and fans. In nearly all of these machines, transducers are positioned to “see through” a direct path to a single constrained rotating component, such as a shaft held in place by a bearing. This transducer is essentially focused on the shaft and the local bearing due to attenuation of the vibration from the shaft and opposite end bearing through a much less direct structural path. In most cases, sufficient external surface area is available to dedicate needed transducers to monitor specific internal components.

However, intricate mechanical components, such as gearboxes, are difficult to monitor, as they involve many internal components with relatively little direct external access to good vibration transmission paths. Similarly, most direct drive industrial machinery operates within reasonably narrow speed and load ranges. This is not typically the case for industrial gearbox applications, further complicating successful
condition monitoring data evaluation.

This paper addresses successful gearbox condition monitoring and evaluation through examples of both field and laboratory testing of one of the most challenging gearbox applications – wind turbines.