This MSc. thesis has been carried out at the university Politecnico di Torino. As, early failure detection has been an integral part of condition monitoring of critical systems, such as wind turbines, helicopter rotor drivetrains etc. On many occasions, driveline components fail catastrophically, leaving no evidence of the root cause of failure and causing extensive damage to test equipment. This can be avoided by detecting failure in early stages. Most of failure detection techniques are based on oil debris monitoring of gears. The objective of this thesis is to find a correlation between oil debris amount, caused by two phenomena wear or pitting and failure mechanism.