Ultrasonic detection of lubricating film collapse in mechanical seals

Mechanical seals generally fail as the result of the collapse of the lubric ating film between the faces. In the present research, a system that detect s the collapse of the lubricating film in a gas seal has been developed. Th e system uses an active ultrasonic transmission technique to monitor the fl uid plm. Sensors are placed behind each stator of a double mechanical seal. A series of ultrasonic sinusoidal,wave packers is generated by one transdu cer while the second transducer monitors the signal transmitted through the seal interface. A weak transmitted signal indicates a continuous fluid fil m, while a strong transmitted signal indicates contact between the seal fac es. The transmitted signal is relatively independent of the seal characteri stics and operating conditions, and can be easily distinguished from machin ery noise since its frequency and amplitude can be controlled.