Ph.D. Thesis Defense by William B. Anderson
Wednesday, April 4, 2001

(Drs. Jacek Jarzynski and Richard Salant, co-advisors)

"Development of a Condition Monitoring System for Mechanical Seals"


Mechanical Seals are important components in pumps, compressors, turbines and other turbomachines.  Such machines rely on the proper operation of the mechanical seals, and the failure of a turbomachine is often the result of seal failure.  A monitoring system that could detect a precursor to seal failure would be beneficial and would allow for preventative action.

Often, the failure of a mechanical seal is the result of excessive face contact, which therefore is a precursor to seal failure.  Research on a mechanical seal monitoring system that detects face contact and measures the degree of contact will be presented.   An ultrasonic pulse-echo technique is the basis of the monitoring system.  Ultrasonic transducers are mounted on the back of the nonrotating seal face.  An ultrasonic wave packet of known frequency and amplitude is transmitted toward the seal interface and the reflected signal amplitude is monitored. A decrease in the signal amplitude indicates contact, while the degree of contact is indicated by the magnitude of signal change.  Experiments showing the feasibility of the system have been conducted with both gas and liquid seals.  A theoretical model of the wave propagation through the seal has been developed to support the experimental results.