Acoustic emission in monitoring sliding contact behaviour

Abstract

This paper describes the usage of acoustic emission (AE) measurement in monitoring sliding contact behaviour in mechanical face seals. The mechanical face seal works normally in boundary lubrication region. If the leakage rate of the seal rises, hydrodynamic lubrication takes a part in the sliding contact. Correspondingly if the cooling water disappears it can lead to a dry contact situation. These kind of situations can contribute to failure of seals. Usually the cooling liquid in a mechanical face seal is water. At high temperatures the sliding contact becomes unstable because of cavitation in the lubrication region. The cavitation is a result of boiling of the lubricant in the contact. This cavitation can effect severe wear in the sliding materials. A measuring gauge was situated quite near the sliding contact because high frequency AE signals attenuate very quickly in boundary surfaces. The seal was tested when the sliding contact was normal and dry and also when the leakage was high. Also tests at high temperatures were made and the temperature region where sliding contact becomes unstable was determined using temperature and AE measurement.