Ultrasonic detector for sensing power station valve closure - employs piezoelectric transducer to sense position of metallic part on valve head

摘要

The system avoids erroneous indications, given by a push rod indicator, which are caused by the build up of oxides. The valve comprises a metallic head on an arm which pivots on a support. A metallic section, at the edge of the head, and adjacent to the valve seat moves with the head to displace between two identical ultrasonic transducer heads. These are supported on a pillar mounted on the valve body. The transducers are connected via coaxial cable to electronic circuits which generate the ultrasonic signals and effect processing of the received signals. The detectors comprise a piezoelectric transducer and a thin, vibrating metal plate. The transducers are formed from a polarised, ferroelectric ceramic.