Structure-borne Acoustic Activity Monitoring
When a pressurized fluid such as steam or water escapes through a leak in piping, valves, or feedwater tubes, it generates acoustic emissions which travel through the component’s structure. Small holes generate high frequency acoustic emissions (above the audio frequency range) as the hole increases in size the low frequency complement of the acoustic emission increase and the airborne noise can be heard.
To detect the acoustic emissions early, the structure-borne waveguide is connected to the component to be monitored. The waveguide serves two functions: (1) it couples the acoustic emissions from the component to the sensing device and (2) it protects the electronic sensing device from the high temperature of the component being monitored.
The sensing device is a piezoelectric crystal which converts the acoustic emission signals to low energy electrical signals.