Valves are used in industrial sites where flows (gas, liquid or diphasic) are in action — for example, industries of energy, oil and gas, water cycle or chemistry. The damage or the maladjustment of valves in operation cause leak flows which induce financial costs, environmental problems and safety hazards. Thus, an accurate live evaluation of operating valves would limit these risks by adjusting them or by performing less expensive maintenances. Hence, we instrumented during for nine months a valve on a nuclear power plant which is closed in normal operating condition. The aim was to measure the Acoustic Emissions AE, produced by leak or passing flows, propagate in valve. There was water vapor in ducts: 64 bar / 280°C at the upstream and 8 bar / 175°C at the downstream. A measurement system of AE, composed of three piezoelectric sensors, was developed to operate at high temperature. Our system acquired continuously and simultaneously data from four measurement channels at a sampling frequency of 1 MHz. The pressure at the downstream — which evolves as a function of operating phases of the industrial facility and, especially here, of the valve opening — was also measured. We correlated pressure measurements with acoustic emissions measurements to identify frequencies excited by AE generated by leak or passing flow in the studied valve. In addition, a data processing analysis to denoise AE signals, contaminated by industrial noises, was developed and validated by our experimental data. From the evolution of AE statistical parameters (like the root mean square or the spectral average characteristic to the acoustic intensity), which are correlated to the rate flow, we detected the apparition of valve opening, damage or maladjustment in an industrial environment.
