Research On Accoustic Emission For On-Line Valve Leak Monitoring Technology

In the system of fluid transportation piping, valve is a common mechanical product, its major action is to isolate the device and the piping system, prevent backflow, control the pressure and flow, so the safety is very important. In the petrochemical system, valve is a common component, of wide varieties and huge quantity, besides in the process period of petrochemical system, the product is always corrosive, flammability and explosive. In-service use, valve leaks can be found all the time, most of them are invisible, so not only raw material and product are wasted, but also the environment is polluted, even disastrous may happen. According to the statistics, about 22% of the industrial valves have leaks, in recent 30 years, there are more than 100 big fires and explosions,35.1% of them bring about leak of valves and pipes; the device of petrochemical system, valve leaks bring on 60% of the exhaust of voc without control. So in the process of petrochemical, it's very important to detect the leaks in time.Acoustic emission is stress wave produced by burst movement in stressed material. When the valve leaks, the fluid will eject from the gap, so the turbulence turn up, the acoustic emission brings forth due to the turbulent flow impacts the interior of the valve. AE signal turn up, which spreads to the valve and excites a sensor, then the AE system will measure if the valve is leaking or not.ISD9203B AE sensor and VAPC 1278 of PAC, besides the labview software are used on this research. The leaks can be monitored at real time, the leak rate can be evaluated at the same time.The use of AE on valve leak is at the initial phase, it's far from full application in the petrochemical system. This research makes further efforts in the use of AE on valve leak, push forward the development of AE in valve leak detection.