Measurement of high amplitude relief valve noise during a full scale blowdown

Dynamic pressure fluctuations inside a pipe were measured downstream of a pressure relief valve during a full scale blowdown test. Nitrogen gas flowed with a maximum rate of 33.5 kg/s through a 3 in.x4 in. relief valve generating a peak dynamic pressure level greater than 650 kPa and sustained levels of over 450 kPa (peak). An accurate estimate of valve-generated noise is necessary when predicting radiated noise and acoustic induced vibration, which has been shown to cause fatigue failures at welded discontinuities in piping systems downstream of high pressure drop devices. These failures can be hazardous and costly, particularly when the process involves hydrocarbons such as natural gas. The measured level is compared to existing noise calculation techniques which appear to under-predict the generated noise.