The Phenomenon Of Surge On Large-scale Valve Trays

When the valve trays operate at low gas load,the interaction between the gas and the liquid will cause the pressure accumulate and release alternatively in the cavity under the plate,accompanied by the fluctuation of pressure.This phenomenon is called the surging of valve tray.The gas load is very lower when the tower start or stop to operate,then the surge will decline the security of tower.The resonance of the equipment will be induced,when the frequency of surge approach the nature frequency of the column,and this will lead to the destruction of tower.Surge can be observed in different size column and its upper limit will enlarge with the increase of diameter.Therefore,the research of the surging behavior in large valve column is the demand of industrial safety.The rectangular double-overflow column whose scale is 6400×800 mm~2 was used to accomplish this research with gas/water system.F-1 valves were installed on the test tray.During the experiment,the real-time pressure signals of liquid and cavity under the plate was monitored.According to these signals,the function of cavity pressure and the motion state of the gas and liquid were obtained in surging cycle.In addition,based on the analysis of hydraulic and spectral characteristics of the surge.The frequency,leakage rate and amplitude of the surge are calculated using the existing model.The vibration of liquid also affect the leakage rate,then the factor of vibration of liquid leakage was considered base on the model of Wang.A new phenomenon that frequency and amplitude was periodically varied was researched,which was called transient surge.In the next moment,based on the existing research results,the liquid layer height,frequency and amplitude during the transient surge period was calculated.Finally,the transient surge was compared with the normal surge.