Design Of Tightness Test Equipment For PE Valve

Because of the good impact resistance,low flow resistance,corrosion resistance,long service cycle and other advantages,PE pipe and valve have gradually become the prior choice in gas pipeline construction.The tightness of PE valve is directly related to public environment safety and personal security,designing a PE valve tightness testing device has a great significance in terms of ensuring product quality,increasing production efficiency,strengthen regulatory of pressure valve products.（1）Based on the technical requirements of product test standard,the principles and characteristics of direct pressure method and differential pressure method are studied;Considering theoretical study and practical test conditions,the differences of sensitivity,accuracy and pressure sensor requirement between the two methods are analyzed,the detection method of pressure tightness are determined.（2）According to the gas dynamics and thermodynamics theory,the mathematical models of tightness test are set up;Through Matlab simulation,the influence of the valve’s body temperature and ambient temperature on the detected pressure data and the impact on the differential pressure caused by gas path asymmetry are simulated,the pressure and differential pressure characteristics during aeration and detection phase in tightness test are obtained;Valves’ recovery time after pressurization of different volume summarized,the theoretical basis for designing leakage criterion are provided.（3）Considering the three core aspects of requirements “sealing,detecting,sentencing” in product test and equipment designing,a tightness test apparatus with high sensitivity is designed based on the principle of differential pressure method.The fever effect of electromagnetic valve on leakage detection is reduced by using pneumatic valve controlled by electromagnetic valve.The high-precision differential pressure sensor and analog-digital conversion chip with high effective resolution are applied,detection accuracy and sensitivity of overall leakage rate are guaranteed.（4）The designed tightness test device for PE valve is fully verified and analyzed by experiment.Parameters in the leakage criterion base on simulation result are adjusted accordingly,the smallest leakage rate that the equipment can detect reaches 8.5 × 10^-4Pa·m³/s,achieves the desired goal.