The Design Of Automatic Helium Leak Detection System Of Thermal Expansion Valve

This paper studied the thermal expansion valve of helium massspectrometer leak detection technology and optimizes the existing leakdetection technology. An automatic mass spectrum leak detection system in avacuum-vessel is designed and developed in order to satisfy the need for highprecision and fast detection of the refrigeration component in large-batchproduction.Firstly, the paper analyzes the disadvantages of the traditional thermal expansionvalve leak detection method in efficiency and accuracy, describes theprinciple and method of helium mass spectrometer leak detection. Thedevelopment of helium mass spectrometer leak detection technology at homeand abroad has been widely investigated; this paper develops an automatichelium mass spectrum leak detection system, which has the vital significance tothe production and testing industry of thermal expansion valve.Secondly, the paper proposes the design of automatic helium massspectrum leak detection system of thermal expansion valve including thehardware architecture and software. The system is composed of pneumaticsystem, electric control system and testing software. Pneumatic system isresponsible for the implementation of the product leak detection work,including the stability of gas leak detection and the vacuum degree necessaryfor the leak detection; Electrical control system to realize the coordinatedcontrol of the various components. Make alternating testing between eachstation, to complete the whole process of leak detection. The software designof the leak detection system comprises the human-computer interactioninterface and PLC software.Finally, the paper analyses the influence factors of leak detection system,study on the mathematical model of vacuum process. The system pipe size andarrangement are calculated to match the pipeline flow and vacuum pump pumping speed, and the whole system was optimized. System achievesmulti-station simultaneous online real-time detection with detection speed of15second for a unit. The smallest leak rate detected is up to1×10-7mbar l/smeeting the specification of high-precision online testing.