Research On Experimental Table To Measure The Flow Rate Characteristic Of High Vacuum Valve

As an important part of vacuum system, high vacuum valve has a greatinfluence on the property of high vacuum system. Nowadays, production is fasterand larger, and the flow rate characteristic of high vacuum valve is expected to begood. The flow rate characteristic of high vacuum valve is usually expressed byconductance value. But it is normally to get the conductance value of vacuum valveby derivation, not by experiment. The purpose of this paper is to design a vacuumexperimental table to measure the conductance value of high vacuum valve in airflow and molecular flow.Considering the advantages and disadvantages of three methods measuringflow rate characteristic of vacuum system, this experimental table choose constantvolume method to measure the conductance value of vacuum valve. Based on theformula of judging gas state, the pressure range of valve in air flow and molecularflow can be computed. Based on the basic equation of vacuum technology andchoose commonly used combinations of vacuum chambers and vacuum pumps.Then decide the specific volume of chamber and the speed of pump. Determine theproject and procedure of experiment table, and select needed vacuum components.After calculating the volume of the vacuum chamber, the diameter and thelength of vacuum chamber can be calculated by utilizing the relationship of volumeand area. Then the thickness and the structure of shell cover of vacuum chambercan be calculated and chosen. The pressure and strain situations of vacuum chamberand channel are analyzed by using finite element software, then choose optimaldimensions.Design the measure and control system to record the change of pressure andtemperature in vacuum experimental table, and this system can also emit signal toopen the gate valve. In order to compute the conductance value of high vacuumvalve, pressure decreasing time must be known, so the pressure sensors must beinstalled. The purpose of the installation of temperature sensors is to know thetemperature variation in vacuum experimental table. When the gate valve is opened,the measure and control system is to record the pressure and temperature changes in experimental table.Based on the designed experimental table project and determined method, usesoftware to simulate the gas extraction process. Then get the time when pressure invacuum experimental table decreases form105Pa to102Pa. the conductance valueof the vacuum valve in air flow can be calculated.