The sealed function of sealed function valve is to point to valve each ability that sealed place prevents medium leak, it is the specifications index with the mainest valve. The sealed place of valve has 3 place: Open shut with valve base the contact between two sealing surface is in; Filling and lever of a powerful person match with what filling cases and be in; Body of a powerful person and the joint that a powerful person builds. Among them the leak of before one place is called inside leakage, what say normally namely close lax, it blocks influence valve the ability of medium. To blocking a powerful person kind for, leakage is unallowed inside. The leak of two place is called after outside leakage, namely medium arrives from the leak inside a powerful person outside a powerful person. Leakage can cause stock loss outside, pollute an environment, serious when still can cause an accident. To combustible explode easily, poisonous or have radiative medium, leakage cannot allow more outside, consequently valve must have reliable sealed property. The meeting after medium of medium of going from place to place has shed valve produces pressure loss (already the pressure of valve around is poor) , namely valve has certain resistance to the flow of medium, medium is about to waste certain energy to overcome the resistance of valve. From the consideration on managing the sources of energy, when design and making valve, want to reduce valve convection to use the instruction of medium as far as possible. Open shut force and open shut pitching moment to open shut force and open shutting pitching moment is to point to valve open or the active force that shut place to must bring to bear on or moment of force. When door of shut off valve, need makes open shut with send a two sealing surface it is certain to form sealed than pressing, overcome lever of a powerful person and filling even at the same time between, between the whorl of lever of a powerful person and nut, etc of place of bearing of ministry of end of lever of a powerful person grinds the attrition force of place, must bring to bear on to be shut certainly consequently force and shut pitching moment, valve is in open in closing a process, what need open shut force and open shutting pitching moment is change, its maximum is the original instantaneous in the final instantaneous that shut or open. Do one's best answers to reduce its to shut when design and making valve force and shut pitching moment. Open shut speed to open closing career is to use valve to finish open or the time that shut behavioral place to need to express. Be opposite commonly of valve open shut speed not to have strict requirement, but some operating mode shut speed to have special demand to opening, if some asks rapid open or shut, produce an accident in case, some demands are slow shut, produce water to attack in case etc, this should try to consider when choosing valve type. Behavioral sensitivity and dependability this is to show valve changes to medium parameter, make the sensitive pitch of corresponding reaction. Wait to throttle, pressure-relief valve, control valve with will adjust for the valve of medium parameter and relief valve, drain valve valve that has specific function, its function sensitivity and dependability are very main specifications index. It shows service life the durable degree of valve, it is the main function index of valve, have very great economy sense. Normally with can assuring sealed requirement open shut a frequency to express, also can express with use time. CNC Milling