ULTRAHIGH PURITY GAS VALVE WITH ENCAPSULATED BELLOWS

摘要

In an ultrahigh purity sealed gas valve of the Y-type having a bellows located in a stem bore, a second seat is provided so that the seat seal engages the second seat to seal off the space within the bonnet tube and the bellows from communicating with the gas flow path, thereby preventing contaminating particles from the bellows from entering the gas system and also decreasing the dead space presented to the closed gas system by the valve. A purge port is located between the open and closed positions of the loseat seal thereby permitting purging gas to bathe the sealing members and the bellows in both positions.