Abstract: A unitary block of steel is formed into a manifold by a feeder bore that is intersected by one or more common branch bores. The common brach bore includes a first branch and a second branch which extend along the common branch bore axis in opposite directions from the feeder bore. The first branch is intersected by a first stem cavity and the second branch is intersected by a second stem cavity, and the valve stems are located in these cavities. In this way, the manifold block is formed by boring operations instead of by casting, the flow of gas through the branches is unimpeded by obstructions or offsets in the flow path.

Abstract: A sealed valve intended for use in ultrahigh purity applications uses a metal-to-metal seal in a crucial, but unacessible, portion of the valve. The metal-to-metal seal avoids the use of a weld which because of the location could not be adequately cleaned, and avoids the use of an O-ring seal. The O-ring seal typically would have a leak rate on the order of 10.sup.-7 standard cubic centimeters per second of helium, but the metal-to-metal seal provides a leakage rate of less than 10.sup.-13 sccm/s. In the preferred embodiment, the seal is formed by forcing a conical part into the opening of a bore. The force used is small emough to avoid permanent deformation of the sealing parts, and thus the seal can be opened and closed any number of times without degradation.

Abstract: 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 seat seal thereby permitting purging gas to bathe the sealing members and the bellows in both positions.