51 which in turn has mounted to its upper surface valve seat 53 which in turn has mounted to its upper surface upper seal 55 the upward facing face of upper seal 55 is in contact with downwardly facing port face 59 of port flange 23 adjacent to and extending outwardly away from fluid port 25 to form the lower surface of port flange 23 lower seal 51 and upper seal 55 are conventional seals as are well known and used in glass lined chemical reactor vessel connectors being in the form generally of flat washer like gaskets examples of suitable seal materials could be neoprene rubber and ptfe fluorinated polymers depending upon the application in which the chemical reactor vessel is being used it is preferred however that the outer diameters of both lower seal 51 and upper seal 55 are no larger than the internal bore 39 of valve housing 19 and that the inner diameters of lower seal 51 and upper seal 55 are generally about equal to or slightly smaller than the diameter of fluid port 25 this is to ensure a full seal across port face 59 and body face 49 and that there is no projection or surface of either which is not fully in contact with and sealed by either lower seal 51 or upper seal 55 thus preferably no surface of port face 59 or body.