the object of the invention is to provide means to connect a valve bonnet with a valve that controls the flow of high temperature fluids such that , no leakage occurs and such that removable assembly may be accomplished without the use of large wrenches and high torques . from the bonnet depends a flange formed so as to encompass the end of the valve body wall so as to allow the end of the flange to be welded to the valve body wall as at so as to seal between the body and bonnet and to withstand fluid and mechanical forces there between and to minimize thermally generated forces there between . the flange is made long enough to allow for a plurality of removals and reattachments and still be sufficiently flexible to relieve thermal stresses between the body and the bonnet .