Union bonnet valve

Claim 1

In a union bonnet valve having a metal body having an outwardly opening recess defining at its inner end a valve chamber, a female threaded outer portion, an annular sealing corner portion between said valve chamber and said outer portion, a first passage opening through an annular valve seat to said valve chamber and defining therewith a valve seat, a second passage opening to said valve chamber in spaced relationship to said valve seat, a metal bonnet extending into said recess, a valve stem longitudinally movably carried by said bonnet and defining an inner movable valve portion selectively seatable on said valve seat for controlling fluid flow between said passages, and a stem-to-bonnet seal accessible from outwardly of said bonnet for movably sealing the stem to said bonnet outwardly of said valve chamber, said seal being removable from the valve with the movable valve portion of the stem seated on said valve seat to permit in-service replacement of the seal when desired, the improvement comprising: an inwardly facing frustoconical surface on said metal bonnet abutting said sealing corner portion and an outwardly facing shoulder outwardly thereof; and a union member having a through bore coaxially mounting said bonnet and having an outer male thread removably secured to said body female threaded portion, and an inwardly facing shoulder engaging said bonnet outwardly facing shoulder to urge said bonnet inwardly facing frustoconical surface nonrotatively sealingly against said body sealing corner portion thereby providing a high pressure metal-to-metal line contact seal comprising the sole means for sealingly securing the bonnet to the body, said bonnet frustoconical surface extending inwardly beyond the sealing corner in the made-up condition of the valve.