In a single-ported double-seated valve mechanism having valve body means having an inlet and outlet communicated by a flow passage, a valve bonnet secured to said valve body means, a valve trim assembly disposed within said valve body means, said valve trim assembly having a valve cage including flow openings therein, a seat ring secured to said valve cage, a valve plug having an enlarged upper diameter slidably disposed within said valve cage, and a spring means within said valve plug, the improvement comprising a first and second valve seal and a first and second sealing edge formed on said valve plug cooperating with said first and second valve seals to control fluid flow through said flow openings in said valve cage,Safety valves said first and second valve seals comprising annular seals, said first seal retained by said seat ring and said second seal retained by said valve cage whereby said first and second valve seals are protected from the fluid flow, said first and second sealing edge comprising a knife edge, said first sealing edge projecting downwardly from the perimeter of the base of said valve plug and said second sealing edge projecting downwardly from the enlarged upper diameter of said valve plug, Bellows Seal Valvessaid first and second sealing edges slightly penetrating said first and second valve seals whereby a leak tight seal may be made without adjustment of seat-to-seat dimensions after dis-assembly and re-assembly.

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