A rotary plug valve having a plug member rotatable in a valve housing between an opened position and a closed position, the housing member having a valve seat therein with a first passage opening to the seat and a second passage opening to the seat, and sealing means such as an endless sealing ring and an endless groove encircling one of the openings of the first and second passages to the seat.PLUG VALVES The rotary plug valve is capable of two-way flow therethrough, and this is realized by providing the passage in the plug member which has the sealing means encircling its opening with a greater width in a plane transversed to the axis of rotation to the plug member than the width of the other passage.Globe Valves By such an arrangement the sealing ring when encircling the opening of the passage functioning as an inlet passage is not lifted from its groove upon closing of the valve as a metal to metal seal between the plug member and the seat of the housing member at the downstream end of the passageway in the plug member is created before a critical flow condition is reached, thus, alleviating the high velocity flow through the plug member which would cause a low pressure condition to exist around the unsupported portion of the sealing ring.

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