Rotary plug valve

A rotary plug valve comprising:

• a valve body defining a generally cylindrical bore and having inlet and outlet fluid passageways disposed therein on opposite sides of said bore, said bore being positioned transversely to said fluid passageways;
• a pair of split, semi-cylindrical complementary liner members, including an upstream liner member and a downstream liner member, together forming a generally cylindrical liner positioned in said bore, said liner having inlet and outlet fluid passageways in said valve body, and said liner including a pair of longitudinally spaced annular grooves extending in substantially parallel planes and spaced along said cylindrical bore from each other;
• a pair of radially elastically deformable, spaced retaining members disposed in tension around said liner and positioned in said annular grooves, said grooves having a depth at least equal to the thickness of the respective retaining member positioned therein whereby the outer cylindrical peripheral surface of said generally cylindrical liner is positioned radially outwardly at all points thereon from the radially outermost portion of each of said radially elastically deformable, spaced retaining members, and said retaining members are spaced radially inwardly from the valve body at a time when the outer cylindrical peripheral surface of said generally cylindrical liner is in contact with said valve body;
• a cylindrical valve plug rotatably positioned within said generally cylindrical liner, and defining a flow passageway therein positioned for alignment and registry with said liner fluid passageways upon rotation, the dimensions of said valve plug, said liner members forming said liner and said retaining members being such that at pressures in the lower part of the working range of said valve, said retaining members are held in an elastically deformed condition and said valve plug and liner are maintained in forceful contact with each other independent of said valve body, and such that at relatively higher pressures above a predetermined intermediate pressure, said retaining members are elastically expanded by the force from the development of line pressure between said upstream liner member and said valve plug, and said upstream liner member and said valve plug separate, reducing the force required to open said valve;
• and
• seal means interposed between said liner and said valve body about the peripheries of said fluid passageways in said liner.