A plug valve having radial ports has a spindle with a plastics sleeve biased by underlying O-rings into sealing contact against the surrounding valve body to subdivide the space between the sleeve and the bore and thereby define at least one discrete passage alignable with selected ports to permit fluid flow therebetween. The valve may be a multiway valve or simply an on/off valve.PLUG VALVES A spherical plug valve comprises a three-part casing, the middle part containing the spherical plug and an annular holding disc for sealing rings on either side of the plug.Safety valves The holding discs are mounted in the planes of separation of the valve casing. Each annular holding disc carries at its inner periphery a sealing ring coacting with the spherical valve plug and at its outer periphery a sealing ring providing the seal between the two adjacent casing parts.Bellows Seal Valves The annular holding disc may be formed by two sheet metal discs which are axially flanged at their inner periphery to form two radially spaced axially extending flanges engaging between themselves the sealing ring coacting with the spherical valve plug. A supporting ring mounted in the middle part of the casing between the plug and the holding disc supports the holding disc against pressure when the valve is in closed position and allows a limited deformation of the holding disc.

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