This invention relates to an improved plug valve, more particularly to a plug valve having a plug shaped so as to provide even wear between the engaging surfaces of the plug valve and valve body, thereby, maximizing the useful life of the valve.
A plug valve, sometimes referred to as a globe valve or a ball valve when the plug is so shaped, comprises a valve body with an inlet passage, an outlet passage and a valve chamber between the inlet and outlet passages. The valve chamber generally has the shape of a body of revolution such as a sphere, a cylinder, or the frustum of a cone, with its axis of rotation usually perpendicular to the inlet and outlet passages which are usually colinear. A valve plug shaped generally to conform to the shape of the valve chamber, is rotatably disposed within the chamber. The valve plug is generally a solid body with a flow passage therethrough. The flow passage is positioned such that when the valve plug is in an open position the flow passage is aligned to provide fluid communication between the inlet and outlet passages. When the valve plug is rotated to a closed position usually at a position 90.degree. from the open position, the flow passage is not aligned with the inlet and outlet passages, and solid portions of the valve plug interrupt fluid communication therebetween. A complete practical plug valve also includes connecting means such as threads or flanges at the openings of the inlet and outlet passages so that the valve may be connected into a fluid pipeline or a conduit to provide control of fluid flow therein. A plug valve also includes rotating means so that the valve plug may be rotated between the open and closed positions. The rotating means usually is a valve stem extending through the valve body and sealed with packing in a manner well known in the art. The valve stem may be rotated manually, by electric or hydraulic means or automatically controlled.
Sealing between the valve plug and the valve body is accomplished either with elastomeric gaskets or by surface to surface pressure between the plug and the valve body. The present invention relates to a plug valve wherein sealing between the valve plug and the valve body is accomplished by surface to surface pressure.
Plug valves of the type described are often used in chemical process applications such as in nuclear fuel processing plants. In such plants, plug valves are used for cell wall block valves or they may be used in pipelines containing nitric acid, hydrofluoric acid, sulfuric acid or sodium-hydroxide. Also in such plants, plug valves are used as process control valves in connection with waste calcinators. In this application, plug valves are used to control the flow of slurries containing solid particulate matter. Especially in this latter application where such valves are operated several times per hour, the valves are subject to wearing between the mating surfaces of the valve plug and the valve body. Such wearing requires frequent maintenance and/or replacement of the valves or valve parts.
Accordingly, it is an object of the present invention to provide a plug valve with improved wear characteristics between the plug and the valve body. Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the embodiments and combinations particularly pointed out in the appended claims.