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Plug valves make use of conical and cylindrical plugs to control the flow or restrict it in a system. The plug contains a hole in the middle that permits flow when the valve is open and the cavity aligns with the flow. By rotating the controlling lever, the plug within the valve assembly rotates as well, causing the cavity to become perpendicular to the flow and thus stopping it.
The design of plug valves enables them to be fully closed or opened with just a quarter turn. This piece provides information on the various kinds of plug valves, their construction and parts, common uses, as well as tips for maintenance and repair.
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Plug valves can be divided into four major groups, depending on their functionality. These groups are lubricated, non-lubricated, multi-port, and eccentric.
Lubricated plug valves contain tiny passages within the plug structure known as radial openings, which enable the movement of a lubricating substance. This lubricant effectively moves throughout the plug's length and its seating surface. Thanks to the lubricant, the act of closing, opening, and regulating a lubricated plug valve becomes smoother. Likewise, this lubricant-coated valve hinders corrosion and ensures a secure seal when closed.
Non-greased stopcock valves are commonly employed in systems with low pressure. In contrast to greased stopcock valves, non-greased ones lack automatic lubrication and are more susceptible to damage and wearing out. As a result, non-greased valves are more affordable compared to their lubricated counterparts. This makes them ideal for applications that demand minimal actuator torque.
Multiport socket valves manage the flow direction within a system using designated socket spaces. Generally, multiport valves possess more than two access points, but the flow is limited to only two ports. Hence, the crucial aspect to contemplate in the design of a multiport socket valve is the plug configuration.
Eccentric plug valves move along an off-center path while controlling the plug, which implies that the plug is not aligned with the seating ring's centerline. In an eccentric plug valve, the plug only makes contact with the seating ring when it is closed. When the valve is open, the eccentric plug does not touch the seating ring.
The primary elements of a plug valve consist of the plug, stem, handle, and body. The handle of the plug valve is connected to the stem, which in turn is connected to the main plug. By rotating the handle, the plug is turned, exerting torque on the upper part of the valve. The orientation of the stem varies depending on the type of plug valve. The main body of the plug valve houses all the major components and ensures the safety of the internal parts.
The plug contained within a plug valve differs in terms of the shape of its opening and overall structure. The shape of the plug, whether rectangular, round, or diamond, is determined by the specific application. Rectangular ports are the most commonly used and allow for the highest flow rate through the plug valve. Round ports are also frequently employed when flow restriction is not a concern. Diamond-shaped ports are ideal for precise control of flow in a system.
