Based on structural design, plug valves are categorized into four types: tight-fit (adjustable), self-sealing, standard, and lubricated (oil-injected). Based on flow path configuration, they are classified into straight-through, three-way, and four-way types; ferrule-type plug valves also exist.
Classified by application, plug valves include: soft-sealed, oil-lubricated hard-sealed, lift-type, and three-way/four-way plug valves.
Soft-Sealed
Soft-sealed plug valves are typically used in demanding environments involving corrosive, highly toxic, or hazardous media; in applications where leakage is strictly prohibited; and in scenarios where valve materials must not contaminate the medium. Valve body materials-such as carbon steel, alloy steel, or stainless steel-are selected based on the working medium.
Oil-Lubricated Hard-Sealed
Oil-lubricated hard-sealed plug valves are categorized into conventional oil-lubricated types and pressure-balanced types. Specially formulated lubricant is injected from the top of the plug into the space between the valve body's tapered bore and the plug itself, creating an oil film that reduces operating torque while enhancing sealing performance and service life. These valves can operate at pressures up to 64 MPa and temperatures up to 325°C, with sizes reaching up to 600 mm in diameter.
Lift-Type
Lift-type plug valves come in various structural designs and are classified by sealing surface material into soft-sealed and hard-sealed types. The basic operating principle involves lifting the plug before rotation during opening-thereby minimizing friction against the valve body's sealing surface-and lowering the plug into contact with the sealing surface only after it has rotated to the closed position.
Three-Way and Four-Way
Three-way and four-way plug valves are suitable for process installations requiring a change in flow direction or the distribution of media. Depending on operating conditions, one can select from soft-sealed sleeve designs, soft-sealed types, or hard-sealed lift-type plug valves.
