A valve assembly has a valve body having an inlet passageway and an outlet passageway. A flow orifice is disposed within valve body and provides flow communication between the inlet passageway and outlet passageway.Plug Valves A valve seat cooperates with the flow orifice and a variable port valve plug to open and close the valve. The valve plug has a plug body with a conically-shaped smooth tapered wall,Globe Valves a proximal end, and a domed distal end surface that smoothly transitions into the tapered wall. The valve plug is movable between an open position out of contact with the valve seat and a closed position borne against the valve seat. A maximum open position of the valve plug relative to the valve seat can be selectively changed to vary flow characteristics through the valve assembly. BALL VALVES A valve assembly comprising: a valve body having an inlet passageway and an outlet passageway; a flow orifice disposed within an orifice region of the valve body and providing flow communication between the inlet passageway and outlet passageway; a variable port valve plug including a plug body with a conically-shaped smooth tapered wall, a proximal end connected to a movable part of the valve assembly, and a domed distal end surface that smoothly transitions into the tapered wall, wherein the valve plug is connected to a solid valve stem and is movable between an open position out of contact with the valve seat and a closed position borne against the valve seat, and wherein a maximum travel position of the valve plug relative to the valve seat in the open position can be selectively changed to vary a flow capacity of the valve assembly; and a valve seat having a first end, a second end, and a seating surface positioned between the first and second ends, the valve seat having an outwardly tapered surface extending from the seating surface toward the first end, the second end of the valve seat extending past the proximal end of the valve body toward the solid valve stem when the valve is in the closed position. A variable port valve plug for a valve is disclosed that can eliminate or significantly reduce the need for manufacturing, maintaining, and replacing different trim sets for the valve. The disclosed valve plug is suitable for many different types of valves. The disclosed example is described with reference to what is known as a sliding stem type valve construction. However, the disclosed plug is equally well suited for many other types and constructions of valves, such as, for example, control valves, throttling valves, or the like. The present disclosure is not intended to be limited to a particular valve type. The disclosed valve construction is also suitable for use with many different types of media. The disclosed variable port valve plug has a shape and contour such that the plug can be positioned relative to a valve seat in a selected one of a plurality of permissible maximum travel positions. In any one of the selectable positions, the variable port valve plug disclosed herein prevents undesirable flow characteristics through the orifice region of the valve and yet changes the flow capacity of the valve. The variable port valve plug can be selectively positioned relative to the seat ring to effectively produce a selected capacity for the valve without having to swap portions of the trim set such as the valve plug and/or the valve seat. The position of the valve plug can be controlled to limit the maximum travel of the valve plug, i.e. its valve open position, as desired.

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