Product Description
Plug valves are valves with cylindrical or conically tapered
“plugs” which can be rotated inside the valve body to control flow
through the valve. The plugs in plug valves have one or more hollow
passageways going sideways through the plug, so that fluid can flow
through the plug when the valve is open. Plug valves are simple and
often economical.When the plug is conically tapered, the
stem/handle is typically attached to the larger diameter end of the
plug. Plug valves usually do not have bonnets but often have the
end of the plug with the handle exposed or mostly exposed to the
outside. In such cases, there is usually not much of a stem. The
stem and handle often come in one piece, often a simple,
approximately L-shaped handle attached to the end of the plug. The
other end of the plug is often exposed to the outside of the valve
too, but with a mechanism that retains the plug in the body.The
simplest and most common general type of plug valve is a 2-port
valve with two positions: open to allow flow, and shut (closed) to
stop flow. Ports are openings in the valve body through which fluid
can enter or leave. The plug in this kind of valve has one
passageway going through it. The ports are typically at opposite
ends of the body; therefore, the plug is rotated a fourth of a full
turn to change from open to shut positions. This makes this kind of
plug valve a quarter-turn valve. There is often a mechanism
limiting motion of the handle to a quarter turn, but not in glass
stopcocks.Slightly conically tapered metal (often brass) plug
valves are often used as simple shut-off valves in household
natural gas lines.It is also possible for a plug valve to have more
than two ports. In a 3-way plug valve, flow from one port could be
directed to either the second or third port. A 3-way plug valve
could also be designed to shift flow between ports 1 and 2, 2 and
3, or 1 and 3, and possibly even connect all three ports together.
The flow-directing possibilities in multi-port plug valves are
similar to the possibilities in corresponding multi-port ball
valves or corresponding multi-port valves with a rotor. An
additional possibility in plug valves is the have one port on one
side of the plug valve and two ports on the other side, with two
diagonal and parallel fluid pathways inside the plug. In this case
the plug can be rotated 180° to connect the port on the one side to
either of the two ports on the other side.