TYPES OF VALVES
A plug valve is a rotational motion valve used to stop or start fluid flow. The name is derived
from the shape of the disk, which resembles a plug. A plug valve is shown in Figure 13. The
simplest form of a plug valve is the petcock. The body of a plug valve is machined to receive
the tapered or cylindrical plug. The disk is a solid plug with a bored passage at a right angle to
the longitudinal axis of the plug.
In the open position, the passage in the plug lines up with the inlet and outlet ports of the valve
Figure 13 Plug Valve
body. When the plug is turned 90 from the open position, the solid part of the plug blocks the
ports and stops fluid flow.