Figure 6-6.Types of globe valve bodies.
from the globular shape of the valve body. Other
types of valves may also have globular-shaped
bodies. Thus, it is the internal structure of the
valve that identifies the type of valve.
The inlet and outlet openings for globe valves
are arranged in a way to satisfy the flow
requirements. Figure 6-6 shows straight-, angle-,
and cross-flow valves.
The moving parts of a globe valve consist of
the disk, the valve stem, and the handwheel. The
stem connects the handwheel and the disk. It is
threaded and fits into the threads in the valve
The part of the globe valve that controls flow
is the disk, which is attached to the valve stem.
(Disks are available in various designs.) The valve
is closed by turning the valve stem in until the disk
is seated into the valve seat. This prevents fluid
from flowing through the valve (fig. 6-7, view A).
The edge of the disk and the seat are very
accurately machined so that they forma tight seal
when the valve is closed. When the valve is open
(fig. 6-7, view B), the fluid flows through the space
between the edge of the disk and the seat. Since
the fluid flows equally on all sides of the center
of support when the valve is open, there is no
unbalanced pressure on the disk to cause uneven
wear. The rate at which fluid flows through the
valve is regulated by the position of the disk in
relation to the seat. The valve is commonly used
as a fully open or fully closed valve, but it may
be used as a throttle valve. However, since the
seating surface is a relatively large area, it is not
suitable as a throttle valve, where fine adjustments
are required in controlling the rate of flow.
The globe valve should never be jammed in
the open position. After a valve is fully opened,
the handwheel should be turned toward the closed
position approximately one-half turn. Unless this
is done, the valve is likely to seize in the open
position, making it difficult, if not impossible, to
close the valve. Many valves are damaged in this
Figure 6-7.Operation of a globe valve.