There are five general body styles of ball valves: single body,
three-piece body, split body, top entry, and welded. The difference
is based on how the pieces of the valve—especially the casing that
contains the ball itself—are manufactured and assembled. The valve
operation is the same in each case.
In addition, there are different styles related to the bore of the
ball mechanism itself.
Ball valves in sizes up to 2 inch generally come in single piece,
two or three piece designs. One piece ball valves are almost always
reduced bore, are relatively inexpensive and generally are
throw-away. Two piece ball valves are generally slightly reduced
(or standard) bore, they can be either throw-away or repairable.
The 3 piece design allows for the center part of the valve
containing the ball, stem & seats to be easily removed from the
pipeline. This facilitates efficient cleaning of deposited
sediments, replacement of seats and gland packings, polishing out
of small scratches on the ball, all this without removing the pipes
from the valve body.
The design concept of a three piece valve is for it to be
A full port or more commonly known full bore ball valve has an
over-sized ball so that the hole in the ball is the same size as
the pipeline resulting in lower friction loss. Flow is unrestricted
but the valve is larger and more expensive so this is only used
where free flow is required, for example in pipelines which require
Reduced port or reduced bore
In Reduced port (more commonly known as reduced bore) ball valves,
flow through the valve is one pipe size smaller than the valve's
pipe size resulting in flow area being smaller than pipe.
A V port ball valve has either a 'v' shaped ball or a 'v' shaped
seat. This allows for linear and even equal percentage flow
characteristics. When the valve is in the closed position and
opening is commenced the small end of the 'v' is opened first
allowing stable flow control during this stage. This type of design
requires a generally more robust construction due to higher
velocities of the fluids, which might damage a standard valve.
These can be referred to as a type of control valve but are
typically not as accurate as a balancing valve, needle valve, globe
valve, or pressure regulating valve.
Many industries encounter problem with residues in the ball valve.
Where the fluid is meant for human consumption, residues may also
be health hazard, and when where the fluid changes from time to
time contamination of one fluid with another may occur. Residues
arise because in the half open position of the ball valve a gap is
created between the ball bore and the body in which fluid can be
To avoid the fluid getting into this cavity, the cavity has to be
plugged, which can be done by extending the seats in such a manner
that it is always in contact with the ball. This type of ball valve
is known as Cavity Filler Ball Valve.
There are a few types of ball valves related to the attachment and
lateral movement of the ball:
A trunnion ball valve has additional mechanical anchoring of the
ball at the top and the bottom, suitable for larger and higher
pressure valves (say, above 10 cm and 40 bars).
A floating ball valve is one where the ball is not held in place by
a trunnion. In normal operation, this will cause the ball to float
downstream slightly. This causes the seating mechanism to compress
under the ball pressing against it. Furthermore, in some types, in
the event of some force causing the seat mechanism to dissipate
(such as extreme heat from fire outside the valve), the ball will
float all the way to metal body which is designed to seal against
the ball providing a somewhat failsafe design.
Manually operated ball valves can be closed quickly and thus there
is a danger of water hammer. Some ball valves are equipped with an
actuator that may be pneumatically, hydraulically or motor
operated. These valves can be used either for on/off or flow
control. A pneumatic flow control valve is also equipped with a
positioner which transforms the control signal into actuator
position and valve opening accordingly.
Schematic 3 way ball valve: L-shaped ball right, T-shaped left
Three- and four-way have an L- or T-shaped hole thr