Plastic ball valves are given their name by the nature […]
Plastic ball valves are given their name by the nature in which they operate, where an internal ball with a bored through center is rotated to either allow or prevent flow through the valve. Ball Valves are part of the quarter-turn valve family, which means they open or close with a 90 degree turn of the handle. Intended for open and close use only, throttling or controlling the flow of media with a plastic ball valve is not recommended and will damage the ball valve itself.
Types of Ball Valves
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.
Full port Ball Valve
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
Reduced port or reduced bore Ball Valve
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.
V Port Ball Valve
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.
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.
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.
Multiport Ball Valve
Three- and four-way have an L- or T-shaped hole through the middle. The different combinations of flow are shown in the figure. It is easy to see that a T valve can connect any pair of ports, or all three, together, but the 45 degree position which might disconnect all three leaves no margin for error. The L valve can connect the center port to either side port, or disconnect all three, but it cannot connect the side ports together.
Multi-port ball valves with 4 ways, or more, are also commercially available, the inlet way often being orthogonal to the plane of the outlets. For special applications, such as driving air-powered motors from forward to reverse, the operation is performed by rotating a single lever four-way valve. The 4-way ball valve has two L-shaped ports in the ball that do not interconnect, sometimes referred to as an "×" port.
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