Different styles 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:
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 pigging.
In reduced port or more commonly known 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. As the flow discharge remains constant and is equal to area of flow (A) times velocity (V), A1V1 = A2V2 the velocity increases with reduced area of flow.
A V port ball valve has either a ’v’ shaped ball or a ’v’ shaped seat. This allows the orifice to be opened and closed in a more controlled manner with a closer to linear flow characteristic. 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.
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