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 ball valve operation is the same in each case.In addition, there are different styles related to the bore of the ball mechanism itself. And depends on the working pressure, the ball valves are divided as low pressure ball valves and high pressure ball valves. In most industries, the ball valves with working pressure higher than 3000 psi are considered as high pressure ball valves. Usually the max. working pressure for the high pressure ball valves is 7500 psi, and depends on the structure, sizes and sealing materials, the max. working pressure of high pressure ball valves can be up to 15000 psi. High pressure ball valves are mostly used in applications under high pressure such as hydraulic systems, so they are known as hydraulic ball valves also.
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 repairable.
Here is an outline:
Reduced port or reduced bore
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 (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, industrial vlave or pressure regulating valve.