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Ball Valve

A ball valve is a valve that opens by turning a handle attached to a ball inside the valve. The ball has a hole, or port, through the middle so that when the port is in line with both ends of the valve, flow will occur. Ball ValveWhen the valve is closed, the hole is perpendicular to the ends of the valve, and flow is blocked. The handle or lever will be inline with the port position letting you “see” the valve’s position. The ball valve, along with the butterfly valve and plug valve, are part of the family of quarter turn valves. Ball valves are durable and usually work to achieve perfect shutoff even after years of disuse. They are therefore an excellent choice for shutoff applications (and are often preferred to globe valves and gate valves for this purpose). They do not offer the fine control that may be necessary in throttling applications but are sometimes used for this purpose.

Ball valves are used extensively in industry because they are very versatile, supporting pressures up to 10,000 psi and temperatures up to 200 Deg C. Sizes from 1/4″ to 12″ are readily available. They are easy to repair, and operate manually or by actuators.

The body of ball valves may be made of metal, plastic or metal with a ceramic center. The ball is often chrome plated to make it more durable.
[edit] Types of ball valve

Types of Ball Valves

There are five general body styles of ball valves: single body, three piece body,split body, top entry, and welded.

There are three general types of ball valves according to bore.

* A full port 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. This is not required for general industrial applications as all types of Valves used in industry like Gate Valves, Plug Valves, Butterfly valves etc have restrictions across the flow and does not permit full flow. This leads to excessive costs for full bore ball valves and is genearlly a unneccessary spending for customers.

* In reduced port ball valves, flow through the valve is one pipe size smaller than the valve’s pipe size resulting in flow area becoming lesser than pipe. But the flow discharge remains constant as it is a Multipler factor of Flow discharge(Q) is equal to Area of Flow (A) into Velocity (V). A1V1=A2V2 i.e the Velocity increase with reduced Area of flow and Velocity decreases with increased 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 would quickly damage a standard valve.

* A trunnion ball valve has a mechanical means of anchoring the ball at the top and the bottom, this design is usually applied on larger and higher pressure valves (say, 4″ and above 600 psi and above).

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 or motor (electric) 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.