A ball valve is a shut-off valve that allows, obstructs, and controls the flow of liquids, gases, and vapors in a piping system by rotating the ball having a bore inside the valve. The ball is mounted against two seats and has a shaft that connects it to the operating and control mechanism that rotates the ball. When the cross-section of the bore is perpendicular to the area of the flow, the fluid is not permitted to pass through the valve. The fluid flows through from the valve, and the fluid flow rate depends on the area of the bore exposed to the floor.
Ball valves are a type of quarter-turn valve along with plug valves and butterfly valves. They can be operated manually or by using an actuator. The simplest operation of a floating ball valve is through the use of a wrench or a lever manually turned by an operator. Torque is applied to rotate the lever arm by 90° by either clockwise or counterclockwise to open or close the valve. If the lever arm is parallel to the pipe, it indicates that the valve is open. If the lever arm is perpendicular to the pipe, it indicates that the valve is closed.
A one-piece ball valve has a single-piece cast body that houses the internal components of the trunnion mounted ball valve. This eliminates the risk of leakage of the fluid from the valve. One-piece ball valves are the cheapest ball valves and always have a reduced bore. A welded one-piece ball valve is more common but cannot be dismantled for cleaning and repaired once damaged; therefore, it is only used for applications with a low possibility of particle build-up, and where sanitation is not a major concern. On the other hand, screwed one-piece ball valves can be cleaned, serviced, and repaired, but dismantling requires special tools.
A vented ball valve is constructed and operates in the same way as a standard fully welded ball valve, except that the vented ball has small orifices drilled into its side. When the valve is closed, the orifice is directed to the outlet side of the valve. The drilled hole is used to vent trapped gases which causes a build-up of internal pressure inside the valve, to prevent leaking, valve failure, and explosion.
A segmented ball valve has a V-shaped notch on its ball. A segmented 3 way ball valve has good flow rate control which depends on the ball rotation. Aside from that, it also has a good shut-off capability. The flow characteristic in a segment ball valve approaches an equal percentage flow characteristic. The flow rate in a segmented ball valve increases exponentially as the ball reaches its fully opened position.