A ball valve is a rotational motion valve that uses a ball-shaped disk to control fluid flow. Balls perform the same function as disks in globe valves. A ball rotates when the valve handle is turned to open the valve, lining up the hole through the ball with the valve body inlet and outlet. By rotating the ball, the hole in the ball becomes perpendicular to the flow openings on the valve body when the valve is shut.
Ball valve actuators are usually quick-acting, which requires a 90° turn of the valve handle to operate. There are also ball valve actuators that are operated by planetary gears. A relatively small handwheel and operating force are sufficient to operate a relatively large valve with this type of gearing.
In some ball valves, a spherical surface-coated plug is located off to one side in the open position and rotates into the flow passage until it blocks the entire flow path. The plug is seated by eccentric movement. No lubrication is required for the valve, which can be used for throttling.
It is generally less expensive and easier to maintain a ball valve compared to other valve configurations. Additionally, ball valves are compact, don't require lubrication, and offer tight sealing with little torque, in addition to quick, quarter turn operation.
Conventional ball valves have poor throttling characteristics. Due to the impingement of high-velocity flow in a throttling position, the partially exposed seat is rapidly eroded. It is possible, however, to use ball valves as control valves when they have been modified to characterize the flow port.
Venturi ball valves are available with reduced and full port patterns. A full port pattern has a ball with a bore equal to the pipe's inside diameter.
Balls are usually metallic in metallic bodies with elastomeric (elastic materials resembling rubber) trim (seats). A plastic construction option is also available.
Various elastomeric materials are used to make resilient seats for ball valves. Teflon (TFE), filled TFE, Nylon, Buna-N, Neoprene, and combinations of these materials are the most common seat materials. These valves cannot be used at high temperatures since they are made from elastomeric materials. In selecting the seat material, it is important to ensure that it is compatible with the materials being handled by the valve.
In a ball valve, the stem is not attached to the ball. The rectangular portion at the ball end fits into a slot cut into the ball. As the stem is turned, the ball can rotate due to the enlargement.
The bonnet cap holds the stem assembly and ball in place on the body. The bonnet cap can be adjusted to compress the packing, which provides the stem seal. Ball valve stems are usually packed with die-formed packing rings of TFE, TFE-filled, or TFE-impregnated material. A ball valve stem can be sealed by an O-ring instead of packing in some cases.
Ball valves may be equipped with stops that restrict rotation to 90°. Some do not have stops and can be rotated 360 degrees. Close or open a ball valve with a 90° rotation, with or without stops.
The valve ball position is indicated by the handle. The valve is open when the handle lies along its axis. A valve is closed when its handle lies 90 degrees across its axis. There is a groove cut into the top face of some ball valve stems that illustrates the flow path through the ball. By observing the groove position, you can determine the position of the port through the ball. Multiport ball valves are particularly advantageous for this feature.
Aira Euro Automation is a leading ball valve manufacturers in India. We have a wide range of industrial ball valves, we also export our product to more than 20 countries around the world.