Ball Valves Industry Information

A ball valve is a stop valve that is designed mostly for on/off service. It is essentially a plug valve with a round hole and a sphere-shaped plug. A ball valve contains a ball with a small hole in the middle that helps to control the flow of materials through the pipe. An actuator, which can be either electric or a manually operated handle, rotates the ball 90%. When the hole of the ball is facing away from the pipe opening, flow is restricted. When it is aligned with the opening, flow is restored. The position of the handle immediately indicates whether the valve is closed or open. Along with being easy to monitor, ball valves are also simple to clean and repair; as the ball rotates, the seat performs a self-wiping action that prevents any buildup.

Ball valve suppliers offer their products with two primary design options. These are the floating ball design, a less costly option for lower duties, and a trunnion ball option, which is used for higher duties and, therefore, more costly. Ball valve suppliers also provide several body styles, including one-piece, two-piece, three-piece, even four- and five-piece and flanged body construction. The type of application determines which ball valve is the most appropriate. Sizes of ball valves range from very small up to 42 inches and up to 7,500 psi in pressure ratings. Although they are manufactured from a wide variety of materials, some common materials are stainless steel, plastic, bronze, copper, cast iron, ductile iron, metal alloys and brass. Metal valves are recommended for gases and high temperature fluids; use plastic valves for liquid applications only.

Bore, or port, sizes differ as well. In a full bore valve, the diameter of the hole in the ball is the same size as the hole in the pipe. Looking down a piece of pipe, in other words, there would not appear to be any constriction at the location of the valve. If the diameter of the hole through the ball is less than that of the pipe, it is referred to as a reduced or standard bore/port. Some valves gradually narrow, while the reduction in others is basically a shoulder. Many times the diameter tapers to the next standard size. There is very little pressure loss difference between the full bore and reduced bore valve.

Advances in ball valve design and materials have significantly increased their popularity. Ball valves can be used for isolation of systems, regulation of some types of low flow (e.g. throttling the flow of air at differential pressures up to 1,000 psi) and backflow prevention, but only with a swing check component. They can handle high pressure and a large volume of fluids, gases and suspended solids (slurries). New valve designs have enabled ball valves to be used in high-vacuum situations. This possibility was not previously considered, due to the inherent tendencies of these valves to leak and trap gas. Ball valve suppliers will also be able to offer aluminum construction in the near future.