A ball valve can be used to stop and start as well as t […]
A ball valve can be used to stop and start as well as throttle or regulate the flow or movement of media through a system. Ball valves are best used for fast-acting stop/start applications. They are considered quick-acting because they only require a 90° turn of the handle to operate the valve. The quarter turn minimizes valve operation time and decreases the possibility of leakage due to wear.
Once a high level of accuracy is not required, you can use Ball valves in throttling service. Throttling causes the partially exposed seat to erode because of the high velocity flow and pressure. The wear will eventually lead to valve leakage. Leakage can be corrected if the manual ball valve is automated and is able to move faster in response to a changing position signal.
The Ball valves can be used in gas and liquid media and they are very efficient. This type of valve can be used for challenging chemicals such as dry chlorine, hydrofluoric acid or hydrochloric acid, and oxygen. Slurry transport is not highly recommended because the slurry tends to solidify in the cavities around the ball and seats. This increases the operating torque and may break the valve.
There are two major common type of Ball valve design, floating ball design and trunnion mounted design.
The former is the most common type of ball valve. In this type, the ball is not fixed to the stem so a wide range of freedom is available. The upstream pressure helps create the seal by pushing the ball back against the rear or downstream seat.
The latter doesn't dislodge due to its pin securing the ball. This design can be used for high velocity systems. Trunnion valves use a special segmented ball. The valve supports the ball with a shaft and the side opposite the shaft using another shaft or post. The shaft can be part of the ball or separate. Trunnion valves provide less friction between the ball and seal.