Ball valves consist of a solid ball held in place within the valve body between two circular resilient seats. The ball is connected to the internal end of the valve stem, and a hand-lever actuator is connected to the external end of the valve stem for manual operation. The ball has a hole (port) in the middle of it. When the valve stem is turned such that the port is parallel to the fluid flow, the valve is in the open position. When the valve stem is turned such that the port is perpendicular to the fluid flow, the valve is in the closed position. Because the hand-lever actuator is installed on the valve
stem parallel to the port, the actuator provides an indication of the valve’s position. Ball valves have a straight-through body configuration and are suitable for bubble-tight shutoff. Ball valves should not be used for throttling duty.
Ball valves are available in one-piece, two-piece and threepiece body designs (listed in the order of increasing cost). One-piece valves cannot be repaired and must be replaced when they fail to function properly. Also, one-piece valves are only available with a reduced-port ball; that is, the port is more than one pipe size smaller than the nominal pipe size. Due to the higher fluid pressure drop associated with the reduced-port, one-piece ball valves are not recommended for use in HVAC piping systems. Repair of two-piece valves is not recommended. However, this type of valve is available with a full- or standard-port ball.17 Three-piece valves offer in-line reparability and are available with a full- or standard-port ball; however, they are also the most expensive option for ball valves