Ball valves consist of a ball that is turned on a vertical axis. A flow passage is bored through the centre of the ball to allow fluid flow. When the flow passage is aligned with the inlet and outlet of the valve, the fluid can flow through the valve. When the ball is turned 90 degrees so that the flow passage is perpendicular to the valve ports, fluid will not flow. For pneumatic applications, bronze ball valves are most commonly used, although ball valves are available in steel and stainless steel construction. Ball valves are available as a two-way or a three-way valve. When a two-way ball valve is closed, fluid flow is blocked, but downstream pressure is not vented. A three-way ball valve blocks the inlet fluid, but also exhausts the pressure downstream. Often for compressed air applications, the exhaust port is a small opening at the bottom of the valve body. Full-ported three-way ball valves are available for applications that require a ported exhaust. Ball valves are often designated by their method of construction. These include; two-piece, three-piece, and unibody.

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