Ball Valves
Ball valves use a metal ball with a hole bored through the center, sandwiched between two seats to control flow. Used in many hydrocarbon process applications, ball valves are capable of throttling gases and vapors and are especially useful for low flow situations.
Ball valves are more effective at forming a tight seal and have more reliability and longevity than gate valves, but tend to be more expensive. They are often used for shutoff and control applications. Because ball valves can open and close immediately, they are more likely than gate valves to cause water hammer.