A ball valve is a device that contains a spherical closure unit that provides an on/off control of flow. The sphere typically comes equipped with a port known as a bore through its center. When the value is positioned correctly so that it aligns in the same direction as the pipeline, it is in an open position where fluid can readily flow through it. Pig valves are known for their reliability and bubble-tight sealing that can be an ideal choice for gas applications where a tight shutoff is absolutely necessary. The body of pig valves is typically made out of steel and can be made more durable with nickel plating. The most common ball valves are considered to be two-way, which allows for flow to travel linearly from the inlet to the exit without issue. Three-way and four-way valves allow for flow to travel in multiple directions, which include 90-degree angles.
There are four general body styles of ball or pig valves that include fully welded, three-piece body, split-body, and top-entry. The differences are largely based on how the pieces of the valve are manufactured and assembled, but the valve operation is the same in each time.
Trunnion Mounted Ball Valve:A trunnion mounted ball valve has additional mechanical anchoring at the top and bottom on the ball. The special mounted ball valve is designed for a larger and higher-pressure valve. The design allows for the reduction in valve torque as the ball is supported in two areas. The trunnion mounted stem can absorb the thrust from the line pressure, preventing excess friction between the ball and seats, so even at full rated working pressure, the operating torque remains low.
Floating Ball Valve: Unlike a mounted ball or a high-pressure valve, a floating ball valve is not held in place by a trunnion, and instead is attached only to the stem. This is sometimes caused by the ball to float slightly downstream. When this occurs, the ball presses against the seat, creating a positive seal.
Rising Stem Ball Valve: Rising stem balls differ from a mounted ball valve and high-pressure valves because it incorporates tilt-and-turn operation, eliminating seal rubbing, which is one of the primary causes of valve failure. When the valve is closed, the core is wedged against the seat, ensuring positive shutoff. When the valve is opened, the core tilts away from the seal, and the flow passes uniformly around the core face. The Cameron ORBIT rising stem ball valve utilizes its operating principle that delivers fast, low-torque operation and long-term reliable performance. Additionally, the valve is able to eliminate and localize high-velocity flow that typically creates uneven seat wear exhibited by an ordinary ball, gate, and pig valves.
Full-Port Ball Valve: Full-ports, also known as a full-bore, has a ball valve with a bore internal diameter (ID) that is approximately equal to the pipeline ID. This allows for significantly reduced friction and pressure loss across the ball valve.