What Are the Ball Valves Types

Rotating motion valves include ball valves. The attached ball rotates when the stem transmits the motion to it. The ball valve seats lie on top of and support this ball of a ball valve. The bore can open or close to facilitate the fluid flow or halt thanks to the rotation of the ball over the valve seats.

When the ball’s port opening lines up with the valve’s inlet and outlet ports, flow through the valve is continuous and only experiences a little pressure decrease if a full-port ball is employed. It goes without saying that using a reduced-port ball results in a greater pressure drop. 

The flow passageways of the ball and the body are lined up when the hand operator is positioned parallel to the pipeline, permitting complete flow through the closing device. The ball’s opening starts to move perpendicular to the flow stream as the hand operator is rotated to the closed position, and the port edges start rotating through the seat.

The port totally perpendicular to the flow stream and blocked when the full quarter-turn is reached. The flow undergoes a double pressure drop via the valve in throttling applications while the ball is in a midturn position, much like a plug valve. 

When a characterizable ball is used to deliver a particular flow to a position, when the ball rotates from closed to open through the seat, a certain amount of the port opening is exposed to the flow at a particular position, until 100 percent flow is obtained at the full-open position.

The ball valve operates in a quarter-turn motion, with 0° denoting full closure and 90° denoting full opening, as with all rotary-action valves. A linear actuator design with a transfer case can convert linear motion to rotational action, or the actuator can be constructed to provide this circular motion, as is the case with a manual hand lever.

A full-port valve has less pressure loss and recovery when the flow passes through it when it is fully open. This is due to the fact that the flow passageway is essentially the same diameter as the inside diameter of the pipe and that there are no obstructions to the flow other than slight geometrical deviations at the orifices.

Full-port valve throttling should be thought of as a two-stage pressure decrease procedure. Full-port valves have two orifices, one on the upstream side and the other on the downstream side, due to the length of the bore through the ball. 

The flow passes through the first restricted orifice as the valve advances to the mid-stroke position, causing a pressure drop, and then moves into the bigger flow bore inside the ball, where the pressure partially recovers. The flow then shifts to the second orifice, when a second pressure decrease and subsequent pressure recovery take place.

Lower process velocities are produced by the dual pressure drops in this two-step procedure, which is advantageous for slurry applications. A full-port valve’s flow rate is controlled by the ball’s hole’s diminishing flow area as the valve rotates in a quarter-turn motion, giving the valve an inherent equal-percentage feature and a truly circular opening. 

The sliding motion of the ball against the seal produces a shearing action like a pair of scissors as the area of the flow route decreases as the valve nears closing. For slurries, where long-entrained fibers or particles can be sheared off and separated at closing, this action is suitable.

The entire face of the ball is totally exposed to the flow when the flow hole is fully closed, as it is now perpendicular to the flow, preventing it from continuing past the ball.

Only one pressure drop is taken through the valve at the orifice where the seal and ball come into touch with each other in the segmented-ball design. The flow is restricted by the geometry of the flow route when the segmented ball is fully open. In essence, this improves throttling because a pressure decrease is taken by flow area reduction.

The flow characteristic is provided by the changing shape of the V-notch or parabolic port as the segmented ball advances through the quarter-turn motion. The sliding seal of the distinguishable ball, like the full-port design, produces a shearing motion for efficiently separating slurries.