VTV Valve : Ball Valve
Floating Ball Valves In this type of valve, the ball has some freedom to move along the axis of the valve while being prevented from rotating againts the stem. When line pressure is applied to the closed ball, it moves slightly (or floats) downstream to maintain contact with the downstream seat where primary sealing occurs. This design is restricted in its use by size and service pressure as the torque required to operate the valve will increase dramatically in accordance with these two factors. Trunnion Mounted Ball Valves The ball is held in a fixed axial position by upper and lower stems (Trunnion) and can move only in rotational mode. The seats are contained in metal carriers which are spring loaded againts the ball. The line pressure applied to a closed valve increases the load on the upstream seat to effect a tight seal. Therefore, the primary sealing is on upstream seat. Independent floating seats are spring loaded to permit draining of the body cavity effectively providing a...