Cast Trunnion ball valve

Cast Trunnion ball valve

A cast trunnion ball valve is trunnion ball valve that utilizes cast steel material. It takes the advantage of the structures of  both trunnion ball valve and the properties of its material. 

Cast steel is an alloy of iron and carbon. It is produced in a two-stage process. First, iron ore is reduced or smelted with coke and limestone in a blast furnace, producing molten iron which is either cast into pig iron or carried to the next stage as molten iron. In the second stage, known as steelmaking, impurities are removed and alloying elements such as manganese, nickel, chromium and vanadium are added to produce the exact steel required. Steel then turn molten steel into blooms, ingots, slabs and sheet through casting, hot rolling and cold rolling.

A trunnion ball valve is often preferred as it has a distinctive lower operating torque than the floating ball valve since pressure forces tending to push the ball downstream are supported by a trunnion rather than the valve seat.

Cast trunnion ball valve is fixed, so that it does not move within medium pressure. Cast trunnion ball valve usually has floating seats.  The seats move within the medium pressure to tight the ball and seal ring to ensure sealing reliability. Bearings could be mounted in top shaft and bottom shaft, which reduces operation torque. This is widely used in valves that can endure high pressure. In certain applications, cast trunnion ball valve has an additional advantage in the fact that when the ball valve is in the closed position the upstream seal is under line pressure while the downstream seal is pressure relieving, eliminating the possibility of a pressure lock in the center cavity.