Floating Ball valves are straight-through flow valves which provide positive shutoff with minimal pressure drop and flow turbulence. The barrier to flow is a ball which is rotated 90 degrees to the direction of flow.
In floating ball valves, the ball has some freedom to move along the axis of the valve. 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.
Because the stem motion from full open to full closed is a 90 degree rotation, ball valves are ideally suited for automatic operation. They may generally be installed without regard for flow direction.