Abstract: A new and improved valve apparatus and method of operating same that moves a flow closure assembly between open and closed positions with a minimum of frictional resistance while effecting a forcible engagement with both upstream and downstream valve seats when in the closed position. The preferred ball-type flow closure assembly is formed of two pivoted sections that are forcibly moved axially or tilted to sealingly engage the longitudinally spaced valve seats to provide upstream and downstream sealing by the valve in moving between an intermediate position and the closed position. The opening to closing movement is effected by rotating the valve actuator stem through an arc slightly greater than a quarter turn to provide a fast response operation. The valve actuator further includes a two part guide means which effects tilting of the ball sections only after or before rotational movement to insure that the ball is released from sealing engagement with both seats by only axial movement.