Abstract: The present invention relates to a ball valve having a housing with an axial passage way through the housing providing fluid communication between first and second ends of the housing. A rotatable ball is arranged within the axial passageway for selectively opening and closing the axial passageway. A seal is arranged within the axial passageway near the first end of the housing such that the seal is adapted to abut a surface on the rotatable ball. A blocking member is provided for selectively preventing axial movement of the seal towards the first end and for permitting axial movement of the seal towards the surface of the rotatable ball independently of the blocking member. In a preferred embodiment, the seal is arranged on a seal carrier which has an annular groove in an outer peripheral surface.