A top entry ball valve consists of a housing having an interior cavity sufficiently large to receive a conventional ball and conventional seat rings through an opening in the housing. A cam arrangement is used to axially load the seat rings, after the ball/seat package has been inserted into the cavity. The cam arrangement comprises a pair of circular cams, each having an undulating annular surface, which is disposed in the housing cavity adjacent one of the seat rings with the respective undulating annular surfaces of the cams being in closely adjacent facing relation to one another. The ball of a
top entry ball valve is installed from the top, and is always used in the applications of long pipes. Beside that, a top entry valve is easy to repair, because it is not necessary to dismiss the whole valve from the pipeline to get out the ball.
After assembly of the valve, one of the circular cams is rotated relative to the other cam to vary the rotational positions of the undulating annular surfaces relative to one another thereby to vary the axial positions of the circular cams relative to one another and relative to the ball and seat rings.
