Satisfactory performance of any fluid piping system depends to a large extent upon efficient valve operation in controlling and regulating the flow of the fluids through the piping in which the valves are connected. Many types of valves are available for this purpose, each exhibiting various advantages and disadvantages in its operation, efficiency and maintenance. From the standpoint of ease of operation and excellent operating efficiency, the ball valve of the so-called "floating ball" type is most desirable. Ball ValvesBecause the sealing element is a spherical plug or ball, its alignment within the valve housing is not essential to a tight shutoff. Accordingly, greater tolerances are permissible in manufacturing the balls and the concave seats of the sealing rings used in the valve assembly. Further, in floating ball valves, the ball is free to move under the influence of the pressure differential across the valve which urges the ball into positive sealing engagement with the concave seat of the downstream sealing ring and the latter into positive sealing engagement with the valve housing seats.

However, Ball Valves, whether of the floating ball or fixed ball type, have not been particularly desirable from the standpoint of maintenance and repair. Since it is important that pressure drop across a valve be maintained as low as possible, the piping leading into and exiting from the valve should be in axial or in-line alignment. With this arrangement, the spherical plug or ball and its sealing ring seats could only be replaced by inserting them from above, with the sealing rings on opposite sides of the ball and in coaxial alignment with the inlet and outlet pipes.

As normal wear of the sealing rings occurred, the valve would begin to leak and with the sealing rings coaxial with the fluid flow, no adjustment of the forces exerted by the sealing rings on the ball could be made. The only way the leaky valve could be put back in condition was to remove the ball and seats from the access above and replace them with new sealing rings, a new ball or both.BALL VALVES To do so required complete disassembly of the valve also requiring shutting down the fluid flow through the piping. Further, if the housing seats for the sealing rings were also worn requiring remachining, the entire valve housing had to be removed from the piping in order to reach the housing seat with the seat machining tool.

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