As an example of conventional Ball Valves, a so-called "union-type ball valve" is known in which a ball is arranged in a cylindrical valve body in such a manner that it can open and close a fluid passage therein. Annular seals abut against the ball from both sides in the fluid passage with the annular seals being pushed towards the ball by seal carriers. In such a ball valve, when connecting sleeves are connected to the valve body, the connecting sleeves push the seal carriers towards the ball.Ball Valves The seal carriers are pushed by the connecting sleeves which are connected to the valve body, for instance, with union nuts, so that the abutment pressures of the annular seals to the ball can be adjusted by tightening or loosening the union nuts. Therefore, when the annular seals are worn to the extent of causing leakage of fluid, the leakage can be eliminated by further tightening the union nuts.

The most serious drawback of a ball valve of this type is that, under the condition that the fluid passage is closed and the fluid pressure is applied, the union nut and the connecting sleeve cannot be removed from the valve body. In order to repair or replace the pipe line connected to the connecting sleeve, it is necessary to loosen the union nut thereby to remove the connecting sleeve. However, if the connecting sleeve is removed, the ball and the seal carrier may blow out of the valve body due to the fluid pressure. Thus, the removal of the connecting sleeve under this condition is dangerous.

In order to eliminate this drawback, a ball valve as disclosed by U.S. Pat. No. 3,550,902, for instance, has been proposed, in which one seal carrier is provided on only one side of the ball while the other seal carrier is made integral with the valve body. With this ball valve, piping is performed with the seal carrier faced towards the side to which the pressure is applied. However, the ball valve is still disadvantageous in that the adjustment to compensate for wear of the annular seals is carried out by further tightening only one of the union nuts.BALL VALVES If tightening is repeatedly carried out in this manner, the center of the ball will be significantly displaced from the center axis of the spindle. As a result, the torque needed for turning the handle to turn the ball thereby to open and close the valve is increased; that is, the valve cannot be smoothly opened and closed. If the handle is forcibly turned, the spindle is pushed from one side only, as a result of which leakage occurs at the seals around the spindle.

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