| 摘要 |
PURPOSE:To reduce the deflection amount and the weight of a valve body by shaping a part of a valve stem supported by bearings into a hollow, closing its external end faces, and specifying the diameter of the part of the valve stem supported by bearings against the diameter of a sealed water surface. CONSTITUTION:On two facing sides of a valve trunk 1 equipped between an upper stream pipe 6 and a downstream pipe 7, bearings 4 are provided to support a valve stem 3 in one body of a valve body 2 rotatably, and on upper and down stream sides of the valve body 2, seal rings 12 and 13 are respectively provided to be easily slided for constructing a ball valve. At this stage, the said valve shaft 3 is shaped into a hollow, and the diamter dh2 of the valve stem 3 is selected 1.0-1.5 times greater than a sealed water face diamter D. In this construction, when an allowable face pressure sigmaPC of bearings 4 is at a certain fixed value, sigmaPC=Fp/(dh2.2l) (where Fp is a hydraulic pressure force) can be obtained, and the valve stem diameter dh2, that is, the pressure-receiving area of bearings 4 can be greater than before. Consequently, a bearing length l can be shortend, and the deflection of the valve body 2 can be reduced by that extent. |
