阀门操作方式及要求中的一句话? The length of the wrench or diameter of the handwheel for direct or gear operated valves shall (after opening and closing a new valve at least four times) be such that a force not exceeding 380 Newton (N) shall be required to operate from either the open or closed position under the maximum differential pressure recommended by the manufacturer. 这句话很长,但是我就是对红色部分比较纠结,,,真不明白一句话里出现两个 shall be 是几个意思??。。。求指教,谢谢!查看更多5个回答 . 5人已关注