The impeller shall be of a multi or single-vaned, fully shrouded enclosed design and shall have large passages to provide smooth flow transition and unimpeded passage of large spherical solids.

• 叶轮应该采用多叶片或单叶片、全包裹封闭式结构。应该配置能够进行流体传输的大型通道，和大型球体实心颗粒能够不受阻碍的通道。