c) Impellers
The impellers are of the enclosed by cast in 13% Cr. steel, finished and polished all over and carefully balanced both statically and dynamically. They are designed to produce high hydraulic efficiency and a continuously rising curve from maximum to minimum capacity. The impellers are arranged in opposed groups, thus assuring hydraulic axial balance without resorting to the use of any high pressure drop balancing devices. The impellers are mounted on the shaft with a light shrink fit against a split ring or shaft shoulder. This arrangement entirely eliminates spacer shaft sleeves and permits the shaft to expand freely without creating any untightening of a sleeve runner assembly.
