Pump Impeller Nomenclature
The inlet of an impeller just before the section where the vanes begin is called the suction eye (see Figure 38). In a closed-impeller pump, the suction eye diameter is taken as the smallest inside diameter of the shroud. In determining the area of the suction eye, the area occupied by the impeller shaft hub is deducted.
The hub is the central part of the impeller that is bored out to receive the pump shaft. The term, however, is also frequently used for the part of the impeller that rotates in the casing fit or in the casing wearing ring. It is then referred to as the outer impeller hub or the wearing-ring hub of the shroud.