A reverse vane impeller has only one set of pumping vanes and one critical tolerance. This single tolerance — between the impeller and the rear cover — establishes:
Seal chamber pressure
Wear between the reverse vane impeller and the rear cover causes axial thrust loads to decrease as the seal chamber gap widens. At the same time, seal chamber pressure increases. By adjusting the setting of the reverse vane impeller against its single tolerance location, the original seal chamber pressure and axial thrust loads are re-established. The result is consistent, like-new performance.