White Knight pumps with liquid-side shafts use hydraulically-loaded seals that allow the perfect amount of pressure to the seal, regardless of the pump operating pressure.
Shaft seals are held into sealing position by the pressure of the liquid being pumped. The seals tighten on the shaft when pumping pressure is high, and the force of the seal decreases as pressure is reduced. This capitalizes on the high flexural, but low elasticity properties of PTFE to produce the perfect seal in chemistries.
Standard versions of hydraulically-loaded shaft seals are capable of running dry for a few minutes without damage to the shaft or seals while still providing ample amounts of suction lift. Dry-run capable versions can run dry for extended periods without damage, but are better suited for applications with flooded suction.