Abstract: In a rotodynamic pump intended for operation at high pressures e.g. 2000 p.s.i. and for pumping contaminated fluids e.g. corrosive water, high pressure sealing assemblies are provided at the through-openings in the pump casing for the pump shaft. Each assembly includes a pair of axially spaced mechanical seals, and each seal comprises a rotor portion fixed to the pump shaft and a stator portion axially movable into sealing engagement with the rotor portion, the stators being located intermediate the rotor portions. A busing is located between the seals and includes conduits supplying oil at a pressure above pump pressure to the innermost seal whence the oil is reduced in pressure and passed to the outermost seal, so that oil is delivered to the facing ends of the stators. The oil serves for lubrication of the sealing interfaces and for the prevention of egress of contaminated material through said innermost seal.