Abstract: A centrifugal pump wherein the back shroud of a brittle impeller of ceramic or glass is coupled to the radially outwardly extending disc of a metallic adapter whose hub receives torque from the pump shaft. The adapter has a flange which surrounds the peripheral surface of the impeller or it has a collar which surrounds a complementary collar of the back shroud. The arrangement is such that the coupling between the adapter and the impeller does not subject the impeller to any tensional or other stresses which would be likely to affect the integrity of the brittle impeller. The disc of the adapter is adjacent the rear side of the back shroud so that the adapter does not interfere with the flow of conveyed material to, in and from the impeller.

Abstract: An underwater pumping arrangement includes a submersible pump having a pump outlet conduit provided with a first connecting flange adapted to register with a second connecting flange of an outflow conduit permanently provided at the bottom of a liquid-filled pit or container to form with the second connecting flange a seal-tight conduit joint. As the pump is lowered into the liquid-filled pit or container towards the bottom thereof, it is guided by cables or rails into a predetermined position in which the first connecting flange registers with the second connecting flange. The pump is provided at its underside with a supporting structure for directly supporting the pump upon the bottom of the pit or container when the pump has been lowered into the predetermined position. One of the two conduits is provided with an expandable-contractable connecting chamber connected to one connecting flange.