Safety device for motor pump group

Safety device for a motor-pump assembly for pumping fluid under pressure comprising a vane wheel integrally connected to a vertical shaft driven in rotation, and emplaced in a pump body, the rim of said wheel normally being horizontally guided by a hydrostatic bearing, characterized in that the safety device comprises a bushing disposed coaxially around said vertical shaft, and means supporting said bushing on an inner wall of said pump body and providing a space horizontally between the interior of said bushing and the exterior of said shaft for flow of fluid therebetween and for causing said shaft and said bushing with fluid therebetween to constitute an inoperative hydrodynamic bearing when said shaft is normally guided by said hydrostatic bearing and to constitute an operative hydrodynamic bearing, that prevents contact of said vane wheel and said hydrostatic bearing, solely by reduction of said space when said hydrostatic bearing fails and permits said shaft to move horizontally toward said bushing, said bushing having labyrinth seal means including a plurality of cavities for limiting the flow of fluid in said space, whereby the dynamic characteristics of said shaft are substantially unaffected by the presence of said hydrodynamic bearing when said hydrostatic bearing is operative and whereby damage to said motor-pump assembly upon failure of said hydrostatic bearing is prevented by operation of said hydrodynamic bearing.