Cryogenic turbo-expander

A cryogenic turbo-expander having a rotary shaft which carries a turbine wheel and carries or is operatively associated with an energy dissipating means and which extends axially through a sleeve, first race means surrounding the shaft and housing first bearing means for the shaft, second race means surrounding the shaft and housing second bearing means for the shaft, the first and second bearing means being axially spaced from one another, wherein each race has an aperture therein extending from an outer to an inner surface thereof communicating with a lubricating oil passage extending from an outer surface to an inner surface of the sleeve, and wherein both race means are arranged so that spent lubricating oil can pass therefrom to a common drain passage, the cryogenic turbo-expander additionally including a reservoir for lubricating oil communicating with the aperture in the first race means via an intermittently-operable oil metering pump and with the aperture in the second race means via an intermittently-operable oil metering pump.