A steam-actuated device for pumping compressible fluids, usually from subatmospheric suction pressure to atmospheric discharge pressure. A steam jet ejector is most frequently used for maintaining vacuum in process equipment in which evaporation or condensation takes place. Because of its simplicity, compactness, reliability, and generally low first cost, it is often preferred to a mechanical vacuum pump for removing air from condensers serving steam turbines, especially for marine service.