Steam engine lubricator. Artwork of a lubricator used in steam engines. This device consists of a manual regulator valve (top) and a sight-feed (glass chamber). When starting the steam engine, the sight-feed chamber was allowed to fill with water by condensation, and then the manual valve was opened and the oil valves opened to allow lubrication to take place. This allowed pressure to build up in the system before fully starting the the engine, and ensured that the system was lubricated at the right moments.