Ramsbottom type The displacement lubricator was introduced in the
United Kingdom in 1860 by
John Ramsbottom. It operates by allowing steam to enter a closed vessel containing oil. After condensing, the water sinks to the bottom of the vessel, causing the oil to rise and overflow into delivery pipes. The oil from the delivery pipes is introduced into the steam pipe, where it is atomised and carried to the valves and cylinders. In early applications in
steam locomotives, either two displacement lubricators (one for each
cylinder) would be positioned at the front of the boiler near the valves, often on either side of the
smokebox or one lubricator would be placed behind the smokebox. The behind-smokebox configuration has the advantage that a good connection can be made to the steam pipe and it was used by the
Great Western Railway. It has the disadvantage that the lubricator's accessibility is reduced and additional drain pipes are required to be connected to the waste to avoid it dripping onto the boiler. The displacement lubricator was a useful stop-gap but had the disadvantage that it was difficult to accurately control over the rate of oil feed and lubrication was only supplied when the engine was doing work (when a locomotive is coasting with the regulator closed, no steam is present to operate the lubricator).
Roscoe type The Roscoe type lubricator improved the situation by providing a valve with which to regulate the flow of steam and hence lubricant. Setting the valve correctly required experience and depended on the speed of the train.
Replacement When more sophisticated lubricators, such as the Wakefield and Detroit types, were developed, displacement lubricators fell out of use but they are still used on model steam engines. ==Hydrostatic lubricator==