Steam generator is the term used to describe a type of boiler used to produce steam for climate control and potable water heating in railroad passenger cars. The output of a railroad steam generator is low pressure, saturated steam that is passed through a system of pipes and conduits throughout the length of the train.
Steam generators were developed when Diesel locomotives started to replace steam locomotives on passenger trains. In most cases, each passenger locomotive was fitted with a steam generator and a feedwater supply tank. The steam generator used some of the locomotive's diesel fuel supply for combustion. In the event a steam generator-equipped locomotive was not available for a run, a so-called "heating car" fitted with one or two steam generators was inserted between the last locomotive in the consist and the rest of the train. In Ireland, Córas Iompair Éireann used "heating cars" as standard and CIE diesel locomotives were not fitted with steam generators.
Contents |
During the early days of passenger railroading, cars were heated by a wood or coal fired stove—if any heat was provided at all. It was difficult to evenly heat the long drafty cars. Passengers near the stove often found it uncomfortably hot, while those further away faced a cold ride. The stoves were also a safety hazard. Often cars were ignited by embers from the stove, especially in a wreck, when a dislodged stove would overturn, dumping burning coals into the car.
The use of steam from the locomotive to heat cars was first employed in the late 19th century. High pressure steam from the locomotive was passed through the train via pipes and hoses. The dangers of this arrangement became evident in the accidents that plagued the industry.
In 1903 Chicago businessman Egbert Gold introduced the "Vapor" car heating system, which used low pressure, saturated steam. The Vapor system was safe and efficient, and became nearly universal in railroad applications.
When steam locomotives began to be retired from passenger runs, Gold's company, now known as the Vapor Car Heating Company, developed a compact water-tube boiler that could be fitted into the rear of a Diesel locomotive's engine room. Known as the Vapor-Clarkson steam generator, it and its competitors (notably the unit built by Elesco) remained a standard railroad appliance until steam heat was phased out.
In Great Britain, steam generators were built for British Railways diesel locomotives [1] by three firms - Spanner [2], Clayton [3] and Stone [4]. All types were notoriously unreliable and failures were very common.
These burned Diesel fuel, which is a lightweight fuel oil. The term steam generator (as opposed to boiler) usually refers to an automated unit with a long spiral tube that water is pumped through and is surrounded by flame and hot gases, with steam issuing at the output end. There is no pressure vessel in the ordinary sense of a boiler. Because there is no capacity for storage, the steam generator's output must change to meet demand. Automatic regulators varied the water feed, fuel feed, and combustion air volume.
By pumping slightly more water in than can be evaporated, the output was a mixture of steam and a bit of water with concentrated dissolved solids. A steam separator removed the water before the steam was fed to the train. An automatic blowdown valve would be periodically cycled to eject solids and sludge from the separator. This reduced limescale buildup caused by boiling hard water. Scale buildup that occurred had to be removed with acid washouts.
In British electric locomotives the steam generator was usually an electric steam boiler, heated by a large electric immersion heater running at the (then) line voltages of 600 volts from a third rail or 1,500 volts from an overhead wire.
Steam heated or cooled rail cars have been replaced or converted to fully electric systems. Wisps of steam issuing from cars are now history in the USA, Canada, and much of the rest of the world.