Steam generator is the term used to describe a type of boiler

Boiler (steam generator)

A boiler or steam generator is a device used to create steam by applying heat energy to water. Although the definitions are somewhat flexible, it can be said that older steam generators were commonly termed boilers and worked at low to medium pressure but, at pressures above this, it is more...

 used to produce steam

Steam

Steam is the technical term for water vapor, the gaseous phase of water, which is formed when water boils. In common language it is often used to refer to the visible mist of water droplets formed as this water vapor condenses in the presence of cooler air...

 for climate control and potable water heating in railroad passenger cars. The output of a railroad steam generator is low pressure, saturated steam

Saturated steam

In thermodynamics, the state of saturation of a fluid indicates that the fluid is at its boiling point temperature. This term can be applied in several ways:*Saturated liquid: fully in the liquid state but is about to vaporize....

 that is passed through a system of pipe

Water pipe

Water pipes are pipes or tubes, frequently made of polyvinyl chloride , ductile iron, steel, cast iron, polypropylene, polyethylene, or copper, that carry pressurized and treated fresh water to buildings , as well as inside the building.-History:For many centuries, lead was the favoured material...

s and conduit

Water pipe

Water pipes are pipes or tubes, frequently made of polyvinyl chloride , ductile iron, steel, cast iron, polypropylene, polyethylene, or copper, that carry pressurized and treated fresh water to buildings , as well as inside the building.-History:For many centuries, lead was the favoured material...

s throughout the length of the train.

Steam generators were developed when Diesel locomotive

Diesel locomotive

A diesel locomotive is a type of railroad locomotive in which the prime mover is a diesel engine, a reciprocating engine operating on the Diesel cycle as invented by Dr. Rudolf Diesel...

s started to replace steam locomotive

Steam locomotive

A steam locomotive is a railway locomotive that produces its power through a steam engine. These locomotives are fueled by burning some combustible material, usually coal, wood or oil, to produce steam in a boiler, which drives the steam engine...

s 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

Combustion

Combustion or burning is the sequence of exothermic chemical reactions between a fuel and an oxidant accompanied by the production of heat and conversion of chemical species. The release of heat can result in the production of light in the form of either glowing or a flame...

. 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

Consist

A consist , in North American railway terminology, is used as a noun to describe the group of rail vehicles that make up a train. A near-equivalent UK term is rake but this excludes the locomotive....

 and the rest of the train.
In Ireland

Ireland

Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...

, Córas Iompair Éireann

Córas Iompair Éireann

Córas Iompair Éireann , or CIÉ, is a statutory corporation of the Irish state, answerable to the Irish Government and responsible for most public transport in the Republic of Ireland and, jointly with its Northern Ireland counterpart, the Northern Ireland Transport Holding Company, between the...

 used "heating cars" as standard and CIE diesel locomotives

Diesel locomotives of Ireland

Although prototype diesel locomotives ran in Britain before World War II, the railways of both the Republic and Northern Ireland changed over much more rapidly from steam to diesel traction, in the 1950s than those in Britain, due to the island's limited coal reserves and ageing steam locomotive...

 were not fitted with steam generators.

Solid fuel

During the early days of passenger railroading, cars were heated by a wood

Wood

Wood is a hard, fibrous tissue found in many trees. It has been used for hundreds of thousands of years for both fuel and as a construction material. It is an organic material, a natural composite of cellulose fibers embedded in a matrix of lignin which resists compression...

 or coal

Coal

Coal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers or veins called coal beds or coal seams. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure...

 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.

High pressure steam

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.

Low pressure steam

In 1903 Chicago

Chicago

Chicago is the largest city in the US state of Illinois. With nearly 2.7 million residents, it is the most populous city in the Midwestern United States and the third most populous in the US, after New York City and Los Angeles...

 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.

Introduction of the steam generator

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

Water-tube boiler

A water tube boiler is a type of boiler in which water circulates in tubes heated externally by the fire. Fuel is burned inside the furnace, creating hot gas which heats water in the steam-generating tubes...

 that could be fitted into the rear of a Diesel locomotive's engine room

Engine room

On a ship, the engine room, or ER, commonly refers to the machinery spaces of a vessel. To increase the safety and damage survivability of a vessel, the machinery necessary for operations may be segregated into various spaces, the engine room is one of these spaces, and is generally the largest...

. 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

Great Britain

Great Britain or Britain is an island situated to the northwest of Continental Europe. It is the ninth largest island in the world, and the largest European island, as well as the largest of the British Isles...

, steam generators were built for British Railways diesel locomotives by three firms - Spanner , Clayton and Stone . All types were notoriously unreliable and failures were very common.

Oil-fired

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

Steam separator

A Steam separator, sometimes referred to as a moisture separator, is a device for separating water droplets from steam. The simplest type of steam separator is the steam dome on a steam locomotive...

 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

Limescale

Limescale is the hard, off-white, chalky deposit found in kettles, hot-water boilers and the inside of inadequately maintained hot-water central heating systems...

 buildup caused by boiling hard water

Hard water

Hard water is water that has high mineral content . Hard water has high concentrations of Ca2+ and Mg2+ ions. Hard water is generally not harmful to one's health but can pose serious problems in industrial settings, where water hardness is monitored to avoid costly breakdowns in boilers, cooling...

. Scale buildup that occurred had to be removed with acid washouts.

Electrically-heated

In British electric locomotive

Electric locomotive

An electric locomotive is a locomotive powered by electricity from overhead lines, a third rail or an on-board energy storage device...

s the steam generator was usually an electric steam boiler

Electric steam boiler

An electric steam boiler is a type of boiler where the steam is generated using electricity, rather than through the combustion of a fuel source. They are used to generate steam for process purposes in many locations, for example laundries, food processing factories and hospitals...

, heated by a large electric immersion heater running at the (then) line voltages

Railway electrification system

A railway electrification system supplies electrical energy to railway locomotives and multiple units as well as trams so that they can operate without having an on-board prime mover. There are several different electrification systems in use throughout the world...

 of 600 volts from a third rail or 1,500 volts from an overhead wire.

Modern times

Steam heated or cooled rail cars have been replaced or converted to fully electric systems

Head end power

Head end power or electric train supply is a rail transport term for the electrical power distribution system on a passenger train. The power source, usually a locomotive at the front or “head” of a train or a generator car, generates all the electricity used for lighting, electrical and other...

. Wisps of steam issuing from cars are now history in the USA, Canada, and much of the rest of the world.

External links

• A web site devoted to locomotive steam generators