Locomotive Steam Generators

A steam generator is an automated boiler carried aboard a diesel-electric or electric locomotive to provide steam for train heating, and, in some cases (for cars using the steam-jet system) air conditioning in summer. When trains were pulled by steam locomotives the locomotive boiler provided steam. When diesel or electric motive power is used a steam generator burning diesel fuel provides the steam. Steam generators are pretty much part of the past as Amtrak and VIA (Canada) have converted to all electric systems.

One might think that steam was an obvious solution to the problem of heating passenger train cars but it was actually many years before steam heating was perfected. Early trains used coal or wood stoves on each car. Given that the cars were wood and often telescoped or reduced to splinters in an accident, the fire danger the stoves presented was tremendous. The problem with early attempts at steam heating was that cars close to the locomotive would be too hot while those at the end of the train were too cold. The solution was the "vapor" system whereby the steam trainline (the piping running the length of each car and linked to adjacent cars via flexible couplings) was kept at high pressure and only a very low pressure was introduced into the car's heating coils via a reduction valve.

The following description appeared in the 1956 Locomotive Cyclopedia:

These requirements have resulted in the development of a series of steam generators with capacities of from 1,600 to 4,500 pounds of water per hour evaporative capacity with steam pressures of over 300 lb. per sq. in. These generators are able, starting cold, to produce steam under pressure in two minutes. Steam generators are designed to create steam for immediate use just as a dynamo generates electrical energy for instant use. The space and weight limitations of the locomotive do not permit facilities for the storage of the produced steam and since the steam requirements are constantly fluctuating the steam generator's output must be automatically controlled. The steam generator components have, therefore been carefully engineered and coordinated to require a minimum of attention w hile on the road. Maintenance and adjustment is handled at terminal points and the engine crews need only to follow simple operating instructions on the road. A remote control panel is now installed in the operating cab of the locomotive to regulate all of the functions of the steam generator and it includes warning lights to indicate the failure of any of the operations of the steam generator while in service.

An additional water supply must be carried on the locomotive for the use of the generator but the fuel supply may be drawn from that furnished for the operation of the Diesel engine. Once the generator has been started the only attention necessary, aside from regulating the steam flow to meet the demand, is to blow down the steam separator periodically and to turn the fuel and water treatment filters occasionally during a run. The blowdown valve may be operated from the control panel but the filters in the engine room must be turned by hand.

Steam Generator Operation

Generally, the operation of the steam generators may be described as follows: the steam generating part of the unit consists of sets of coiled water tubing nested and connected in series to form a single tube several hundred feet long. Water is pumped into the coil inlet and converted to steam as it progresses through the coils. Heat is obtained by the burning of Diesel fuel oil which is combined with compressed air and carried through an atomizing nozzle in a fuel spray device into a firepot above the coils. The fuel oil is mixed with air supplied by a blower and is ignited by a ontinuous spark produced electrically. The fire and hot gasses flow downward and then outward through the nest of coils.

The operation of the steam generator is fully automatic. A motor converter drives the blower, water pump and the fuel pump at a constant speed. The water bypass regulator controls the steam generator output automatically by regulating the amount of water fed to the coils. Before the water enters the coils it is passed through a control which regulates the fuel to the spray nozzle in direct proportion to the amount of water entering the coils. This control also adjusts the damper to provide the proper amount of air for efficient combustion.

Some anecdotes by W.A. Gardner, then of EMD

More Pictures

Cutaway View (note the coiled tube)
Steam generator being installed in F-M Train Master
Steam generator aboard the late Glenn Monhart's E-4
Another view of the above
Steam Generator in the weeds at Illinois Railway Museum
The Superheater Company (ELESCO) made them, too

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