The Ultimate Steam Page

Steam Locomotive Boiler Water Treatment
Research and Development on the FCAF

added July 21, 2001

photos and info courtesy Shaun McMahon

Brief Background on Steam Locomotive Water Treatment

A continuing problem since the development of the first steam locomotives has been treatment of the boiler water. Water contains impurities (minerals, metals, etc.) which can cause problems in steam boilers. Since the vast majority of steam locomotives built are non-condensing (i.e.- water is used once and exhausted out of the stack) water treatment is more difficult than on ships and stationary power plants which condense their water and re-use it. In a steam locomotive, the impurities in the water become concentrated inside the boiler over time, and eventually precipitate out of the solution onto the internal surfaces of the boiler. This process is called fouling. These materials can slow the transfer of heat from the fuel to the water and decrease the locomotive's efficiency and power. They can also cause accelerated corrosion of the boiler's metal surfaces, increasing maintenance requirements and decreasing the life of boiler components. Some water conditions cause the water in the boiler to "foam", which can cause many problems. Operators attempted to minimize foaming by periodically "blowing down" the boiler, or releasing small amounts of hot water from the low points of the boiler while the boiler was in steam. If this had to be done very often, a great deal of fuel and water could be wasted. Certain geographical areas have much worse water than others, so while this phenomena was a nuisance for all railways, it was a tremendous problem for some.

Normal practice on steam locomotives was to "wash out" locomotive boilers at least monthly. The locomotive would have to be taken out of service, have its fire extinguished, and a series of plugs all over the boiler are removed. A high-pressure water spray is directed into the boiler through these openings and and the undersirable materials are flushed out, a process which could take several hours. After this, the plugs are reinstalled in the boiler, the boiler is refilled, the fire is re-started, steam is raised, and the locomotive could be returned to service. This process often required the locomotive to be out of service for an entire day, and represented a significant cost is labor and lack of availability of the locomotive. A worse problem was that some fouling materials hardened onto boiler surfaces and could not be removed by a washout. If fouling becomes sufficiently severe, it can actually cause the temperature of parts of the boiler such as firebox surfaces and tubes to become so great that they can be permanently damaged.

The whole water issue was another "nail in the coffin" of steam locomotives when diesel locomotives were introduced. However, the application of sound engineering principals has shown that problems associated with water can be virtually eliminated from steam locomotive operation.

By the 1930's, railway suppliers had begun to develop chemical treatment systems which somewhat reduced these problems. By adding appropriate chemicals to the water prior to its introduction to the boiler, fouling can be significantly reduced. Some railways were more advanced in their water treatment than others. In France, an advanced treatment system was developed known as TIA which significantly reduced water problems with locomotive boilers.

L. D. Porta developed a simplified version of the French water treatment system and applied it to many locomotives in Argentina. Advances in this system allowed locomotives to operate for 6 months or more, even in "bad water" districts, between boiler washouts. In addition, hard fouling of internal boiler surfaces was completely eliminated, greatly extending boiler life. Some locomotives using Porta's treatment system operated nearly 30 years with no replacement of tubes or firebox sheets.

Shaun McMahon, Chief Mechanical Officer of the FCAF, has cooperated with Porta over the last few years in further advancing his water treatment system and applying it to the steam locomotives of the FCAF. The following photos show recent work done on the railway in applying Porta's water treatment system to the line's steam locomotives.

Water Samples & Analysis Equipment

The above photo shows Shaun's workbench with water samples, chemicals for analysis, scale, etc. This gives some idea of the materials and equipment required to maintain the desired water chemistry in the line's locomotives.

Closeup of Boiler Water Samples

This photo shows samples of boiler water taken from Camila at a recent (June 2001) boiler washout undergoing analysis at the FCAF shops. Note the murky brown appearance of the water samples. While this condition would appear undesirable to the layman, it in fact illustrates very good water chemistry because a high level of Total Disolved Solids (TDS) is being maintained. High TDS results from impurities in the water being maintained in suspension, rather than "plating out" on heat transfer surfaces inside the boiler. As the TDS in the boiler rises, impurities collect in the low points of the boiler are flushed out periodically by blowing down the boiler. Porta's system requires less frequent blowdowns which minimizes wasted fuel and water. The downside of maintaining high TDS is a tendency for the boiler to "foam". However, this is dealt with through the addition of special "anti-foaming" agents and the use of the foam indicator system illustrated below.

Modified Boiler Washout Plugs

The above photo shows three modified boiler washout plugs which have been machined to accept standard automotive type 14 mm threaded spark plugs. The spark plugs are used to sense the level of foam in the boiler. Foam is a natural consequence of maintaining high TDS in the boiler (see above), but it can be controlled through the use of anti-foaming agents. This system allows the locomotive operator to monitor the level of the foam within the boiler so that the water chemistry can be adjusted if necessary. The drawing underneath the plugs is a schematic diagram drawn by L. D. Porta showing the circuit wiring for the foam level indication system. Each of the three plugs has a corresponding indicator light in the cab which provide an accurate indication of the foam level within the boiler.

Foam Sensors Ready for Installation in Camila's Boiler

A presentation on this work will be made at the upcoming World Steam and Tourist Trains Conference and Exhibit being held at the FCAF in October. See the News page for more details on the conference.