Franco-Crosti boiler
Encyclopedia
Boiler
A boiler is a closed vessel in which water or other fluid is heated. The heated or vaporized fluid exits the boiler for use in various processes or heating applications.-Materials:...
used for steam locomotives. It was designed in the 1930s by Attilio Franco and Dr Piero Crosti, two engineers working for the Ferrovie dello Stato
Ferrovie dello Stato
Ferrovie dello Stato is a government-owned holding which manage infrastructure and service on the Italian rail network. The subsidiary Trenitalia is the main rail operator in Italy.-Organization:Ferrovie dello Stato subsidiaries are:...
(FS), the Italian state railway.
Purpose
The Franco-Crosti boiler is a modification of the conventional fire tube boiler design used on most steam locomotives. Unlike conventional boilers the heat remaining in the exhaust gases is used to preheat the water supply for the main boiler using a secondary heat exchange mechanism. This mechanism, known as the feedwater heaterFeedwater heater
A feedwater heater is a power plant component used to pre-heat water delivered to a steam generating boiler. Preheating the feedwater reduces the irreversibilities involved in steam generation and therefore improves the thermodynamic efficiency of the system...
is essentially a secondary boiler. The preheated feedwater is fed at full boiler pressure into the main boiler via clack valves
Check valve
A check valve, clack valve, non-return valve or one-way valve is a mechanical device, a valve, which normally allows fluid to flow through it in only one direction....
.
The feedwater heater is not designed to produce steam, instead raising the temperature of the feedwater. This allows the heater to utilize the remaining energy in the exhaust gases effectively.
Design
The typical configuration of a Franco-Crosti boiler had a relatively conventional main boiler with one or two secondary feedwater heaters running parallel to the boiler barrel. Where the loading gaugeLoading gauge
A loading gauge defines the maximum height and width for railway vehicles and their loads to ensure safe passage through bridges, tunnels and other structures...
did not allow the feedwater heater to be placed beside the boiler it was mounted beneath.
When the locomotive is started, cold water is fed directly into the main boiler which operates normally with the exhaust gases flowing out of the main chimney via the smokebox. Once the boiler is producing steam, the exit from the smokebox into the main chimney is closed and the exhaust gases instead flow through the feedwater heater and exit via the secondary chimney located towards the rear of the locomotive. Water fed into the boiler is now pre-heated in the feedwater heater and enters the boiler at higher than normal temperature and pressure.
Belgium
The first Franco-Crosti boilered locomotive was built for the Belgian State RailwaysNMBS/SNCB
The National Railway Company of Belgium, known as the or the Société Nationale des Chemins de fer Belges is the Belgian national railway operator.It is usually referred to in English as "Belgian Railways" or the SNCB....
as No. 2096 in 1932. This massive 0-6-2 + 2-4-2-4-2 + 2-6-0 locomotive weighed 248 tons and developed around 3,000 horsepower. It was essentially two Franco-Crosti boilered locomotives joined back-to-back and was one of the most powerful articulated locomotives ever built.
During the German
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
occupation of Belgium in the Second World War the locomotive was separated into two 0-6-2+2-6-2T locomotives. These locomotives were captured by invading Russia
Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...
n troops in 1945 and at least one of them was still in service in Poland
Poland
Poland , officially the Republic of Poland , is a country in Central Europe bordered by Germany to the west; the Czech Republic and Slovakia to the south; Ukraine, Belarus and Lithuania to the east; and the Baltic Sea and Kaliningrad Oblast, a Russian exclave, to the north...
in 1955.
Italy
The first Italian Franco-Crosti boilered locomotive was a modified Class 671 locomotive built for the Ferrovie dello StatoFerrovie dello Stato
Ferrovie dello Stato is a government-owned holding which manage infrastructure and service on the Italian rail network. The subsidiary Trenitalia is the main rail operator in Italy.-Organization:Ferrovie dello Stato subsidiaries are:...
in 1939. This became the only member of the cab forward
Cab forward
The term cab forward refers to various rail and road vehicle designs which place the driver's compartment substantially farther towards the front than is common practice.- Rail locomotives :...
Class 672.
Following the experimental conversion of 672.001 a new class of Franco-Crosti boilered locomotives were built in 1940 and 1941. These were the Class 683, of which five were built as rebuilds of Class 685 locomotives. These were the first Franco-Crosti locomotives to also use Caprotti valve gear
Caprotti valve gear
The Caprotti valve gear is a type of steam engine valve gear invented in the early 1920's by Italian architect and engineer Arturo Caprotti. It uses camshafts and poppet valves rather than the piston valves used in other valve gear...
. These locomotives survived the war and continued in use until the last was withdrawn in 1962.
In 1940 the first of the Class 743 class were built. These were entirely new locomotives with two feedwater heaters, one on each side of the boiler. In all 94 of this class were built for FS.
In 1952 and 1953, 35 of the Class 625 locomotives were converted to use Franco-Crosti boilers with side feedwater heaters. These locomotives became the Class 623. Several survived into the 1970s.
Finally in 1954 the last Italian Franco-Crosti locomotives were built, the Class 741. Unlike the other Italian classes, these had a single feedwater heater mounted directly below the main boiler. In total 81 of these locomotives were built, again surviving into the 1970s.
West Germany
In 1951 the Deutsche BundesbahnDeutsche Bundesbahn
The Deutsche Bundesbahn or DB was formed as the state railway of the newly established Federal Republic of Germany on September 7, 1949 as a successor of the Deutsche Reichsbahn-Gesellschaft '...
(DB) rebuilt two Franco-Crosti boilered locomotives with two feedwater heaters located below the main boiler. These were variants of the standard DB class 52 design but were registered as class 42.90 due to the higher axle load.
These locomotives were followed in 1954–1958 by the conversion of 31 class 50
DRB Class 50
Because the Deutsche Bundesbahn had sufficient goods train locomotives, they could quickly phase out the DRB Class 52 engines, so that the ageing boilers on the Class 50s could be replaced by those of the Class 52s. Even the 'bathtub' tender of the Kriegslokomotiven was used by the 50s amongst...
locomotives in a 2-10-0 tender configuration with single feedwater heater located under the boiler. These thirty locos formed the new class 50.40 and proved quite successful economically but had problems with corrosion. All locomotives were withdrawn by 1967.
Great Britain
BR standard class 9F
The British Railways BR Standard Class 9F 2-10-0 is a class of steam locomotive designed for British Railways by Robert Riddles. The Class 9F was the last in a series of standardised locomotive classes designed for British Railways during the 1950s, and was intended for use on fast, heavy freight...
locomotives, Nos 92020-9
BR Standard Class 9F 92020-9
British Railways Standard Class 9F steam locomotives Nos 92020-9 were experimentally built with Franco-Crosti boilers, thus forming a subclass...
, were built with Franco-Crosti boilers in 1955. Like the German 50.40 these were 2-10-0 tender locomotives with a single feedwater heater under the main boiler.
The standard funnel was retained, but was only used for lighting-up and was blanked when running. The final chimney was located on the right-hand (fireman's) side, just forward of the firebox. The Crosti preheaters provided less improvement than had been expected, and were a problem for maintenance, owing to acidic fluegases condensing in the feedwater heater and causing corrosion. All were converted back to a more standard form within a few years, the preheaters remaining in place, but blanked off, as seen in the accompanying photograph.
Ireland
In 1951 Oliver BulleidOliver Bulleid
Oliver Vaughan Snell Bulleid was a British railway and mechanical engineer best known as the Chief Mechanical Engineer of the Southern Railway between 1937 and the 1948 nationalisation, developing many well-known locomotives.- Early life and Great Northern Railway :He was born in Invercargill,...
was the chief mechanical engineer of the 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...
and was experimenting with new forms of steam locomotive. He converted a 1907 Coey locomotive to use a Franco-Crosti boiler similar to the original Italian designs and to burn peat. The locomotive was a poor steamer and eventually was fitted with a forced-draught fan powered by a diesel engine carried on a wagon behind the tender.