South African Class 25 4-8-4
Encyclopedia
Between 1953 and 1955 the South African Railways placed ninety Class 25 condensing steam locomotives
with a 4-8-4
Northern wheel arrangement in service. The Class 25NC
, placed in service at the same time, is the non condensing version of the Class 25 condensing locomotive.
(SWA), the South African Railways (SAR) began to give serious consideration to the possibility of introducing condensing locomotives as far back as the late 1930s. At one time it was considered to convert Class 12A 4-8-2
locomotives into condensing locomotives, but this never realised.
It was only after World War II
that extensive condensing tests were carried out with the modified Class 20 2-10-2
locomotive. The approximately 90% water and 10% coal savings that were achieved in 1950 and 1951 during the tests with the Class 20 in the Transvaal, the Karoo and in SWA, led to the decision to proceed with the design of a new condensing locomotive.
condensing locomotive, can be considered as the ultimate in SAR non-articulated locomotive design. It was designed under the direction of L.C. Grubb, Chief Mechanical Engineer (CME) of the SAR from 1949 to 1954.
The design work on the locomotive’s condensing apparatus and the condensing tender was carried out by Henschel and Son
, who built one locomotive complete with tender, number 3451, works number 28730. This locomotive was then dispatched to the North British Locomotive Company
(NBL) in Glasgow, who built the rest of the Class 25 locomotives, numbers 3452 to 3540, as well as the first eleven Class 25NC non condensing versions of the Class 25, numbers 3401 to 3411. They were delivered between 1953 and 1955.
Henschel built the other thirty-nine non condensing locomotives, numbers 3412 to 3450, as well as sixty-one of the condensing tenders, to which they held the patent. The other twenty-nine condensing tenders were built by NBL. One more condensing tender was later built by the Salt River shops of the SAR on a spare frame that was delivered as part of the original order.
These tenders were large and complex enough that Henschel allocated separate builder’s or works numbers to them. At approximately 57 feet (17.4 m) in length they are about 15 feet (4.6 m) longer than their locomotives. One third of the total length of the tender is taken up by the water tank and coal bunker, while the rest is taken up by eight large radiators on each side, cooled by five steam driven roof mounted fans.
The condensing tenders were rather appropriately classified as Type CZ, since CZ is also the motor vehicle registration letters of Beaufort West
, the capital town of the Karoo
where the Class 25 was to serve.
The crossheads, of the Alligator type, were split on the vertical centre line and clamped on to the end of the piston rods, which had three coned rings engaging in grooves in the crossheads. The coupling rods differed from the usual in the provision of three independent rods, thereby doing away with four knuckle joints and pins.
The draught turbine gave the locomotive its characteristic whining sound while running. On the Class 25 visual evidence of this altered smokebox is the locomotive’s banjo face, the distinctively shaped smokebox front. Spent steam was fed through the thick pipe on the locomotive’s left side back to the condensing tender, where five steam turbine driven fans in the roof blew air down through the radiators on each side of the tender.
The system proved to be extremely efficient and reduced water consumption by as much as 90% by using the same water up to eight times over, giving the Class 25 locomotive a range of 800 kilometres (497.1 mi) between water refills. In addition, the hot recycled feedwater resulted in a significantly reduced coal consumption.
Since spent steam was not expelled through the chimney, the condensers sounded unlike any other steam locomotive on South African rails. The non condensing and free exhausting Class 25NC had the usual loud bark of a steam locomotive, especially under load, while the condensing Class 25 had more of a hoarse hollow chuff sound in addition to its turbine whine.
Considerable trouble was also experienced with the induced draught equipment. The blower blades suffered heavy edge wear and blade fractures in both the blower and steam turbine wheels, which called for intense investigation by SAR engineers, Henschel representatives and the CSIR. These problems were eventually resolved and the locomotives proceeded to give a very good account of themselves.
and the Kalahari, where water is a scarce resource. They initially served on the unelectrified main line from Touws River
via Beaufort West
to De Aar, where they handled all goods and passenger traffic, including passenger trains like the Blue Train. When the section from Touws River to Beaufort West was electrified, the Class 25 continued working between Beaufort West and De Aar, but it now also worked between De Aar and Kimberley
, across from Kimberley to Bloemfontein in the east, as well as westward from Kimberley to Postmasburg, Hotazel and Sishen
in the Kalahari, hauling iron and manganese ore.
In the process their condensing tenders were also rebuilt to ordinary coal-and-water tenders by removing the condensing radiators and roof fans and replacing it with a massive water tank. Since the Type CZ tenders were built on single cast steel main frames, it was impractical to attempt to shorten them, which resulted in the rebuilt Type CZ tenders with their long round topped water tanks. Locomotives with these rebuilt tenders were soon nicknamed "Worshond" (Sausage dog or Dachshund).
When the Class 25 condensers were converted to Class 25NC non condensers, their number plates were copied and recast with the additional "NC" for "Non Condensing" squeezed in next to the existing "25", which resulted in a lopsided class indication on their plates. Locomotives with all four characters neatly in line and centred were therefore usually identifiable as original Class 25NCs.
After they were relieved of their condensing gear, these locomotives served for another eleven years before being retired from the SAR when steam was finally completely replaced by electric and diesel-electric traction.
Steam locomotive condensing apparatus
A steam locomotive condensing apparatus differs in purpose from the usual closed cycle steam engine condenser, in that its function is primarily either to recover water, or to avoid excessive emissions to the atmosphere, rather than maintaining a vacuum to improve both efficiency and power...
with a 4-8-4
4-8-4
Under the Whyte notation classification of steam locomotives, 4-8-4 represents the wheel arrangement of four leading wheels on two axles , eight powered and coupled driving wheels on four axles, and four trailing wheels on two axles .Other equivalent classifications are:UIC classification: 2D2...
Northern wheel arrangement in service. The Class 25NC
South African Class 25NC 4-8-4
Between 1953 and 1955 the South African Railways placed fifty Class 25NC steam locomotives with a 4-8-4 wheel arrangement in service. The Class 25NC is the non condensing version of the Class 25 condensing locomotive, of which ninety were placed in service at the same time...
, placed in service at the same time, is the non condensing version of the Class 25 condensing locomotive.
Background
Because of the difficulties experienced in obtaining adequate supplies of suitable water in arid regions like the Great Karoo between Touws River and De Aar and from there into South West AfricaSouth West Africa
South-West Africa was the name that was used for the modern day Republic of Namibia during the earlier eras when the territory was controlled by the German Empire and later by South Africa....
(SWA), the South African Railways (SAR) began to give serious consideration to the possibility of introducing condensing locomotives as far back as the late 1930s. At one time it was considered to convert Class 12A 4-8-2
South African Class 12A 4-8-2
Between 1919 and 1929 the South African Railways placed sixty-seven Class 12A steam locomotives with a 4-8-2 Mountain wheel arrangement in service.-Manufacturers:...
locomotives into condensing locomotives, but this never realised.
It was only after World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
that extensive condensing tests were carried out with the modified Class 20 2-10-2
South African Class 20 2-10-2
In 1935 the South African Railways placed one Class 20 steam locomotive with a Santa Fe wheel arrangement in service. In 1950 it was modified to an experimental condensing locomotive.-Design:...
locomotive. The approximately 90% water and 10% coal savings that were achieved in 1950 and 1951 during the tests with the Class 20 in the Transvaal, the Karoo and in SWA, led to the decision to proceed with the design of a new condensing locomotive.
Builders
The end result, the Class 25 4-8-44-8-4
Under the Whyte notation classification of steam locomotives, 4-8-4 represents the wheel arrangement of four leading wheels on two axles , eight powered and coupled driving wheels on four axles, and four trailing wheels on two axles .Other equivalent classifications are:UIC classification: 2D2...
condensing locomotive, can be considered as the ultimate in SAR non-articulated locomotive design. It was designed under the direction of L.C. Grubb, Chief Mechanical Engineer (CME) of the SAR from 1949 to 1954.
The design work on the locomotive’s condensing apparatus and the condensing tender was carried out by Henschel and Son
Henschel & Son
Henschel & Son was a German company, situated in Kassel, best known during the 20th century as a maker of transportation equipment, including locomotives, trucks, buses and trolleybuses, and armoured fighting vehicles and weapons....
, who built one locomotive complete with tender, number 3451, works number 28730. This locomotive was then dispatched to the North British Locomotive Company
North British Locomotive Company
The North British Locomotive Company was created in 1903 through the merger of three Glasgow locomotive manufacturing companies; Sharp Stewart and Company , Neilson, Reid and Company and Dübs and Company , creating the largest locomotive manufacturing company in Europe.Its main factories were...
(NBL) in Glasgow, who built the rest of the Class 25 locomotives, numbers 3452 to 3540, as well as the first eleven Class 25NC non condensing versions of the Class 25, numbers 3401 to 3411. They were delivered between 1953 and 1955.
Henschel built the other thirty-nine non condensing locomotives, numbers 3412 to 3450, as well as sixty-one of the condensing tenders, to which they held the patent. The other twenty-nine condensing tenders were built by NBL. One more condensing tender was later built by the Salt River shops of the SAR on a spare frame that was delivered as part of the original order.
These tenders were large and complex enough that Henschel allocated separate builder’s or works numbers to them. At approximately 57 feet (17.4 m) in length they are about 15 feet (4.6 m) longer than their locomotives. One third of the total length of the tender is taken up by the water tank and coal bunker, while the rest is taken up by eight large radiators on each side, cooled by five steam driven roof mounted fans.
The condensing tenders were rather appropriately classified as Type CZ, since CZ is also the motor vehicle registration letters of Beaufort West
Beaufort West
Beaufort West is a town in the Western Cape province in South Africa. It is the largest town in the arid Great Karoo region, and forms part of the Beaufort West Local Municipality, with 37 000 inhabitants in 2001....
, the capital town of the Karoo
Karoo
The Karoo is a semi-desert region of South Africa. It has two main sub-regions - the Great Karoo in the north and the Little Karoo in the south. The 'High' Karoo is one of the distinct physiographic provinces of the larger South African Platform division.-Great Karoo:The Great Karoo has an area of...
where the Class 25 was to serve.
Characteristics
Roller bearings were used throughout, including on the three-axle tender bogies, the coupling and connecting rods as well as the crosshead gudgeon pins, while the locomotive’s leading bogies and drivers had Cannon-type axle boxes. The cylinders and underframes were cast in one piece, while the steel cylinders and steam chests were fitted with cast iron liners. The tender underframe was also a one piece steel casting. Since it was entirely mounted on roller bearings, very little effort was required to move these locomotives.The crossheads, of the Alligator type, were split on the vertical centre line and clamped on to the end of the piston rods, which had three coned rings engaging in grooves in the crossheads. The coupling rods differed from the usual in the provision of three independent rods, thereby doing away with four knuckle joints and pins.
Condensing
With the Class 25 condensing locomotive, spent steam was recycled and condensed back to water for repeated use. Since the steam wasn’t expelled up the chimney, the Class 25’s smokebox contained a steam turbine driven fan beneath the chimney in order to keep the draught going, with deflector plates to prevent char from causing excessive wear on the fan blades. Most of the char was collected at the bottom of the smokebox front, from where it was discharged through a steam ejector pipe that exhausted immediately in front of the chimney.The draught turbine gave the locomotive its characteristic whining sound while running. On the Class 25 visual evidence of this altered smokebox is the locomotive’s banjo face, the distinctively shaped smokebox front. Spent steam was fed through the thick pipe on the locomotive’s left side back to the condensing tender, where five steam turbine driven fans in the roof blew air down through the radiators on each side of the tender.
The system proved to be extremely efficient and reduced water consumption by as much as 90% by using the same water up to eight times over, giving the Class 25 locomotive a range of 800 kilometres (497.1 mi) between water refills. In addition, the hot recycled feedwater resulted in a significantly reduced coal consumption.
Since spent steam was not expelled through the chimney, the condensers sounded unlike any other steam locomotive on South African rails. The non condensing and free exhausting Class 25NC had the usual loud bark of a steam locomotive, especially under load, while the condensing Class 25 had more of a hoarse hollow chuff sound in addition to its turbine whine.
Teething troubles
Soon after being placed in service, however, problems were experienced with connecting rods failing, big end bearings breaking up as well as cracks developing in the motion girder of the Alligator crossheads. After investigations by SAR engineers, with assistance from the South African Council for Scientific and Industrial Research (CSIR), the crossheads, slide bars and coupling rods were modified, with the crossheads converted to the multiple-bearing type with single guide bars, while the three independent coupling rods were replaced with the more conventional single coupling rod with knuckle joints.Considerable trouble was also experienced with the induced draught equipment. The blower blades suffered heavy edge wear and blade fractures in both the blower and steam turbine wheels, which called for intense investigation by SAR engineers, Henschel representatives and the CSIR. These problems were eventually resolved and the locomotives proceeded to give a very good account of themselves.
Service
The Class 25 was built specifically for work in the KarooKaroo
The Karoo is a semi-desert region of South Africa. It has two main sub-regions - the Great Karoo in the north and the Little Karoo in the south. The 'High' Karoo is one of the distinct physiographic provinces of the larger South African Platform division.-Great Karoo:The Great Karoo has an area of...
and the Kalahari, where water is a scarce resource. They initially served on the unelectrified main line from Touws River
Touws River (town)
Touws River is a small railway town of 6,800 people in the Western Cape province of South Africa. It is located on the river of the same name, about north-east of Cape Town.-History:...
via Beaufort West
Beaufort West
Beaufort West is a town in the Western Cape province in South Africa. It is the largest town in the arid Great Karoo region, and forms part of the Beaufort West Local Municipality, with 37 000 inhabitants in 2001....
to De Aar, where they handled all goods and passenger traffic, including passenger trains like the Blue Train. When the section from Touws River to Beaufort West was electrified, the Class 25 continued working between Beaufort West and De Aar, but it now also worked between De Aar and Kimberley
Kimberley, Northern Cape
Kimberley is a city in South Africa, and the capital of the Northern Cape. It is located near the confluence of the Vaal and Orange Rivers. The town has considerable historical significance due its diamond mining past and siege during the Second Boer War...
, across from Kimberley to Bloemfontein in the east, as well as westward from Kimberley to Postmasburg, Hotazel and Sishen
Sishen
Sishen is a town in Northern Cape, South Africa. It is the location of a large iron ore mine.- Transport :The mine is connected to the port of Saldanha Bay by the Sishen-Saldanha Railway Line. The line is electrified at 50 kV AC and the trains using this line are amongst the heaviest trains in the...
in the Kalahari, hauling iron and manganese ore.
Reclassification
The Class 25 was a complex locomotive that required high maintenance, especially on the turbine blower fans in the smokebox, whose blades needed to be replaced frequently due to damage by solid particles in the exhaust. The equally complex condensing tender also required frequent maintenance. Between 1973 and 1980, after serving for twenty years and partially motivated by the spread of electric and diesel-electric traction over routes that were previously served exclusively by the Class 25, all but three of the Class 25 condensing locomotives, numbers 3451, 3511 and 3540, were converted to free exhausting and non condensing locomotives as they went through the workshops for major overhauls. The converted locomotives were reclassified to Class 25NC.In the process their condensing tenders were also rebuilt to ordinary coal-and-water tenders by removing the condensing radiators and roof fans and replacing it with a massive water tank. Since the Type CZ tenders were built on single cast steel main frames, it was impractical to attempt to shorten them, which resulted in the rebuilt Type CZ tenders with their long round topped water tanks. Locomotives with these rebuilt tenders were soon nicknamed "Worshond" (Sausage dog or Dachshund).
When the Class 25 condensers were converted to Class 25NC non condensers, their number plates were copied and recast with the additional "NC" for "Non Condensing" squeezed in next to the existing "25", which resulted in a lopsided class indication on their plates. Locomotives with all four characters neatly in line and centred were therefore usually identifiable as original Class 25NCs.
After they were relieved of their condensing gear, these locomotives served for another eleven years before being retired from the SAR when steam was finally completely replaced by electric and diesel-electric traction.
Gallery
The main picture shows preserved number 3511 "Frieda" at Hartswater in the Cape Province on 24 April 1981.See also
- Steam locomotive condensing apparatusSteam locomotive condensing apparatusA steam locomotive condensing apparatus differs in purpose from the usual closed cycle steam engine condenser, in that its function is primarily either to recover water, or to avoid excessive emissions to the atmosphere, rather than maintaining a vacuum to improve both efficiency and power...
- South African Class 20 2-10-2South African Class 20 2-10-2In 1935 the South African Railways placed one Class 20 steam locomotive with a Santa Fe wheel arrangement in service. In 1950 it was modified to an experimental condensing locomotive.-Design:...
- South African Class 25NC 4-8-4South African Class 25NC 4-8-4Between 1953 and 1955 the South African Railways placed fifty Class 25NC steam locomotives with a 4-8-4 wheel arrangement in service. The Class 25NC is the non condensing version of the Class 25 condensing locomotive, of which ninety were placed in service at the same time...
- Tender locomotive numbering and classification
- The 4-8-4 "Northern"
- List of South African locomotive classes