SAR standard boiler

AG Watson with a class 16E steam locomotive , which is equipped with the SAR standard 3A boiler and a standard driver's cab.

Standard boiler 3A on a class 16E steam locomotive. The arrow points to the regulator box behind the chimney.

Standard boiler 1 on a class 24 steam locomotive . The boiler feed valve with the feed lines and the steam dome can be seen behind the regulator box.

Standard boiler 1A on a class 19D steam locomotive

Standard boiler 2 on a class 14R locomotive

Standard boiler 2A on a class 15AR locomotive

The SAR Standardkessel or Watson standard boiler is a steam boiler for locomotives , which in the 1930s with the series of South African Railways was used (SAR). The development goes back to AG Watson, senior engineer at SAR, and was intended to reduce the number of boiler types used in order to lower costs for spare parts inventory and maintenance.

technology

When AG Watson took office in 1929, the railroad used 88 different types of locomotives with around 50 different types of boilers. AG Watson developed seven standard boilers with the designations 1, 1A, 2, 2A, 2B, 3A and 3B, which should replace the large number of different boilers. They are derived from the basic types 1, 2 and 3, which differ in the bowl diameter and grate surface . Variations in the length of the basic types resulted in the variants denoted by appended letters.

The boilers equipped with superheaters were kept as simple as possible in terms of design by using conventional standing boilers with a vaulted ceiling and thus dispensing with measures that were already known at the time to increase the performance of the radiant heating surface , such as Belpaire standing boilers and combustion chambers . The fire boxes were initially made of copper, later of steel. The grate areas of basic types 1 and 2 were almost the same with a little less than 3.5 m² and resulted in a narrow fire box that fit between the cranked frame cheeks on older locomotives. The basic type 3 had a fire box with a grate surface of almost 6 m², which was placed on the bar frame so that it protruded beyond its sides.

All standard boilers have a rectangular box-shaped structure behind the chimney in which the regulator was housed - a distinguishing feature for this type of construction. Behind this box, the boiler feed valve, designed as a double check valve, was located in the middle of the boiler for basic boiler types 1 and 2; for basic type 3, it was located a little below the boiler apex on the left-hand side due to the clearance profile . With all standard boiler types, the feed water was fed to the valve via pipes rising upwards at an angle along both sides of the boiler. Basic types 1 and 2 had a steam dome behind the feed valve, basic type 3 was designed without a steam dome due to the narrow vehicle outline.

designation

The series designation of locomotives that received an SAR standard boiler during an overhaul was supplemented with an R , which stood for reboilered " reboilered ". For example, a class 19A locomotive became the class 19AR after the new boiler.

Locomotives that were already delivered with the standard boiler, such as the 16E series , did not receive the additional R. Often, but not necessarily, the standard boiler was used together with the standard driver's cab, also developed by Watson, which can be recognized by the steeply sloping front wall.

An exception was the 12AR series , which received a replacement boiler that was adapted to the series and had a similar structure to the standard boiler . With a grate area of 3.8 m², this type was between types 2 and 3. A shortened version of the same boiler was used in the new S1 series locomotives .

Technical specifications


designation	Inner diameter	Distance between the pipe walls	Radiant heating surface	Tube heating surface (total)	Superheater heating surface	Grate surface	Used on the locomotive series
1	5 ft 1,524 m	17 ft 9 in 5,410 m	123 sq ft 11,427 m²	1,497 sq ft 139,076 m²	366 sq ft 34,003 m²	36 sq ft 3,345 m²	5R , 5BR , 10CR , 24
1A	5 ft 1,524 m	20 ft 2 in 6,147 m	123 sq ft 11,427 m²	1,700 sq ft 157,935 m²	404 sq ft 37,533 m²	36 sq ft 3,345 m²	19R / BR / C / D , 19AR
2	5 ft 7½ in 1,715 m	19 ft 4 in 5,893 m	142 sq ft 13,192 m²	1,933 sq ft 179,582 m²	492 sq ft 45,708 m²	37 sq ft 3,437 m²	3R , 3BR , 4AR , 12R , 14R , 14CR
2A	5 ft 7½ in 1,715 m	21 ft 8 in 6,604 m	142 sq ft 13,192 m²	2,171 sq ft 201,692 m²	537 sq ft 49,889 m²	37 sq ft 3,437 m²	15AR , 15BR
2 B	5 ft 7½ in 1,715 m	18 ft 4 in 5,588 m	142 sq ft 13,192 m²	1,836 sq ft 170,570 m²	472 sq ft 43,850 m²	37 sq ft 3,437 m²	16R / CR
3A	6 ft 2 ¹ / ₄ in 1,886 m	19 ft ½ in 5,804 m	206 sq ft 19,138 m²	2,682 sq ft 249,166 m²	592 sq ft 54,999 m²	63 sq ft 5,853 m²	16E
3B	6 ft 2 ¹ / ₄ in 1,886 m	22 ft 6 in 6,858 m	206 sq ft 19,138 m²	3,168 sq ft 294,317 m²	676 sq ft 62,802 m²	63 sq ft 5,853 m²	15E , 15F , 21 , 23

Individual evidence

^ ^A ^b ^c Donald Frank Holland: Steam Locomotives of the South African Railways . 1st edition. Volume 2: 1910–1955. Purnell, 1972, ISBN 0-7153-5427-2 .

[holland-1] A ^b ^c Donald Frank Holland: Steam Locomotives of the South African Railways . 1st edition. Volume 2: 1910–1955. Purnell, 1972, ISBN 0-7153-5427-2 .