South African Class 15CA 4-8-2

The locomotives were delivered with 57 inches (1,448 millimetres) diameter coupled wheels and their boilers were set at an operating pressure of 200 pounds per square inch (1,379 kilopascals). All their coupled wheels were eventually retyred to a 60 inches (1,524 millimetres) diameter and to compensate for the loss of tractive effort due to the larger diameter wheels, their operating boiler pressure was increased from 200 to 210 pounds per square inch (1,379 to 1,448 kilopascals) by an adjustment of the setting of their safety valves. This modification enabled these mixed traffic locomotives to handle the fastest mainline passenger trains.[1][6][7]

In addition, all those locomotives which had been built with 23 inches (584 millimetres) bore cylinders had their cylinders reamed to a bore of 24 inches (610 millimetres).[2]

When larger tyres were fitted to their coupled wheels, the old tyres were left in position and turned down on the wheel centres to serve as liners and the new tyres were then shrunk on over the liners. The leading coupled wheels, which had been flangeless as built, were flanged during the retyring. The practice of increasing the diameter of coupled wheels, wheel spacing and other considerations permitting, was begun by A.G. Watson during his term in office as CME and was continued by his successors. The reduction of tractive effort caused by the larger wheels was made up by increasing boiler pressure or by fitting larger cylinders or both, as required. This policy resulted in more mileage between heavy repairs, less cost-per-mile on repairs and locomotives capable of higher speeds.[2]

During the early 1940s, three of the Class 15CB and Class 15CA locomotives were reboilered with new boilers numbered in the range from 9504 to 9506. These boilers were of similar dimensions as the originals but with a different tube arrangement. It was designed by Dr. M.M. Loubser, CME at the time. The reboilered locomotives were not reclassified.[6][7]

The Class 15CA locomotives were placed in service on the mainline between Cape Town and Kimberley but like the Class 15CB, they were later transferred to Bloemfontein. From here they worked throughout the Free State until they were eventually relocated to the Eastern Transvaal system. There they worked out of Pretoria to Pietersburg in the north and from there to Tzaneen in the east and Messina on the Rhodesian border in the north. Some also worked out of Witbank and Breyten.[3][4]

In the early 1960s, a few joined the Class 15CB on the Natal North Coast line. Here they were used on, amongst others, the night and day passenger trains to and from Empangeni on the north coast line and on passenger trains to and from Kelso on the south coast line. In 1983, they all went from there to the Cape Northern system for use on the lines from Beaconsfield in Kimberley, working north to Mafeking and south to De Aar. Eventually nearly forty of them ended up as heavy shunters at Kaserne and Germiston in Johannesburg where they replaced the Class 12AR and Class S1.[3][4][8][9]

15CA 2828 is now plinthed at the Gospel Express, Vinkrivier Station, R60, Robertson, is the Western Cape, South Africa. 2828 completes the 11 coaches stationed at Vink, as accommodation for the Gospel Express Christian Centre.

Three Class 15CA locomotives were sold into industrial service. Numbers 2807 and 2839 went to Dunn's Locomotive Works and were eventually sold to Rustenburg Platinum Mines. No. 2811 went to South Witbank Colliery as their no. 4.[4][10]