In 1927, the South African Railways placed ten Class U Union Garratt articulated steam locomotives with a 2-6-2+2-6-2 Double Prairie type wheel arrangement in service.

One reason which had been put forward for the construction of the rear end on the Modified Fairlie principle was to enable the coal bunker to be rigidly in line with the boiler frame to ensure a satisfactory arrangement for the installation of the mechanical stoker.

The main frame therefore carried the smokebox, boiler, firebox, cab and coal bunker, as well as the underbelly water tank.

Two reasons were given for the removal, firstly that the locomotives were being used in short-haul service on the Reef by then and secondly that the stokers were difficult to clear in the event of a blockage.

The overhang, laden with the coal bunker of which more than 80% extended beyond the rear pivot centre, was subjected to severe vertical vibration while the locomotive was in motion and this led to structural weakening of the frame over time.

[1][3][7] The Union Garratts, referred to as U-boats by the enginemen, were placed in service at Glencoe to work the difficult section of the Natal mainline through Newcastle and the reverses at Ingogo across the continental divide at Laing's Nek to Volksrust.

Since they were no longer required to drag freights for hours on end up 1 in 50 (2%) gradients, their mechanical stokers were removed.

The Central South African Railways (CSAR) introduced Gould knuckle couplers on the rolling stock of its Limited Express and Imperial Mail passenger trains in 1904.