More were purchased for the Otavi Railway and the Tsumeb Copper Corporation during the subsequent years, eventually bringing the total number of these locomotives to 21 by 1958.

[1] As a result of heavy traffic demands on the Otavi Railway in South West Africa (SWA), three additional locomotives were ordered in 1931.

The company operated the 352-mile long (566-kilometre) narrow-gauge Otavi Railway across the Namib Desert from Swakopmund on the Atlantic coast to Tsumeb and Grootfontein in northern SWA.

[2][3] Ten more of these locomotives were built for the Otavi line by Société Franco-Belge and delivered in two batches of five in 1950 and 1953, numbered in the ranges from NG120 to NG124 and NG132 to NG136 respectively.

In the 1920s, one of the Class NG5 locomotives was sent to the Avontuur Railway in South Africa for trials, but since it jammed on the tighter curves in the Langkloof despite having one set of flangeless coupled wheels, it was returned to SWA.

[1] The usual practice of the SAR in the steam era was to design locomotives in their own drawing offices and to then go out and find a builder.

The seats of the driver and stoker were mounted on poles which allowed them to be swung around to outside the cab and crews could often be seen riding outside in hot weather.

[1][2] This linking of a pony truck and coupled axle is known as a Krauss-Helmholtz bogie, an invention of Richard von Helmholtz who was the chief designer at the Krauss works in Munich from 1884 to 1917.

On standard-gauge railways in Europe, the inclusion of a Krauss-Helmholtz bogie has allowed the use of large 2-10-0 locomotives on sharply curved mountain sections.

A second tender version was delivered with the later batches of locomotives, with the coal bunker sides set inward for reasons unknown.

The first one was offloaded in Port Elizabeth in April 1961, still equipped with a single central buffer and side chains, the preferred drawgear on the ex-German lines in SWA.

Garratts initially continued to operate in the Langkloof since the Class NG15 was not allowed to work beyond Humansdorp from Port Elizabeth because of a lack of turning facilities, the only existing triangle at the time being the one at the end of the line at Avontuur.

The Class NG15s and their crews were soon doing round trips of just over 200 miles (322 kilometres) in one shift to Assegaaibos and back, unheard of in the Garratt days.

[6][9][10] In 1990, numbers NG19 and NG146 were sold to private individuals and relocated to the Alfred County Railway (ACR) at Port Shepstone in Natal.

The locomotive was eventually sold by its owner to the Brecon Mountain Railway in the United Kingdom and was loaded on a road rig for transport to Durban Harbour on 17 September 2001.