In the 1930s, many serving locomotives were reboilered with a standard boiler type, designed by then Chief Mechanical Engineer A.G. Watson, as part of his standardisation policy.
Such Watson Standard reboilered locomotives were reclassified by adding an "R" suffix to their classification number.

When 29 of the Class 3 locomotives, all except no.
1457, were eventually reboilered with superheated Watson Standard no.
2 boilers, they were therefore reclassified to Class 3R. Their original Belpaire boilers were fitted with Ramsbottom safety valves, while the Watson Standard boilers were fitted with Pop safety valves.
The most obvious visual difference between an original and a Watson Standard reboilered locomotive is usually a rectangular regulator cover on the smokebox of the reboilered locomotive just to the rear of the chimney, but this was not always the case, as illustrated below.
In the case of the Class 3R locomotive, an even more obvious visual distinction is the absence of the Belpaire firebox hump between the cab and the boiler.

Locomotives usually had their slide valves replaced with piston valves upon being fitted with superheated Watson Standard boilers, but the Class 3R retained their slide valves throughout their working lives.

By the late 1960s, towards the end of their service lives, the Class 3 was distributed between the Orange Free State and the Cape Western systems.
By this time, they were all used on shunting and pickup service, mainly around Bloemfontein, Beaufort West, Touws River and Cape Town.
By 1970, the entire Class was concentrated in the Cape Western region.
Despite their small 45 ¹⁄₂ inches (1,156 millimetres) coupled wheels, they could handle 50 miles per hour (80 kilometres per hour) with ease and became the preferred power for Bellville haulers until the Class 14CRB took over this service.
The Class 3 were finally withdrawn from service in 1974.
In the 1930s, many serving locomotives were reboilered with a standard boiler type, designed by then Chief Mechanical Engineer A.G. Watson, as part of his standardisation policy. Such Watson Standard reboilered locomotives were reclassified by adding an "R" suffix to their classification number.
When 29 of the Class 3 locomotives, all except no. 1457, were eventually reboilered with superheated Watson Standard no. 2 boilers, they were therefore reclassified to Class 3R. Their original Belpaire boilers were fitted with Ramsbottom safety valves, while the Watson Standard boilers were fitted with Pop safety valves. The most obvious visual difference between an original and a Watson Standard reboilered locomotive is usually a rectangular regulator cover on the smokebox of the reboilered locomotive just to the rear of the chimney, but this was not always the case, as illustrated below. In the case of the Class 3R locomotive, an even more obvious visual distinction is the absence of the Belpaire firebox hump between the cab and the boiler.
Locomotives usually had their slide valves replaced with piston valves upon being fitted with superheated Watson Standard boilers, but the Class 3R retained their slide valves throughout their working lives.
By the late 1960s, towards the end of their service lives, the Class 3 was distributed between the Orange Free State and the Cape Western systems. By this time, they were all used on shunting and pickup service, mainly around Bloemfontein, Beaufort West, Touws River and Cape Town. By 1970, the entire Class was concentrated in the Cape Western region. Despite their small 45 ¹⁄₂ inches (1,156 millimetres) coupled wheels, they could handle 50 miles per hour (80 kilometres per hour) with ease and became the preferred power for Bellville haulers until the Class 14CRB took over this service. The Class 3 were finally withdrawn from service in 1974.
South African Class 3 4-8-2