During the 1930s, many of the Class 7 series locomotives were equipped with superheated boilers and piston valves.
On the Classes 7B and 7C, this conversion was sometimes indicated with an "S" suffix to the class number on the locomotive number plates, but on the rest of the Class 7 family this distinction was rarely applied.
The superheated versions could be identified by the position of the chimney on the smokebox.
The chimney was displaced forward to provide space behind it in the smokebox for the superheater header.
During the 1930s, many of the Class 7 series locomotives were equipped with superheated boilers and piston valves. On the Classes 7B and 7C, this conversion was sometimes indicated with an "S" suffix to the class number on the locomotive number plates, but on the rest of the Class 7 family this distinction was rarely applied. The superheated versions could be identified by the position of the chimney on the smokebox. The chimney was displaced forward to provide space behind it in the smokebox for the superheater header.
South African Class 7B 4-8-0