The final three were built with boilers of 175psi capacity.

Eight were withdrawn by the end of 1935, while four others survived with new boilers until the mid-1950s.

This was not a great success and they were later rebuilt with conventional boilers.

Improved design meant they produced comparable power with just three boilers, rather than four.

It ran with tapered boilers of various types from April 1906.

The members of the class were fitted with domeless boilers.

Heat for the village is thus generated in a central boiler house with two boilers.

She was also equipped with six boilers, but this one could hold 4,400 cotton bales.

The S3s lasted well, some being rebuilt with different boilers and new cylinders.

Mallard was fitted with twelve boilers during its 25 year career.