The B class locomotives are regarded as the first mainline VR motive power, and were highly successful in passenger operations.

They featured an unusual design of firebox, which had two separate chambers, each with its own firedoor, divided by a water space that effectively acted as a thermic syphon, and joined at the tubeplate.

That configuration was designed to extract the maximum heat from the wood fuels the VR used in its early years.

B50 was selected to haul the first Victorian Railways Royal Train in 1867,[9] taking Prince Alfred Duke of Edinburgh to Ballarat, Bendigo and Castlemaine.

While the B class locomotives were highly successful on the expensively engineered 1860s mainlines for which they were designed, they were less suited for the more cheaply built extensions to the VR system.

The last two in service (B56 & B76) spent their final days shunting carriages at Spencer Street Station and North Melbourne yards, and were withdrawn for scrapping in May and June 1917.

An unknown boiler from either a B or O class was used until 1941 to power refrigeration plant at Spencer Street where ice was made for T vans.