The Johnson boiler is a water-tube boiler used for ship propulsion. The Johnson design was developed by the British engineer J. Johnson in the late 1920s. A patent was granted in 1931, and one of these boilers was installed in the RMS Empress of Britain. This was a time when water-tube boilers were being adopted in fast turbine ships, such as naval warships and passenger liners. There was also a shift to oil firing rather than coal burning. Oil had several advantages for a fast ship, particularly a warship that needed to combine both efficiency for long range with the ability to generate high power on demand when full speed was needed. Oil required fewer stokers, and a smaller crew required less space aboard given over to mess spaces. Refuelling was also quicker and cleaner with oil than w