Filmed on Tuesday 8th February 2022
A warming fire is lit in the 9F the day before it in steam insurance exam. The warming fire slowly heats the boiler overnight so the copper firebox and water are already warm the following day when a full fire is placed in the 9F for its in steam boiler exam. Lighting a warming fire places less stress on the boiler than if a fire was lit in a cold loco as the expansion of the boiler is gradual over 12 to 24 hours rather then over a few hours.
