Before firing a boiler the complete boiler should be inspected. The furnace should be inspected and cleaned both internally and externally. Any structure pipelines that might restrict normal expansion of the unit should be cleaned. All vent valves on the boiler (economiser, drum, superheater) are to be opened before filling up the boiler. In most of the cases separate filling lines are provided. Filling is done through the header drains provided in evaporating section. Economiser coils also be filled thro’ its drain or thro’ the main feed line All the time of filling operations gauge glass must be brought on line .As the boiler is filled up water will start raising in the drum and appear in the gauge glass. Filling is continued till it rises up to recommended operating level. The quality of feed water and its temp are quite important. If the feed water temperature is high, the utmost care should be taken to avoid temperature strains or shocks by slow feeding. Here boiler temperature is relative to the boiler metal temperature. In general the temperature of feed water should not differ more than 50 deg Cfrom drum metal temperature at the time of filling