Normal Operation, Startup, and Shutdown Procedures
A repeatable sequence
Startup follows a fixed order: verify water level and that the boiler is filled to the proper point, confirm all valves in the correct lineup, check the fuel train and draft, purge the furnace for the full timed period, establish pilot and prove it, light the main burner, then warm the boiler slowly and bring it up under controlled firing. On a cold boiler, warm-up is gradual; uneven heating strains tube sheets and refractory. When cutting a boiler into a steam header, drain and warm the header, equalize pressure, and open the stop valve slowly.
Water level and blowdown
Normal level is roughly the middle of the gauge glass - commonly stated as one-half to two-thirds visible. The glass must be blown down and verified with try cocks each shift. Bottom blowdown is short, with the boiler under light load, one valve opened fully and then closed before the other, and never with a dry or unattended boiler. Surface blowdown is continuous or periodic to control TDS.
Shutdown
Secure the fuel first, then allow the boiler to cool gradually; do not dump a hot boiler's water or shock it with cold feed. For short outages keep it hot and monitored; for layup use wet layup with treated, deaerated water and an oxygen scavenger, or dry layup with desiccant for long or freezing outages.
Traps
Skipping the purge, lighting off with the furnace full of gas, raising pressure too quickly, opening the main stop against a cold header, and blowing down a boiler at high firing rate are the classic errors questions probe. Also, "normal level" is mid-glass - not at the top of the glass, where carryover risk rises.
Worked example
A boiler is at 100 psig and must tie into a header at 95 psig. Warm the header and drains first, then open the stop valve slowly until pressures equalize; a fast open sends a slug of condensate and steam down the line, producing water hammer and possibly gasket damage.