Emergency Procedures, Abnormal Conditions, and Accident Prevention
Core concepts
Emergencies require immediate, correct action. On low water: secure fuel, do not add water until the boiler cools and the cause is found. On high water (carryover, water in the steam line): reduce feed, increase blowdown, and drain the steam line. On foaming/priming: reduce firing, increase surface blowdown, and check for oil or high TDS. On flame failure: the safeguard trips fuel; investigate before relighting, and always prepurge before retry. On tube failure: secure fuel, isolate the boiler, and evacuate the area if steam is escaping. On safety valve failure to relieve: reduce firing and pressure immediately and shut down.
Accident prevention includes housekeeping (no oil-soaked rags, clear exits), lockout/tagout before maintenance, proper PPE, and never bypassing safety devices. Know the difference between a fusible plug (melts at high temperature to warn of low water) and a safety valve (relieves pressure).
Traps
Questions test the first action in a low-water condition (secure fuel, not add water), whether the boiler can be relit after a flame failure without prepurge (no), and the correct response to a safety valve that will not open (reduce firing, do not force the valve).
Worked example
Rule of thumb: in any abnormal condition, the first action is to make the boiler safe (stop fuel), then diagnose; never add water to a hot, dry boiler or relight without a purge.