Boiler Construction, Design, and Fittings
A candidate must be able to trace the pressure boundary from the shell or tubes through the fittings that protect and control it. Know the difference between a boiler proper and its appurtenances: fittings are attached directly to the pressure vessel (safety and relief valves, water columns and gauge glasses, pressure gauges, try cocks, blowoff valves, feed and main steam stop valves, low-water fuel cutouts), while accessories are external (feed pumps, economizers, air preheaters, draft fans, water treatment).
Understand basic shell geometry, tube arrangements (fire-tube versus water-tube), stayed surfaces, and why flat surfaces need stays. Know that a water column slows the rise and fall of water level so the gauge glass reads a steady average, and that gauge glass connections must be kept clear. Learn the blowoff valve rule: the valve closest to the boiler is the quick-opening type and must be clearly marked; a second slow-opening valve may follow. Safety valves must be set at or below the maximum allowable working pressure and must discharge freely to atmosphere.
Traps: confusing fittings with accessories; assuming a gauge glass is a level control; forgetting that a water column must have visible try cocks at the lowest permissible water level; and mixing up the quick-opening versus slow-opening blowoff arrangement. Also watch for questions that imply a stop valve or check valve provides overpressure protection-only the safety/relief valve does.
Rule of thumb: if it touches the pressure boundary and protects or indicates, it is a fitting; if it conditions feed, air, or fuel outside the vessel, it is an accessory.