Steam Boilers - Design, Construction, and Fittings
Domain 1: Steam Boilers - Design, Construction, and Fittings
This domain tests how a 2nd Class candidate reads a boiler as a pressure vessel and as a fitted system: fire-tube versus water-tube construction, pressure parts, supports, inspection openings, and the fittings that protect the vessel and the operator.
Core rules
- Pressure parts include shell, drum, tubes, headers, furnaces, and tube sheets. No welding, caulking, or alteration of pressure parts without an approved procedure and authorized inspection.
- Required fittings normally include safety valve(s), pressure gauge, gauge glass with try cocks or equivalent, low-water fuel cutoff, feedwater stop and check valves, main steam stop valve, and bottom blowdown valve.
- Safety valve capacity must equal or exceed the boiler maximum evaporation; set pressure must not exceed MAWP. A check valve belongs in the feedwater line, not as the only isolation.
- Gauge glass connections must be open and visible; the lowest visible reading must sit above the lowest permissible water level.
Worked example
A fire-tube boiler has MAWP 150 psig and maximum evaporation 10,000 lb/hr. Two safety valves are each rated 6,000 lb/hr at 150 psig. Total capacity is 12,000 lb/hr, so capacity exceeds maximum evaporation and the arrangement is acceptable. If one valve were rated 4,000 lb/hr, total 10,000 lb/hr would only equal the maximum; verify the exact rule and valve certification before accepting.
Traps
Confusing MAWP with operating pressure; leaving gauge-glass isolation valves closed; treating a feedwater check valve as a block valve; and assuming any safety valve can be set above MAWP.