🔍 Key Concepts

• 46 CFR requirements for boiler safety devices • Purpose and operation of fusible plugs in firetube boilers • Relationship between plug melting point and maximum allowable steam temperature

💭 Think About

• Think about why a fusible plug is installed in a boiler and what dangerous condition it is supposed to warn of or protect against. • Should the plug melt at a temperature that is close to normal operating steam temperature, or well above it? How much safety margin makes sense? • Which of these temperatures seems most reasonable for a low‑melting alloy that must stay solid in normal operation but melt before the boiler shell or tubes are seriously damaged?

✅ Before You Answer

• Verify in 46 CFR, Subchapter F – Marine Engineering, in the section covering fusible plugs or boiler fittings. • Check what typical saturated steam temperatures are at common marine boiler pressures (e.g., 150–250 psi) and compare them to the choices. • Confirm that the selected temperature allows the plug to remain solid at normal operating conditions but melt reliably in an overheating/low‑water situation.