🔍 Key Concepts

• Fuel oil heater shutdown sequence on marine boilers or diesel systems • Relationship between steam supply (heat source) and fuel oil flow (heated medium) • Risks of overheating, coking, or boiling fuel oil trapped in a heater

💭 Think About

• What happens to the fuel oil inside the heater if you remove the heat source first but keep fuel flowing for a short time? • What happens if you shut off the steam while the heater is still full of oil under pressure but with no flow? • Which sequence minimizes the chance of fuel oil overheating, boiling, or coking inside the heater?

✅ Before You Answer

• Identify which option properly controls oil flow before or after removing heat, in a logical order • Check which choice could trap stagnant oil in a hot heater and create a hazard • Eliminate any option that introduces unnecessary system upset, such as suddenly changing pressure or bypassing temperature control without need