🔍 Key Concepts

• effects of low exhaust (stack) gas temperatures in diesel and boiler systems • how sulfur compounds in fuel behave at different temperatures • where thermal stress is most severe: during rapid temperature changes or at extreme high temperatures

💭 Think About

• Think about what happens to the sulfur in fuel oil when exhaust gases cool below a certain temperature on metal surfaces. • Ask yourself: which component is most at risk when cooler, moist exhaust gases contact relatively cold steel surfaces? • Consider which option is specifically linked to a chemical reaction that depends strongly on temperature, rather than mechanical stress from temperature gradients.

✅ Before You Answer

• Verify which problem is commonly associated with dew point of exhaust gases and cold surfaces in stacks and economizers. • Check which choice relates to corrosion inside uptakes rather than pure mechanical/thermal cracking. • Confirm which listed stress (economizer or air heater) is more related to rapid high temperature changes than to gases being too cool overall.