When reviewing the engine log on a steam ship, you notice a lower than normal feedwater temperature, high furnace pressure and higher than normal superheater temperature. Which of the following could be a possible cause?
ā¢ Heat transfer sequence in a boiler gas path: furnace ā screen/water wall tubes ā superheater ā economizer ā¢ How gas-side fouling at different locations affects gas temperature, steam temperature, and feedwater temperature ā¢ Relationship between furnace pressure, gas flow resistance, and fouling in the gas passes
ā¢ Think about where in the gas path a blockage or fouling would cause furnace pressure to rise and gas flow to be restricted. ā¢ Ask yourself: if less hot gas reaches the economizer, what happens to the feedwater outlet temperature? ā¢ Consider which component, if insulated by soot or fouling on the gas side, would cause the superheater outlet steam temperature to go up rather than down.
ā¢ Match each symptom (low feedwater temp, high furnace pressure, high superheater temp) with its most likely location in the gas path. ā¢ Verify how gas-side fouling upstream vs. downstream of the superheater would change superheater outlet temperature. ā¢ Confirm whether too much excess air would normally raise or lower furnace pressure and how it would affect superheater and economizer temperatures.
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