Question 62 OSE02 - Assistant Engineer - OSV

The Correct Answer is C ### Why Option C is Correct: **C) The boiler draft must be increased AND the boiler fires must be lit before tubes can be safely blown.** 1. **Increased Boiler Draft is Required:** When soot blowers are activated, they inject high-pressure steam (or sometimes air) into the furnace and uptake areas to dislodge soot and ash deposits. This process temporarily increases the volume of exhaust gases and dislodged particulate matter. If the boiler draft (the flow of air through the furnace and up the stack, typically maintained by forced or induced draft fans) is not increased, the positive pressure created by the soot blowing steam can push gases and sparks out of the access doors, inspection ports, or observation ports, creating a dangerous flashback hazard for personnel. Increasing the draft ensures that the negative pressure inside the furnace remains sufficient to safely carry all gases and debris up the stack. 2. **Boiler Fires Must Be Lit (or "On-Line"):** Soot blowing is performed to clean heat transfer surfaces while the boiler is operating under load (generating steam). Blowing tubes when the boiler is secured (fires off) is ineffective and unnecessary, as the primary purpose is to maintain heat transfer efficiency during operation. Furthermore, the heat generated by the continuous firing helps to dry out the steam used for blowing, preventing water/steam droplets from condensing on and sticking to the tubes, which could lead to further fouling or corrosion. ### Why the Other Options are Incorrect: **A) The boiler draft must be decreased AND the boiler fires must be lit before tubes can be safely blown.** * **Incorrect (Draft):** Decreasing the draft while blowing greatly increases the risk of flashback and fire hazard, as the furnace pressure will become too high, potentially forcing hot gases and sparks out into the boiler room. **B) The boiler draft must be increased AND the boiler fires must be secured before tubes can be safely blown.** * **Incorrect (Fires):** Soot blowing is a maintenance procedure performed while the boiler is under load (fires lit) to maintain efficiency. Blowing tubes while the fires are secured is contrary to standard operational practice. **D) The boiler draft must be decreased AND the boiler fires must be secured before tubes can be safely blown.** * **Incorrect (Both):** This combination creates two hazards/inefficiencies: decreased draft poses a flashback risk, and secured fires mean the procedure is ineffective for maintaining operational heat transfer efficiency.