Question 69 QMED04 - Boiler Technician-Watertender

The Correct Answer is B **Explanation of Correct Option (B):** The main feed pump drive turbine (often a steam turbine) uses steam to drive the pump. The steam exiting this turbine is exhaust steam, which is typically low-pressure and relatively low-temperature (although still superheated or saturated). In modern naval and power plant systems, this exhaust steam is a valuable source of heat energy. Its normal destination is the **Deaerating Feed Tank (DFT)** via the **auxiliary exhaust steam line**. The DFT requires steam to heat the feedwater to saturation temperature and facilitate the removal of dissolved non-condensible gases (primarily oxygen and carbon dioxide). Using the exhaust steam from major auxiliary drives (like the main feed pump turbine) for this purpose maximizes thermal efficiency by recovering waste heat, thereby reducing the amount of high-pressure or auxiliary boiler steam that would otherwise be needed for DFT heating. **Explanation of Incorrect Options:** **A) Deaerating feed tank via the main feed pump discharge line:** This is incorrect. The main feed pump discharge line carries high-pressure, relatively cool feedwater *away* from the DFT and toward the boiler/reactor steam generator. Exhaust steam is routed to the DFT's steam inlet, which is separate from the feedwater flow path. **C) Main condenser via the auxiliary exhaust steam line:** While the main condenser is the ultimate destination for *low-quality* steam sources or during periods of low DFT demand, routing this exhaust directly to the main condenser is generally undesirable as it bypasses a crucial heat recovery step (heating the DFT feedwater). Sending it to the DFT first maximizes efficiency. The DFT is the primary, normal destination for this auxiliary exhaust. **D) SSTG condensers via the auxiliary exhaust steam line:** This is incorrect. SSTG stands for Ship Service TurboGenerator. The SSTG has its own condenser system designed to condense its specific exhaust steam. The auxiliary exhaust from the main feed pump drive turbine is not normally routed to the SSTG condensers; it is routed to the central auxiliary exhaust system (which feeds the DFT).