Question 8

The Correct Answer is C **Explanation for Option C (Main feed system):** The Main Feed System is designed specifically to supply deaerated and heated feedwater to the boiler drums, even when the boiler is operational (under load) or in an idle state. When a boiler is idle and its water level needs to be raised (e.g., for startup preparation, chemical treatment circulation, or compensating for shrink/leakage), the Main Feed Pump (or sometimes the auxiliary feed pump if included in this system infrastructure) is the primary means of delivering the necessary water volume against the boiler's internal pressure. This system ensures the water quality meets boiler standards and can overcome the pressure differential. **Explanation for Incorrect Options:** * **A) Condensate recirc system:** This system typically involves circulating condensate internally within the condensate purification or storage stages (like the hotwell or deaerator) to maintain quality or temperature. It is not designed to pump water directly into the high-pressure environment of the boiler drum. * **B) Auxiliary condensate system:** While sometimes used for specialized tasks, the term "auxiliary condensate" generally refers to handling condensate from minor heat exchangers (like steam tracing or gland steam condensers). This water is usually collected and returned to the main condensate path; it does not possess the pressure capability or primary function to feed the main boiler drum. * **D) Main condensate system:** The Main Condensate System collects condensate from the main condenser (after the turbine) and pumps it forward to the deaerator/feedwater heaters. While it handles the water that eventually becomes feedwater, it operates at lower pressures than the boiler and is not the final system responsible for injecting water into the boiler drum.