Question 34 QMED01 - Junior Engineer

The Correct Answer is A ### Explanation for Option A (Correct) Cooling water used in the vent condenser (or gland steam condenser, which serves a similar function in recovering steam/vapors) of a deaerating contact (DC) heater must be pure water, typically condensate, to prevent contamination of the boiler feedwater cycle. The vent condenser's function is to condense steam vented from the DC heater, thus recovering heat and valuable purified water (condensate). The cooling medium is almost universally supplied by the **main condensate pump (MCP)** or, in some systems, an **auxiliary condensate pump (ACP)**. These pumps handle the flow of condensate returning from the main condenser before it is pumped through subsequent feedwater heaters and into the DC heater itself. Using condensate as the cooling medium ensures that the recovered heat is efficiently utilized (preheating the condensate) and maintains the water purity required for the system. ### Why Other Options Are Incorrect **B) main feed pump (MFP):** The main feed pump handles water (feedwater) *after* it has been heated and deaerated, and is responsible for pumping it at very high pressure into the boiler or steam generator. The pressure and temperature of water at the MFP discharge are far too high to be economically or practically used as cooling water in a low-pressure vent condenser. **C) feed booster pump (FBP):** The feed booster pump is often positioned immediately before the main feed pump to ensure the MFP has sufficient net positive suction head (NPSH). The water it handles is high-pressure feedwater. Using this flow for cooling would disrupt the main boiler feed flow and is unnecessary, as the condensate system is already available and better suited. **D) salt water circulator:** Salt water (or raw water/cooling tower water) is highly corrosive and impure. Introducing a cooling medium external to the steam cycle, especially non-deaerated or potentially scaling water, is strictly avoided in applications like vent condensers and gland steam condensers, as any leakage would severely contaminate the boiler feedwater, leading to corrosion and scale formation in the boiler tubes.