Question 68 QMED03 - Oiler

The Correct Answer is D **Explanation of why Option D is correct:** Two-stage air ejector assemblies are designed to remove non-condensable gases (primarily air) from the main condenser, which is necessary to maintain a high vacuum for efficient turbine operation. The process starts with the first stage: * **First Stage Function:** The first stage air ejector uses high-velocity steam nozzles (motive steam) to entrain the steam/air mixture drawn directly from the main condenser (suction). * **Discharge Location:** The kinetic energy of the motive steam compresses this mixture (raising its pressure above atmospheric) and discharges it into the **intercondenser**. The intercondenser then condenses most of the motive steam before the remaining air/steam mixture proceeds to the second stage. Therefore, the statement that "The steam/air mixture from the main condenser is discharged by the first stage air ejector to the intercondenser" accurately describes the initial function and flow path of the assembly. **Explanation of why Options A, B, and C are incorrect:** **A) Air is removed from the condensate as it passes through the tubes.** * **Incorrect:** While air is removed from the condenser system, the primary function of the air ejector itself is to remove the air/steam mixture from the vapor space of the main condenser, not directly from the liquid condensate that is passing through the tubes of the intercondenser or aftercondenser. The condensate passing through the tubes acts as the cooling medium to condense the motive steam. **B) The first stage air ejector takes suction on the second stage to increase vacuum.** * **Incorrect:** The stages operate in series, but the flow is sequential from the lowest pressure point (the main condenser) outward. The **first stage** takes suction directly from the **main condenser**. The **second stage** takes suction on the outlet of the **intercondenser** (which is the discharge of the first stage) to further compress the remaining non-condensables. The first stage cannot take suction on the second stage; doing so would reverse the intended pressure differential. **C) Steam to the aftercondenser is condensed and returned to the main condenser via the loop seal.** * **Incorrect:** While the steam used in the air ejectors is condensed in the aftercondenser (and intercondenser), the resulting liquid (condensate) is generally returned to the **condensate pump suction line** or the **main condenser hotwell**, not directly back to the main condenser via a loop seal. A loop seal (or barometric leg) is specifically used to drain the condensate from the intercondenser and aftercondenser back to a lower pressure point while preventing air from leaking back in, but the destination is the hotwell/condensate system, not the main condenser vapor space. More importantly, the cooling medium is typically the main condensate, and the drain is returned to the main condensate flow, not the main condenser hotwell *via* the loop seal.