Question 7 QMED01 - Junior Engineer

The Correct Answer is B. **Explanation of why Option B is correct:** In marine engineering, particularly concerning critical systems like the fuel oil supply for main propulsion boilers, redundancy and operational flexibility are paramount. 1. **Redundancy (N+1 principle):** When two items (such as boilers or propulsion units) require a supply, the components providing that supply (like heaters or pumps) are typically installed in pairs (two units). Each unit is designed to handle the full load requirement, ensuring that if one unit fails or requires maintenance, the standby unit can immediately take over and maintain full plant operation. If there are two main boilers (which together constitute the full load of the plant), a single fuel oil service heater must be able to heat enough fuel to supply *both* boilers running at full capacity. 2. **System Setup:** The fuel oil system usually includes two heaters and two service pumps. Standard operational philosophy dictates running one heater and one pump while keeping the second set on standby. Therefore, the single operating heater (H-1) must be sized to meet the demands of the entire propulsion load (B-1 + B-2). The description in Option B ("Each heater has the capacity to supply heated fuel to both boilers under full load with one service pump running") accurately reflects this necessary operational standard and sizing requirement. **Explanation of why the other options are incorrect:** * **A) Each heater has the capacity to supply heated fuel to both boilers under full load with both service pumps running.** * This scenario implies a potential oversizing of the heater capacity relative to the pumps, or a misunderstanding of operational standard. While the heater must handle the full boiler load, the flow rate is managed by the pumps. In a typical setup, running both service pumps simultaneously would be unusual unless there was a deficiency in the system, as one pump is usually sufficient to meet the maximum flow requirements of the boilers (otherwise, the pumps would lack proper redundancy). The critical factor is that the heater capacity is matched to the boiler demand, not the simultaneous operation of both redundant pumps. * **C) Each heater has the capacity to supply heated fuel to just one boiler under full load with one service pump running.** * This setup violates the fundamental requirement for redundancy and operational stability. If one heater could only supply one boiler, the entire plant could never run at full capacity (both boilers running) unless both heaters were online. If one heater failed, the plant would immediately lose 50% of its propulsion power. Marine regulations and standards require that a single critical component (like a service heater) must be capable of supporting the full propulsion demand. * **D) Each heater has the capacity to supply heated fuel to just one boiler under full load with both service pumps running.** * This option combines the flaw of Option C (insufficient capacity to run the full plant load) with the unnecessary operation of both redundant pumps (as noted in Option A). A heater sized only for one boiler means the plant cannot achieve full power, regardless of the pump arrangement.