Question 7 QMED03 - Oiler

The Correct Answer is A **Explanation for Option A (Correct):** The suction strainer is designed to filter out solid contaminants (sludge, rust, debris) from the heavy fuel oil (HFO) before it reaches the pump and purifier. As these contaminants build up on the strainer mesh, the effective area available for the oil to flow through decreases. This restriction in flow causes the pressure on the inlet side of the strainer to remain relatively high, while the pressure on the outlet (pump suction) side drops significantly. The difference between these two pressures—the pressure drop or differential pressure—**increases**. An abnormally high differential pressure is the primary and direct indication that the strainer is clogged and requires cleaning. **Why the other options are incorrect:** * **B) A drop in purifier bowl speed:** Purifier bowl speed is governed by the motor and clutch system, or by hydraulic pressure if it's a hydraulic drive. While a severe lack of HFO flow (caused by a completely clogged strainer) might eventually cause issues with proper functioning, a change in strainer condition directly reflects as a pressure drop, not immediately or primarily as a change in bowl speed. * **C) An increase in fuel oil supply temperature to the bowl:** The fuel oil supply temperature is controlled by the pre-heater and the temperature control system. Strainer clogging is a mechanical flow restriction issue and does not directly cause the temperature to increase. In fact, a severe flow restriction might slightly decrease the flow rate through the heater, but the control system would typically maintain the target temperature. * **D) A decreased pressure drop across the strainer (less differential):** A decreased pressure drop would indicate that the flow resistance has lessened. This usually means the strainer is clean, or possibly that the strainer mesh has failed (torn or punctured), allowing oil and debris to flow through without restriction. Neither scenario indicates the strainer needs cleaning due to clogging.