A high pressure differential across a fuel oil strainer indicates what condition?

A high pressure differential across a fuel oil strainer signifies that the strainer is becoming obstructed or dirty. When fuel passes through a strainer, it encounters resistance from contaminants and particulates that accumulate on the filtering medium. If the strainer is clean, the pressure drop across it will be minimal. Conversely, a significant increase in pressure differential indicates that the flow of fuel is impeded due to a buildup of dirt or impurities within the strainer. This condition necessitates cleaning or replacement of the strainer to ensure proper fuel flow and system operation.

Other options suggest scenarios that are inconsistent with a high pressure differential. For example, a clean fuel oil strainer would exhibit low pressure differential, and the idea of needing new fuel oil does not relate directly to the state of the strainer. Additionally, normal operating conditions would not typically present a high pressure differential, as that would indicate some form of obstruction rather than smooth operation. Therefore, the correct identification of a dirty fuel oil strainer aligns with the implications of having a high pressure differential in the system.