Question 47 OSE02 - Assistant Engineer - OSV

The Correct Answer is A. **Explanation for Option A (Correct):** Option A is correct because the discovery of hard debris (broken piston rings or exhaust valves) impacting the turbocharger inlet screen indicates that the screen experienced significant mechanical shock and localized stress. Even if the screen appears undamaged to the naked eye (Option D), it may have developed microscopic cracks or stress risers, especially around welds or mounting points, due to the high-velocity impact of the debris. If left unchecked, these invisible flaws could propagate under the extreme operating conditions (high temperature, vibration, and rotational forces) of the turbocharger, leading to catastrophic screen failure and subsequent ingestion of the broken screen pieces into the turbine wheel. Therefore, a Non-Destructive Testing (NDT) method like magnafluxing (magnetic particle inspection) is required to detect surface and near-surface cracks and ensure the integrity of the screen before the engine is returned to service. **Explanation of Incorrect Options:** * **B) The screen should be replaced without conducting any further checking or investigation.** While replacement is the safest ultimate choice if any damage is found, replacing it automatically without inspection is generally wasteful and unnecessary if the screen is intact and passes NDT. Furthermore, if the replacement screen is installed incorrectly or the root cause of the debris is not fully addressed, the problem will recur. The primary requirement after potential hard debris impact is assessing integrity, not automatic replacement. * **C) The screen should be placed in a press to remove any indentations from impingement.** Turbocharger screens are precision components designed to strict geometric standards. Attempting to physically press or reform the screen to remove indentations is likely to introduce new stresses, further weaken the structure, distort the mesh, or damage critical dimensions, making it unusable and potentially more dangerous than leaving it slightly indented. Mechanical repair attempts are not standard practice for such safety components. * **D) The screen should be replaced only when damage is obvious to the naked eye.** Relying solely on visual inspection is inadequate after a known high-impact event involving hard metal debris. As explained in the justification for A, microscopic cracks or underlying structural fatigue are highly probable, and these invisible defects can lead to failure under operational stresses. Safety critical components must be tested using NDT (like magnafluxing) when damage is suspected but not visually confirmed.