Question 54 OSE01 - Chief Engineer - OSV

The Correct Answer is A **Why Option A is Correct:** The presence of large, hard debris (broken piston rings or exhaust valves) in the foreign object trap box indicates that the exhaust inlet screen has successfully performed its primary function: protecting the delicate, high-speed turbocharger turbine blades from catastrophic damage. However, the impact forces from such debris—especially hard metallic pieces—can cause stress fractures, cracks, or fatigue damage in the screen material that are not immediately visible to the naked eye. Magnaflux (magnetic particle inspection) is a standard non-destructive testing (NDT) method used specifically for ferromagnetic materials (like steel screens) to detect surface and subsurface cracks, inclusions, and flaws. Since a failed screen would allow debris to destroy the turbocharger, it is critical maintenance practice to perform NDT (Magnaflux) to ensure the screen's structural integrity is 100% sound before returning the engine to service. **Why Other Options Are Incorrect:** * **B) The screen should be replaced only when damage is obvious to the naked eye.** This is incorrect because relying only on visual inspection risks missing micro-cracks or stress risers induced by the impact. If these non-visible flaws propagate under engine vibration and heat, the screen could fail later, releasing the debris it previously trapped, or breaking into pieces itself, leading to severe turbocharger damage. * **C) The screen should be replaced without conducting any further checking or investigation.** This is a needlessly expensive and inefficient practice. If the screen appears undamaged and passes NDT (Magnaflux), it can be reused, saving the cost of a new, often specialized, component. Replacement should only occur if NDT reveals damage. * **D) The screen should be placed in a press to remove any indentations from impingement.** This is incorrect and potentially dangerous. Applying pressure to a screen that has already been subjected to severe impact stress may worsen existing stress fractures or introduce new damage, further compromising its integrity. Screens are typically robust and designed to withstand some impingement; if the damage is severe enough to require pressing, the component should be replaced after NDT confirms it is unusable.