Question 46 OSE02 - Assistant Engineer - OSV

The Correct Answer is C **Explanation of why option C ("Aluminum dust residue") is correct:** Roots-type blowers commonly utilize aluminum alloy housings or rotors for reduced weight and inertia. The presence of aluminum dust residue (fine aluminum particles) in the air boxes strongly suggests that there is internal mechanical failure within the blower itself. This dust is likely generated by physical rubbing or grinding between the rotors and the casing, or between the rotors themselves (rotor-to-rotor contact), usually due to failed bearings, excessive wear, or damaged timing gears causing the rotors to lose clearance and make physical contact. Since the blower is actively shedding its own material, it is experiencing catastrophic failure and must be replaced immediately to prevent further damage and complete engine shutdown. **Explanation of why other options are incorrect:** * **A) Water accumulations:** While water in the air box is undesirable (it can lead to corrosion and poor combustion), it usually indicates a problem with the charge air cooler (leaking tubes) or moisture carryover from the atmosphere/intake, not a catastrophic failure of the Roots-type blower itself. * **B) Oil accumulations:** Oil in the air box is a common condition that usually indicates either excessive lube oil being carried over from the crankcase (if the engine is trunk-piston type) or worn seals/bearings within the blower's gearcase allowing lubricating oil to leak into the air stream. While this requires maintenance, it does not mandate immediate replacement of the blower in the same way that aluminum dust (mechanical destruction) does. * **D) Iron dust residue:** If iron dust residue were present, it would typically indicate wear or failure of steel components, such as timing gears or large engine components (like cylinder liner or piston ring wear) that have been carried up into the scavenging air stream. While dangerous, the presence of aluminum dust specifically points directly to the self-destruction of the aluminum Roots blower components (casings or rotors), making it the most direct and immediate indicator of required blower replacement.