Question 9 OSE02 - Assistant Engineer - OSV

The Correct Answer is D. **Why Option D ("Lubricating oil supply header pressure") is correct:** Lubricating oil (LO) is the most critical parameter to confirm immediately upon starting any large diesel engine. The lubricating oil system provides pressurized oil to the main bearings, connecting rod bearings, camshafts, turbocharger bearings, and piston cooling channels (if applicable). Without sufficient LO pressure, metal-to-metal contact and friction occur almost instantly, leading to immediate catastrophic failure of critical components (such as wiping out the main bearings) within seconds or, at best, minutes. Therefore, the operator must verify LO pressure delivery *first* to ensure the engine is not running dry. If LO pressure is not established immediately, the engine must be shut down (tripped) without delay. **Why the other options are incorrect:** * **A) Sea water pump discharge pressure:** While necessary for continuous cooling, the engine has significant thermal inertia. Running the engine briefly (seconds to a minute) without confirming sea water pressure will not cause immediate catastrophic damage. The engine uses jacket water (closed loop) for primary cooling, and the sea water (open loop) cools the jacket water; therefore, damage due to a lack of sea water is not instantaneous upon startup. * **B) Cylinder jacket water pump discharge pressure:** Jacket water (fresh water) circulation is vital for cooling, but similar to sea water, thermal damage takes time to manifest. While low jacket water pressure can cause localized hotspots and eventually lead to engine shutdown via high temperature alarms, the damage is not instantaneous upon startup in the way that damage from a lack of lubrication is. * **C) Fuel oil supply header pressure:** Sufficient fuel pressure is required for the engine to continue running effectively and maintain power, and low pressure may eventually cause the engine to misfire or stop. However, the momentary lack of correct fuel pressure immediately upon starting does not cause physical, irreparable damage to the internal moving components of the engine, unlike the lack of lubricating oil pressure.