When interpreting the engine lube oil supply header pressures for the main engines on your OSV, what statement is true assuming that the lube oil pump is engine-driven?
• Relationship between oil temperature and viscosity and how that affects pressure in a piping system • Effect of engine-driven pump speed (rpm) on flow rate and pressure in a lube oil system • Normal behavior of lube oil header pressure as engine load and speed change
• If the lube oil gets hotter and its viscosity changes, what usually happens to resistance to flow and therefore pressure? • For an engine-driven lube oil pump, what happens to the pump output when engine rpm rises—does it generally move more or less oil? • Try to match the expected trend for temperature vs. pressure and rpm vs. pressure to eliminate the choices that clearly don't fit real engine behavior.
• Be clear on how higher temperature affects oil thickness (viscosity) and thus pressure drop in the system. • Confirm that an engine-driven pump usually increases flow (and thus pressure) with higher rpm, within normal operating range. • Eliminate any answer choice where both temperature and rpm effects contradict typical lube oil system behavior.
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