The tank-type full-flow lubricating oil filter is situated on the discharge side of the engine-driven lube oil pump on the main engines on your fishing factory ship. Assuming oil pressure readings are observed at constant engine rpm and lube oil temperature, what is the indication of gradually clogging filter elements as long as the bypass relief valve remains closed?
• Pressure drop across a filter when flow and viscosity are constant • Relationship between restriction in a line and upstream vs. downstream pressure • Role of a closed bypass relief valve in keeping oil flow through the filter
• If the filter gets more and more clogged, does it become easier or harder for oil to flow through? How does that affect pressure on the upstream (inlet) side? • With the pump, engine rpm, and oil temperature all constant, what should happen to the downstream (outlet) pressure if less oil can get through the filter element? • Think of a partially closed valve in a piping system: where would you expect the higher pressure to be – before or after that restriction?
• Keep in mind that pump output and flow demand are being held constant (rpm and temperature don’t change). • Assume the bypass relief valve stays closed, so all flow must still go through the filter media itself. • Ask: as the restriction increases, should the pressure before the filter and pressure after the filter move in the same direction or opposite directions?
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