🔍 Key Concepts

• hydraulic oil properties under pressure in closed systems • relationship between pressure, volume, and compressibility of liquids • how temperature vs. pressure usually affects viscosity and special points like pour point or floc point

💭 Think About

• Think about whether hydraulic oil behaves as a nearly incompressible liquid or a compressible fluid when high pressure is applied. What does that imply for its volume? • Consider what mainly changes viscosity in practical systems: is it temperature or pressure that operators usually monitor for viscosity changes? • Ask yourself which of the listed properties (viscosity, volume, floc point) is most sensitive to temperature changes rather than pressure changes in typical hydraulic applications.

✅ Before You Answer

• Be clear on the definition of viscosity (resistance to flow) and what normally causes it to go up or down in lubricating and hydraulic oils. • Recall that most liquids, including hydraulic oil, are treated as virtually incompressible in marine engineering calculations—what does that say about volume change under pressure? • Know what floc point relates to (wax or additive separation with cooling) and whether it is specified as a function of temperature or pressure.