What is the normal hydraulic reservoir quantity range expressed as a percentage?

• A. 10% to 40%
• B. 45% to 85%
• C. 60% to 90%
• D. 20% to 60%

Answer: (B)

Maintaining the hydraulic reservoir at a mid-range level ensures the system always has enough fluid to meet demand and absorb temperature-driven expansion, while keeping the pump inlet submerged to avoid air ingestion. The typical recommendation is to keep the reservoir in about the 45% to 85% range.

If the level drops too low, the pump can cavitate or starve for fluid, reducing hydraulic power and risking system fault. If the level is too high, overfilling can lead to spills, increased pressure, and reduced ability to accommodate thermal expansion or detect leaks. Keeping within the 45% to 85% window strikes a balance between availability and system safety.