What is the purpose of the hydraulic reservoir in a hydraulic system?

• A. To filter contaminants from hydraulic fluid.
• B. To store fluid, accommodate expansion, and provide fluid during pump startup or minor leaks.
• C. To regulate the temperature of hydraulic fluid.
• D. To serve as a safety overflow for the system.

Answer: (B)

The hydraulic reservoir is there to store the fluid, provide space for thermal expansion, and supply fluid to the pump when needed. It acts as a buffer so the pump has a ready supply during startup and while small leaks or pressure changes occur, helping prevent the pump from starving and reducing cavitation. The reservoir also allows entrained air to separate from the fluid and vent out, which aids system reliability. Filtration is handled by filters, cooling is managed by separate cooling paths, and overflow considerations come from reservoir sizing and venting, not its primary role. So the main purpose is to hold fluid, accommodate expansion, and ensure the pump has fluid availability during startup or minor leaks.