What is a hydraulic accumulator and how does it function in a system?

• A. A reservoir used to cool fluid.
• B. A device used to filter contaminants.
• C. A sensor that monitors pressure fluctuations.
• D. A device storing energy as compressed gas or fluid under pressure to smooth pulsations and provide instantaneous flow during demand.

Answer: (D)

The key idea is that a hydraulic accumulator acts as an energy-storage device to smooth out flow and supply fluid quickly when needed. In most designs, it’s a cylinder with fluid on one side and a compressible gas on the other, separated by a bladder, diaphragm, or piston. As the pump pressurizes the liquid, the gas is compressed and stores energy. When demand rises or pressure would otherwise drop, the stored energy pushes fluid into the circuit, providing instant flow and helping keep system pressure steady. This also dampens pressure pulsations and reduces water hammer, protecting components and making the system respond more smoothly. The main purpose is energy storage in compressed gas or fluid to support instantaneous demand and smooth out pulsations.