Direct contact-type accumulators are characterized by which arrangement?

Direct contact-type accumulators are characterized by which arrangement?

• A. Hydraulic oil and pneumatic medium are directly in contact in a vertical cylinder
• B. A bladder separates gas and oil
• C. A piston barrier between oil and gas
• D. A diaphragm barrier

Answer: (A)

Direct-contact accumulators store energy by compressing gas directly with the hydraulic oil, with no barrier between them. The typical arrangement is a vertical cylinder where the hydraulic oil and the pneumatic medium (gas) are in direct contact, so as oil pressure rises, it directly compresses the gas at the interface, and as oil is released, the gas expands. The interface between oil and gas moves within the same chamber, providing fast response and high energy density because there’s no separating membrane, bladder, or piston.

The other designs keep oil and gas separated by a barrier—a bladder, a diaphragm, or a piston—so there’s no direct contact between the two fluids. That's why those configurations are not direct-contact types.