Electro-Hydraulics and Mechanical Systems Practice Test 2026 - Free Practice Questions and Study Guide

Direct contact-type accumulators have the hydraulic oil and the pneumatic medium in the same chamber, with no barrier between them. In a vertical cylinder, the gas sits in direct contact with the oil, so when the system draws oil, the gas compresses and provides the stored energy through its spring-like action. This simple arrangement means there’s no separating membrane, piston, or diaphragm between the fluids, which gives a fast response and compact design. The other common designs use a barrier—such as a bladder, a piston, or a diaphragm—to keep oil and gas apart, which is why those configurations are not direct-contact types.