The HPW air-oil actuator is used as a linking element in hydropneumatic actuators between the compressed air and the hydraulic system. Open-circuit hydropneumatic systems of this type generally consist of an air-oil actuator, a flow control valve (or control block comprising several such valves) and an actuating cylinder, according to the direction of energy transfer. The energy of the compressed air is transferred from the upstream pneumatic circuit to the hydraulic system. Modern electrical signal processing systems determine the sequences in the pneumatic section via simple EP converters.

On the other hand, the qualitative motion sequence in the hydraulic system can also be influenced by applying signals to the hydraulic flow via EP converters and the aforementioned pneumatically adjustable hydropneumatic flow control valves. Hydraulic flows in such hydropneumatic systems are very suitable for solving a number of actuation problems. The compressed air energy is readily available due to the high flow speeds and is transferred to the hydraulic section with very little loss due to the use of the latest technology. The hydraulic flow is free of periodical spurious oscillation and, when used in conjunction with the aforementioned air-oil actuator, is also free of non-periodical spurious oscillation. This very disturbing type of oscillation is often caused by trapped, non-dissolved air and unsuitable seal combinations combined with a degreased hydraulic pressure medium.